Guide for

Industrial Waste 

Management

Protecting

Land

Ground Water

Surface Water

Air

Building

Partnerships
vii.

Introduction

In the Guide, you will find:

• Considerations for siting industrial waste management units

• Methods for characterizing waste constituents

• Fact sheets and Web sites with information about individual waste constituents

• Tools to assess risks that might be posed by the wastes

• Principles for building stakeholder partnerships

• Opportunities for waste minimization

• Guidelines for safe unit design

• Procedures for monitoring surface water, air, and ground water

• Recommendations for closure and post-closure care

Each year, approximately 7.6 billion tons of industrial solid waste are generated and disposed

of at a broad spectrum of American industrial facilities. State, tribal, and some local governments

have regulatory responsibility for ensuring proper management of these wastes, and their programs vary considerably. In an effort to establish a common set of industrial waste management

guidelines, EPA and state and tribal representatives came together in a partnership and developed

the framework for this voluntary Guide. EPA also convened a focus group of industry and public

interest stakeholders chartered under the Federal Advisory Committee Act to provide advice

throughout the process. Now complete, we hope the Guide will complement existing regulatory

programs and provide valuable assistance to anyone interested in industrial waste management.

EPA’s Guide for Industrial Waste Management

Introduction

Welcome to EPA’s Guide for Industrial Waste Management. The purpose of the Guide is to provide facility managers, state and tribal

regulators, and the interested public with recommendations and

tools to better address the management of land-disposed, non-hazardous industrial wastes. The Guide can help facility managers make

environmentally responsible decisions while working in partnership

with state and tribal regulators and the public. It can serve as a

handy implementation reference tool for regulators to complement

existing programs and help address any gaps. The Guide can also

help the public become more informed and more knowledgeable in

addressing waste management issues in the community.
viii.

What Are the Underlying Principles of the Guide?

When using the Guide for Industrial Waste Management, please keep in mind that it reflects

four underlying principles:

• Protecting human health and the environment. The purpose of the Guide is to promote sound waste management that protects human health and the environment. It

takes a multi-media approach that emphasizes surface-water, ground-water, and air

protection, and presents a comprehensive framework of technologies and practices that

make up an effective waste management system.

• Tailoring management practices to risks. There is enormous diversity in the type

and nature of industrial waste and the environmental settings in which it is managed.

The Guide provides conservative management recommendations and simple-to-use

modeling tools to tailor management practices to waste- and location-specific risks. It

also identifies in-depth analytic tools to conduct more comprehensive site-specific

analyses.

• Affirming state and tribal leadership. States, tribes, and some local governments

have primary responsibility for adopting and implementing programs to ensure proper

management of industrial waste. This Guide can help states, tribes, and local governments in carrying out those programs. Individual states or tribes might have more

stringent or extensive regulatory requirements based on local or regional conditions or

policy considerations. The Guide complements, but does not supersede, those regulatory programs; it can help you make decisions on meeting applicable regulatory

requirements and filling potential gaps. Facility managers and the public should consult with the appropriate regulatory agency throughout the process to understand regulatory requirements and how to use this Guide.

• Fostering partnerships. The public, facility managers, state and local governments,

and tribes share a common interest in preserving quality neighborhoods, protecting the

environment and public health, and enhancing the economic well-being of the community. The Guide can provide a common technical framework to facilitate discussion and

help stakeholders work together to achieve meaningful environmental results.

What Can I Expect to Find in the Guide?

The Guide for Industrial Waste Management is available in both hard-copy and electronic versions. The hard-copy version consists of five volumes. These include the main volume and four

supporting documents for the ground-water and air fate-and-transport models that were developed by EPA specifically for this Guide. The main volume presents comprehensive information

and recommendations for use in the management of land-disposed, non-hazardous industrial

waste that includes siting the waste management unit, characterizing the wastes that will be

disposed in it, designing and constructing the unit, and safely closing it. The other four volumes are the user’s manuals and background documents for the ground-water fate-and-transport model—the Industrial Waste Evaluation Model (IWEM)—and the air fate-and-transport

model—the Industrial Waste Air Model (IWAIR).

Introduction
ix.

The electronic version of the Guide, which can be obtained either on CD-ROM or from EPA’s

Web site <www.epa.gov/epaoswer/non-hw/industd/index.htm>, contains a large collection of

additional resources. These include an audio-visual tutorial for each main topic of the Guide;

the IWEM and IWAIR models developed by EPA for the Guide; other models, including the

HELP (Hydrologic Evaluation of Landfill Performance) Model for calculating infiltration rates;

and a large collection of reference materials to complement the information provided in each of

the main chapters, including chemical fact sheets from the Agency for Toxic Substances and

Disease Registry, links to Web sites, books on pertinent topics, copies of applicable rules and

regulations, and lists of contacts and resources for additional information. The purpose of the

audio-visual tutorials is to familiarize users with the fundamentals of industrial waste management and potentially expand the audience to include students and international users.

The IWEM and IWAIR models that come with the electronic version of the Guide are critical

to its purpose. These models assess potential risks associated with constituents in wastes and

make recommendations regarding unit design and control of volatile organic compounds to

help mitigate those risks. To operate, the models must first be downloaded from the Web site or

the CD-ROM to the user’s personal computer.

What Wastes Does the Guide Address?

The Guide for Industrial Waste Management addresses non-hazardous industrial waste subject

to Subtitle D of the Resource Conservation and Recovery Act (RCRA). The reader is referred to

the existence of 40 CFR Part 257, Subparts A and B, which provide federal requirements for

non-hazardous industrial waste facilities or practices. Under RCRA, a waste is defined as nonhazardous if it does not meet the definition of hazardous waste and is not subject to RCRA

Subtitle C regulations. Defining a waste as non-hazardous under RCRA does not mean that the

management of this waste is without risk.

This Guide is primarily intended for new industrial waste management facilities and units,

such as new landfills, new waste piles, new surface impoundments, and new land application

units. Chapter 7B–Designing and Installing Liners, and Chapter 4–Considering the Site, are

clearly directed toward new units. Other chapters, such as Chapter 8–Operating the Waste

Management System, Chapter 9–Monitoring Performance, Chapter 10–Taking Corrective

Action, Chapter 11–Performing Closure and Post-Closure Care, while primarily intended for

new units, can provide helpful information for existing units as well.

What Wastes Does the Guide Not Address?

The Guide for Industrial Waste Management is not intended to address facilities that primarily

handle the following types of waste: household or municipal solid wastes, which are managed

in facilities regulated by 40 CFR Part 258; hazardous wastes, which are regulated by Subtitle C

of RCRA; mining and some mineral processing wastes; and oil and gas production wastes;

mixed wastes, which are solid wastes mixed with radioactive wastes; construction and demolition debris; and non-hazardous wastes that are injected into the ground by the use of shallow

underground injection wells (these injection wells fall under the Underground Injection Control

(UIC) Program).

Introduction
x.

Furthermore, while the Guide provides many tools for assessing appropriate industrial waste

management, the information provided is not intended for use as a replacement for other existing EPA programs. For example, Tier 1 ground-water risk criteria can be a useful conservative

screening tool for certain industrial wastes that are to be disposed in new landfills, surface

impoundments, waste piles, or land application units, as intended by the Guide. These

ground-water risk criteria, however, cannot be used as a replacement for sewage sludge standards, hazardous waste identification exit criteria, hazardous waste treatment standards, MCL

drinking water standards, or toxicity characteristics to identify when a waste is hazardous—all

of which are legally binding and enforceable. In a similar manner, the air quality tool in this

Guide does not and cannot replace Clean Air Act Title V permit conditions that may apply to

industrial waste disposal units. The purpose of this Guide is to help industry, state, tribal, and

environmental representatives by providing a wealth of information that relays and defers to

existing legal requirements.

What is the Relationship Between This Guide and Statutory or

Regulatory Provisions?

Please recognize that this is a voluntary guidance document, not a regulation, nor does it

change or substitute for any statutory or regulatory provisions. This document presents technical information and recommendations based on EPA’s current understanding of a range of

issues and circumstances involved in waste management The statutory provisions and EPA regulations contain legally binding requirements, and to the extent any statute or regulatory provision is cited in the Guide, it is that provision, not the Guide, which is legally binding and

enforceable. Thus, this Guide does not impose legally binding requirements, nor does it confer

legal rights or impose legal obligations on anyone or implement any statutory or regulatory

provisions. When a reference is made to a RCRA criteria, for example, EPA does not intend to

convey that any recommended actions, procedures, or steps discussed in connection with the

reference are required to be taken. Those using this Guide are free to use and accept other

technically sound approaches. The Guide contains information and recommendations designed

to be useful and helpful to the public, the regulated community, states, tribes, and local governments. The word “should” as used in the Guide is intended solely to recommend particular

action and does not connote a requirements. Similarly, examples are presented as recommendations or demonstrations, not as requirements. To the extent any products, trade name, or company appears in the Guide, their mention does not constitute or imply endorsement or

recommendation for use by either the U.S. Government or EPA. Interested parties are free to

raise questions and objections about the appropriateness of the application of the examples

presented in the Guide to a particular situation.

Introduction
Part I

Getting Started

Chapter 1

Understanding Risk and Building Partnerships
Contents

I. Understanding Risk Assessment ................................................................................................................1 - 1

A. Introduction to Risk Assessment ..........................................................................................................1 - 1

B. Types of Risk..........................................................................................................................................1 - 2

C. Assessing Risk........................................................................................................................................1 - 3

1. Hazard Identification ........................................................................................................................1 - 5

2. Exposure Assessment: Pathways, Routes, and Estimation ..................................................................1 - 5

3. Risk Characterization ........................................................................................................................1 - 8

4. Tiers for Assessing Risk....................................................................................................................1 - 10

D. Results ................................................................................................................................................1 - 10

II. Information on Environmental Releases................................................................................................1 - 11

III. Building Partnerships............................................................................................................................1 - 11

A. Develop a Partnership Plan..................................................................................................................1 - 12

B. Inform the State and Public About New Facilities or Significant 

Changes in Facility Operating Plans ....................................................................................................1 - 13

C. Make Knowledgeable and Responsible People Available for Sharing Information ................................1 - 16

D. Provide Information About Facility Operations....................................................................................1 - 16

Understanding Risk and Building Partnerships Activity List........................................................................1 - 19

Resources ....................................................................................................................................................1 - 20

Appendix ....................................................................................................................................................1 - 22

Tables:

Table 1: Effective Methods for Public Notification ....................................................................................1- 14

Figures:

Figure 1: Multiple Exposure Pathways/Routes............................................................................................1 - 7
Getting Started—Understanding Risk and Building Partnerships

1-1

Residents located near waste management units want to understand

the management activities taking

place in their neighborhoods. They

want to know that waste is being

managed safely, without danger to public

health or the environment. This requires an

understanding of the basic principles of risk

assessment and the science behind it.

Opportunities for dialogue between facilities,

states, tribes, and concerned citizens, including a discussion of risk factors, should take

place before decisions are made. Remember,

successful partnerships are an ongoing activity. 

I. Understanding

Risk Assessment

Environmental risk communication skills

are critical to successful partnerships between

companies, state regulators, the public, and

other stakeholders. As more environmental

management decisions are made on the basis

of risk, it is increasingly important for all interested parties to understand the science behind

risk assessment. Encouraging public participation in environmental decision-making means

ensuring that all interested parties understand

the basic principles of risk assessment and can

converse equally on the development of

assumptions that underlie the analysis. 

A. Introduction to Risk

Assessment 

This Guide provides simple-to-use risk

assessment tools that can assist in determining

the appropriate waste management practices

for surface impoundments, landfills, waste

piles, and land application units. The tools

estimate potential human health impacts from

a waste management unit by modeling two

possible exposure pathways: releases through

volatile air emissions and contaminant migration into ground water. Although using the

tools is simple, it is still essential to understand the basic concepts of risk assessment to

be able to interpret the results and understand

the nature of any uncertainties associated with

the analysis. This section provides a general

overview of the scientific principles underlying the methods for quantifying cancer and

Understanding Risk and Building Partnerships

This chapter will help you:

• Understand the basic principles of risk assessment and the science

behind it. 

• Build partnerships between a company that generates and manages waste, the community within which the company lives and

works, and the state agency that regulates the company in order

to build trust and credibility among all parties.

This chapter will help address the following questions.

• What is risk and how is it assessed?

• What are the benefits of building

partnerships?

• What methods have been successful

in building partnerships?

• What is involved in preparing a

stakeholder meeting?
1-2

Getting Started—Understanding Risk and Building Partnerships

noncancer risk. Ultimately, understanding the

scientific principles will lead to more effective

use of the provided tools.

B. Types of Risk

Risk is a concept used to describe situations or circumstances that pose a hazard to

people or things they value. People encounter

a myriad of risks during common everyday

activities, such as driving a car, investing

money, and undergoing certain medical procedures. By definition, risk is comprised of

two components: the probability that an

adverse event will occur and the magnitude

of the consequences of that adverse event. In

capturing these two components, risk is typically stated in terms of the probability (e.g.,

one chance in one million) of a specific

harmful “endpoint” (e.g., accident, fatality,

cancer).

In the context of environmental management and this section in the Guide, risk is

defined as the probability or likelihood that

public health might be unacceptably impacted from exposure to chemicals contained in

waste management units. The risk endpoints

resulting from the exposure are typically

grouped into two major consequence categories: cancer risk and noncancer risk. 

The cancer risk category captures risks

associated with exposure to chemicals that

might initiate cancer. To determine a cancer

risk, one must calculate the probability of an

individual developing any type of cancer during his or her lifetime from exposure to carcinogenic hazards. Cancer risk is generally

expressed in scientific notation; in this notation, the chance of 1 person in 1,000,000 of

developing cancer would be expressed as 1 x

10-6 or 1E-6.

The noncancer risk category is essentially a

catch-all category for the remaining health

effects resulting from chemical exposure.

Noncancer risk encompasses a diverse set of

effects or endpoints, such as weight loss,

enzyme changes, reproductive and developmental abnormalities, and respiratory reactions. Noncancer risk is generally assessed by

comparing the exposure or average intake of a

chemical with a corresponding reference (a

health benchmark), thereby creating a ratio.

The ratio so generated is referred to as the

hazard quotient (HQ). An HQ that is greater

than 1 indicates that the exposure level is

above the protective level of the health benchmark, whereas, an HQ less than 1 indicates

that the exposure is below the protective level

established by the health benchmark.

It is important to understand that exposure

to a chemical does not necessarily result in an

adverse health effect. A chemical’s ability to

initiate a harmful health effect depends on

the toxicity of the chemical as well as the

route (e.g., ingestion, inhalation) and dose

(the amount that a human intakes) of the

exposure. Health benchmark values are used

to quantify a chemical’s possible toxicity and

ability to induce a health effect, and are

derived from toxicity data. They represent a

“dose-response”1 estimate that relates the likelihood and severity of adverse health effects

to exposure and dose. The health benchmark

is used in combination with an individual’s

exposure level to determine if there is a risk.

Because individual chemicals generate different health effects at different doses, benchmarks are chemical specific; additionally,

since health effects are related to the route of

exposure and the timing of the exposure,

health benchmarks are specific to the route

and the duration (acute, subchronic, or

chronic) of the exposure. The definitions of

acute, subchronic, and chronic exposures

vary, but acute typically implies an exposure

of less than one day, subchronic generally

indicates an exposure of a few weeks to a few

months, and chronic exposure can span periods of several months to several years.

1 Dose-response is the correlative relationship between the dose of a chemical received by a subject and the

degree of response to that exposure.
Getting Started—Understanding Risk and Building Partnerships

1-3

The health benchmark for carcinogens is

called the cancer slope factor. A cancer slope

factor (CSF) is defined as the upper-bound2

estimate of the probability of a response per

unit intake of a chemical over a lifetime and is

expressed in units of (mg/kg-d). The slope factor is used to estimate an upper-bound probability of an individual developing cancer as a

result of a lifetime of exposure to a particular

concentration of a carcinogen.

A reference dose (RfD) for oral exposure

and reference concentration (RfC) for inhalation exposure are used to evaluate noncancer

effects. The RfD and RfC are estimates of daily

exposure levels to individuals (including sensitive populations) that are likely to be without an appreciable risk of deleterious effects

during a lifetime and are expressed in units of

mg/kg-d (RfD) or mg/m3 (RfC).

Most health benchmarks reflect some

degree of uncertainty because of the lack of

precise toxicological information on the people who might be most sensitive (e.g., infants,

elderly, nutritionally or immunologically compromised) to the effects of hazardous substances. There is additional uncertainty

because most benchmarks must be based on

studies performed on animals, as relevant

human studies are lacking. From time-to-time

benchmark values are revised to reflect new

toxicology data on a chemical. In addition,

because many states have developed their own

toxicology benchmarks, both the groundwater and air tools in this Guide enable a user

to input alternative benchmarks to those that

are provided. 

There are several sources for obtaining

health benchmarks, some of which are summarized in the text box on the following page.

Most of these sources have toxicological profiles and fact sheets on specific chemicals that

are written in a general manner and summarize the potential risks of a chemical and how

it is currently regulated. One good Internet

source is the Agency for Toxic Substances and

Disease Registry (ATSDR) <www.atsdr.cdc.

gov>. ATSDR provides fact sheets for many

chemicals. These fact sheets are easy to understand and provide general information regarding the chemical in question. An example for

cadmium is provided in the appendix at the

end of this chapter. Additional Internet sites

are also available such as: the Integrated Risk

Information System (IRIS); EPA’s Office of Air

Quality Planning and Standards Hazardous Air

Pollutants Fact Sheets; EPA’s Office of Ground

Water and Drinking Water Contaminant Fact

Sheets; New Jersey’s Department of Health,

Right to Know Program’s Hazardous Substance

Fact Sheets; Environmental Defense’s

Chemical Scorecard; EPA’s Office of Pollution

Prevention and Toxics (OPPT) Chemical Fact

Sheets, American Chemistry Council (ACC),

and several others. Visit the Envirofacts

Warehouse Chemical References Complete

Index at <www.epa.gov/enviro/html/emci/

chemref/complete_index.html> for links to

these Web sites.

C. Assessing Risk

Sound risk assessment involves the use of

an organized process of evaluating scientific

data. A risk assessment ultimately serves as

2 Upper-bound is a number that is greater than or equal to any number in a set.

Example of Health Benchmarks for

Acrylonitrile

Chronic:

inhalation CSF: 0.24 (mg/kg-d)

oral CSF: 0.54 (mg/kg-d)

RfC: 0.002 mg/m3

RfD: 0.001 mg/kg-d

Subchronic:

RfC: 0.02 mg/m3

Acute:

ATSDR MRL: 0.22 mg/m3
1-4

Getting Started—Understanding Risk and Building Partnerships

guidance for making management decisions by

providing one of the inputs to the decision

making process. Risk assessment furnishes beneficial information for a variety of situations,

such as determining the appropriate pollution

control systems for an industrial site, predicting

the appropriateness of different waste management options or alternative waste management

unit configurations, or identifying exposures

that might require additional attention.

The risk assessment process involves data

collection activities, such as identifying and

characterizing the source of the environmental

pollutant, determining the transport of the pollutant once it is released into the environment,

determining the pathways of human exposure,

and identifying the extent of exposure for individuals or populations at risk.

Performing a risk assessment is complex and

requires knowledge in a number of scientific

disciplines. Experts in several areas, such as

toxicology, geochemistry, environmental engineering, and meteorology, can be involved in

performing a risk assessment. For the purpose

of this section, and for brevity, the basic components important to consider when assessing

risk are summarized in three main categories

listed below. A more extensive discussion of

these components can be found in the references listed at the end of this section. The

three main categories are:

Sources for Health Benchmarks

Integrated Risk Information System (IRIS) The

Integrated Risk Information System (IRIS) is the

Agency's official repository of Agency-wide, consensus,

chronic human health risk information. IRIS contains

Agency consensus scientific positions on potential

adverse human health effects that might result from

chronic (or lifetime) exposure to environmental contaminants. IRIS information includes the reference dose for

noncancer health effects resulting from oral exposure,

the reference concentration for noncancer health effects

resulting from inhalation exposure, and the carcinogen

assessment for both oral and inhalation exposure. IRIS

can be accessed at <www.epa.gov/iris>.

Health Effects Assessment Summary Tables

(HEAST) HEAST is a comprehensive listing compiled

by EPA consisting of risk assessment information relative

to oral and inhalation routes for chemicals. HEAST

benchmarks are considered secondary to those contained in IRIS. Although the entries in HEAST have

undergone review and have the concurrence of individual Agency Program Offices, they have either not been

reviewed as extensively as those in IRIS or they do not

have as complete a data set as is required for a chemical

to be listed in IRIS. HEAST can be ordered from NTIS

by calling 1-800-553-IRIS or accessing their Website at

<www.ntis.gov>.

Agency for Toxic Substances and Disease Registry

(ATSDR) The Comprehensive Environmental Response,

Compensation, and Liability Act (CERCLA), requires

that the Agency for Toxic Substances and Disease

Registry (ATSDR) develop jointly with the EPA, in order

of priority, a list of hazardous substances most commonly found at facilities on the CERCLA National Priorities

List; prepare toxicological profiles for each substance

included on the priority list of hazardous substances;

ascertain significant human exposure levels (SHELs) for

hazardous substances in the environment, and the associated acute, subchronic, and chronic health effects; and

assure the initiation of a research program to fill identified data needs associated with the substances. The

ATSDR Minimal Risk Levels (MRLs) were developed as

an initial response to the mandate. MRLs are based on

noncancer health effects only and are not based on a

consideration of cancer effects. MRLs are derived for

acute (1-14 days), intermediate (15-364 days), and

chronic (365 days and longer) exposure durations, for

the oral and inhalation routes of exposure. ATSDR's toxicological profiles can be accessed at <www.atsdr.cdc.

gov/toxfaq.html>. 
Getting Started—Understanding Risk and Building Partnerships

1-5

1. Hazard Identification: identifying

and characterizing the source of the

potential risk (e.g., chemicals managed in a waste management unit).

2. Exposure Assessment: determining

the exposure pathways and exposure

routes from the source to an individual.

3. Risk Characterization: integrating

the results of the exposure assessment with information on who is

potentially at risk (e.g., location of

the person, body weights) and chemical toxicity information. 

1. Hazard Identification

For the purpose of the Guide, the source

of the potential risk has already been identified: waste management units. However,

there must be a release of chemicals from a

waste management unit for there to be exposure and risk. Chemicals can be released from

waste management units by a variety of

processes, including volatilization (where

chemicals in vapor phase are released to the

air), leaching to ground water (where chemicals travel through the ground to a groundwater aquifer), particulate emission (where

chemicals attached to particulate matter are

released in the air when the particulate matter becomes airborne), and runoff and erosion (where chemicals in soil water or

attached to soil particles move to the surrounding area). 

To consider these releases in a risk assessment, information characterizing the waste

management unit is needed. Critical parameters include the size of the unit and its location. For example, larger units have the

potential to produce larger releases. Units

located close to the water table might produce greater releases to ground water than

units located further from the water table.

Units located in a hot, dry, windy climate can

produce greater volatile releases than units in

a cool, wet, non-windy climate.

2. Exposure Assessment:

Pathways, Routes, and

Estimation

Individuals and populations can come into

contact with environmental pollutants by a

variety of exposure mechanisms and processes. The mere presence of a hazard, such as

toxic chemicals in a waste management unit,

does not denote the existence of a risk.

Exposure is the bridge between what is considered a hazard and what actually presents a

risk. Assessing exposure involves evaluating

the potential or actual pathways for and

extent of human contact with toxic chemicals. The magnitude, frequency, duration, and

route of exposure to a substance must be

considered when collecting all of the data

necessary to construct a complete exposure

assessment.

The steps for performing an exposure

assessment include identifying the potentially

exposed population (receptors); pathways of

exposure; environmental media that transport

the contaminant; contaminant concentration

at a receptor point; and receptor’s exposure

time, frequency, and duration. In a deterministic exposure assessment, single values are

assigned to each exposure variable. For example, the length of time a person lives in the

same residence adjacent to the facility might

be assumed to be 30 years. Alternatively, in a

probabilistic analysis, single values can be

replaced with probability distribution functions that represent the range in real-world

variability, as well as uncertainty. Using the

time in residence example, it might be found

that 10 percent of the people adjacent to the

facility live in their home for less than three

years, 50 percent less than six years, 90 percent less than 20 years, and 99 percent less

than 27 years.
1-6

Getting Started—Understanding Risk and Building Partnerships

A probabilistic risk assessment is performed by running the equations that

describe each distribution in a program in

conjunction with a Monte Carlo program.

The Monte Carlo program randomly selects a

value from the designated distribution and

mathematically treats it with numbers randomly selected from distributions for other

parameters. This process is repeated a number of times (e.g., 10,000 times) to generate a

distribution of theoretical values. The person

assessing risk then uses his or her judgement

to select the risk value (e.g., 50th or 90th

percentile).

The output of the exposure assessment is a

numerical estimate of exposure and intake of

a chemical by an individual. The intake information is then used in concert with chemicalspecific health benchmarks to quantify risks

to human health.

Before gathering these data, it is important

to understand what information is necessary

for conducting an adequate exposure assessment and what type of work might be

required. Exposures are commonly determined by using mathematical models of

chemical fate and transport to determine

chemical movement in the environment in

conjunction with models of human activity

patterns. The information required for performing the exposure assessment includes

site-specific data such as soil type, meteorological conditions, ground-water pH, and

location of the nearest receptor. Information

must be gathered for the two components of

exposure assessment: exposure

pathways/routes and exposure quantification/estimation.

a. Exposure Pathways/Routes

An exposure pathway is the course the

chemical takes from its source to the individual or population it reaches. Chemicals cycle

in the environment by crossing through the

different types of media which are considered

exposure pathways: air, soil, ground water,

surface water, and biota (Figure 1). As a result

of this movement, a chemical can be present

in various environmental media, and human

exposure often results from multiple sources.

The relative importance of an exposure pathway depends on the concentration of a chemical in the relevant medium and the rate of

intake by the exposed individual. In a comprehensive risk assessment, the risk assessor

identifies all possible site-specific pathways

through which a chemical could move and

reach a receptor. The Guide provides tools to

model the transport and movement of chemicals through two environmental pathways: air

and ground water.

The transport of a chemical in the environment is facilitated by natural forces: wind and

water are the primary physical processes for

distributing contaminants. For example,

atmospheric transport is frequently caused by

ambient wind. The direction and speed of the

wind determine where a chemical can be

found. Similarly, chemicals found in surface

water and ground water are carried by water

currents or sediments suspended in the water. 

The chemistry of the contaminants and of

the surrounding environment, often referred

to as the “system,” also plays a significant role

in determining the ultimate distribution of

pollutants in the various types of media.

Physical-chemical processes, including dissolution/precipitation, volatilization, photolytic

and hydrolytic degradation, sorption, and

complexation, can influence the distribution

of chemicals among the different environmental media and the transformation from

one chemical form to another3

. An important

component of creating a conceptual model

for performing a risk assessment is the identification of the relevant processes that occur in

a system. These complex processes depend

on the conditions at the site and specific

chemical properties. 

3 Kolluru, Rao (1996).
Getting Started—Understanding Risk and Building Partnerships

1-7

Whereas the exposure pathway dictates the

means by which a contaminant can reach an

individual, the exposure route is the way in

which that chemical comes in contact with

the body. To generate a health effect, the

chemical must come in contact with the body.

In environmental risk assessment, three exposure routes are generally considered: ingestion, inhalation, and dermal absorption. As

stated earlier, the toxicity of a chemical is specific to the dose received and its means of

entry into the body. For example, a chemical

that is inhaled might prove to be toxic and

result in a harmful health effect, whereas the

same chemical might cause no reaction if

ingested, or vice-versa. This phenomenon is

due to the differences in physiological

response once a chemical enters the body. A

chemical that is inhaled reaches the lungs and

enters the blood system. A chemical that is

ingested might be metabolized into a different

chemical that might result in a health effect or

into another chemical that is soluble and can be excreted.

Some contaminants can also be

absorbed by the skin. The skin is

not very permeable and usually

provides a sufficient barrier against

most chemicals. Some chemicals,

however, can pass through the

skin in sufficient quantities to

induce severe health effects. An

example is carbon tetrachloride,

which is readily absorbed through

the skin and at certain doses can

cause severe liver damage. The

dermal route is typically considered in worker scenarios in which

the worker is actually performing

activities that involve skin contact

with the chemical of concern. The

tools provided in the Guide do 

not address the dermal route of

exposure.

b. Exposure Quantification/Estimation

Once appropriate fate-and-transport modeling has been performed for each pathway,

providing an estimate of the concentration of

a chemical at an exposure point, the chemical

intake by a receptor must be quantified.

Quantifying the frequency, magnitude, and

duration of exposures that result from the

transport of a chemical to an exposure point

is critical to the overall assessment. For this

step, the risk assessor calculates the chemicalspecific exposures for each exposure pathway

identified. Exposure estimates are expressed

in terms of the mass of a substance in contact

with the body per unit body weight per unit

time (e.g., milligrams of a chemical per kilogram body weight per day, also expressed as

mg/kg-day).

The exposure quantification process

involves gathering information in two main

areas: the activity patterns and the biological

Figure 1. Multiple Exposure Pathways/Routes (National Research

Council, “Frontiers in Assesssing Human Exposure,” 1991)
1-8

Getting Started—Understanding Risk and Building Partnerships

characteristics (e.g., body weight, inhalation

rate) of receptors. Activity patterns and biological characteristics dictate the amount of a

constituent that a receptor can intake and the

dose that is received per kilogram of body

weight. Chemical intake values are calculated

using equations that include variables for

exposure concentration, contact rate, exposure

frequency, exposure duration, body weight,

and exposure averaging time. The values of

some of these variables depend on the site

conditions and the characteristics of the

potentially exposed population. For example,

the rate of oral ingestion of contaminated food

is different for different subgroups of receptors, which might include adults, children,

area visitors, subsistence farmers, and subsistence fishers. Children typically drink greater

quantities of milk each day than adults per

unit body weight. A subsistence fisher would

be at a greater risk than another area resident

from the ingestion of contaminated fish.

Additionally, a child might have a greater rate

of soil ingestion than an adult due to playing

outdoors or hand-to-mouth behavior patterns.

The activities of individuals also determine the

duration of exposure. A resident might live in

the area for 20 years and be in the area for

more than 350 days each year. Conversely, a

visitor or a worker will have shorter exposure

times. After the intake values have been estimated, they should be organized by population as appropriate (e.g., children, adult

residents) so that the results in the risk characterization can be reported for each population group. To the extent feasible, site-specific

values should be used for estimating the exposures; otherwise, default values suggested by

the EPA in The Exposure Factors Handbook

(EPA, 1995) can be used.

3. Risk Characterization

In the risk-characterization process, the

health benchmark information (i.e., cancer

slope factors, reference doses, reference concenKey Chemical Processes

Sorption: the partitioning of a chemical between the liquid and solid phase determined by its affinity for adhering

to other solids in the system such as soils and sediment.

The amount of chemical that “sorbs” to solids and does not

move through the environment is dependent upon the

characteristics of the chemical, the characteristics of the

surrounding soils and sediments, and the quantity of the

chemical. A sorption coefficient is the measure of a chemical’s ability to sorb. If too much of the chemical is present,

the available binding sites on soils and sediments will be

filled and sorption will not continue.

Dissolution/precipitation: the taking in or coming out of

solution by a substance. In dissolution a chemical is taken

into solution; precipitation is the formation of an insoluble

solid. These processes are a function of the nature of the

chemical and its surrounding environment and are dependent on properties such as temperature and pH. A chemical’s

solubility is characterized by a solubility product. Chemicals

that tend to volatilize rapidly are not highly soluble.

Degradation: the break down of a chemical into other

substances in the environment. Some degradation processes

include biodegradation, hydrolysis, and photolysis. Not all

degradation products have the same risk as the “parent”

compound. Although most degradation products present

less risk than the parent compound, some chemicals can

break down into “daughter” products that are more harmful

than the parent compound. In performing a risk assessment

it is important to consider what the daughter products of

degradation might be.

Bioaccumulation: the take up/ingestion and storage of a

substance into an organism. For substances that bioaccumulate, the concentrations of the substance in the organism

can exceed the concentrations in the environment since the

organism will store the substance and not excrete it. 

Volatilization: the partitioning of a compound into a

gaseous state. The volatility of a compound is dependent

on its water solubility and vapor pressure. The extent to

which a chemical can partition into air is described by one

of two constants: Henry's Law or Rauolt's Law. Other factors that are important to volatility are atmospheric temperature and waste mixing.
Getting Started—Understanding Risk and Building Partnerships

1-9

trations) and the results of the exposure assessment (estimated intake or dose by potentially

exposed populations) are integrated to arrive at

quantitative estimates of cancer and noncancer

risks. To characterize the potential noncarcinogenic effects, comparisons are made between

projected intake levels of substances and reference dose or reference concentration values. To

characterize potential carcinogenic effects,

probabilities that an individual will develop

cancer over a lifetime are estimated from projected intake levels and the chemical-specific

cancer slope factor value. This procedure is the

final calculation step. This step determines who

is likely to be affected and what the likely

effects are. Because of all the assumptions

inherent in calculating a risk, a risk characterization cannot be considered complete unless

the numerical expressions of risk are accompanied by explanatory text interpreting and qualifying the results. As shown in the text box, the

risk characterization step is different for carcinogens and noncarcinogens.

Another consideration during the riskcharacterization phase is the cumulative

effects of multiple exposures. A given population can be exposed to multiple chemicals

from several exposure routes and sources.

Multiple constituents might be managed in a

single waste management unit, for example,

and by considering one chemical at a time,

the risks associated with the waste management unit might be underestimated. The EPA

has developed guidance outlined in the Risk

Assessment Guidance for Superfund, Volume I

(U.S. EPA, 1989b) to assess the overall potential for cancer and noncancer effects posed by

multiple chemicals. The risk assessor, facility

manager, and other interested parties should

determine the appropriateness of adding the

risk contribution of each chemical for each

pathway to calculate a cumulative cancer risk

or noncancer risk. The procedures for adding

risks differ for carcinogenic and noncarcinogenic effects.

The cancer-risk equation described in the

adjacent box estimates the incremental individual lifetime cancer risk for simultaneous

exposure to several carcinogens and is based

on EPA (1989a) guidance. The equation combines risks by summing the risks to a receptor from each of the carcinogenic chemicals.

Assessing cumulative effects from noncarcinogens is more difficult and contains a

greater amount of uncertainty than an assessment for carcinogens. As discussed earlier,

noncarcinogenic risk covers a diverse set of

health effects and different chemicals will

have different effects. To assess the overall

potential for noncarcinogenic effects posed by

more than one chemical, EPA developed a

hazard index (HI) approach. The approach

assumes that the magnitude of an adverse

Calculating Risk

Cancer Risks:

Incremental risk of cancer = average

daily dose (mg/kg-day) * slope factor

(mg/kg-day)

Non-Cancer Risks:

Hazard quotient = exposure or intake

(mg/kg-day) or (mg/m3

)/ RfD (mg/kgday) or RfC (mg/m3

)

Cancer Risk Equation for

Multiple Substances

RiskT = Riski

where:

RiskT = the total cancer risk,

expressed as a unitless probability.

Riski = the sum of the risk estimates

for all of the chemical risks.
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Getting Started—Understanding Risk and Building Partnerships

health effect is proportional to the sum of the

hazard quotients of each of the chemicals

investigated. In keeping with EPA’s Risk

Assessment Guidance, hazard quotients should

only be added for chemicals that have the

same critical effect (e.g., both chemicals affect

the liver or both initiate respiratory distress).

As a result, an extensive knowledge of toxicology is needed to sum the hazard quotients

to produce a hazard index. Segregation of

hazard indices by effect and mechanism of

action can be complex, time-consuming, and

will have some degree of uncertainty associated with it. This analysis is not simple and

should be performed by a toxicologist.

4. Tiers for Assessing Risk

As part of the Guide, EPA has used a 3-

tiered approach for assessing risk associated

with air and water releases from waste management units. Under this approach, an

acceptable level of protection is provided

across all tiers, but with each progressive tier

the level of uncertainty in the risk analysis is

reduced. Reducing the level of uncertainty in

the risk analysis might reduce the level of

control required by a waste management unit

(if appropriate for the site), while maintaining

an acceptable level of protection. The facility

performing the risk assessment accepts the

higher costs associated with a more complex

risk assessment in return for greater certainty

and potentially reduced construction and

operating costs.

The advantages and relative costs of each

tier are outlined below.

Tier 1 Evaluation

• Allows for a rapid but conservative

assessment.

• Lower cost.

• Requires minimal site data.

• Contaminant fate-and-transport and

exposure assumptions are developed

using conservative, non-site specific

assumptions provided by EPA. The

values are provided in “look-up

tables” that serve as a quick and

straightforward means for assessing

risk. These values are calculated to be

protective over a broad range of conditions and situations and are by

design very conservative.

Tier 2 Evaluation

• Represents a higher level of complexity.

• Moderate cost.

• Provides the ability to input some

site-specific data into the risk assessment and thus provides a more accurate representation of site risk.

• Uses relatively simplistic fate and

transport models.

Tier 3 Evaluation

• Provides a sophisticated risk assessment.

• Higher cost.

• Provides the maximum use of sitespecific data and thus provides the

most accurate representation of site

risk.

• Uses more complex fate-and-transport models and analyses.

D. Results

The results of a risk assessment provide a

basis for making decisions but are only one

element of input into the process of designing

a waste management unit. The risk assessment does not constitute the only basis for

management action. Other factors are also

important, such as technical feasibility of

options, public values, and economics.

Understanding and interpreting the results

for the purpose of making decisions also

requires a thorough knowledge of the
assumptions that were applied during the

risk assessment. Ample documentation

should be assembled to describe the scenarios

that were evaluated for the risk assessment

and any uncertainty associated with the estimate. Information that should be considered

for inclusion in the risk assessment documentation include: a description of the contaminants that were evaluated; a description of

the risks that are present (i.e., cancer, noncancer); the level of confidence in the information used in the assessment; the major

factors driving the site risks; and the characteristics of the exposed population. The

results of a risk assessment are essentially

meaningless without the information on how

they were generated.

II. Information on

Environmental

Releases

There are several available sources of information that citizens can review to understand

chemical risk better and to review potential

environmental release from waste management units in their communities. The

Emergency Planning and Community Rightto-Know Act (EPCRA) of 1986 provides one

such resource. EPCRA created the Toxic

Release Inventory (TRI) reporting program

which requires facilities in designated

Standard Industry Codes (see 40 CFR

§372.22) with more than 10 employees that

manufacture or process more than 25,000

pounds, or otherwise use more than 10,000

pounds, of a TRI- listed chemical to report

their environmental releases annually to EPA

and state governments. Environmental releases include the disposal of wastes in landfills,

surface impoundments, land application

units, and waste piles. EPA compiles these

data in the TRI database and release this

information to the public annually. Facility

operators might wish to include TRI data in

the facility’s information repository. TRI data,

however, are merely raw data. When estimating risk, other considerations need to be

examined and understood too, such as the

nature and characteristics of the specific facility and surrounding community.

In 1999, EPA promulgated a final rule that

established alternate thresholds for several

persistent, bioaccumulative, and toxic (PBT)

chemicals (see 64 FR 58665; October 29,

1999). In this rule, EPA has added seven

chemicals to the EPCRA Section 313 list of

TRI chemicals and lowered the reporting

thresholds for another 18 PBT chemicals and

chemical categories. For these 18 chemicals,

the alternate thresholds are significantly lower

than the standard reporting thresholds of

25,000 pounds manufactured or processed,

and 10,000 pounds otherwise used.

EPCRA is based on the belief that citizens

have a right to know about potential environmental risks caused by facility operations in

their communities, including those posed as a

result of waste management. TRI data, therefore, provide yet another way for residents to

learn about the waste management activities

taking place in their neighborhood and to

take a more active role in decisions that

potentially affect their health and environment. More information on TRI and access to

TRI data can be obtained from EPA’s Web site

<www.epa.gov/tri>.

III. Building

Partnerships

Building partnerships between all stakeholders—the community, the facility, and the

regulators—can provide benefits to all parties, such as:

Getting Started—Understanding Risk and Building Partnerships

1-11
• Better understanding of waste management activities at an industrial

facility.

• Better understanding of facility, state,

and community issues.

• Greater support of industry procedures and state policies.

• Reduced delays and costs associated

with opposition and litigation.

• A positive image for a company and

relationship with the state and community.

Regardless of the size or type of a facility’s

waste management unit, facilities, states, and

local communities can all follow similar principles in the process of building partnerships.

These principles are described in various

state public involvement guidance documents, various EPA publications, and state

requirements for waste facilities. These principles embody sound business practices and

common sense and can go beyond state

requirements that call for public participation

during the issuance of a permit. The Guide

recommends principles that can be adopted

throughout the operating life of a facility, not

just during the permitting process. Following

these principles will help all involved consider the full range of activities possible to give

partners an active voice in the decision-making process, and in so doing, will result in a

positive working relationship.

A. Develop a Partnership

Plan

The key to effective involvement is good

planning. Developing a plan for how and

when to involve all parties in making decisions will help make partnership activities run

smoothly and achieve the best results.

Developing a partnership plan also helps identify concerns and determine which involvement activities best

address those concerns.

The first step in

developing a partnership plan is to

work with the state

agency to understand what involvement requirements

exist. Existing state

requirements dealing with partnership plans must be followed.

(Internet sites for all state environmental

agencies are available from <www.astswmo.

org/links.htm>.) After this step, you should

assess the level of community interest generated by a facility’s waste management activities. Several criteria influence the amount of

public interest, including implications for

public health and welfare, current relationships between the facility and community

members, and the community’s political and

economic climate. Even if a facility has not

generated much public interest in the past,

involving the public is a good idea. Interest

in a facility can increase suddenly when

changes to existing activities are proposed or

when residents’ attitudes and a community’s

political or economic climate change.

To gauge public interest in a facility’s waste

management activities and to identify the

community’s major concerns, facility representatives should conduct interviews with

community members. They can first talk

with members of community groups, such as

civic leagues, religious organizations, and

business associations. If interest in the facility’s waste management activities seems high,

facility representatives can consider conducting a more comprehensive set of community

interviews. Other individuals to interview

include the facility’s immediate neighbors,

representatives from other agencies and envi1-12

Getting Started—Understanding Risk and Building Partnerships
ronmental organizations, and any individuals

in the community who have expressed interest in the facility’s operations.

Using the information gathered during the

interviews, facility representatives can develop a list of the community’s concerns regarding the facility’s waste management activities.

They can then begin to engage the community in discussions about how to address those

concerns. These discussions can form the

basis of a partnership plan.

B. Inform the State and

Public About New

Facilities or Significant

Changes in Facility

Operating Plans

A facility’s decision to change its operations provides a valuable opportunity for

involvement. Notifying the state and public

of new units and proposed changes at existing facilities gives these groups the opportunity to identify applicable state requirements

and comment on matters that apply to them.

What are examples of effective

methods for notifying the public?

Table 1 presents examples of effective

methods for public notification and associated advantages and disadvantages. The

method used at a particular facility, and

within a particular community, will depend

on the type of information or issues that

need to be communicated and addressed.

Public notices usually provide the name and

address of the facility representative and a

brief description of the change being considered. After a public notice is issued, a facility

can develop informative fact sheets to

explain proposed changes in more detail.

Fact sheets and public notices can include

the name and telephone number of a contact

person who is available within the facility to

answer questions. 

What is involved in preparing a

meeting with industry, community,

and state representatives?

Meetings can be an effective means of giving and receiving comments and addressing

concerns. To publicize a meeting, the date,

time, and location of the meeting should be

placed in a local newspaper and/or advertised

on the radio. To help ensure a successful dialogue, meetings should be at times convenient for members of the community, such as

early in the evenings during the week, or on

weekends. An interpreter might need to be

obtained if the local community includes residents whose primary language is not English. 

Prior to a meeting, the facility representative should develop a waste management plan

or come to the meeting prepared to describe

how the industrial waste from the facility will

be managed. A waste management plan provides a starting point for public comment and

input. Keep data presentations simple and

provide information relevant to the audience.

Public speakers should be able to respond to

both general and technical questions. Also,

the facility representative should review and

be familiar with the concerns of groups or citizens who have

previously

expressed an

interest in the

facility’s operations. In addition, it is

important to

anticipate questions and plan

how best to

respond to these

questions at a

meeting.

Getting Started—Understanding Risk and Building Partnerships

1-13
1-14

Getting Started—Understanding Risk and Building Partnerships

Methods Features Advantages Disadvantages 

Briefings Personal visit or phone call to Provides background information. Requires time.

key officials or group leaders to Determines reactions before an issue 

announce a decision, provide “goes public.” Alerts key people to 

background information, or issues that might affect them. 

answer questions.

Mailing of key Mailing technical studies or Provides full and detailed information Costs money to print and 

technical reports or environmental reports to other to people who are most interested. mail. Some people might not 

environmental agencies, leaders of organized Often increases the credibility of read the reports.

documents groups, or other interested parties. studies because they are fully visible.

News conferences Brief presentation to reporters, Stimulates media interest in a story. Reporters will only come if 

followed by a question-and- Direct quotations often appear in the announcement or presenanswer period, often television and radio. Might draw tation is newsworthy. Cannot 

accompanied by handouts of attention to an announcement or control how the story is prepresenter’s comments. generate interest in public meetings. sented, although some direct 

quotations are likely. 

Newsletters Brief description of what is going Provides more information than can Requires staff time. Costs 

on, usually issued at key intervals be presented through the media to money to prepare, print, and 

for all people who have shown those who are most interested. Often mail. Stories must be objecinterest. used to provide information prior to tive and credible, or people 

public meetings or key decision points. will react to the newsletters 

Helps to maintain visibility during as if they were propaganda. 

extended technical studies.

Newspaper inserts Much like a newsletter, but Reaches the entire community with Requires staff time to prepare 

distributed as an insert in a important information. Is one of the the insert, and distribution 

newspaper. few mechanisms for reaching everyone costs money. Must be prein the community through which you pared to newspaper’s layout 

can tell the story your way. specifications.

Paid advertisements Advertising space purchased in Effective for announcing meetings or Advertising space can be 

newspapers or on the radio or key decisions or as background costly. Radio and television 

television. material for future media stories. can entail expensive production costs to prepare the ad.

News releases A short announcement or news Might stimulate interest from the Might be ignored or not 

story issued to the media to get media. Useful for announcing read. Cannot control how 

interest in media coverage of the meetings or major decisions or as the information is used. 

story. background material for future media 

stories.

Presentations to civic Deliver presentations, enhanced Stimulates communication with key Few disadvantages, except 

and technical groups with slides or overheads, to key community groups. Can also provide some groups can be hostile. 

community groups. in-depth responses.

Press kits A packet of information Stimulates media interest in the story. Few disadvantages, except 

distributed to reporters. Provides background information that cannot control how the 

reporters can use for future stories. information is used and 

might not be read.

Advisory groups and A group of representatives of key Promotes communication between Potential for controversy 

task forces interested parties is established. key constituencies. Anticipates public exists if “advisory” recomPossibly a policy, technical, or reaction to publications or decisions. mendations are not followed.

citizen advisory group. Provides a forum for reaching Requires substantial commitconsensus. ment of staff time to provide 

support to committees. 

Table 1

Effective Methods for Public Notification
State representatives also should anticipate and be prepared to answer questions

raised during the meeting. State representatives should be prepared to answer questions on specific regulatory or compliance

issues, as well as to address how the facility

has been working in cooperation with the

state agency. The following are some questions that are often asked at meetings.

• What are the risks to me associated

with the operations?

• Who should I contact at the facility if

I have a question or concern?

• How will having the facility nearby

benefit the area?

• Will there be any noticeable day-today effects on the community?

• Which processes generate industrial

waste, and what types of waste are

generated?

• How will the waste streams be treated or managed?

• What are the construction plans for

any proposed containment facilities?

• What are the intended methods for

monitoring and detecting emissions

or potential releases?

• What are the plans to address accidental releases of chemicals or wastes

at the site?

• What are the plans for financial

assurance, closure, and post-closure

care?

• What are the applicable state regulations?

• How long will it take to issue the

permit?

• How will the permit be issued?

• Who should I contact at the state

agency if I have questions or concerns about the facility?

At the meeting, the facility representative

should invite public and state comments on

the proposed change(s), and tell community

Getting Started—Understanding Risk and Building Partnerships

1-15

U.S. EPA 1990. Sites for Our Solid Waste: A Guidebook for Effective Public Involvement.

Methods Features Advantages Disadvantages 

Focus groups Small discussion groups Provides in-depth reaction to ideas or Gets reactions, but no 

established to give “typical” decisions. Good for predicting knowledge of how many 

reactions of the public. emotional reactions people share those reactions. 

Conducted by a professional Might be perceived as an 

facilitator. Several sessions can be effort to manipulate the 

conducted with different groups. public. 

Telephone line Widely advertised phone number Gives people a sense that they know Is only as effective as the 

that handles questions or provides whom to call. Provides a one-step person answering the telecentralized source of information. service of information. Can handle phone. Can be expensive. 

two-way communication.

Meetings Less formal meetings for people Highly legitimate forum for the public Unless a small-group discusto present positions, ask to be heard on issues. Can be sion format is used, it permits

questions, and so forth. structured to permit small group only limited dialogue. Can 

interaction— anyone can speak. get exaggerated positions or 

grandstanding. Requires staff 

time to prepare for meetings.

Table 1

Effective Methods for Public Notification (cont.)
1-16

Getting Started—Understanding Risk and Building Partnerships

members where, and to whom, they should

send written comments. A facility can choose

to respond to comments in several ways. For

example, telephone calls, additional fact

sheets, or additional meetings can all be used

to address comments. Responding promptly

to residents’ comments and concerns demonstrates an honest attempt to address them. 

C. Make Knowledgeable

and Responsible People

Available for Sharing

Information

Having a facility representative available to

answer the public’s questions and provide

information helps assure citizens that the

facility is actively listening to their concerns.

Having a state contact available to address the

public’s concerns about the facility can also

make sure that concerns are being heard and

addressed.

In addition to identifying a contact person,

facilities and states should consider setting up

a telephone line staffed by employees for citizens to call and obtain information promptly

about the facility. Opportunities for face-toface interaction between community members and facility representatives include onsite

information offices, open houses, workshops,

or briefings.

Information

offices function

similarly to information repositories, except that

an employee is

present to answer

questions. Open

houses are informal meetings on

site where residents can talk to

company officials

one-to-one. Similarly, workshops and briefings enable community members, state officials,

and facility representatives to interact, ask

questions, and learn about the activities at the

facility. Web sites can also serve as a useful

tool for facility, state, and community representatives to share information and ask questions.

D. Provide Information

About Facility

Operations

Providing information about facility operations is an invaluable way to help the public

understand waste management activities.

Methods of informing communities include

conducting facility tours; maintaining a publicly accessible information repository on site

or at a convenient offsite public building such

as a library; developing exhibits to explain

operations; and distributing information

through the publications of established organizations. Examples of public involvement

activities are presented in the following pages.

Conduct facility tours. Scheduled facility

tours allow community members and state

representatives to visit the facility and ask

questions about how it operates. By seeing a

facility first-hand, residents learn how waste

is managed and can become more confident

that it is being managed safely. Individual citizens, local officials, interest groups, students,

and the media might want to take advantage

of facility tours. In planning tours, determine

the maximum number of people that can be

taken through the facility safely and think of

ways to involve tour participants in what they

are seeing, such as providing hands-on

demonstrations. It is also a good idea to have

facility representatives available to answer

technical questions in an easy-to-understand

manner.
Maintain a publicly accessible information repository. An information repository is

simply a collection of documents describing

the facility and its activities. It can include

background information on the facility, the

partnership plan (if developed), permits to

manage waste on site, fact sheets, and copies

of relevant guidance and regulations. The

repository should be in a convenient, publicly

accessible place. Repositories are often maintained on site in a public “reading room” or

off site at a public library, town hall, or public

health office. Facilities should publicize the

existence, location, and hours of the repository and update the information regularly.

Develop exhibits that explain facility

operations. Exhibits are visual displays, such

as maps, charts, diagrams, or photographs,

accompanied by brief text. They can provide

technical information in an easily understandable way and an opportunity to illustrate creatively and informatively issues of

concern. When developing exhibits, identify

the target audience, clarify which issue or

aspect of the facility’s operations will be the

exhibit’s focus, and determine where the

exhibit will be displayed. Public libraries,

convention halls, community events, and

shopping centers are all good, highly visible

locations for an exhibit.

Use publications and mailing lists of

established local organizations. Existing

groups and publications often provide access

to established communication networks. Take

advantage of these networks to minimize the

time and expense required to develop mailing

lists and organize meetings. Civic or environmental groups, rotary clubs, religious organizations, and local trade associations might

have regular meetings, newsletters, newspapers, magazines, or mailing lists that could be

useful in reaching interested members of the

community.

Getting Started—Understanding Risk and Building Partnerships

1-17
1-18

Getting Started—Understanding Risk and Building Partnerships

American Chemistry Council’s

Responsible Care®

To address citizens’ concerns about the manufacture, transport, use, and disposal of chemical

products, the American Chemistry Council (ACC)

launched its Responsible Care® program in 1988.

To maintain their membership in ACC, companies

must participate in the Responsible Care® program. One of the key components of the program

is recognizing and responding to community concerns about chemicals and facility operations.

ACC member are committed to fostering an

open dialogue with residents of the communities in

which they are located. To do this, member companies are required to address community concerns in

two ways: (1) by developing and maintaining community outreach programs, and (2) by assuring that

each facility has an emergency response program in

place. For example, member companies provide

information about their waste minimization and

emissions reduction activities, as well as provide

convenient ways for citizens to become familiar

with the facility, such as tours. Many companies

also set up Community Advisory Panels. These

panels provide a mechanism for dialogue on issues

between plants and local communities. Companies

must also develop written emergency response

plans that include information about how to communicate with members of the public and consider

their needs after an emergency.

Responsible Care® is just one example of how

public involvement principles can be incorporated

into everyday business practices. The program also

shows how involving the public makes good business sense. For more information about

Responsible Care®, contact ACC at 703 741-5000. 

AF&PA’s Sustainable Forestry

Initiative

Public concern about the future of America’s

forests coupled with the American Forest & Paper

Association’s (AF&PA’s) belief that “sound environmental policy and sound business practice go hand

in hand” fueled the establishment of the

Sustainable Forestry Initiative (SFI). Established in

1995, the SFI outlines principles and objectives for

environmental stewardship with which all AF&PA

members must comply in order to retain membership. SFI encourages protecting wildlife habitat

and water quality, reforesting harvested land, and

conserving ecologically sensitive forest land. SFI

recognizes that continuous public involvement is

crucial to its ultimate goal of “ensuring that future

generations of Americans will have the same abundant forests that we enjoy today.”

The SFI stresses the importance of reaching out

to the public through toll-free information lines,

environmental education, private and public sector

technical assistance programs, workshops, videos,

and other means. To help keep the public

informed of achievements in sustainable forestry,

members report annually on their progress, and

AF&PA distributes the resulting publication to

interested parties. In addition, AF&PA runs two

national forums a year, which bring together loggers, landowners, and senior industry representatives to review progress toward SFI objectives. 

Many AF&PA state chapters have developed

additional activities to inform the public about the

SFI. For example, in New Hampshire, AF&PA

published a brochure about sustainable forestry

and used it to brief local sawmill officials and the

media. In Vermont, a 2-hour interactive television

session allowed representatives from industry, public agencies, environmental organizations, the academic community, and private citizens to share

their views on sustainable forestry. Furthermore, in

West Virginia, AF&PA formed a Woodland Owner

Education Committee to reach out to nonindustrial

private landowners.

For more information about the SFI, contact

AF&PA at 800 878-8878, or visit the Web site

<www.afandpa.org>.
Getting Started—Understanding Risk and Building Partnerships

1-19

You should consider the following activities in understanding risk and building partnerships between

facilities, states, and community members when addressing potential waste management practices.

■ Understand the definition of risk.

■ Review sources for obtaining health benchmarks.

■ Understand the risk assessment process including the pathways and routes of potential exposure

and how to quantify or estimate exposure.

■ Be familiar with the risk assessment process for cancer risks and non-cancer risks.

■ Develop exhibits that provide a better understanding of facility operations.

■ Identify potentially interested/affected people.

■ Notify the state and public about new facilities or significant changes in facility operating plans.

■ Set up a public meeting for input from the community.

■ Provide interpreters for public meetings.

■ Make knowledgeable and responsible people available for sharing information.

■ Develop a partnership plan based on information gathered in previous steps.

■ Provide tours of the facility and information about its operations.

■ Maintain a publicly accessible information repository or onsite reading room.

■ Develop environmental risk communication skills.

Understanding Risk and Building

Partnerships Activity List
1-20

Getting Started—Understanding Risk and Building Partnerships

American Chemistry Council. 2001 Guide to Community Advisory Panels.

American Chemistry Council. Revised 2001. Environmental Justice and Your Community: A Plant

Manager’s Introduction.

American Chemistry Council. Responsible Care® Overview Brochure.

Council in Health and Environmental Science, ENVIRON Corporation. 1986. Elements of Toxicology

and Chemical Risk Assessment.

Executive Order 12898. 1994. Federal Actions to Address Environmental Justice in Minority

Populations and Low-income Populations. February.

Holland, C.D., and R.S. Sielken, Jr. 1993. Quantitative Cancer Modeling and Risk Assessment.

Kolluru, Rao, Steven Bartell, et al. 1996. Risk Assessment and Management Handbook: For

Environmental, Health, and Safety Professionals.

Louisiana Department of Environmental Quality. 1994. Final Report to the Louisiana Legislature on

Environmental Justice.

Lu, Frank C. 1996. Basic Toxicology: Fundamentals, Target Organs, and Risk Assessment.

National Research Council. 1983. Risk Assessment in the Federal Government: Managing the Process.

Public Participation and Accountability Subcommittee of the National Environmental Justice Advisory

Council (A Federal Advisory Committee to the U.S. EPA). 1996. The Model Plan for Public

Participation. November. 

Texas Natural Resource Conservation Commission. 1993. Texas Environmental Equity and Justice Task

Force Report: Recommendations to the Texas Natural Resource Conservation Commission.

Travis, C.C. 1988. Carcinogenic Risk Assessment.

U.S. EPA. 1996a. RCRA Public Involvement Manual. EPA530-R-96-007.

Resources
Getting Started—Understanding Risk and Building Partnerships

1-21

U.S. EPA. 1996b. 1994 Toxics Release Inventory: Public Data Release, Executive Summary. EPA745-S96-001.

U.S. EPA. 1995a. Decision-maker’s Guide to Solid Waste Management, Second Edition. EPA530-R-95-

023.

U.S. EPA. 1995b. The Exposure Factors Handbook. EPA600-P-95-002A-E.

U.S. EPA. 1995c. OSWER Environmental Justice Action Agenda. EPA540-R-95-023.

U.S. EPA. 1992. Environmental Equity: Reducing Risk for all Communities. EPA230-R-92-008A.

U.S. EPA. 1990. Sites for our Solid Waste: A Guidebook for Effective Public Involvement. EPA530-

SW-90-019.

U.S. EPA. 1989a. Chemical Releases and Chemical Risks: A Citizen’s Guide to Risk Screening. EPA560-

2-89-003.

U.S. EPA. 1989b. Risk Assessment Guidance for Superfund. EPA540-1-89-002.

U.S. Government Accounting Office. 1995. Hazardous and Nonhazardous Waste: Demographics of

People Living Near Waste Facilities. GAO/RCED-95-84.

Ward, R. 1995. Environmental Justice in Louisiana: An Overview of the Louisiana Department of

Environmental Quality’s Environmental Justice Program.

Western Center for Environmental Decision-Making. 1996. Public Involvement in Comparative Risk

Projects: Principles and Best Practices: A Source Book for Project Managers.

Resources (cont.)
1-22

Getting Started—Understanding Risk and Building Partnerships

 

 

Appendix
Getting Started—Understanding Risk and Building Partnerships

1-23
Part I

Getting Started

Chapter 2 

Characterizing Waste
Contents

I. Waste Characterization Through Process Knowledge..............................................................................2 - 2

II. Waste Characterization Through Leachate Testing ..................................................................................2 - 3

A. Sampling and Analysis Plan ..................................................................................................................2 - 4

1. Representative Waste Sampling..........................................................................................................2 - 6

2. Representative Waste Analysis ..........................................................................................................2 - 8

B. Leachate Test Selection ..........................................................................................................................2 - 9

1. Toxicity Characteristic Leaching Procedure (TCLP) ........................................................................2 - 10

2. Synthetic Precipitation Leaching Procedure (SPLP)..........................................................................2 - 11

3. Multiple Extraction Procedure (MEP) ..............................................................................................2 - 12

4. Shake Extraction of Solid Waste with Water or Neutral Leaching Procedure ..................................2 - 13

III. Waste Characterization of Volatile Organic Emissions ..........................................................................2 - 13

Waste Characterization Activity List ............................................................................................................2 - 15

Resources ....................................................................................................................................................2 - 16

Appendix ....................................................................................................................................................2 - 18
Getting Started—Characterizing Waste

2-1

Understanding the physical and

chemical properties of a waste

using sampling and analysis

techniques is the cornerstone

upon which subsequent steps in

the Guide are built. It is necessary for gauging

what risks a waste might pose to surface water,

ground water, and air and drives waste management unit design and operating decisions.

Knowing the composition of the waste is also

necessary when determining the constituents

for which to test. And, as discussed in Chapter

3–Integrating Pollution Prevention, knowledge

of the physical and chemical properties of the

waste is crucial in identifying pollution prevention opportunities.

In many instances, you can use knowledge

of waste generation processes, analytical testing, or some combination of the two to estimate waste generation rates and waste constituent concentrations. To the extent that the

waste is not highly variable, the use of process

knowledge can be a sound approach to waste

characterization and can prove more reasonable and cost effective than frequent sampling

of the waste. It is important to note, however,

that owners or operators using process knowledge to characterize a waste in lieu of testing

are still responsible for the accuracy of their

determinations. No matter what approach is

used in characterizing a waste, the goal is to

maximize the available knowledge that is necessary to make the important decisions

described in later chapters of the Guide. Also,

as changes are made to the industrial processes or waste management practices, it might be

necessary to recharacterize a waste in order to

accurately make waste management decisions

and evaluate risk. 

In considering the use of process knowledge or analytical testing, it is important to

note that the ground water and air emissions

models that accompany the Guide use constituent concentrations to estimate risk. Input

requires specific concentrations which cannot

be precisely estimated solely by knowledge of

the processes that generate the waste. Further,

when wastes are placed in a waste management unit, such as a landfill or surface

Characterizing Waste

This chapter will help you:

• Understand the industrial processes that generate a waste. 

• Determine the waste’s physical and chemical properties. 

• Estimate constituent leaching to facilitate ground-water risk analysis. 

• Quantify total constituent concentrations to facilitate air emissions

analysis.

This chapter will help you address the

following questions:

• How can process knowledge be used

to characterize a waste?

• Which constituent concentrations

should be quantified?

• Which type of leachate test should be

used?
2-2

Getting Started—Characterizing Waste

impoundment, they are subjected to various

physical, chemical, and biological processes

that can result in the creation of new compounds in the waste, changes in the mass and

volume of the waste, and the creation of different phases within the waste and within the

landfill or impoundment. In order to accurately predict the concentration of the contaminants in the leachate, these changes must

be accounted for. 

Accurate waste management unit constituent characterization is also necessary for

input to the modeling tools provided in the

Guide. Because model input requires specific

data, model output will be based on the accuracy of the data input. Process knowledge

alone (unless based on previous testing) might

not be sufficiently accurate to yield reliable

results. Leachate testing (discussed later in

this chapter), for example, will likely give you

a more precise assessment of waste constituent concentrations than process knowledge. Also note that whether you are using

process knowledge, testing, or a combination

of both, sources of model input data must be

well documented so that an individual evaluating the modeling results understands the

background supporting the assessment. 

I. Waste

Characterization

Through Process

Knowledge

A waste characterization begins with an

understanding of the industrial processes that

generate a waste. You must obtain enough

information about the process to enable

proper characterization of the waste, for

example, by reviewing process flow diagrams

or plans and determining all inputs and outputs. You should also be familiar with other

waste characteristics such as the physical

state of the waste, the volume of waste produced, and the general composition of the

waste. In addition, many industries have

thoroughly tested and characterized their

wastes over time, therefore it might be beneficial to contact your trade association to determine if waste characterizations have already

been performed and are available for processes similar to yours. Additional resources can

assist in waste characterization by providing

information on waste constituents and potential concentrations. Some examples include:

• Chemical engineering designs or

plans for the process, showing

process input chemicals, expected

primary and secondary chemical

reactions, and products.

• Material Safety Data Sheets (MSDSs)

for materials involved. (Note that not

all MSDSs contain information on all

constituents found in a product.)

• Manufacturer’s literature.

• Previous waste analyses.

• Literature on similar processes.

• Preliminary testing results, if available.

A material balance exercise using process

knowledge can be useful in understanding

where wastes are generated within a process

and in estimating concentrations of waste constituents particularly where analytical test data
Getting Started—Characterizing Waste

2-3

are limited. In a material balance, all input

streams, such as raw materials fed into the

processes, and all output streams, such as

products produced and waste generated, are

calculated. Flow diagrams can be used to identify important process steps and sources where

wastes are generated. Characterizing wastes

using material balances can require considerable effort and expense, but can help you to

develop a more complete picture of the waste

generation process(es) involved. 

Note that a thorough assessment of your

production processes can also serve as the

starting point for facility-wide waste reduction, recycling, or pollution prevention

efforts. Such an assessment will provide the

information base to explore many opportunities to reduce or recycle the volume or toxicity of wastes. Refer to Chapter 3–Integrating

Pollution Prevention for ideas, tools, and references on how to proceed.

While the use of process knowledge is

attractive because of the cost savings associated with using existing information, you must

ensure that this information accurately characterizes your wastes. If using process

descriptions, published data, and documented studies to determine waste characteristics,

the data should be scrutinized carefully to

determine if there are any differences between

the processes in the studies and the waste

generating process at your facility, that the

studies are acceptable and accurate (i.e.,

based on valid sampling and analytical techniques), and that the information is current. 

If there are discrepancies, or if you begin a

new process or change any of the existing

processes at your facility (so that the documented studies and published data are no

longer applicable), you are encouraged to

consider performing additional sampling and

laboratory analysis to accurately characterize

the waste and ensure proper management.

Also, if process knowledge is used in addition

to, or in place of, sampling and analysis, you

should clearly document the information

used in your characterization assessment to

demonstrate to regulatory agencies, the public, and other interested parties that the information accurately and completely

characterizes the waste. The source of this

information should be clearly documented. 

II. Waste

Characterization

Through

Leachate Testing

Although sampling and laboratory analysis

is not as economical and might not be as

convenient as using process knowledge, it

does have advantages. The resulting data usually provide the most accurate information

available on constituent concentration levels.

What is process

knowledge?

Process knowledge refers to detailed

information on processes that generate

wastes. It can be used to partly, or in

many cases completely, characterize

waste to ensure proper management.

Process knowledge includes:

• Existing published or documented

waste analysis data or studies conducted on wastes generated by

processes similar to that which generated the waste.

• Waste analysis data obtained from

other facilities in the same industry.

• Facility’s records of previously performed analyses.
2-4

Getting Started—Characterizing Waste

Incomplete or mis-characterization of waste

can lead to improper waste management, inaccurate modeling outputs, or erroneous decisions concerning the type of unit to be used,

liner selection, or choice of land application

methods. Note that process knowledge allows

you to eliminate unnecessary or redundant

waste testing by helping you focus on which

constituents to measure in the waste. Again,

thorough documentation of both the process

knowledge used (e.g., studies, published data),

as well as the analytical data is important. 

The intent of leachate and extraction testing

is to estimate the leaching potential of constituents of concern to water sources. It is

important to estimate leaching potential in

order to accurately estimate the quantity of

chemicals that could potentially reach groundor surface-water resources (e.g., drinking

water supply wells, waters used for recreation). The Industrial Waste Management

Evaluation Model (IWEM) developed for the

Guide uses expected leachate concentrations

for the waste management units as the basis

for liner system design recommendations.

Leachate tests will allow you to accurately

quantify the input terms for modeling. 

If the total concentration of all the constituents in a waste has been estimated using

process knowledge (which could include previous testing data on wastes known to be very

similar), estimates of the maximum possible

concentration of these constituents in leachate

can be made using the dilution ratio of the

leachate test to be performed. 

For example, the Toxicity Characteristic

Leachate Procedure (TCLP) allows for a total

constituent analysis in lieu of performing the

test for some wastes. If a waste is 100 percent

solid, as defined by the TCLP method, then

the results of the total compositional analysis

may be divided by twenty to convert the total

results into the maximum leachable concentration1

. This factor is derived from the 20:1 liquid to solid ratio employed in the TCLP. This

is a conservative approach to estimating

leachate concentrations and does not factor in

environmental influences, such as rainfall. If a

waste has filterable liquid, then the concentration of each phase (liquid and solid) must be

determined. The following equation may be

used to calculate this value:2

(V1)(C1) + (V2)(C2)

V1 + 20V2

Where: 

V1 = Volume of the first phase (L)

C1 = Concentration of the analyte of concern in the first phase (mg/L)

V2 = Volume of the second phase (L)

C2 = Concentration of the analyte of concern in the second phase (mg/L)

Because this is only a screening method for

identifying an upper-bound TCLP leachate

concentration, you should consult with your

state or local regulatory agency to determine

whether process knowledge can be used to

accurately estimate maximum risk in lieu of

leachate testing.

A. Sampling and Analysis

Plan

One of the more critical elements in proper

waste characterization is the plan for sampling

and analyzing the waste. The sampling plan is

usually a written document that describes the

objectives and details of the individual tasks of

1 This method is only appropriate for estimating maximum constituent concentration in leachate for nonliquid wastes (e.g., those wastes not discharged to a surface impoundment). For surface impoundments,

the influent concentration of heavy metals can be assumed to be the maximum theoretical concentration

of metals in the leachate for purposes of input to the ground-water modeling tool that accompanies this

document. To estimate the leachate concentration of organic constituents in liquid wastes for modeling

input, you will need to account for losses occurring within the surface impoundment before you can estimate the concentration in the leachate (i.e., an effluent concentration must be determined for organics).

2 Source: Office of Solid Waste Web site at <www.epa.gov/sw-846/sw846.htm>.
Getting Started—Characterizing Waste

2-5

a sampling effort and how they will be performed. This plan should be carefully thought

out, well in advance of sampling. The more

detailed the sampling plan, the less opportunity for error or misunderstanding during

sampling, analysis, and data interpretation.

To ensure that the sampling plan is

designed properly, a wide range of personnel

should be consulted. It is important that the

following individuals are involved in the

development of the sampling plan to ensure

that the results of the sampling effort are precise and accurate enough to properly characterize the waste:

• An engineer who understands the

manufacturing processes.

• An experienced member of the sampling team.

• The end user of the data.

• A senior analytical chemist.

• A statistician.

• A quality assurance representative.

It is also advisable that you consult the

analytical laboratory to be used when developing your sampling plan.

Background information on the processes

that generate the waste and the type and

characteristics of the waste management unit

is essential for developing a sound sampling

plan. Knowledge of the unit location and situation (e.g., geology, exposure of the waste to

the elements, local climatic conditions) will

assist in determining correct sample size and

sampling method. Sampling plan design will

depend on whether you are sampling a waste

prior to disposal in a waste management unit

or whether you are sampling waste from an

existing unit. When obtaining samples from

an existing unit, care should be taken to

avoid endangering the individuals collecting

the samples and to prevent damaging the unit

itself. Reasons for obtaining samples from an

existing unit include, characterizing the waste

in the unit to determine if the new waste

being added is compatible, checking to see if

the composition of the waste is changing over

time due to various chemical and biological

breakdown processes, or characterizing the

waste in the unit or the leachate from the

unit to give an indication of expected concentrations in leachate from a new unit.

The sampling plan must be correctly

defined and organized in order to get an

accurate estimation of the characteristics of

the waste. Both an appropriate sample size

and proper sampling techniques are necessary. If the sampling process is carried out

correctly, the sample will be representative

and the estimates it generates will be useful

for making decisions concerning proper management of the waste and for assessing risk. 

In developing a sampling plan, accuracy is

of primary concern. The goal of sampling is to

get an accurate estimate of the waste’s characteristics from measuring the sample’s characteristics. The main controlling factor in

deciding whether the estimates will be accurate is how representative the sample is (discussed in the following section). Using a small

sample increases the possibility that the sample will not be representative, but a sample

that is larger than the minimum calculated

sample size does not necessarily increase the

probability of getting a representative sample.

As you are developing the sampling plan, you

should address the following considerations:

• Data quality objectives.

• Determination of a representative

sample.

• Statistical methods to be employed in

the analyses.

• Waste generation and handling

processes.
2-6

Getting Started—Characterizing Waste

• Constituents/parameters to be sampled.

• Physical and chemical properties of

the waste.

• Accessibility of the unit.

• Sampling equipment, methods, and

sample containers.

• Quality assurance and quality control

(e.g., sample preservation and handling requirements).

• Chain-of-custody.

• Health and safety of employees.

Many of these considerations are discussed

below. Additional information on data quality

objectives and quality assurance and quality

control can be found in Test Methods for

Evaluating Solid Waste, Physical/Chemical

Methods—SW-846 (U.S. EPA, 1996e), Guidance

for the Data Quality Objectives Process (U.S.

EPA, 1996b), Guidance on Quality Assurance

Project Plans (U.S. EPA, 1998a), and Guidance

for the Data Quality Assessment: Practical

Methods for Data Analysis (U.S. EPA, 1996a).3

A determination as to the constituents that

will be measured can be based on process

knowledge to narrow the focus and expense

of performing the analyses. Analyses should

be performed for those constituents that are

reasonably expected to be in the waste at

detectable levels (i.e., test method detection

levels). Note that the Industrial Waste

Management Evaluation Model (IWEM) that

accompanies this document recommends

liner system designs, if necessary, or the

appropriateness of land application based on

calculated protective leachate thresholds

(Leachate Concentration Threshold Values or

LCTVs) for various constituents that are likely to be found in industrial waste and pose

hazards at certain levels to people and the

environment. The constituents that are evaluated are listed in Table 1.2 of the Industrial

Waste Management Evaluation Model Technical

Background Document (U.S. EPA 2002). The

LCTV tables also are included in the IWEM

Technical Background Document and the model

on the CD-ROM version of this Guide, and

can be used as a starting point to help you

determine which constituents to measure. It

is not recommended that you sample for all

of the organic chemicals and metals listed in

the tables, but rather use these tables as a

guide in conjunction with knowledge concerning the waste generating practices to

determine which constituents to measure.

1. Representative Waste

Sampling

The first step in any analytical testing

process is to obtain a sample that is representative of the physical and chemical composition of a waste. The term “representative

sample” is commonly used to denote a sample

that has the same properties and composition

in the same proportions as the population

from which it was collected. Finding one sample which is representative of the entire waste

can be difficult unless you are dealing with a

homogenous waste. Because most industrial

wastes are not homogeneous, many different

factors should be considered in obtaining

samples. Examples of some of the factors that

should be considered include:

• Physical state of the waste. The

physical state of the waste affects

most aspects of a sampling effort. The

sampling device will vary according

to whether the sample is liquid, solid,

gas, or multiphasic. It will also vary

according to whether the liquid is

viscous or free-flowing, or whether

the solid is hard, soft, powdery,

monolithic, or clay-like. 

• Composition of the waste. The

samples should represent the average

concentration and variability of the

waste in time or over space.

3 These and other EPA publications can be found at the National Environmental Publications Internet

site (NEPIS) at <www.epa.gov/ncepihom/nepishom/>.
Getting Started—Characterizing Waste

2-7

• Waste generation and handling processes. Processes to

consider include: if the waste

is generated in batches; if

there is a change in the raw

materials used in a manufacturing process; if waste composition can vary substantially

as a function of process temperatures or pressures; and if

storage time affects the waste’s

characteristics/composition.

• Transitory events. Start-up,

shut-down, slow-down, and

maintenance transients can

result in the generation of a

waste that is not representative

of the normal waste stream. If

a sample was unknowingly

collected at one of these intervals, incorrect conclusions

could be drawn.

You should consult with your state or

local regulatory agency to identify any

legal requirements or preferences before

initiating sampling efforts. Refer to

Chapter 9 of the EPA’s SW-846 test

methods document (see side bar) for

detailed guidance on planning, implementing, and assessing sampling events. 

To ensure that the chemical information obtained from waste sampling

efforts is accurate, it must be unbiased

and sufficiently precise. Accuracy is

usually achieved by incorporating

some form of randomness into the

sample selection process and by selecting an appropriate number of samples.

Since most industrial wastes are heterogeneous in terms of their chemical

properties, unbiased samples and

appropriate precision can usually be

achieved by simple random sampling.

In this type of sampling, all units in

the population (essentially all locations

More information on Test Methods

for Evaluating Solid Waste, Physical/

Chemical Methods—SW-846

EPA has begun replacing requirements mandating the use of specific measurement methods or

technologies with a performance-based measurement system (PBMS). The goal of PBMS is to

reduce regulatory burden and foster the use of

innovative and emerging technologies or methods. The PBMS establishes what needs to be

accomplished, but does not prescribe specifically

how to do it. In a sampling situation, for example, PBMS would establish the data needs, the

level of uncertainty acceptable for making decisions, and the required supporting documentation; a specific test method would not be

prescribed. This approach allows the analyst the

flexibility to select the most appropriate and cost

effective test methods or technologies to comply

with the criteria. Under PBMS, the analyst is

required to demonstrate the accuracy of the measurement method using the specific matrix that is

being analyzed. SW-846 serves only as a guidance

document and starting point for determining

which test method to use.

SW-846 provides state-of-the-art analytical test

methods for a wide array of inorganic and organic

constituents, as well as procedures for field and

laboratory quality control, sampling, and characteristics testing. The methods are intended to promote accuracy, sensitivity, specificity, precision,

and comparability of analyses and test results. 

For assistance with the methods described in SW846, call the EPA Method Information

Communication Exchange (MICE) Hotline at 703

676-4690 or send an e-mail to mice@cpmx.saic.com.

The text of SW-846 is available online at:

<www.epa.gov/sw-846/main.htm>. A hard copy

or CD-ROM version of SW-846 can be purchased

by calling the National Technical Information

Service (NTIS) at 800 553-6847.
2-8

Getting Started—Characterizing Waste

or points in all batches of waste from which a

sample could be collected) are identified, and

a suitable number of samples is randomly

selected from the population.

The appropriate number of samples to

employ in a waste characterization is at least

the minimum number of samples required to

generate a precise estimate of the true mean

concentration of a chemical contaminant in a

waste. A number of mathematical formulas

exist for determining the appropriate number

of samples depending on the statistical precision required. Further information on sampling designs and methods for calculating

required sample sizes and optimal distribution of samples can be found in Gilbert

(1987), Winer (1971), and Cochran (1977)

and Chapter 9 of EPA SW-846.

The type of sampling plan developed will

vary depending on the sampling location.

Solid wastes contained in a landfill or waste

pile can be best sampled using a threedimensional random sampling strategy. This

involves establishing an imaginary threedimensional grid or sampling points in the

waste and then using random-number tables

or random-number generators to select points

for sampling. Hollow-stem augers combined

with split-spoon samplers are frequently

appropriate for sampling landfills. 

If the distribution of waste components is

known or assumed for liquid or semi-solid

wastes in surface impoundments, then a twodimensional simple random sampling strategy

might be appropriate. In this strategy, the top

surface of the waste is divided into an imaginary grid and grid sections are selected using

random-number tables or random-number

generators. Each selected grid point is then

sampled in a vertical manner along the entire

length from top to bottom using a sampling

device such as a weighted bottle, a drum

thief, or Coliwasa. 

If sampling is restricted, the sampling strategy should, at a minimum, take sufficient

samples to address the potential vertical variations in the waste in order to be considered

representative. This is because contained

wastes tend to display vertical, rather than

horizontal, non-random heterogeneity due to

settling or the layering of solids and denser

liquid phases. Also, care should be taken

when performing representative sampling of a

landfill, waste pile, or surface impoundment

to minimize any potential to create hazardous

conditions. (It is possible that the improper

use of intrusive sampling techniques, such as

the use of augers, could accelerate leaching by

creating pathways or tunnels that can accelerate leachate movement to ground water.)

To facilitate characterization efforts, consult

with state and local regulatory agencies and a

qualified professional to select a sampling plan

and determine the appropriate number of samples, before beginning sampling efforts. You

should also consider conducting a detailed

waste-stream specific characterization so that

the information can be used to conduct waste

reduction and waste minimization activities. 

Additional information concerning sampling plans, strategies, methods, equipment,

and sampling quality assurance and quality

control is available in Chapters 9 and 10 of the

SW-846 test methods document. Electronic

versions of these chapters have been included

on the CD-ROM version of the Guide.

2. Representative Waste Analysis

After a representative sample has been collected, it must be properly preserved to maintain the physical and chemical properties that

it possessed at the time of collection. Sample

types, sample containers, container preparation, and sample preservation methods are

critical for maintaining the integrity of the

sample and obtaining accurate results.

Preservation and holding times are also
Getting Started—Characterizing Waste

2-9

4 There are several general categories of phases in which samples can be categorized: solids, aqueous,

sludges, multiphase samples, ground water, and oil and organic liquid. You should select a test that is

designed for the specific sample type.

important factors to consider and will vary

depending on the type of constituents being

measured (e.g., VOCs, heavy metals, hydrocarbons) and the waste matrix (e.g., solid,

liquid, semi-solid).

The analytical chemist then develops an

analytical plan which is appropriate for the

sample to be analyzed, the constituents to be

analyzed, and the end use of the information

required. The laboratory should have standard

operating procedures available for review for

the various types of analyses to be performed

and for all associated methods needed to complete each analysis, such as instrument maintenance procedures, sample handling

procedures, and sample documentation procedures. In addition, the laboratory should have

a laboratory quality assurance/quality control

statement available for review which includes

all key personnel qualifications.

The SW-846 document contains information on analytical plans and methods.

Another useful source of information regarding the selection of analytical methods and

quality assurance/quality control procedures

for various compounds is the Office of Solid

Waste Methods Team home page at

<www.epa.gov/sw-846/index.htm>.

B. Leachate Test Selection

Leaching tests are used to estimate potential concentration or amount of waste constituents that can leach from a waste to

ground water. Typical leaching tests use a

specified leaching fluid mixed with the solid

portion of a waste for a specified time. Solids

are then separated from the leaching solution

and the solution is tested for waste constituent concentrations. The type of leaching

test performed can vary depending on the

chemical, biological, and physical characteristics of the waste; the environment in which

the waste will be placed; as well as the recommendations or requirements of your state

and local regulatory agencies.

When selecting the most appropriate analytical tests, consider at a minimum the physical state of the sample, the constituents to be

analyzed, detection limits, and the specified

holding times of the analytical methods.4 It

might not be cost-effective or useful to conduct a test with detection limits at or greater

than the constituent concentrations in a

waste. Process knowledge can help you predict whether the concentrations of certain

constituents are likely to fall below the detection limits for anticipated methods.

After assessing the state of the waste, assess

the environment of the waste management

unit in which the waste will be placed. For

example, an acidic environment might

require a different test than a non-acidic environment in order to best reflect the conditions under which the waste will actually

leach. If the waste management unit is a

monofill, then the characteristics of the waste

will determine most of the unit’s conditions.

Conversely, if many different wastes are being

co-disposed, then the conditions created by

Which leaching test is

appropriate?

Selecting an appropriate leachate test

can be summarized in the following four

steps:

1. Assess the physical state of the waste

using process knowledge.

2. Assess the environment in which the

waste will be placed.

3. Consult with your state and/or local

regulatory agency.

4. Select an appropriate leachate test

based on the above information.
2-10

5 EPA has only reviewed and evaluated those test methods found in SW-846. The EPA has not reviewed

or evaluated the other test methods and cannot recommend use of any test methods other than those

found in SW-846.

6 EPA is undertaking a review of the TCLP test and how it is used to evaluate waste leaching (described

in the Phase IV Land Disposal Restrictions rulemaking, 62 Federal Register 25997; May 26, 1998). EPA

anticipates that this review will examine the effects of a number of factors on leaching and on

approaches to estimating the likely leaching of a waste in the environment. These factors include pH,

liquid to solid ratios, matrix effects and physical form of the waste, effects of non-hazardous salts on

the leachability of hazardous metal salts, and others. The effects of these factors on leaching might or

might not be well reflected in the leaching tests currently available. At the conclusion of the TCLP

review, EPA is likely to issue revisions to this guidance that reflect a more complete understanding of

waste constituent leaching under a variety of management conditions.

7 The TCLP was developed to replace the Extraction Procedure Toxicity Test method which is designated

as EPA Method 1310 in SW-846.

Getting Started—Characterizing Waste

the co-disposed wastes must be considered,

including the constituents that can be leached

by the subject waste.

A qualified laboratory should always be used

when conducting analytical testing. The laboratory can be in-house or independent. When

using independent laboratories, ensure that

they are qualified and competent to perform

the required tests. Some laboratories might be

proficient in one test but not another. You

should consult with the laboratory before finalizing your test selection to make certain that

the test can be performed. When using analytical tests that are not frequently performed,

additional quality assurance and quality control

practices might need to be implemented to

ensure that the tests are conducted correctly

and that the results are accurate.

A brief summary of the TCLP and three

other commonly used leachate tests is provided below (procedures for the EPA test methods are included in SW-846 and for the

ASTM method in the Annual Book of ASTM

Standards). These summaries are provided as

background and are not meant to imply that

these are the only tests that can be used to

accurately predict leachate potential. Other

leachate tests have been developed and might

be suitable for testing your waste. The table

in the appendix at the end of this chapter

provides a summary of over 20 leachate tests

that have been designed to estimate the

potential for contaminant release, including

several developed by ASTM.5 You should consult with state and local regulatory agencies

and/or a laboratory that is familiar with

leachate testing methods to identify the most

appropriate test and test method procedures

for your waste and sample type.

1. Toxicity Characteristic Leaching

Procedure (TCLP)

The TCLP6 is the test method used to determine whether a waste is hazardous due to its

characteristics as defined in the Resource

Conservation and Recovery Act (RCRA), 40

CFR Part 261. The TCLP estimates the leachability of certain toxicity characteristic hazardous

constituents from solid waste under a defined

set of laboratory conditions. It evaluates the

leaching of metals, volatile and semi-volatile

organic compounds, and pesticides from

wastes. The TCLP was developed to simulate

the leaching of constituents into ground water

under conditions found in municipal solid

waste (MSW) landfills. The TCLP does not simulate the release of contaminants to non-ground

water pathways. The TCLP is most commonly

used by EPA, state, and local agencies to classify

waste. It is also used to determine compliance

with some land disposal restrictions (LDRs) for

hazardous wastes. The TCLP can be found as

EPA Method 1311 in SW-846.7 A copy of

Method 1311 has been included on the CDROM version of the Guide.

For liquid wastes, (i.e., those containing

less than 0.5 percent dry solid material) the

waste after filtration through a glass fiber fil-
ter is defined as the TCLP extractant. The

concentrations of constituents in the liquid

extract are then determined. 

For wastes containing greater than or equal

to 0.5 percent solids, the liquid, if any, is separated from the solid phase and stored for

later analysis. The solids must then be

reduced to particle size, if necessary. The

solids are extracted with an acetate buffer

solution. A liquid-to-solid ratio of 20:1 by

weight is used for an extraction period of 18

± 2 hours. After extraction, the solids are filtered from the liquid through a glass fiber filter and the liquid extract is combined with

any original liquid fraction of the wastes.

Analyses are then conducted on the liquid filtrate/leachate to determine the constituent

concentrations. 

To determine if a waste is hazardous

because it exhibits the toxicity characteristic

(TC), the TCLP method is used to generate

leachate under controlled conditions as discussed above. If the TCLP liquid extract contains any of the constituents listed in Table 1

of 40 CFR Part 261 at a concentration equal

to or greater than the respective value in the

table, the waste is considered to be a TC hazardous waste, unless exempted or excluded

under Part 261. Although the TCLP test was

designed to determine if a waste is hazardous,

the importance of its use for waste characterization as discussed in this chapter is to

understand the parameters to be considered

in properly managing the wastes. 

You should check with state and local regulatory agencies to determine whether the

TCLP is likely to be the best test for evaluating the leaching potential of a waste or if

another test might better predict leaching

under the anticipated waste management

conditions. Because the test was developed by

EPA to determine if a waste is hazardous

(according to 40 CFR 261.24) and focused

on simulating leaching of solid wastes placed

in a municipal landfill, this test might not be

appropriate for your waste because the leaching potential for the same chemical can be

quite different depending on a number of factors. These factors include the characteristics

of the leaching fluid, the form of the chemical

in the solids, the waste matrix, and the disposal conditions. 

Although the TCLP is the most commonly

used leachate test for estimating the actual

leaching potential of wastes, you should not

automatically default to it in all situations or

conditions and for all types of wastes. While

the TCLP test might be conservative under

some conditions (i.e., overestimates leaching

potential), it might underestimate leaching

under other extreme conditions. In a landfill

that has primarily alkaline conditions, the

TCLP is not likely to be the optimal method

because the TCLP is designed to replicate

leaching in an acidic environment. For materials that pose their greatest hazard when

exposed to alkaline conditions (e.g., metals

such as arsenic and antimony), use of the

TCLP might underestimate the leaching

potential. When the conditions of your waste

management unit are very different from the

conditions that the TCLP test simulates,

another test might be more appropriate.

Further, the TCLP might not be appropriate

for analyzing oily wastes. Oil phases can be

difficult to separate (e.g., it might be impossible to separate solids from oil), oily material

can obstruct the filter (often resulting in an

underestimation of constituents in the

leachate), and oily materials can yield both

oil and aqueous leachate which must be analyzed separately.8

2. Synthetic Precipitation

Leaching Procedure (SPLP)

The SPLP (designated as EPA Method 1312

in SW-846) is currently used by several state

agencies to evaluate the leaching of conGetting Started—Characterizing Waste

2-11

8 SW-846 specifies several procedures that should be followed when analyzing oily wastes.
stituents from wastes. The SPLP was designed

to estimate the leachability of both organic

and inorganic analytes present in liquids, soils,

and wastes. The SPLP was originally designed

to assess how clean a soil was under EPA’s

Clean Closure Program. Even though the federal hazardous waste program, did not adopt

it for use, the test can still estimate releases

from wastes placed in a landfill and subject to

acid rain. There might be, however, important

differences between soil as a constituent

matrix (for which the SPLP is primarily used)

and the matrix of a generated industrial waste.

A copy of Method 1312 has been included on

the CD-ROM version of the Guide.

The SPLP is very similar to the TCLP

Method 1311. Waste samples containing

solids and liquids are handled by separating

the liquids from the solid phase, and then

reducing solids to particle size. The solids are

then extracted with a dilute sulfuric

acid/nitric acid solution. A liquid-to-solid

ratio of 20:1 by weight is used for an extraction period of 18±2 hours. After extraction,

the solids are filtered from the liquid extract

and the liquid extract is combined with any

original liquid fraction of the wastes.

Analyses are then conducted on the liquid filtrate/leachate to determine the constituent

concentrations.

The sulfuric acid/nitric acid extraction

solution used in the SPLP was selected to

simulate leachate generation, in part, from

acid rain. Also note that in both the SPLP

and TCLP, some paint and oily wastes might

clog the filters used to separate the liquid

extract from the solids prior to analysis,

resulting in under reporting of the extractable

constituent concentrations.

3. Multiple Extraction Procedure

(MEP)

The MEP (designated as EPA Method 1320

in SW-846) was designed to simulate the

leaching that a waste will undergo from repetitive precipitation of acid rain on a landfill to

determine the highest concentration of each

constituent that is likely to leach in a real

world environment. Currently, the MEP is used

in EPA’s hazardous waste delisting program. A

copy of Method 1320 has been included on

the CD-ROM version of the Guide.

The MEP can be used to evaluate liquid,

solid, and multiphase samples. Waste samples are extracted according to the Extraction

Procedure (EP) Toxicity Test (Method 1310

of SW-846). The EP test is also very similar

to the TCLP Method 1311. A copy of Method

1310 has been included on the CD- ROM

version of the Guide.

In the MEP, liquid wastes are filtered

through a glass fiber filter prior to testing.

Waste samples containing both solids and liquids are handled by separating the liquids

from the solid phase, and then reducing the

solids to particle size. The solids are then

extracted using an acetic acid solution. A liquid- to-solid ratio of 16:1 by weight is used

for an extraction period of 24 hours. After

extraction, the solids are filtered from the liquid extract, and the liquid extract is combined

with any original liquid fraction of the waste. 

The solids portion of the sample that

remains after application of Method 1310 are

then re-extracted using a dilute sulfuric

acid/nitric acid solution. As in the SPLP, this

acidic solution was selected to simulate

2-12

Getting Started—Characterizing Waste
leachate generation, in part, from acid rain.

This time a liquid-to-solid ratio of 20:1 by

weight is used for an extraction period of 24

hours. After extraction, the solids are once

again filtered from the liquid extract, and the

liquid extract is combined with any original

liquid fraction of the waste. 

These four steps are repeated eight additional times. If the concentration of any constituent of concern increases from the 7th or

8th extraction to the 9th extraction, the procedure is repeated until these concentrations

decrease.

The MEP is intended to simulate 1,000

years of freeze and thaw cycles and prolonged

exposure to a leaching medium. One advantage of the MEP over the TCLP is that the

MEP gradually removes excess alkalinity in

the waste. Thus, the leaching behavior of

metal contaminants can be evaluated as a

function of decreasing pH, which increases

the solubility of most metals. 

4. Shake Extraction of Solid

Waste with Water or Neutral

Leaching Procedure

The Shake Extraction of Solid Waste with

Water, or the Neutral Leaching Procedure,

was developed by the American Society for

Testing and Materials (ASTM) to assess the

leaching potential of solid waste and has been

designated as ASTM D-3987-85. This test

method provides for the shaking of an extractant (e.g., water) and a known weight of

waste of specified composition to obtain an

aqueous phase for analysis after separation.

The intent of this test method is for the final

pH of the extract to reflect the interaction of

the liquid extractant with the buffering capacity of the solid waste. 

The shake test is performed by mixing the

solid sample with test water and agitating

continuously for 18±0.25 hours. A liquid-tosolid ratio of 20:1 by weight is used. After

agitation the solids are filtered from the liquid

extract, and the liquid is analyzed.

The water extraction is meant to simulate

conditions where the solid waste is the dominant factor in determining the pH of the

extract. This test, however, has only been

approved for certain inorganic constituents,

and is not applicable to organic substances

and volatile organic compounds (VOCs). A

copy of this procedure can be ordered by

calling ASTM at 610 832-9585 or online at

<www.astm.org>.

III. Waste

Characterization

of Volatile

Organic

Emissions

To determine whether volatile organic

emissions are of concern at a waste management unit, determine the concentration of the

VOCs that are reasonably expected to be

emitted. Process knowledge is likely to be

less accurate for determining VOCs than

measured values. As discussed earlier in this

chapter, modeling results for waste management units will only be as accurate as the

input data. Therefore, sampling and analytical

testing might be necessary if organic concentrations cannot be estimated confidently

using process knowledge. 

Table 2 in Chapter 5–Protecting Air Quality

can be used as a starting point to help you

determine which air emissions constituents to

measure. It is not recommended that you

sample for all of the volatile organics listed in

Table 2, but rather use Table 2 as a guide in

conjunction with process knowledge to narrow the sampling effort and thereby minimize

Getting Started—Characterizing Waste

2-13
unnecessary sampling costs. A thorough

understanding of process knowledge can help

you determine what is reasonably expected to

be in the waste, so that it is not necessary to

sample for unspecified constituents.

Many tests have been developed for quantitatively extracting volatile and semi-volatile

organic constituents from various sample

matrices. These tests tend to be highly

dependent upon the physical characteristics

of the sample. You should consult with state

and local regulatory agencies before implementing testing. You can refer to SW-846

Method 3500B for guidance on the selection

of methods for quantitative extraction or

dilution of samples for analysis by one of the

volatile or semi-volatile determinative methods. After performing the appropriate extraction procedure, further cleanup of the sample

extract might be necessary if analysis of the

extract is prevented due to interferences

coextracted from the sample. Method 3600

of SW-846 provides additional guidance on

cleanup procedures. 

Following sample preparation, a sample is

ready for further analysis. Most analytical

methods use either gas chromatography

(GC), high performance liquid chromatography (HPLC), gas chromatography/mass spectrometry (GC/MS), or high performance

liquid chromatography/mass spectrometry

(HPLC/MS). SW-846 is designed to allow the

methods to be mixed and matched, so that

sample preparation, sample cleanup, and

analytical methods can be properly

sequenced for the particular analyte and

matrix. Again, you should consult with state

and local regulatory agencies before finalizing

the selected methodology.

2-14

Getting Started—Characterizing Waste
Getting Started—Characterizing Waste

2-15

To determine constituent concentrations in a waste you should:

■ Assess the physical state of the waste using process knowledge.

■ Use process knowledge to identify constituents for further analysis.

■ Assess the environment in which the waste will be placed.

■ Consult with state and local regulatory agencies to determine any specific testing requirements.

■ Select an appropriate leachate test or organic constituent analysis based on the above information.

Waste Characterization Activity List
2-16

Getting Started—Characterizing Waste

ASTM. 1995. Annual Book of ASTM Standards.

ASTM. Standard Methods for Examination of Water and Wastewater.

ASTM. D-3987-85. Standard Test Method for Shake Extraction of Solid Waste with Water

California EPA. Handbook for the Analysis and Classification of Wastes.

California EPA. 1995. Preliminary Proposal to Require the TCLP in Lieu of the Waste Extraction

Test. Memorandum to James Carlisle, Department of Toxics Substances Control, from Jon

Marshack, California Regional Water Quality Control Board. December 18.

California EPA. 1994. Regulation Guidance: When Extraction Tests are Not Necessary.

California EPA. 1994. Regulation Guidance: TCLP vs. WET.

California EPA. 1993. Regulation Guidance: Lab Methods.

California EPA. 1993. Regulation Guidance: Self-Classification.

Cochran, W.G. 1977. Sampling Techniques. Third Edition. New York: John Wiley and Sons. 

Dusing, D.C., Bishop, P.L., and Keener, T.C. 1992. Effect of Redox Potential on Leaching from

Stabilized/Solidified Waste Materials. Journal of Air and Waste Management Association. 42:56.

January.

Gilbert, R.O. 1987. Statistical Methods for Environmental Pollution Monitoring. New York: Van

Nostrand Reinhold Company.

Kendall, Douglas. 1996. Impermanence of Iron Treatment of Lead-Contaminated Foundry Sand—

NIBCO, Inc., Nacogdoches, Texas. National Enforcement Investigations Center Project PA9. April.

Kosson, D.S., H.A. van der Sloot, F. Sanchez, and A.C. Garrabrants. 2002. An Integrated

Framework for Evaluating Leaching in Waste Management and Utilization of Secondary Materials.

Environmental Engineering Science, In-press.

New Jersey Department of Environmental Protection. 1996. Industrial Pollution Prevention Trends

in New Jersey. 

Resources
Getting Started—Characterizing Waste

2-17

Northwestern University. 1995. Chapter 4—Evaluation of Procedures for Analysis and Disposal of

Lead- Based Paint-Removal Debris. Issues Impacting Bridge Painting: An Overview. Infrastructure

Technology Institute. FHWA/RD/94/098. August.

U.S. EPA 2002. Industrial Waste Managment Evaluation (IWEM) Technical Background Document.

EPA530-R-02-012.

U.S. EPA. 1998a. Guidance on Quality Assurance Project Plans: EPA QA/G-5. EPA600-R-98-018.

U.S. EPA. 1998b. Guidance on Sampling Designs to Support QA Project Plans. QA/G-5S

U.S. EPA. 1997. Extraction Tests. Draft.

U.S. EPA. 1996a. Guidance for the Data Quality Assessment: Practical Methods for Data Analysis:

EPAQA/G-9. EPA600-R-96-084.

U.S. EPA. 1996b. Guidance for the Data Quality Objectives Process: EPA QA/G-4. EPA600-R-96-055.

U.S. EPA. 1996c. Hazardous Waste Characteristics Scoping Study.

U.S. EPA. 1996d. National Exposure Research Laboratory (NERL)-Las Vegas: Site Characterization

Library, Volume 2.

U.S. EPA. 1996e. Test Methods for Evaluating Solid Waste Physical/Chemical Methods—SW846. Third

Edition.

U.S. EPA. 1995. State Requirements for Non-Hazardous Industrial Waste Management Facilities.

U.S. EPA. 1993. Identifying Higher-Risk Wastestreams in the Industrial D Universe: The State

Experience. Draft.

U.S. EPA. 1992. Facility Pollution Prevention Guide. EPA600-R-92-088.

U.S. EPA Science Advisory Board. 1991. Leachability Phenomena: Recommendations and Rationale for

Analysis of Contaminant Release by the Environmental Engineering Committee. EPA-SAB-EEC-92-003.

Winer, B.J. 1971. Statistical Principles in Experimental Design. New York: McGraw-Hill.

Resources (cont.)
Test Method Leaching Fluid Liquid:Solid Maximum Number of Time of Comments

Ratio Particle Size Extractions Extractions

I. Static Tests

A. Agitated Extraction Tests

Toxicity 0.1 N acetic acid solution, 20:1 9.5 mm 1 18 ±2 hours Co-disposal scenario might 

Characteristic pH 2.9, for alkaline wastes not be appropriate; no 

Leaching 0.1 N sodium acetate allowance for structural 

Procedure (1311) buffer solution, pH 5.0, integrity testing of 

for non-alkaline wastes monolithic samples

Extraction 0.5 N acetic acid (pH-5.0) 16:1 during 9.5 mm 1 24 hours High alkalinity samples can 

Procedure extraction result in variable data

Toxicity Test (1310) 20:1 final 

dilution

ASTM D3987-85 ASTM IV reagent water 20:1 As in 1 18 hours Not validated for organics

Shake Extraction environment 

of Solid Waste (as received)

with Water

California WET 0.2 M sodium citrate 10:1 2.0 mm 1 48 hours Similar to EP, but sodium

(pH- 5.0) citrate makes test more 

aggressive

Ultrasonic Distilled water 4:1 Ground 1 30 minutes New—little performance 

Agitation data

Method for 

Accelerating Batch 

Leaching Test9

Alternative TCLP TCLP acetic acid solutions 20:1 <9.5 1 8 hours Uses heat to decrease 

for Construction, extraction time

Demolition and 

Lead Paint 

Abatement Debris10

Extraction Soxhlet with THF and 100g:300mL 9.5 mm 3 24 hours (EP)

Procedure for Oily toluene EP on remaining 20:1

Waste (1330) solids

Synthetic #1 Reagent water to pH 4.2 20:1 9.5 mm 1 18±2 hours ZHE option for organics

Precipitation with nitric and sulfuric 

Leaching Procedure acids (60/40) 

(1312) #2 Regent water to pH 5.0 

with nitric and sulfuric 

acids (60/40)

Equilibrium Leach Distilled water 4:1 150 mm 1 7 days Determines contaminants 

Test that have been insolubilized 

by solidification

2-18

Getting Started—Characterizing Waste

9 Bisson, D.L.; Jackson D.R.; Williams K.R.; and Grube W.E. J. Air Waste Manage. Assoc., 41: 1348-1354.

10 Olcrest, R. A Representative Sampling and Alternative Analytical Toxic Characteristic Leachate Procedure

Method for Construction, Demolition, and Lead Paint Abatement Debris Suspected of Containing Leachable

Lead, Appl. Occup. Environ. Hyg. 11(1), January 1996.

Appendix: Example Extraction Tests (Draft 9/30/97)
B. Non-Agitated Extraction Tests

Static Leach Test Can be site specific, 3 VOL/surface 40 mm2 1 >7 days Series of optional steps 

Method (material standard leachates: water, 10 cm surface area increasing complexity of 

characteristic brine, silicate/bicarbonate analysis

centre- 1)

High Temperature Same as MCC-1 (conducted VOL/Surface 40 mm2 1 >7 Days Series of optional steps 

Static Leach Tests at 100°C) 10 cm Surface Area increasing complexity of 

Method (material analysis

characterization 

centre-2)

C. Sequential Chemical Extraction Tests

Sequential 0.04 m acetic acid 50:1 9.5 mm 15 24 hours per 

Extraction Tests extraction

D. Concentration Build-Up Test

Sequential 5 leaching solutions of Varies from 150 mm 5 Varies 3 or Examines partitioning of 

Chemical increasing acidity 16.1 to 40.1 14 days metals into different 

Extraction fractions or chemicals forms

Standard Leach DI water SYN Landfill 10:1, 5:1, As in 3 3 or 14 days Sample discarded after each 

Test, Procedure C 7.5:1 environment leach, new sample added to 

(Wisconsin) existing leachate

II. Dynamic Tests (Leaching Fluid Renewed)

A. Serial Batch (Particle)

Multiple Extraction Same as EP TOX, then 20:1 9.5 mm 9 (or more) 24 hours per

Procedure (1320) with synthetic acid rain extraction

(sulfuric acid, nitric acid 

in 60:40% mixture)

Monofill Waste Distilled/deionized water 10:1 per 9.5 mm or 4 18 hours per

Extraction or other for specific site extraction monolith extraction

Procedures

Graded Serial Batch Distilled water Increases N/A >7 Until steady 

(U.S. Army) from 2:1 to state

96:1

Sequential Batch Type IV reagent water 20:1 As in 10 18 hours

Ext. of Waste with environment

Water ASTM 

D-4793-93

Getting Started—Characterizing Waste

2-19

Test Method Leaching Fluid Liquid:Solid Maximum Number of Time of Comments

Ratio Particle Size Extractions Extractions
Use of Chelating Demineralized water with 50 or 100 <300 μm 1 18, 24, or Experimental test based on 

Agent to Determine EDTA, sample to a final 48 hours Method 7341

the Metal pH of 7±0.5

Availability for 

Leaching Soils and 

Wastes11

B. Flow Around Tests

IAEA Dynamic DI water/site water N/A One face >19 >6 months

Leach Test prepared

(International 

Atomic Energy 

Agency)

Leaching Tests on 0.1N acetic acid 20:1 0.6 μm-70μm 1 24 hours S/S technologies most valid 

Solidified Products12 (Procedure A) when applied to wastes 

2:1 (6 hrs.) contaminated by inorganic 

& 10:1 pollutants

(18 hrs.) 

(Procedure B)

DLT DI water N/A Surface 18 196 days

washing

C. Flow Through Tests

ASTM D4874-95 Type IV reagent water One void 10 mm 1 24 hours

Column Test volume

III. Other Tests

MCC-5s Soxhlet DI/site water 100:1 Out and 1 0.2 ml/min

Test (material washed

characteristic center)

ASTM C1308-95 Only applicable if diffusion 

Accelerated Leach is dominant leaching 

Test13 mechanism

Generalized Acid Acetic acid 20:1 Able to pass 1 48 hours Quantifies the alkalinity of 

Neutralization through an binder and characterizes 

Capacity Test14 ASTM No. 40 buffering chemistry

sieve

Acid Neutralization HNO3, solutions of 3:1 150 mm 1 48 hours per 

Capacity increasing strength extraction

2-20

11 Garrabrants, A.C. and Koson, D.S.; Use of Chelating Agent to Determine the Metal Availability for Leaching

from Soils and Wastes, unpublished.

12 Leaching Tests on Solidified Products; Gavasci, R., Lombardi, F., Polettine, A., and Sirini, P.

13 C1308-95 Accelerated Leach Test for Diffusive Releases from Solidified Waste and a Computer Program to

Model Diffusive, Fractional Leaching from Cylindrical Wastes.

14 Generalized Acid Neutralization capacity Test; Isenburg, J. and Moore, M.

Getting Started—Characterizing Waste

Test Method Leaching Fluid Liquid:Solid Maximum Number of Time of Comments

Ratio Particle Size Extractions Extractions
Part I

Getting Started

Chapter 3

Integrating Pollution Prevention
Contents

I. Benefits of Pollution Prevention..................................................................................................................3 - 3

II. Implementing Pollution Prevention ........................................................................................................3 - 5

A. Source Reduction ..................................................................................................................................3 - 5

B. Recycling ..............................................................................................................................................3 - 7

C. Treatment ..............................................................................................................................................3 - 8

III. Where to Find Out More: Technical and Financial Assistance ..............................................................3 - 10

Integrating Pollution Prevention Activity List ..............................................................................................3 - 14

Resources ....................................................................................................................................................3 - 15

Figure 1: Waste Management Hierarchy........................................................................................................3 - 2
Getting Started—Integrating Pollution Prevention

3-1

P

ollution prevention describes a variety of practices that go beyond traditional environmental compliance

or single media permits for water,

air, or land disposal and begin to

address the concept of sustainability in the

use and reuse of natural resources. Adopting

pollution prevention policies and integrating

pollution prevention into operations provide

opportunities to reduce the volume and toxicity of wastes, reduce waste disposal needs,

and recycle and reuse materials formerly handled as wastes. In addition to potential savings on waste management costs, pollution

prevention can help improve the interactions

among industry, the public, and regulatory

agencies. It can also reduce liabilities and risks

associated with releases from waste management units and closure and post-closure care

of waste management units.

Pollution prevention is comprehensive.

It emphasizes a life-cycle approach to assessing a facility’s physical plant, production

processes, and products to identify the best

opportunities to minimize environmental

impacts across all media. This approach also

ensures that actions taken in one area will not

increase environmental problems in another

area, such as reducing wastewater discharges

but increasing airborne emissions of volatile

organic compounds. Pollution prevention

requires creative problem solving by a broad

cross section of employees to help achieve

environmental goals. In addition to the environmental benefits, implementing pollution

prevention can often benefit a company in

many other ways. For example, redesigning

production processes or finding alternative

material inputs can also improve product

quality, increase efficiency, and conserve raw

materials. Some common examples of pollution prevention activities include: redesigning

Integrating Pollution Prevention

This chapter will help you:

• Consider pollution prevention options when designing a waste

management system. Pollution prevention will reduce waste disposal needs and can minimize impacts across all environmental

media. Pollution prevention can also reduce the volume and toxicity of waste. Lastly, pollution prevention can ease some of the

burdens, risks, and liabilities of waste management.

This chapter will help address the following questions.

• What are some of the benefits of pollution prevention?

• Where can assistance in identifying

and implementing specific pollution

prevention options be obtained?
3-2

Getting Started—Intregrating Pollution Prevention

processes or products to reduce raw material

needs and the volume of waste generated;

replacing solvent based cleaners with aqueous

based cleaners or mechanical cleaning systems; and instituting a reverse distribution

system where shipping packaging is returned

to the supplier for reuse rather than discard.

The Pollution Prevention Act of 1990

established a national policy to first, prevent

or reduce waste at the point of generation

(source reduction); second, recycle or reuse

waste materials; third, treat waste; and finally,

dispose of remaining waste in an environmentally protective manner (see Figure 1).

Some states and many local governments

have adopted similar policies, often with

more specific and measurable goals.

Source Reduction means any practice

which (i) reduces the amount of any substance, pollutant, or contaminant entering

any wastestream or otherwise released into

the environment, prior to recycling, treatment, or disposal; and (ii) reduces the risks

to public health and the environment associated with the release of such substances, pollutants, or contaminants.

Recycling requires an examination of

waste streams and production processes to

identify opportunities. Recycling and beneficially reusing wastes can help reduce disposal

costs, while using or reusing recycled materials as substitutes for feedstocks can reduce

raw materials costs. Materials exchange programs can assist in finding uses for recycled

materials and in identifying effective substitutes for raw materials. Recycling not only

helps reduce the overall amount of waste sent

for disposal, but also helps conserve natural

resources by replacing the need for virgin

materials.

Treatment can reduce the volume and

toxicity of a waste. Reducing a waste’s volume

and toxicity prior to final disposal can result

in long-term cost savings. There are a considerable number of levels and types of treatment from which to choose. Selecting the

right treatment option can help simplify disposal options and limit future liability.

Figure 1. Waste Management Hierarchy
Getting Started—Integrating Pollution Prevention

3-3

Over the past 10 years, interest in all aspects

of pollution prevention has blossomed, and

governments, businesses, academic and

research institutions, and individual citizens

have dedicated greater resources to it. Many

industries are adapting pollution prevention

practices to fit their individual operations.

Pollution prevention can be successful when

flexible problem-solving approaches and solutions are implemented. Fitting these steps into

your operation’s business and environmental

goals will help ensure your program’s success.

Throughout the Guide several key steps are

highlighted that are ideal points for implementing pollution prevention to help reduce

waste management costs, increase options, or

reduce potential liabilities by reducing risks

that the wastes might pose. For example:

Waste characterization is a key component of the Guide. It is also a key component

of a pollution prevention opportunity assessment. An opportunity assessment, however, is

more comprehensive since it also covers material inputs, production processes, operating

practices, and potentially other areas such as

inventory control. When characterizing a

waste, consider expanding the opportunity

assessment to cover these aspects of the business. An opportunity assessment can help

identify the most efficient, cost-effective, and

environmentally friendly combination of

options, especially when planning new products, new or changed waste management practices, or facility expansions.

Land application of waste might be a preferred waste management option because land

application units can manage wastes with high

liquid content, treat wastes through biodegradation, and improve soils due to the organic

material in the waste. Concentrations of constituents might limit the ability to take full

advantage of land application. Reducing the

concentrations of constituents in the waste

before it is generated or treating the waste prior

to land application can provide the flexibility to

use land application and ensure that the practice will be protective of human health and the

environment and limit future liabilities.

I. Benefits of

Pollution

Prevention

Pollution prevention activities benefit

industry, states, and the public by protecting

the environment and reducing health risks,

and also provide businesses with financial and

strategic benefits.

Protecting human health and the environment. By reducing the amount of contaminants released into the environment and the

volume of waste requiring disposal, pollution

prevention activities protect human health and

the environment. Decreasing the volume or

toxicity of process materials and wastes can

reduce worker exposure to potentially harmful

constituents. Preventing the release and disposal of waste constituents to the environment

also reduces human and wildlife exposure and

habitat degradation. Reduced consumption of

raw materials and energy conserves precious

natural resources. Finally reducing the volume

of waste generated decreases the need for construction of new waste management facilities,

preserving land for other uses such as recreation or wildlife habitat.

Cost savings. Many pollution prevention

activities make industrial processes and equipment more resource-efficient. This increased

production efficiency saves raw material and

labor costs, lowers maintenance costs due to

newer equipment, and potentially lowers oversight costs due to process simplification. When

planning pollution prevention activities, consider the cost of the initial investment for

audits, equipment, and labor. This cost will
3-4

Getting Started—Intregrating Pollution Prevention

vary depending on

the size and complexity of waste

reduction activities. In addition,

consider the payback time for the

investment.

Prioritize pollution

prevention activities to maximize

cost savings and

health and environmental benefits.

Simpler design and operating conditions.

Reducing the risks associated with wastes can

allow wastes to be managed under less stringent design and operating conditions. For

example, the ground-water tool in Chapter 7,

Section A – Assessing Risk might indicate that

a composite liner is recommended for a specific waste stream. A pollution prevention opportunity assessment also might imply that by

implementing a pollution prevention activity

that lowers the concentrations of one or two

problematic waste constituents in that waste

stream, a compacted clay liner can provide

sufficient protection. When the risks associated with waste disposal are reduced, the longterm costs of closure and post-closure care can

also be reduced.

Improved worker safety. Processes

involving less toxic

and less physically

dangerous materials

can improve worker

safety by reducing

work-related injuries

and illnesses. In

addition to strengthening morale,

improved worker

safety also reduces

health-related costs from lost work days,

health insurance, and disability payments.

Lower liability. A well-operated unit minimizes releases, accidents, and unsafe wastehandling practices. Reducing the volume and

toxicity of waste decreases the impact of these

events if they occur. Reducing potential liabilities decreases the likelihood of litigation and

cleanup costs.

Higher product quality. Many corporations

have found that higher product quality results

from some pollution prevention efforts. A significant part of the waste in some operations

consists of products that fail quality inspections, so minimizing waste in those cases is

inextricably linked with process changes that

improve quality. Often, managers do not realize

how easy or technically feasible such changes

are until the drive for waste reduction leads to

exploration of the possibilities.

Building community relations. Honesty

and openness can strengthen credibility

between industries, communities, and regulatory agencies. If you are implementing a pollution prevention program, make people aware

of it. Environmental protection and economic

growth can be compatible objectives.

Additionally, dialogue among all parties in the

development of pollution prevention plans can

help identify and address concerns.
3-5

Getting Started—Integrating Pollution Prevention

II. Implementing

Pollution

Prevention

When implementing pollution prevention,

consider a combination of options that best

fits your facility and its products. There are a

number of steps common to implementing

any facility-wide pollution prevention effort.

An essential starting point is to make a clear

commitment to identifying and taking advantage of pollution prevention opportunities.

Seek the participation of interested partners,

develop a policy statement committing the

industrial operation to pollution prevention,

and organize a team to take responsibility for

it. As a next step, conduct a thorough pollution prevention opportunity assessment. Such

an assessment will help set priorities according to which options are the most promising.

Another feature common to many pollution

prevention programs is measuring the program’s progress.

The actual pollution prevention practices

implemented are the core of a program. The

following sections give a brief overview of

these core activities: source reduction, recycling, and treatment. To find out more, contact some of the organizations listed

throughout this chapter.

A. Source Reduction

As defined in the Pollution Prevention Act

of 1990, source reduction means any practice

which (i) reduces the amount of any hazardous substance, pollutant, or contaminant

entering any wastestream or otherwise

released into the environment, prior to recycling, treatment, or disposal; and (ii) reduces

the hazards to public health and the environment associated with the release of such substances, pollutants, or contaminants. The

term includes equipment or technology modifications; process or procedure modifications; reformulations or redesign of products;

substitution of raw materials; and improvements in housekeeping, maintenance, training, or inventory control.

Reformulation

or redesign of

products. One

source reduction

option is to reformulate or redesign

products and

processes to incorporate materials

more likely to produce lower-risk

wastes. Some of the

most common

practices include eliminating metals from

inks, dyes, and paints; reformulating paints,

inks, and adhesives to eliminate synthetic

organic solvents; and replacing chemicalbased cleaning solvents with water-based or

citrus-based products. Using raw materials

free from even trace quantities of contaminants, whenever possible, can also help

reduce waste at the source.

When substituting materials in an industrial process, it is important to examine the

effect on the entire waste stream to ensure

that the overall risk is being reduced. Some

changes can shift contaminants to another

medium rather than actually reduce waste

generation. Switching from solvent-based to

water-based cleaners, for example, will

reduce solvent volume and disposal cost, but

is likely to dramatically increase wastewater

volume. Look at the impact of wastewater

generation on effluent limits and wastewater

treatment sludge production.

Technological modifications. Newer

process technologies often include better

waste reduction features than older ones. For

industrial processes that predate considera-
3-6

Getting Started—Intregrating Pollution Prevention

tion of waste and risk reduction, adopting

new procedures or upgrading equipment can

reduce waste volume, toxicity, and management costs. Some examples include redesigning equipment to cut losses during batch

changes or during cleaning and maintenance,

changing to mechanical cleaning devices to

avoid solvent use, and installing more energyand material-efficient equipment. State technical assistance centers, trade associations,

and other organizations listed in this chapter

can help evaluate the potential advantages

and savings of such improvements.

In-process recycling (reuse). In-process

recycling involves the reuse of materials, such

as cutting scraps, as inputs to the same

process from which they came, or uses them

in other processes or for other uses in the

facility. This furthers waste reduction goals by

reducing the need for treatment or disposal

and by conserving energy and resources. A

common example of in-process recycling is

the reuse of wastewater.

Good housekeeping procedures. Some of

the easiest, most cost-effective, and most widely used waste reduction techniques are simple

improvements in housekeeping. Accidents and

spills generate avoidable disposal hazards and

expenses. They are less likely to occur in

clean, neatly organized facilities.

Good housekeeping techniques that reduce

the likelihood of accidents and spills include

training employees to manage waste and

materials properly; keeping aisles wide and

free of obstructions; clearly labeling containers with content, handling, storage, expiration, and health and safety information;

spacing stored materials to allow easy access;

surrounding storage areas with containment

berms to control leaks or spills; and segregating stored materials to avoid cross-contamination, mixing of incompatible materials, and

unwanted reactions. Proper employee training is crucial to implementing a successful

waste reduction program, especially one featuring good housekeeping procedures. Case

study data indicate that effective employee

training programs can reduce waste disposal

volumes by 10 to 40 percent.1

Regularly scheduled maintenance and

plant inspections are also useful. Maintenance

helps avoid the large cleanups and disposal

operations that can result from equipment

failure. Routine maintenance also ensures that

equipment is operating at peak efficiency, saving energy, time, and materials. Regularly

scheduled or random, unscheduled plant

inspections help identify potential problems

before they cause waste management problems. They also help identify areas where

improving the efficiency of materials management and handling practices is possible. If

possible, plant inspections, periodically performed by outside inspectors who are less

familiar with day-to-day plant operations, can

bring attention to areas for improvement that

are overlooked by employees accustomed to

the plant’s routine practices.

Storing large volumes of raw materials

increases the risk of an accidental spill and

the likelihood that the materials will not be

used due to changes in production schedules,

new product formulations, or material degradation. Companies are sometimes forced to

dispose of materials whose expiration dates

have passed or that are no longer needed.

Efficient inventory control allows a facility to

avoid stocking materials in excess of its ability to use them, thereby decreasing disposal

volume and cost. Many companies have successfully implemented “just-in-time” manufacturing systems to avoid the costs and risks

associated with maintaining a large onsite

inventory. In a “just-in-time” manufacturing

system, raw materials arrive as they are needed and only minimal inventories are maintained on site.

1 Freeman, Harry. 1995. Industrial Pollution Prevention Handbook. McGraw-Hill, Inc. p. 13.
Getting Started—Integrating Pollution Prevention

3-7

Segregating waste streams is another good

housekeeping procedure that enables a facility to avoid contaminating lower risk wastes

with hazardous constituents from another

source. Based on a waste characterization

study, it might be more efficient and costeffective to manage wastes separately by recycling some, and treating or disposing of

others. Waste segregation can also help

reduce the risks associated with handling

waste. Separating waste streams allows some

materials to be reused, resulting in additional

cost savings. Emerging markets for recovered

industrial waste materials are creating new

economic incentives to segregate waste

streams. Recovered materials are more attractive to potential buyers if it can be ensured

that they are not tainted with other waste

materials. For example, if wastes from metalfinishing facilities are segregated by type,

metal-specific-bearing sludge can be recovered more economically and the segregated

solvents and waste oils can be recycled.

B. Recycling

Recycling involves collecting, processing, and

reusing materials that

would otherwise be handled as wastes. The following discussion highlights a few of the

ways to begin this process.

Materials exchange programs. Many local

governments and states have established materials exchange programs to facilitate transactions between waste generators and industries

that can use wastes as raw materials. Materials

exchanges are an effective and inexpensive way

to find new users and uses for a waste. Most

are publicly funded, nonprofit organizations,

although some charge a nominal fee to be listed with them or to access their online databases. Some actively work to promote exchanges

between generators and users, while others

simply publish lists of generators, materials,

and buyers. Some waste exchanges also sponsor workshops and conferences to discuss

waste-related regulations and to exchange

information. More than 60 waste and materials

exchanges operate in North America. Below

are four examples of national, state, and local

exchange programs. Each program’s Web site

also provides links to other regional, national,

and international materials exchange networks.

• EPA’s Jobs Through Recycling (JTR)

Web site <www.epa.gov/jtr/comm/

exchange.htm> provides descriptions

of and links to international, national,

and state-specific materials exchange

programs and organizations.

• Recycler’s World <www.recycle.net/

exch/index.html> is a world-wide

materials trading site with links to

dozens of state and regional exchange

networks.

• CalMAX (California Materials

Exchange) <www.ciwmb.ca.gov/

calmax> is maintained by the

California Integrated Waste

Management Board and facilitates

waste exchanges in California and

provides links to other local and

national exchange programs.

• King County, Washington’s IMEX

<www.metrokc.gov/hazwaste/imex/

exchanges.html/> is a local industrial materials exchange program that

also provides an extensive list of

state, regional, national, and international exchange programs.

Beneficial use. Beneficial use involves

substituting a waste material for another

material with similar properties. Utility companies, for example, often use coal combustion ash as a construction material, road base,

or soil stabilizer. The ash replaces other, non-
3-8

Getting Started—Intregrating Pollution Prevention

recycled materials, such as fill or Portland

cement, not only avoiding disposal costs but

also generating revenue. Other examples of

beneficial use include using wastewaters and

sludges as soil amendments (see Chapter 7,

Section C–Designing a Land Application

Program) and using foundry sand in asphalt,

concrete, and roadbed construction.

Many regulatory agencies require approval

of planned beneficial use activities and may

require testing of the materials to be reused.

Others may allow certain wastes to be designated for beneficial use, as long as the required

analyses are completed. Pennsylvania, for

example, allows application of a “coproduct”

designation to, and exemption from waste regulations for “materials which are essentially

equivalent to and used in place of an intentionally manufactured product or produced

raw material and... [which present] no greater

risk to the public or the environment.”

Generally, regulatory agencies want to ensure

that any beneficially used materials are free

from significantly increased levels of constituents that might pose a greater risk than

the materials they are replacing. Consult with

the state agency for criteria and regulations

governing beneficial use.

In a continuing effort to promote the use of

materials recovered from solid waste, the

Environmental Protection Agency (EPA) has

instituted the Comprehensive Procurement

Guideline (CPG) program. Using recycled-content products ensures that materials collected

in recycling programs will be used again in the

manufacture of new products. The CPG program is authorized by Congress under Section

6002 of the Resource Conservation and

Recovery Act (RCRA) and Executive Order

13101. Under the CPG program, EPA is

required to designate products that are or can

be made with recovered materials and to recommend practices for buying these products.

Once a product is designated, procuring agencies are required to purchase it with the highest recovered material content level practicable. As of January 2001, EPA has designated

54 items within eight product categories

including items such as retread tires, cement

and concrete containing coal fly ash and

ground granulated blast furnace slag, traffic

barricades, playground surfaces, landscaping

products, and nonpaper office products like

binders and toner cartridges. While directed

primarily at federal, state, and local procuring

agencies, CPG information is helpful to everyone interested in purchasing recycled-content

products. For further information on the CPG

program, visit: <www.epa.gov/cpg>.

C. Treatment

Treatment of non-hazardous industrial

waste is not a federal requirement, however,

it can help to reduce the volume and toxicity

of waste prior to disposal. Treatment can also

make a waste amenable for reuse or recycling.

Consequently, a facility managing non-hazardous industrial waste might elect to apply

treatment. For example, treatment might be

incorporated to address volatile organic compound (VOC) emissions from a waste managment unit, or a facility might elect to treat a

waste so that a less stringent waste management system design could be used. Treatment

involves changing a waste’s physical, chemical, or biological character or composition

through designed techniques or processes.

There are three primary categories of treatment—physical, chemical, and biological. 

Physical treatment involves changing the

waste’s physical properties such as its size,

shape, density, or state (i.e., gas, liquid, solid).

Physical treatment does not change a waste’s

chemical composition. One form of physical

treatment, immobilization, involves encapsulating waste in other materials, such as plastic,

resin, or cement, to prevent constituents from

volatilizing or leaching. Listed below are a few

examples of physical treatment.
Getting Started—Integrating Pollution Prevention

3-9

• Immobilization:

Encapsulation

Thermoplastic binding

• Carbon absorption:

Granular activated carbon (GAC)

Powdered activated carbon (PAC)

• Distillation:

Batch distillation

Fractionation

Thin film extraction

Steam stripping

Thermal drying

• Filtration

• Evaporation/volatilization

• Grinding

• Shredding

• Compacting

• Solidification/addition of absorbent

material

Chemical treatment involves altering a

waste’s chemical composition, structure, and

properties through chemical reactions.

Chemical treatment can consist of mixing the

waste with other materials (reagents), heating

the waste to high temperatures, or a combination of both. Through chemical treatment,

waste constituents can be recovered or

destroyed. Listed below are a few examples of

chemical treatment.

• Neutralization

• Oxidation

• Reduction

• Precipitation

• Acid leaching

• Ion exchange

• Incineration

• Thermal desorption

• Stabilization

• Vitrification

• Extraction:

Solvent extraction

Critical extraction

• High temperature metal recovery

(HTMR)

Biological treatment can be divided into two

categories–aerobic and anaerobic. Aerobic biological treatment uses oxygen-requiring

microorganisms to decompose organic and

non-metallic constituents into carbon dioxide,

water, nitrates, sulfates, simpler organic products, and cellular biomass (i.e., cellular growth

and reproduction). Anaerobic biological treatment uses microorganisms, in the absence of

oxygen, to transform organic constituents and

nitrogen-containing compounds into oxygen

and methane gas (CH4(g)). Anaerobic biological treatment typically is performed in an

enclosed digestor unit. Listed below are a few

examples of biological treatment.

• Aerobic:

Activated sludge

Aerated lagoon

Trickling filter

Rotating biological contactor (RBC)

• Anaerobic digestion

The range of treatment methods from

which to choose is as diverse as the range of

wastes to be treated. More advanced treatment will generally be more expensive, but

by reducing the quantity and risk level of the

waste, costs might be reduced in the long

run. Savings could come from not only lower

disposal costs, but also lower closure and

post-closure care costs. Treatment and posttreatment waste management methods can be

selected to minimize both total cost and environmental impact, keeping in mind that treatment residuals, such as sludges, are wastes

themselves that will need to be managed.
3-10

Getting Started—Intregrating Pollution Prevention

III. Where to Find

Out More:

Technical and

Financial

Assistance

There is a wealth of information available to

help integrate pollution prevention into an

operation. As a starting point, a list of references to technical and financial resources is

included in this section. The Internet can be

an excellent source of background information

on the various resources to help begin the

search for assistance. Waste reduction information and technologies are constantly changing.

To follow new developments you should maintain technical and financial contacts and continue to use these resources even after

beginning waste reduction activities. Eventually, you can build a network of contacts to support all your various technical needs.

Where Can Assistance Be

Obtained?

Several types of organizations offer assistance. These include offices in regulatory

agencies, university departments, nonprofit

foundations, and trade associations.

Additionally, the National Institute of

Standards and Technology (NIST) Manufacturing Extension Partnerships (MEPs)

<www.mep.nist.gov> also provide waste

reduction information. Look for waste reduction staff within the media programs (air,

water, solid/hazardous waste) of regulatory

agencies or in the state commissioner’s office,

special projects division, or pollution prevention division. Some states also provide technical assistance for waste reduction activities,

such as recycling, through a business advocate or small business technical assistance

program. EPA’s U.S. State & Local Gateway

Web site <www.epa.gov/epapages/

statelocal/envrolst.htm> is a helpful tool for

locating your state environmental agency.

The listings below identify some primary

sources for technical assistance that might

prove helpful. This list serves as a starting

point only and is by no means exhaustive.

There are many additional organizations that

offer pollution prevention assistance on

regional, state, and local levels. 

• American Forest and Paper

Association (AF&PA) is the national trade association of the forest,

paper, and wood products industries.

It offers documents that might help

you find buyers for wood and paper

wastes. <www.afandpa.org> Phone:

800 878-8878 e-mail: INFO@

afandpa.ccmail.compuserve.com

• California Integrated Waste

Management Board. This Web site

contains general waste prevention

background and business waste

reduction program overviews, fact

sheets, and information about market

development for recycled materials

and waste reduction training.

<www.ciwmb.ca.gov/WPW>

• Center for Environmental Research

Information (CERI) provides technical guides and manuals on waste

reduction, summaries of pollution

prevention opportunity assessments,
and waste reduction alternatives for

specific industry sectors.

<www.epa.gov/ttbnrmrl/ttmat.htm>

Phone: 513-569-7562 e-mail:

ord.ceri@epamail.epa.gov

• Enviro$en$e, part of the U.S. EPA’s

Web site, provides a single repository

for pollution prevention, compliance

assurance, and enforcement information and data bases. Its search engine

searches multiple Web sites (inside

and outside the EPA), and offers

assistance in preparing a search.

<es.epa.gov> 

• National Pollution Prevention

Roundtable (NPPR) promotes the

development, implementation, and

evaluation of pollution prevention.

NPPR’s Web site provides an abridged

online version of The Pollution

Prevention Yellow Pages <www.p2.

org/inforesources/nppr_yps.html>,

a listing of local, state, regional and

national organizations, including

state and local government programs,

federal agencies, EPA pollution prevention coordinators, and non-profit

groups that work on pollution prevention. <www.p2.org> Phone: 202

466-P2P2

• P2 GEMS. This site, an Internet

search tool operated by the

Massachusetts Toxics Use Reduction

Institute, can help facility planners,

engineers, and managers locate

process and materials management

information over the Web. It includes

information on over 550 sites valuable for toxics use reduction planning

and pollution prevention.

<www.edu/p2gems.org>

• Pollution Prevention Information

Clearinghouse (PPIC). PPIC maintains a collection of EPA non-regulatory documents related to waste

reduction. <www.epa.gov/opptintr/

library/libppic.htm> Phone: 202

260-1023 e-mail: ppic@epamail.

epa.gov

• U.S. Department of Energy (DOE)

Industrial Assessment Centers

(IACs). DOE’s Office of Industrial

Technologies sponsors free industrial

assessments for small and mediumsized manufacturers. Teams of engineering students from the centers

conduct energy audits or industrial

assessments and provide recommendations to manufacturers to help

them identify opportunities to

improve productivity, reduce waste,

and save energy. <www.oit.doe.gov/

iac>

What Types of Technical

Assistance Are Available?

Many state and local governments have

technical assistance programs that are distinct

from regulatory offices. In addition, nongovernmental organizations conduct a wide

range of activities to educate businesses about

the value of pollution prevention. These

efforts range from providing onsite technical

assistance and sharing industry-specific experiences to conducting research and developing education and outreach materials on

waste reduction topics. The following examples illustrate what services are available: 

• NIST technical centers. There are

NIST-sponsored Manufacturing

Technology Centers throughout the

country as part of the grassroots

Manufacturing Extension Partnership

(MEP) program. The MEP program

helps small and medium-sized companies adopt new waste reduction

Getting Started—Integrating Pollution Prevention

3-11
technologies by providing technical

information, financing, training, and

other services. The NIST Web site

<www.nist.gov> has a locator that

can help you find the nearest center.

• Trade associations. Trade associations provide industry-specific assistance through publications,

workshops, field research, and consulting services. EPA’s WasteWise

program <www.ergweb.com/wwta

/intro.asp> provides an online

resources directory which can help

you locate specific trade associations.

The National Trade and Professional

Associations of the Unites States’

Directory of Trade Associations

(Washington, DC: Columbia Books,

Inc., 2000) is another useful resource.

• Onsite technical assistance audits.

These audits are for small (and sometimes larger) businesses. The assessments, which take place outside of

the regulatory environment and on a

strictly voluntary basis, provide businesses with information on how to

save money, increase efficiency, and

improve community relations. DOE’s

Office of Industrial Technologies

<www.oit.doe.gov/iac> provides

such assessments for small and 

medium-sized manufacturers.

• Information clearinghouses. Many

organizations maintain repositories of

waste reduction information and

serve as starting points to help businesses access this information. EPA’s

Pollution Prevention Information

Center (PPIC) <www.epa.gov/opptintr/library/libppic.htm> is one

example.

• Facility planning assistance. A number of organizations can help businesses develop, review, or evaluate

facility waste reduction plans. State

waste reduction programs frequently

prepare model plans designed to

demonstrate activities a business can

implement to minimize waste. 

• Research and collaborative projects. Academic institutions, state

agencies and other organizations frequently participate in research and

collaborative projects with industry

to foster development of waste

reduction technologies and management strategies. Laboratory and field

research activities include studies,

surveys, database development, data

collection, and analysis.

• Hotlines. Some states operate telephone assistance services to provide

technical waste reduction information

to industry and the general public.

Hotline staff typically answer questions, provide referrals, and distribute

printed technical materials on request.

• Computer searches and the

Internet. The Internet brings many

pollution prevention resources to a

user’s fingertips. The wide range of

resources available electronically can

provide information about innovative

waste-reducing technologies, efficient

industrial processes, current state

and federal regulations, and many

other pertinent topics. Independent

searches can be done on the Internet,

and some states perform computer

searches to provide industry with

information about waste reduction.

EPA and many state agencies have

Web sites dedicated to these topics,

with case studies, technical explanations, legal information, and links to

other sites for more information.

3-12

Getting Started—Intregrating Pollution Prevention
• Workshops, seminars, and training.

State agencies, trade associations, and

other organizations conduct workshops, seminars, and technical training on waste reduction. These events

provide information, identify

resources, and facilitate networking.

• Grants and loans. A number of

states distribute funds to independent

groups that conduct waste reduction

activities. These groups often use

such support to fund research and to

run demonstration and pilot projects.

Getting Started—Integrating Pollution Prevention

3-13
To address pollution prevention you should:

■ Make waste management decisions by considering the priorities set by the full range of pollution

prevention options—first, source reduction; second, reuse and recycling; third, treatment; last, disposal.

■ Explore the cost savings and other benefits available through activities that integrate pollution prevention.

■ Develop a waste reduction policy.

■ Conduct a pollution prevention opportunity assessment of facility processes.

■ Research potential pollution prevention activities.

■ Consult with public and private agencies and organizations providing technical and financial assistance for pollution prevention activities.

■ Plan and implement activities that integrate pollution prevention.

Integrating Pollution

Prevention Activity List

3-14

Getting Started—Intregrating Pollution Prevention
Getting Started—Integrating Pollution Prevention

3-15

Erickson, S. and King, B. 1999. Fundamentals of Environmental Management. John Wiley and Sons,

Inc.

Freeman, Harry. 1995. Industrial Pollution Prevention Handbook. McGraw-Hill, Inc.

“Green Consumerism: Commitment Remains Strong Despite Economic Pessimism.” 1992. Cambridge

Reports. Research International. (October).

Habicht, F. Henry. 1992. U.S. EPA Memorandum on EPA Definition of Pollution Prevention (May).

Higgins, Thomas E., ed. 1995. Pollution Prevention Handbook. CRC-Lewis Publishers.

“Moving from Industrial Waste to Coproducts.” 1997. Biocycle. (January)

National Pollution Prevention Roundtable. 1995. The Pollution Prevention Yellow Pages.

Pollution Prevention Act of 1990. (42 U.S.C. 13101 et seq., Pub.L. 101-508, November 5, 1990).

Rossiter, Alan P., ed. 1995. Waste Minimization Through Process Design. McGraw-Hill, Inc.

U.S. EPA. 2001. Pollution Prevention Clearinghouse: Quarterly List of Pollution Prevention

Publications, Winter 2001. EPA742-F-01-004.

U.S. EPA. 1998. Project XL: Good for the Environment, Good for Business, Good for Communities.

EPA100–F-98-008.

U.S. EPA. 1997. Developing and Using Production Adjusted Measurements of Pollution Prevention.

EPA600-R-97-048.

U.S. EPA. 1997. Guide to Accessing Pollution Prevention Information Electronically. EPA742-B-97-003

U.S. EPA. 1997. Pollution Prevention 1997: A National Progress Report. EPA742-R-97-001.

U.S. EPA. 1997. Technical Support Document for Best Management Practices Programs—Spent

Pulping Liquor Management, Spill Prevention, and Control.

U.S. EPA. 1996. Environmental Accounting Project: Quick Reference Fact Sheet. EPA742-F-96-001.

Resources
3-16

Getting Started—Intregrating Pollution Prevention

U.S. EPA. 1996. Profiting from Waste Reduction in Your Small Business. EPA742-B-88-100.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Paints and Coatings. EPA600-S-95-009.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Bourbon Whiskey. EPA600-S-95-010.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Automotive Battery Separators. EPA600-S-95-011.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Automotive Lighting Equipment and Accessories. EPA600-S-95-012.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Locking Devices. EPA600-S-95-013.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Combustion Engine Piston Rings. EPA600-S-95-015.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Metal Fasteners.EPA600-S-95-016.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Stainless Steel Pipes and Fittings. EPA600-S-95-017.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Outboard Motors. EPA600-S-95-018.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Electroplated Truck Bumpers. EPA600-S-95-019.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Printed Circuit

Board Plant.EPA600-S-95-020.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Folding Paperboard Cartons. EPA600-S-95-021.

Resources (cont.)
Getting Started—Integrating Pollution Prevention

3-17

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Rebuilt Industrial Crankshafts. EPA600-S-95-022.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Pressure-sensitive Adhesive Tape. EPA600-S-95-023.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Wooden Cabinets. EPA600-S-95-024.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Power Supplies. EPA600-S-95-025.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Food Service Equipment. EPA600-S-95-026.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Metal Parts

Coater. EPA600-S-95-027.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Gear Cases for Outboard Motors. EPA600-S-95-028.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Electrical Load Centers. EPA600-S-95-029.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Pharmaceuticals. EPA600-S-95-030.

U.S. EPA. 1995. Environmental Research Brief: Pollution Prevention Assessment for a Manufacturer of

Aircraft Landing Gear. EPA600-S-95-032.

U.S. EPA. 1995. EPA Standards Network Fact Sheet: Role of Voluntary Standards. EPA741-F-95-005.

U.S. EPA. 1995. Introduction to Pollution Prevention: Training Manual. EPA742-B-95-003.

U.S. EPA. 1995. Recent Experience in Encouraging the Use of Pollution Prevention in Enforcement

Settlements: Final Report. EPA300-R-95-006.

U.S. EPA. 1995. Recycling Means Business. EPA530-K-95-005.

Resources (cont.)
U.S. EPA. 1994. Final Best Demonstrated Available Technology (BDAT) Background Document for

Universal Standards, Volume B: Universal Standards for Wastewater forms of Listed Hazardous Wastes,

Section 5, Treatment Performance Database. EPA530-R-95-033.

U.S. EPA. 1994. Review of Industrial Waste Exchanges. EPA530-K-94-003.

U.S. EPA. 1993. Guidance Manual for Developing Best Management Practices. EPA833-B-93-004.

U.S. EPA. 1993. Primer for Financial Analysis of Pollution Prevention Projects. EPA600-R-93-059.

U.S. EPA. 1992. Facility Pollution Prevention Guide. EPA600-R-92-008.

U.S. EPA. 1992. Practical Guide to Pollution Prevention Planning for the Iron and Steel Industries.

EPA742-B-92-100

U.S. EPA. 1991. Pollution Prevention Strategy. EPA741-R-92-001.

U.S. EPA. 1991. Treatment Technology Background Document; Third Third; Final. EPA530-SW-90-

059Z.

U.S. EPA. 1990. Guide to Pollution Prevention: Printed Circuit Board Manufacturing Industry. EPA625-

7-90-007

U.S. EPA. 1990. Waste Minimization: Environmental Quality with Economic Benefits. EPA530-SW-90-

044.

U.S. EPA. 1989. Treatment Technology Background Document; Second Third; Final. EPA530-SW-89-

048A.

3-18

Getting Started—Intregrating Pollution Prevention

Resources (cont.)
Part I

Getting Started

Chapter 4

Considering the Site
Contents

I. General Siting Considerations ....................................................................................................................4 - 3

A. Floodplains............................................................................................................................................4 - 3

B. Wetlands................................................................................................................................................4 - 6

C. Active Fault Areas ................................................................................................................................4 - 10

D. Seismic Impact Zones ..........................................................................................................................4 - 12

E. Unstable Areas ....................................................................................................................................4 - 14

F. Airport Vicinities..................................................................................................................................4 - 18

G. Wellhead Protection Areas ..................................................................................................................4 - 19

II. Buffer Zone Considerations ..................................................................................................................4 - 20

A. Recommended Buffer Zones ................................................................................................................4 - 21

B. Additional Buffer Zones ......................................................................................................................4 - 22

III. Local Land Use and Zoning Considerations..........................................................................................4 - 23

IV. Environmental Justice Considerations ..................................................................................................4 - 23

Considering the Site Activity List ................................................................................................................4 - 25

Resources ....................................................................................................................................................4 - 27

Appendix: State Buffer Zone Considerations ..............................................................................................4 - 30

Tables:

Table 1: Examples of Improvement Techniques for Liquefiable Soil Foundation Conditions ..................4 - 12
Getting Started—Considering the Site

4-1

Many hydrologic and geologic

settings can be effectively utilized for protective waste

management. There are,

however, some hydrologic

and geologic conditions that are best avoided

all together if possible. If they cannot be

avoided, special design and construction precautions can minimize risks. Floodplains,

earthquake zones, unstable soils, and areas at

risk for subsurface movement need to be

taken into account just as they would be

when siting and constructing a manufacturing plant or home. Catastrophic events associated with these locations could seriously

damage or destroy a waste management unit,

release contaminants into the environment,

and add substantial expenses for cleanup,

repair, or reconstruction. If problematic site

conditions cannot be avoided, engineering

design and construction techniques can

address some of the concerns raised by locating a unit in these areas. 

Many state, local, and tribal governments

require buffer zones between waste management units and other nearby land uses. Even

if buffer zones are not required, they can still

provide benefits now and in the future. Buffer

zones provide time and space to contain and

remediate accidental releases before they

reach sensitive environments or sensitive

populations. Buffer zones also help maintain

good community relations by reducing disruptions associated with noise, traffic, and

Considering the Site

This chapter will help you:

• Become familiar with environmental, geological, and manmade features that influence siting decisions.

• Identify nearby areas or land uses that merit buffer zones and place

your unit an appropriate distance from them.

• Comply with local land use and zoning restrictions, including any

amendments occurring during consideration of potential sites.

• Understand existing environmental justice issues as you consider a

new site.

• Avoid siting a unit in hydrologic or geologic problem areas, without

first designing the unit to address conditions in those areas.

This chapter will help address the following questions:

• What types of sites need special consideration?

• How will I know whether my waste

management unit is in an area requiring special consideration?

• Why should I be concerned about siting a waste management unit in such

areas?

• What actions can I take if I plan to site

a unit in these areas?
4-2

Getting Started—Considering the Site

wind-blown dust, often the source of serious

neighborhood concerns.

In considering impacts on the surrounding

community, it is important to understand

whether the community, especially one with a

large minority and low income population,

already faces significant environmental

impacts from existing industrial activities. You

should develop an understanding of the community’s current environmental problems and

work together to develop plans that can

improve and benefit the environment, the

community, the state, and the company.

How should a waste

management unit site

assessment begin?

In considering whether to site a new waste

management unit or laterally expand an existing unit, certain factors will influence the siting process. These factors include land

availability, distance from waste generation

points, ease of access, local climatic conditions, economics, environmental considerations, local zoning requirements, and potential

impacts on the community. As prospective

sites are identified, you should become familiar with the siting considerations raised in this

chapter. Determine how to address concerns at

each site to minimize a unit’s adverse impacts

on the environment in addition to the environment’s adverse impacts on the unit. You should

choose the site that best balances protection of

human health and the environment with operational goals. In addition to considering the

issues raised in this chapter, you should check

with state and local regulatory agencies early

in the siting process to identify other issues

and applicable restrictions.

Another factor to consider is whether there

are any previous or current contamination

problems at the site. It is recommended that

potential sites for new waste management

units be free of any contamination problems.

An environmental site assessment (ESA) may

be required prior to the disturbance of any

land area or before property titles are transferred. An ESA is the process of determining

whether contamination is present on a parcel

of property. You should check with the EPA

regional office and state or local authorities to

determine if there are any ESA requirements

prior to siting a new unit or expanding an

existing unit. If there are no requirements,

you might want to consider performing an

ESA in order to ensure that there are no contamination problems at the site. 

Many companies specialize in site screening,

characterization, and sampling of different

environmental media (i.e., air, water, soil) for

potential contamination. A basic ESA (often

referred to as the Phase I Environmental Site

Assessment process) typically involves

researching prior land use, deciding if sampling of environmental media is necessary

based on the prior activities, and determining

contaminate fate and transport if contamination has occurred. Liability issues can arise if

the site had contamination problems prior to

construction or expansion of the waste management unit. Information on the extent of

contamination is needed to quantify cleanup

costs and determine the cleanup approach.

Cleanup costs can represent an additional,

possibly significant, project cost when siting a

waste management unit.

As discussed later in this chapter, you will

also need to consider other federal laws and

regulations that could affect siting. For example, the Endangered Species Act (16 USC

Sections 1531 et seq.) provides for the designation and protection of threatened or endangered wildlife, fish, and plant species, and

ensures the conservation of the ecosystems on

which such species depend. It is the responsibility of the facility manager to check with

and obtain a Section 10 permit from the

Secretary of the Interior if the construction or

operation of a waste management unit might

potentially impact any endangered or threat-
Getting Started—Considering the Site

4-3

1 This agency of the U.S. Department of Agriculture was formerly known as the Soil Conservation

Service (SCS).

ened species or its critical habitat. Thus, you

might not be able to site a new waste management unit in an area where endangered or

threatened species live, or expand an existing

unit into such an area. As another example,

the National Historic Preservation Act (16

USC Sections 470 et seq.) protects historic

sites and archaeological resources. The facility

manager of a waste management unit should

be aware of the properties listed on the

National Register of Historic Properties. The

facility manager should consult with the state

historic preservation office to ensure that the

property to be used for a new unit or lateral

expansion of an existing unit will not impact

listed historic properties, or sites with archeological significance. Other federal laws or

statutes might also require consideration. It is

the ultimate responsibility of the facility

owner or manager to comply with the

requirements of all applicable federal and

state statutes when siting a waste management unit.

Additional factors, such as proximity to

other activities or sites that affect the environment, also might influence siting decisions.

To determine your unit’s proximity to other

facilities or industrial sites, you can utilize

EPA’s Envirofacts Warehouse. The Envirofacts

Web site at <www.epa.gov/enviro/index_

java.html> provides users with access to several EPA databases that will provide you with

information about various environmental

activities including toxic chemical releases,

water discharges, hazardous waste handling

processes, Superfund status, and air releases.

The Web site allows you to search one database or several databases at a time about a

specific location or facility. You can also create maps that display environmental information using the “Enviromapper” application

located at <www.epa.gov/enviro/html/mod/

index.html>. Enviromapper allows users to

map different types of environmental information, including the location of drinking

water supplies, toxic and air releases, hazardous waste sites, water discharge permits,

and Superfund sites at the national, state, and

county levels.

EPA’s Waste Management—Facility Siting

Application is a powerful new Web-based

tool that provides assistance in locating waste

management facilities. The tool allows the

user to enter a ZIP code; city and state; or latitude and longitude to identify the location of

fault lines, flood planes, wetlands, and karst

terrain in the selected area. The user also can

use the tool to display other EPA regulated

facilities, monitoring sites, water bodies, and

community demographics. The Facility Siting

Application can be found at <www.epa.gov/

epaoswer/non-hw/industd/index.htm>.

I. General Siting

Considerations

Examining the topography of a site is the

first step in siting a unit. Topographic information is available from the U.S. Geological

Survey (USGS), the Natural Resources

Conservation Service (NRCS)1

, the state’s geological survey office or environmental regulatory agency, or local colleges and universities.

Remote sensing data or maps from these organizations can help you determine whether

your prospective site is located in any of the

areas of concern discussed in this section.

USGS maps can be downloaded or ordered

from their Web site at <mapping.usgs.gov>.

Also, the University of Missouri-Rolla maintains a current list of state geological survey

offices on its library’s Web site at

<www.umr.edu/~library/geol/geoloff.html>.

A. Floodplains

A floodplain is a relatively flat, lowland

area adjoining inland and coastal waters. The
4-4

Getting Started—Considering the Site

100-year floodplain—the area susceptible to

inundation during a large magnitude flood

with a 1 percent chance of recurring in any

given year—is usually the floodplain of concern for waste management units. You should

determine whether a candidate site is in a

100-year floodplain. Siting a waste management unit in a 100-year floodplain increases

the likelihood of floods inundating the unit,

increases the potential for damage to liner systems and support components (e.g., leachate

collection and removal systems or other unit

structures), and presents operational concerns.

This, in turn, creates environmental and

human health and safety concerns, as well as

legal liabilities. It can also be very costly to

build a unit to withstand a 100-year flood

without washout of waste or damage to the

unit, or to reconstruct a unit after such a

flood. Further, locating your unit in a floodplain can exacerbate the damaging effects of a

flood, both upstream and downstream, by

reducing the temporary water storage capacity

of the floodplain. As such, it is preferable to

locate potential sites outside the 100-year

floodplain.

How is it determined if a

prospective site is in a 100-year

floodplain?

The first step in determining whether a

prospective site is located in a 100-year floodplain is to consult with the Federal Emergency

Management Agency (FEMA). FEMA has prepared flood hazard boundary maps for most

regions. If a prospective site does not appear

to be located in a floodplain, further exploration is not necessary. If uncertainty exists as

to whether the prospective site might be in a

floodplain, several sources of information are

available to help make this determination.

More detailed flood insurance rate maps

(FIRMs) can be obtained from FEMA. FIRMs

divide floodplain areas into three zones: A, B,

and C. Class A zones are the most susceptible

to flooding while class C zones are the least

susceptible. FIRMs can be obtained from

FEMA’s Web site at <msc.fema.gov/MSC/

hardcopy.htm>.

Additional information can be found on

flood insurance rate maps in FEMA’s publication How to Read a Flood Insurance Rate Map

(visit: <www.fema.gov/nfip/ readmap.htm>).

FEMA also publishes The National Flood

Insurance Program Community Status Book

which lists communities with flood insurance

rate maps or floodway maps. Floodplain maps

can also be obtained through the US

Geological Survey (USGS); National Resources

Conservation Service (NRCS); the Bureau of

Land Management; the Tennessee Valley

Authority; and state, local, and tribal agencies.2

Note that river channels shown in floodplain maps can change due to hydropower or

flood control projects. As a result, some floodplain boundaries might be inaccurate. If you

suspect this to be the case, consult recent aerial photographs to determine how river channels have been modified.

2 Copies of flood maps from FEMA are available at Map Service Center, P.O. Box 1038, Jessup, MD 20794-

1038, by phone 800 358-9616, or the Internet at <www.fema.gov/nfip/readmap.htm>.

Flood waters overflowed from the

Mississippi River (center) into its floodplain

(foreground) at Quincy, Illinois in the 1993

floods that exceeded 100-year levels in parts

of the Midwest.
Getting Started—Considering the Site

4-5

If maps cannot be obtained, and

a potential site is suspected to be

located in a floodplain, you can

conduct a field study to delineate

the floodplain and determine the

floodplain’s properties. To perform

a delineation, you can draw on

meteorological records and physiographic information, such as existing and planned watershed land

use, topography, soils and geographic mapping, and aerial photographic interpretation of land

forms. Additionally, you can use

the U.S. Water Resources Council’s

methods of determining flood

potential based on stream gauge

records, or you can estimate the

peak discharge to approximate the

probability of exceeding the 100-

year flood. Contact the USGS,

Office of Surface Water, for additional information concerning

these methods.3

What can be done if a

prospective site is in a

floodplain?

If a new waste management unit

or lateral expansion will be sited in

a floodplain, design the unit to prevent the washout of waste, avoid significant alteration of flood flow, and maintain

the temporary storage capacity of the floodplain. Engineering models can be used to

estimate a floodplain’s storage capacity and

floodwater flow velocity. The U.S. Army

Corps of Engineers (USACE) Hydrologic

Engineering Center has developed several

computer models for simulating flood properties.4 The models can predict how a waste

management unit sited in a floodplain can

affect its storage capacity and can also simulate flood control structures and sediment

transport. If a computer model predicts that

placement of the waste management unit in

the floodplain raises the base flood level by

more than 1 foot, the unit might alter the

storage capacity of the floodplain. If designing a new unit, you should site it to minimize

these effects. The impact of your unit’s location on the speed and flow of flood waters

determines the likelihood of waste washout.

To quantify this, estimate the shear stress on

the unit’s support components caused by the

impinging flood waters at the depth, velocity,

3 Information on stream gaging and flood forecasting can be obtained from the USGS, Office of Surface

Water, at 413 National Center, Reston, VA 22092, by phone 703 648-5977, or the Internet at

<water.usgs.gov>.

4 The HEC-1, HEC-2, HEC-5, and HEC-6 software packages are available free of charge through the

USACE Web site at <http://www.hec.usace.army.mil/software/software_distrib/>.

FEMA provides flood maps like this one for most floodplains

Source: FEMA, Q3 Flood Data Users Guide <www.fema.gov/msc>.
4-6

Getting Started—Considering the Site

and duration associated with the peak (i.e.,

highest) flow period of the flood.

While these methods can help protect

your unit from flood damage and washout,

be aware that they can further contribute to a

decrease in the water storage and flow capacity of the floodplain. This, in turn, can raise

the level of flood waters not only in your area

but in upstream and downstream locations,

increasing the danger of flood damage and

adding to the cost of flood control programs.

Thus, serious consideration should be given

to siting a waste management unit outside a

100-year floodplain.

B. Wetlands

Wetlands, which include swamps, marshes,

and bogs, are vital and delicate ecosystems.

They are among the most productive biological communities on earth and provide habitat

for many plants and animals. The U.S. Fish

and Wildlife Service estimates that up to 43

percent of all endangered or threatened

species rely on wetlands for their survival.5

5 From EPA’s Wetlands Web site, Values and Functions of Wetlands factsheet, <www.epa.gov/owow/

wetlands/facts/fact2.html>.

Riprap (rock cover) reduces stream channel erosion (left) and gabions (crushed rock encased

in wire mesh) help stabilize erodible slopes (right).

Sources: U.S. Department of the Interior, Office of Surface Mining (left); The Construction

Site—A Directory To The Construction Industry (right).

Knowing the behavior of waters at their

peak flood level is important for determining whether waste will wash out.
Getting Started—Considering the Site

4-7

6 For the full text of the Clean Water Act, including Section 404, visit the U.S. House of Representatives

Internet Law Library Web site at <uscode.house.gov/download.htm>, under Title 33, Chapter 26.

Wetlands protect water quality by assimilating

water pollutants, removing sediments containing heavy metals, and recharging groundwater supplies. Wetlands also prevent

potentially extensive and costly floods by temporarily storing flood waters and reducing

their velocity. These areas also offer numerous

recreational opportunities.

Potential adverse impacts associated with

locating your unit in a wetland include dewatering the wetland (i.e., causing removal or

drainage of water), contaminating the wetland, and causing loss of wetland acreage.

Damage could also be done to important wetland ecosystems by destroying their aesthetic

qualities and diminishing wildlife breeding

and feeding opportunities. Siting in a wetland

increases the potential for damage to your

unit, especially your liner system and structural components, as a result of ground settlement, action of the high water table, and

flooding. Alternatives to siting a waste management unit in a wetland area should be

given serious consideration based upon

Section 404 requirements in the Clean Water

Act (CWA) as discussed below.

If a waste management unit is to be sited in

a wetland area, the unit will be subject to

additional regulations. In particular, Section

404 of the Clean Water Act (CWA) authorizes

the Secretary of the Army, acting through the

Chief of Engineers, to issue permits for the

discharge of dredged or fill material into wetlands and other waters of the United States.6

Activities in waters of the United States regulated under this permitting program include

“placement of fill material for construction or

maintenance of any liner, berm, or other

infrastructure associated with solid waste

landfills,” as well as fills for development,

water resource projects, infrastructure

improvements, and conversion of wetlands to

uplands for farming and forestry (40 CFR

Section 232.2—definition of “discharge of fill

material”). EPA regulations under Section 404

(33 United States Code Section 1344) stipulates that no discharge of dredged or fill material can be permitted if a practicable

alternative exists that is less damaging to the

aquatic environment or if the nation’s waters

would be significantly degraded. Therefore, in

Different types of wetlands: spruce bog (left) and eco pond in the Florida Everglades (right).

For regulatory purposes under the Clean

Water Act, wetlands are defined as areas

“that are inundated or saturated by surface or ground water at a frequency and

duration sufficient to support, and that

under normal circumstances do support,

a prevalence of vegetation typically adapted for life in saturated soil conditions.”

40 Code of Federal Regulations (CFR) 232.2(r)
4-8

Getting Started—Considering the Site

7 To contact NWI, write to National Wetlands Inventory Center, 9720 Executive Center Drive, Suite 101,

Monroe Building, St. Petersburg, FL 33702, call 727 570-5400, or fax 727 570-5420. For additional

information online or to search for maps of your area, visit: <www.nwi.fws.gov>.

compliance with the guidelines established

under Section 404, all permit applicants must:

• Take steps to avoid wetland impacts

where practicable.

• Minimize impacts to wetlands where

they are unavoidable.

• Compensate for any remaining,

unavoidable impacts by restoring or

creating wetlands.

The EPA and USACE jointly administer a

review process to issue permits for regulated

activities. For projects with potentially significant impacts, an individual permit is usually

required. For most discharges with only minimal adverse effects, USACE may allow applicants to comply with existing general

permits, which are issued on a nationwide,

regional, or statewide basis for particular

activity categories as a means to expedite the

permitting process. In making permitting

decisions, the agencies will consider other

federal laws that might restrict placement of

waste management units in wetlands. These

include the Endangered Species Act; the

Migratory Bird Conservation Act; the Coastal

Zone Management Act; the Wild and Scenic

Rivers Act; the Marine Protection, Research

and Sanctuaries Act; and the National

Historic Preservation Act.

How is it determined if a

prospective site is in a wetland?

As a first step, determine if the prospective

site meets the definition of a wetland. If the

prospective site does not appear to be a wetland, then no further exploration is necessary.

If it is uncertain whether the prospective site

is a wetland, then several sources are available to help you make this determination and

define the boundaries of the wetland.

Although this can be a challenging process, it

will help you avoid future liability since filling a wetland without the appropriate federal,

state, or local permits would be a violation of

many laws. It might be possible to learn the

extent of wetlands without performing a new

delineation, since many wetlands have previously been mapped. The first step, therefore,

should be to determine whether wetlands

information is available for your area. 

At the federal level, four agencies are principally involved with wetlands identification

and delineation: USACE, EPA, the U.S. Fish

and Wildlife Service (FWS), and National

Resource Conservation Service (NRCS). EPA

also has a Wetlands Information Hotline (800

832-7828) and a wetlands Web site at <www.

epa.gov/owow/wetlands> which provides

information about EPA’s wetlands program;

facts about wetlands; the laws, regulations,

and guidance affecting wetlands; and science,

education, and information resources for wetlands. The local offices of NRCS (in agricultural areas) or regional USACE Engineer

Divisions and Districts <www.usace.army.

mil/divdistmap.html> might know whether

wetlands in the vicinity of the potential site

have already been delineated.

Additionally, FWS maintains the National

Wetlands Inventory (NWI) Center,7 from

which you can obtain wetlands mapping for

much of the United States. This mapping,

however, is based on aerial photography,

which is not reliable for specific field determinations. If you have recently purchased

your site, you also might be able to find out

from the previous property owner whether

any delineation has been completed that

might not be on file with these agencies. Even

if existing delineation information for the site

is found, it might still be prudent to contact a

qualified wetlands consultant to verify the

wetland boundaries, especially if the delineation is not a field determination or is more

than a few years old.

If the existence of a wetland is uncertain,

you should obtain a wetlands delineation.
Getting Started—Considering the Site

4-9

8 Currently, there is no federal certification program. In March 1995, USACE proposed standards for a

Wetlands Delineator Certification Program (WDCP), but the standards have not been finalized. If the

WDCP standards are finalized and implemented, you should use WDCP-certified wetland consultants.

9 The 1987 manual can be ordered from the National Technical Information Service (NTIS) at 703 605-

6000 or obtained online at <www.wes.army.mil/el/wetlands/wlpubs.html>.

This procedure should be performed only by

an individual with experience in performing a

wetlands delineation8 using standard delineation procedures or applicable state or local

delineation standards. The delineation procedure, with which you should become familiar

before hiring a delineator, involves collecting

maps, aerial photographs, plant data, soil surveys, stream gauge data, land use data, and

other information. Note that it is mandatory

that wetlands delineation for CWA Section

404 permitting purposes be conducted in

accordance with the 1987 U.S. Army Corps of

Engineers Wetlands Delineation Manual9

(USACE, 1991). The manual provides guidelines and methods for determining whether

an area is a wetland for purposes of Section

404. A three-parameter approach for assessing the presence and location of hydrophytic

vegetation (i.e., plants that are adapted for life

in saturated soils), wetland hydrology, and

hydric soils is discussed.

What can be done if a

prospective site is in a wetland?

Before constructing a waste management

unit in a wetland area, consider whether you

can locate the unit elsewhere. If an alternative

location can be identified, strongly consider

pursuing such an option, as required by

Section 404 of the CWA. Because wetlands

are important ecosystems that should be protected, identification of practicable location

alternatives is a necessary first step in the siting process. Even if no viable alternative locaNWI wetland resource maps like this one show the locations of various different types of 

wetlands and are available for many areas.

Source: NWI web site, sample GIS Think Tank maps page, <wetlands.fws.gov/>.
4-10

10 Information about ordering these maps is available by calling 888 ASK-USGS or 703 648-6045.

11 The National Aerial Photographic Program (NAPP) and the National High Altitude Program (NHAP),

both administered by USGS, are sources of aerial photographs. To order from USGS, call 605 594-

6151. For more information, see <edc.usgs.gov/nappmap.html>. Local aerial photography firms and

surveyors are also good sources of information.

Getting Started—Considering the Site

tions are identified, it might be beneficial to

keep a record of the alternatives investigated,

noting why they were not acceptable. Such

records might be useful during the interaction between facilities, states, and members of

the community.

If no alternatives are available, you should

consult with state and local regulatory agencies concerning wetland permits. Most states

operate permitting programs under the CWA,

and state authorities can guide you through

the permitting process. To obtain a permit,

the state might require that the unit facility

manager assess wetland impacts and then:

• Prevent contamination from leachate

and runoff.

• Minimize dewatering effects.

• Reduce the loss of wetland acreage.

• Protect the waste management unit

against settling.

C. Active Fault Areas

Faults occur when stresses in a geologic

material exceed its ability to withstand these

forces. Areas surrounding faults are subject to

earthquakes and ground failures, such as

landslides or soil liquefaction. Fault movement can directly weaken or destroy structures, or seismic activity associated with

faulting can cause damage to structures

through vibrations. Structural damage to the

waste management unit could result in the

release of contaminants. In addition, fault

movement might create avenues to groundwater supplies, increasing the risk of groundwater contamination.

Liquefaction is another common problem

encountered in areas of seismic activity. The

vibrating motions caused by an earthquake

tend to rearrange the sand grains in soils. If

the grains are saturated, the saturated granular material turns into a viscous fluid, a

process referred to as liquefaction. This

diminishes the bearing capacity of the soils

and can lead to foundation and slope failures.

To avoid these hazards, do not build or

expand a unit within 200 feet of an active

fault. If it is not possible to site a unit more

than 200 feet from an active fault, you should

design the unit to withstand the potential

ground movement associated with the fault

area. A fault is considered active if there has

been movement along it within the last 10,000

to 12,000 years.

How is it determined if a

prospective site is in a fault area?

A series of USGS maps, Preliminary Young

Fault Maps, Miscellaneous Field Investigation

916, identifies active faults.10 These maps,

however, might not be completely accurate

due to recent shifts in fault lines. If a prospective site is well outside the 200 foot area of

concern, no fault area considerations exist. If

it is unclear how close a prospective site is to

an active fault, further evaluation will be necessary. A geologic reconnaissance of the site

and surrounding areas can be useful in verifying that active faults do not exist at the site.

If a prospective site is in an area known or

suspected to be prone to faulting, you should

conduct a fault characterization to determine

if the site is near a fault. A characterization

includes identifying linear features that suggest the presence of faults within a 3,000-foot

radius of the site. Such features might be

shown or described on maps, aerial photographs,11 logs, reports, scientific literature,

or insurance claim reports, or identified by a

detailed field reconnaissance of the area.

If the characterization study reveals faults

within 3,000 feet of the proposed unit or lat-
Getting Started—Considering the Site

4-11

eral expansion, you should conduct further

investigations to determine whether any of

the faults are active within 200 feet of the

unit. These investigations can involve drilling

and trenching the subsurface to locate fault

zones and evidence of faulting. Perpendicular

trenching should be used on any fault within

200 feet of the proposed unit to examine the

seismic epicenter for indications of recent

movement.

What can be done if a prospective

site is in a fault area?

If an active fault exists on the site where

the unit is planned, consider placing the unit

200 feet back from the fault area. Even with

such setbacks, only place a unit in a fault area

if it is possible to ensure that no damage to

the unit’s structural integrity would result. A

setback of less than 200 feet might be adequate if ground movement would not damage

the unit.

If a lateral expansion or a new unit will be

located in an area susceptible to seismic activity, there are two particularly important issues

to consider: horizontal acceleration and

movement affecting side slopes. Horizontal

acceleration becomes a concern when a location analysis reveals that the site is in a zone

with a risk of horizontal acceleration in the

range of 0.1 g to 0.75 g (g = acceleration of

gravity). In these zones, the unit design

should incorporate measures to protect the

unit from potential ground shifts. To address

side slope concerns, you should conduct a

seismic stability analysis to determine the

most effective materials and gradients for protecting the unit’s slopes from any seismic

instabilities. Also, design the unit to withstand the impact of vertical accelerations.

If the unit is in an area susceptible to liquefaction, you should consider ground

improvement measures. These measures

include grouting, dewatering, heavy tamping,

and excavation. See Table 1 for examples of

techniques that are currently used.

Additional engineering options for fault

areas include the use of flexible pipes for

runoff and leachate collection, and redundant

containment systems. In the event of foundation soil collapse or heavy shifting, flexible

runoff and leachate collection pipes—along

with a bedding of gravel or permeable material—can absorb some of the shifting-related

stress to which the pipes are subjected. Also

consider a secondary containment measure,

such as an additional liner system. In earthquake-like conditions, a redundancy of this

nature might be necessary to prevent contamination of the surrounding area if the primary

liner system fails.

In this aerial view, the infamous San Andreas

fault slices through the Carrizo Plain east of

San Luis Obispo, California.

Source: USGS.
4-12

Getting Started—Considering the Site

D. Seismic Impact Zones

A seismic impact zone is an area having a

2 percent or greater probability that the maximum horizontal acceleration caused by an

earthquake at the site will exceed 0.1 g in 50

years. This seismic activity can damage

leachate collection and removal systems, leak

detection systems, or other unit structures

through excessive bending, shearing, tension,

and compression. If a unit’s structural components fail, leachate can contaminate surrounding areas. Therefore, for safety reasons,

it is recommended that a unit not be located

in a seismic impact zone. If a unit must be

sited in a seismic impact zone, the unit

should be designed to withstand earthquakerelated hazards, such as landslides, slope failures, soil compaction, ground subsidence,

and soil liquefaction.

Additionally, if you build a unit in a seismic impact zone, avoid rock and soil types

that are especially vulnerable to earthquake

shocks. These include very steep slopes of

weak, fractured, and brittle rock or unsaturated loess,12 which are vulnerable to transient

shocks caused by tensional faulting. Avoid

Source: RCRA Subtitle D (258) Seismic Design Guidance for Municipal Solid Waste Landfill Facilities. (EPA, 1995c).

Method Principle Most Suitable Soil Applications

Conditions/Types 

Blasting Shock waves and vibrations cause Saturated, clean sands; partly Induce liquefaction in controlled and 

limited liquefaction, displacement, saturated sands and silts after limited stages and increase relative density 

remolding, and settlement to higher flooding. to potentially nonliquefiable range. 

density.

Vibrocompaction Densification by vibration and Cohesionless soils with less Induce liquefaction in controlled and 

compaction of backfill material of sand than 20 percent fines. limited stages and increase relative density 

or gravel. to nonliquefiable condition. The dense 

column of backfill provides (a) vertical 

support, (b) drainage to relieve pore water 

pressure, and (c) shear resistance in horizontal and inclined directions. Used to 

stabilize slopes and strengthen potential 

failure surfaces.

Compaction piles Densification by displacement of pile Loose sandy soils; partly Useful in soils with fines. Increases relative 

volume and by vibration during driving; saturated clayey soils; loess. density to nonliquefiable condition. 

increase in lateral effective earth Provides shear resistance in horizontal and 

pressure. inclined directions. Used to stabilize 

slopes and strengthen potential failure 

surfaces.

Displacement and Highly viscous grout acts as radial All soils. Increase in soil relative density and 

compaction grout hydraulic jack when pumped in under horizontal effective stress. Reduce 

high pressure. liquefaction potential. Stabilize the ground 

against movement.

Mix-in-place piles Lime, cement, or asphalt introduced Sand, silts, and clays; all soft Slope stabilization by providing shear 

and walls through rotating auger or special in- or loose inorganic soils. resistance in horizontal and inclined 

place mixer. directions, which strengthens potential 

failure surfaces or slip circles. A wall could 

be used to confine an area of liquefiable 

soil.

Heavy tamping Repeated application of high- intensity Cohesionless soils best; other Suitable for some soils with fines; usable 

(dynamic impacts at surface. types can also be improved. above and below water. In cohesionless 

compaction) soils, induces liquefaction in controlled 

and limited stages and increases relative 

density to potentially nonliquefiable range. 

Table 1

Examples of Improvement Techniques for Liquefiable Soil Foundation Conditions

12 Loess is a wind-deposited, moisture-deficient silt that tends to compact when wet.
13 For information on ordering these maps, call 888 ASK-USGS, write to USGS Information Services, Box

25286, Denver, CO 80225, or fax 303 202-4693. Online information is available at

<ask.usgs.gov/products.html>.

14 To contact NEIC, call 303 273-8500, write to United States Geological Survey, National Earthquake

Information Center, Box 25046, DFC, MS 967, Denver, CO 80225, fax 303 273-8450, or e-mail

sedas@neic.cr.usgs.gov. For online information, visit: <neic.usgs.gov>.

Getting Started—Considering the Site

4-13

loess and saturated sand as well, because seismic shocks can liquefy them, causing sudden

collapse of structures. Similar effects are possible in sensitive cohesive soils when natural

moisture exceeds the soil’s liquid limit. For a

discussion of liquid limits, refer to the “Soil

Properties” discussion in Chapter 7, Section B

– Designing and Installing Liners. Earthquakeinduced ground vibrations can also compact

loose granular soils. This could result in large

uniform or differential settlements at the

ground surface.

How is it determined if a

prospective site is in a seismic

impact zone?

If a prospective site is in an area with no

history of earthquakes, then seismic impact

zone considerations might not exist. If it is

unclear whether the area has a history of seismic activity, then further evaluation will be

necessary. As a first step, consult the USGS

field study map series MF-2120, Probabilistic

Earthquake Acceleration and Velocity Maps for

the United States and Puerto Rico.

13 These maps

provide state- and county-specific information

about seismic impact zones. Additional information is available from the USGS National

Earthquake Information Center (NEIC),14

which maintains a database of known earthquake and fault zones. Further information

concerning the USGS National Seismic Hazard

Mapping Project can be accessed at <geohazards.cr.usgs.gov/eq>. USGS’s Web site also

allows you to find ground motion hazard

parameters (including peak ground acceleration and spectra acceleration) for your site by

entering a 5 digit ZIP code

<eqint.cr.usgs.gov/eq/html/zipcode.

shtml>, or a latitude-longitude coordinate

pair <eqint.cr.usgs.gov/eq/html/lookup.

shtml>. The USGS Web site explains how

these values can be used to determine the

probability of excedance for a particular level

of ground motion at your site. This can help

you determine if the structural integrity of the

unit is susceptible to damage from ground

motion.

For waste management unit siting purposes, use USGS’ recently revised Peak

Acceleration (%g) with 2 % Probability of

Exceedance in 50 Years maps available at 

<geohazards.cr.usgs.gov/eq/hazmapsdoc/

junecover.html>. It is important to note that

ground motion values having a 2 percent

probability of exceedance in 50 years are

approximately the same as those having 10

percent probability of being exceeded in 250

years. According to USGS calculations, the

annual exceedance probabilities of these two

differ by about 4 percent (for a more complete

discussion visit: <geohazards.cr.usgs.

gov/eq/faq/parm08.html>).

If a site is or might be in a seismic impact

zone, it is useful to analyze the effects of seismic activity on soils in and under the unit.

Computer software programs are available that

can evaluate soil liquefaction potential

(defined in Section C of this chapter). LIQUFAC, a software program developed by the

Naval Facilities Engineering Command in

Washington, DC, can calculate safety factors

for each soil layer in a given soil profile and

the corresponding one dimensional settlements due to earthquake loading.

What can be done if a

prospective site is in a seismic

impact zone?

If a waste management unit cannot be sited

outside a seismic impact zone, structural components of the unit—including liners, leachate

collection and removal systems, and surfacewater control systems—should be designed to

resist the earthquake-related stresses expected

in the local soil. You should consult professionals experienced in seismic analysis and
design to ensure that your unit is designed

appropriately. To determine the potential

effects of seismic activity on a structure, the

seismic design specialist should evaluate soil

behavior with respect to earthquake intensity.

This evaluation should account for soil

strength, degree of compaction, sorting (organization of the soil particles), saturation, and

peak acceleration of the potential earthquake.

After conducting an evaluation of soil

behavior, choose appropriate earthquake protection measures. These might include shallower slopes, dike and runoff control designs

using conservative safety factors, and contingency plans or backup systems for leachate

collection if primary systems are disrupted.

Unit components should be able to withstand

the additional forces imposed by an earthquake within acceptable margins of safety.

Additionally, well-compacted, cohesionless

embankments or reasonably flat slopes in

insensitive clay (clay that maintains its compression strength when remolded) are less

likely to fail under moderate seismic shocks

(up to 0.15 g - 0.20 g). Embankments made

of insensitive, cohesive soils founded on

cohesive soils or rock can withstand even

greater seismic shocks. For earthen embankments in seismic regions, consider designing

the unit with internal drainage and core

materials resistant to fracturing. Also, prior to

or during unit construction in a seismic

impact zone, you should evaluate excavation

slope stability to determine the appropriate

grade of slopes to minimize potential slip.

For landfills and waste piles, using shallower waste side slopes is recommended, as

steep slopes are more vulnerable to slides

and collapse during earthquakes. Use fill

sequencing techniques that avoid concentrating waste in one area of the unit for an

extended period of time. This prevents waste

pile side slopes from becoming too steep and

unstable and alleviates differential loading of

the foundation components. Placing too

much waste in one area of the unit can lead

to catastrophic shifting during an earthquake

or heavy seismic activity. Shifting of this

nature can cause failure of crucial system

components or of the unit in general.

In addition, seismic impact zones have

design issues in common with fault areas,

especially concerning soil liquefaction and

earthquake-related stresses. To address liquefaction, consider employing the soil improvement techniques described in Table 1.

Treating liquefiable soils in the vicinity of the

unit will improve foundation stability and

help prevent uneven settling or possible collapse of heavily saturated soils underneath or

near the unit.

To protect against earthquake-related

stresses, consider installing redundant liners

and special leachate collection and removal

system components, such as secondary liner

systems, composite liners, and leak detection

systems combined with a low permeability

soil layer. These measures function as backups to the primary containment and collection systems and provide a greater margin of

safety for units during possible seismic stresses. Examples of special leachate systems

include high-strength, flexible materials for

leachate containment systems; geomembrane

liner systems underlying leachate containment systems; and perforated polyvinyl chloride or high-density polyethylene piping in a

bed of gravel or other permeable material.

E. Unstable Areas

Siting in unstable areas should be avoided

because these locations are susceptible to naturally occurring or human-induced events or

forces capable of impairing the integrity of a

waste management unit. Naturally occurring

unstable areas include regions with poor soil

foundations, regions susceptible to mass

movement, or regions containing karst ter4-14

Getting Started—Considering the Site
rain, which can include hidden sinkholes.

Unstable areas caused by human activity can

include areas near cut or fill slopes, areas

with excessive drawdown of ground water,

and areas where significant quantities of oil

or natural gas have been extracted. If it is

necessary to site a waste management unit in

an unstable area, technical and construction

techniques should be considered to mitigate

against potential damage.

The three primary types of failure that can

occur in an unstable area are settlement, loss

of bearing strength, and sinkhole collapse.

Settlement can result from soil compression if

your unit is, or will be located in, an unstable

area over a thick, extensive clay layer. The

unit’s weight can force water from the compressible clay, compacting it and allowing the

unit to settle. Settlement can increase as

waste volume increases and can result in

structural failure of the unit if it was not

properly engineered. Settlement beneath a

waste management unit should be assessed

and compared to the elongation strength and

flexibility properties of the liner and leachate

collection pipe system. Even small amounts

of settlement can seriously damage leachate

collection piping and sumps. A unit should

be engineered to minimize the impacts of settlement if it is, or will be in an unstable area.

Loss of bearing strength is a failure mode

that occurs in soils that tend to expand and

rapidly settle or liquefy. Soil contractions and

expansions can increase the risk of leachate or

waste release. Another example of loss of bearing strength occurs when excavation near the

unit reduces the mass of soil at the toe of the

slope, thereby reducing the overall strength

(resisting force) of the foundation soil.

Catastrophic collapse in the form of sinkholes can occur in karst terrain. As water,

especially acidic water, percolates through

limestone, the soluble carbonate material dissolves, leaving cavities and caverns. Land

overlying caverns can collapse suddenly,

resulting in sinkholes that can be more than

100 feet deep and 300 feet wide.

How is it determined if a

prospective site is in an 

unstable area?

If a stability assessment has not been performed on a potential site, you should have a

qualified professional conduct one before

designing a waste management unit on the

prospective site. The qualified professional

should assess natural conditions, such as soil

geology and geomorphology, as well as

human-induced surface and subsurface features or events that could cause differential

ground settlement. Naturally unstable conditions can become more unpredictable and

destructive if amplified by human-induced

changes to the environment. If a unit is to be

built at an assessed site that exhibits stability

problems, tailor the design to account for any

instability detected. A stability assessment

typically includes the following steps:

Screen for expansive soils. Expansive

soils can lose their ability to support a foundation when subjected to certain natural or

human-induced events, such as heavy rain or

explosions. Expansive soils usually are clayrich and, because of their molecular structure, tend to swell and shrink by taking up

and releasing water. Such soils include smectite (montmorillonite group) and vermiculite

clays. In addition, soils rich in white alkali

(sodium sulfate), anhydrite (calcium sulfate),

or pyrite (iron sulfide) can also swell as water

content increases. These soils are more common in the arid western states.

Check for soil subsidence. Soils subject

to rapid subsidence include loesses, unconsolidated clays, and wetland soils. Unconsolidated clays can undergo considerable

compaction when oil or water is removed.

Similarly, wetland soils, which by their

Getting Started—Considering the Site

4-15
15 For information on ordering this map, call 888 ASK-USGS, write USGS Information Services, 

Box 25286, Denver, CO 80255, or fax 303 202-4693. Online information is available at 

<www-atlas.usgs.gov/atlasmap.html>.

nature are water-bearing, are also subject to

subsidence when water is withdrawn.

Look for areas subject to mass movement or slippage. Such areas are often situated on slopes and tend to have rock or soil

conditions conducive to downhill sliding.

Examples of mass movements include

avalanches, landslides, and rock slides. Some

sites might require cutting or filling slopes

during construction. Such activities can cause

existing soil or rock to slip.

Search for karst terrain. Karst features

are areas containing soluble bedrock, such as

limestone or dolomite, that have been dissolved and eroded by water, leaving characteristic physiographic features including

sinkholes, sinking streams, caves, large

springs, and blind valleys. The principal concern with karst terrains is progressive or catastrophic subsurface failure due to the

presence of sinkholes, solution cavities, and

subterranean caverns. Karst features can also

hamper detection and control of leachate,

which can move rapidly through hidden conduits beneath the unit. Karst maps, such as

Engineering Aspects of Karst, Scale 1:7,500,000,

Map No. 38077-AW-NA-07M-00, produced by

the USGS15 and state specific geological maps

can be reviewed to identify karst areas.

Scan for evidence of excessive groundwater drawdown or oil and gas extraction.

Removing underground water can increase

the effective overburden on the foundation

soils underneath the unit. Excessive drawdown of water might cause settlement or

bearing capacity

failure on the

foundation soils.

Extraction of oil

or natural gas

can have similar

effects.

Investigate

the geotechnical

and geological

characteristics

of the site. It is

important to

establish soil

strengths and

other engineering properties. A

geotechnical

engineering con4-16

Getting Started—Considering the Site

Subsidence, slippage, and

other kinds of slope failure

can damage structures.

Sinkholes, like this one that occurred just north of Orlando, Florida in 1981, are a risk of

development in Karst terrain. Left: aerial view (note baseball diamond for scale); right:

ground-level view. Photos courtesy of City of Winter Park, Florida public relations office.
sultant can accomplish this by performing

standard penetration tests, field vane shear

tests, and laboratory tests. This information

will determine how large a unit you can safely

place on the site. Other soil properties to

examine include water content, shear

strength, plasticity, and grain size distribution.

Examine the liquefaction potential. It is

extremely important to ascertain the liquefaction

potential of embankments, slopes, and foundation soils. Refer to Section C of this chapter for

more information about liquefiable soils.

What can be done if a

prospective site is in an 

unstable area?

It is advisable not to locate or expand your

waste management unit in an unstable area. If

your unit is or will be located in such an area,

you should safeguard the structural integrity

of the unit by incorporating appropriate measures into the design. The integrity of the unit

might be jeopardized if this is not done.

For example, to safeguard the structural

integrity of side slopes in an unstable area,

reduce slope height, flatten slope angle, excavate a bench in the upper portion of the slope,

or buttress slopes with compacted earth or rock

fill. Alternatively, build retaining structures,

such as retaining walls or slabs and piles. Other

approaches include the use of geotextiles and

geogrids to provide additional strength, wick

and toe drains to relieve excess pore pressures,

grouting, and vacuum and wellpoint pumping

to lower ground- water levels. In addition, surface drainage can be controlled to decrease

infiltration, thereby reducing the potential for

mud and debris slides.

Additional engineering concerns arise in

the case of waste management units in areas

containing karst terrain. The principal concern with karst terrains is progressive or catastrophic subsurface failure due to the

presence of sinkholes, solution cavities, and

subterranean caverns. Extensive subsurface

characterization studies should be completed

before designing and building in these areas.

Subsurface drilling, sinkhole monitoring, and

geophysical testing are direct means that can

be used to characterize a site. Geophysical

techniques include electromagnetic conductivity, seismic refraction, ground-penetrating

radar, and electrical resistivity (see the box

below for more information). More than one

technique should be used to confirm and correlate findings and anomalies, and a qualified

geophysicist should interpret the results of

these investigations. 

Remote sensing techniques, such as aerial

photograph interpretation, can also provide

additional information on karst terrains.

Surface mapping can help provide an understanding of structural patterns and relationships in karst terrains. An understanding of

local carbonate geology and stratigraphy can

help with the interpretation of both remote

sensing and geophysical data.

You should incorporate adequate engineering controls into any waste management unit

located in a karst terrain. In areas where karst

development is minor, loose soils overlying

the limestone can be excavated or heavily

compacted to achieve the needed stability.

Similarly, in areas where the karst voids are

relatively small, the voids can be filled with

slurry cement grout or other material.

Engineering solutions can compensate for

the weak geologic structures by providing

ground supports. For example, ground modifications, such as grouting or reinforced raft

foundations, could compensate for a lack of

ground strength in some karst areas. Raft

constructions, which are floating foundations

consisting of a concrete footing extending

over a very large area, reduce and evenly distribute waste loads where soils have a low

bearing capacity or where soil conditions are

variable and erratic. Note, however, that raft

foundations might not always prevent the

Getting Started—Considering the Site

4-17
extreme collapse and settlement that can

occur in karst areas. In addition, due to the

unpredictable and catastrophic nature of

ground failure in unstable areas, the construction of raft foundations and other

ground modifications tends to be complex

and can be costly, depending on the size of

the area.

F. Airport Vicinities

The vicinity of an airport includes not only

the facility itself, but also large reserved open

areas beyond the ends of runways. If a unit is

intended to be sited near an airport, there are

particular issues that take on added importance in such areas. You should familiarize

yourself with Federal Aviation Administration

(FAA) regulations and guidelines. The primary concern associated with waste management

units near airports is the hazard posed to aircraft by birds, which often feed at units managing putrescible waste. Planes can lose

propulsion when birds are sucked into jet

engines, and can sustain other damage in collisions with birds. Industrial waste management units that do not receive putrescible

wastes should not have a problem with birds.

Another area of concern for landfills and

waste piles near airports is the height of the

accumulated waste. If you own or operate

such a unit, you should exercise caution

when managing waste above ground level.

How is it determined if a

prospective site will be located

too close to an airport?

If the prospective site is not located near

any airports, additional evaluation is not necessary. If there is uncertainty whether the

prospective site is located near an airport,

obtain local maps of the area using the various

Internet resources previously discussed or

from state and local regulatory agencies to

identify any nearby public-use airports.

4-18

Getting Started—Considering the Site

Geophysical Techniques

Electromagnetic Conductivity or

Electromagnetic Induction (EMI). A transmitter

coil generates an electromagnetic field which

induces eddy currents in the earth located below

the transmitter. These eddy currents create secondary electromagnetic fields which are measured

by a receiver coil. The receiver coil produces an output voltage that can be related to subsurface conductivity variations. Analysis of these variations

allows users to map subsurface features, stratigraphic profiles, and the existence of buried objects.

Seismic Refraction. An artificial seismic source

(e.g., hammer, explosives) creates compression

waves that are refracted as they travel along geologic

boundaries. These refracted waves are detected by

electromechanical transducers (geophones) which

are attached to a seismograph that records the time

of arrival of all waves (refracted and non-refracted).

These travel times are compared and analyzed to

identify the number of stratigraphic layers and the

depth of each layer.

Ground-Penetrating Radar. A transmitting

antenna dragged along the surface of the ground

radiates short pulses of high-frequency radio

waves into the ground. Subsurface structures

reflect these waves which are recorded by a

receiving antenna. The variations in reflected

return signals are used to generate an image or

map of the subsurface structure.

Electrical Resistivity. An electrical current is

injected into the ground by a pair of surface electrodes (called the current electrodes). By measuring

the resulting voltage (potential field) between a second pair of electrodes (called the potential electrodes), the resistivity of subsurface materials is

measured. The measured resistivity is then compared to known values for different soil and rock

types. Increasing the distance between the two pairs

of electrodes increases the depth of measurement.
Topographic maps available from USGS are

also suitable for determining airport locations.

If necessary, FAA can provide information on

the location of all public-use airports. In accordance with FAA guidance, if a new unit or an

expansion of an existing unit will be within 5

miles of the end of a public-use airport runway, the affected airport and the regional FAA

office should be notified to provide them an

opportunity for review and comment.

What can be done if a

prospective site is in an 

airport vicinity?

If a proposed waste management unit or a

lateral expansion is to be located within

10,000 feet of an airport used by jet aircraft

or within 5,000 feet of an airport used only

by piston-type aircraft, design and operate

your unit so it does not pose a bird hazard to

aircraft. For above-ground units, design and

operate your unit so it does not interfere

with flight patterns. If it appears that height

is a potential concern, consider entrenching

the unit or choosing a site outside the airport’s flight patterns. Most nonhazardous

industrial waste management units do not

usually manage wastes that are attractive

food sources for birds, but if your unit handles waste that potentially attracts birds, take

precautions to prevent birds from becoming

an aircraft hazard. Discourage congregation

of birds near your unit by preventing water

from collecting on site; eliminating or covering wastes that might serve as a source of

food; using visual deterrents, including realistic models of the expected scavenger birds’

natural predators; employing sound deterrents, such as cannon sounds, distress calls

of scavenger birds, or the sounds of the

birds’ natural predators; removing nesting

and roosting areas (unless such removal is

prohibited by the Endangered Species Act);

or constructing physical barriers, such as a

canopy of fine wires or nets strung around

the disposal and storage areas when practical

or technically feasible.

G. Wellhead Protection

Areas

Wellhead protection involves protecting

the ground-water resources that supply public drinking water systems. A wellhead protection area (WHPA) is the area most

susceptible to contamination surrounding a

wellhead. WHPAs are designated and often

regulated to prevent public drinking water

sources from becoming contaminated. The

technical definition, delineation, and regulation of WHPAs vary from state to state. You

should contact your state or local regulatory

agency to determine what wellhead protection measures are in place near prospective

sites. Section II of this chapter provides

examples of how some states specify minimum allowable distances between waste

management units and public water supplies,

as well as drinking water wells. Locating a

waste management unit in a WHPA can create a potential avenue for drinking water contamination through accidental release of

leachate, contaminated runoff, or waste. In

addition, some states might have additional

restrictions for areas in designated “sole

source aquifier” systems.

How is it determined if a

prospective site is in a wellhead

protection area?

A list of state wellhead protection program

contacts is available on EPA’s Web site at

<www.epa.gov/ogwdw/safewater/source/

contacts.html>. Also, USGS, NRCS, local

water authorities, and universities can provide maps and further expertise that can help

you to identify WHPAs. If there is uncertainty

regarding the proximity of the prospective

site to a WHPA, contact the appropriate state

or local regulatory agency.

Getting Started—Considering the Site

4-19
What can be done if a

prospective site is in a wellhead

protection area?

If a new waste management unit or lateral

expansion will be located in a WHPA or suspected WHPA, consider design modifications

to help prevent any ground-water contamination. For waste management units placed

in these areas, work with state regulatory

agencies to ensure that appropriate groundwater barriers are installed between the unit

and the ground-water table. These barriers

should be designed using materials of

extremely low permeability, such as

geomembrane liners or low permeability soil

liners. The purpose of such barriers is to

prevent any waste, or leachate that has percolated through the waste, from reaching the

ground water and possibly affecting the public drinking water source.

In addition to ground-water barriers, the

use of leachate collection, leak detection, and

runoff control systems should also be considered. Leachate contamination is possibly the

greatest threat to a public ground-water supply posed by a waste management unit.

Incorporation of leachate collection, leak

detection, and runoff control systems should

further prevent any leachate from escaping

into the ground water. Further discussion

concerning liner systems, leachate collection

and removal systems, and leak detection systems is included in Chapter 7, Section

B–Designing and Installing Liners.

Control systems that separate storm-water

run-on from any water that has contacted

waste should also be considered. Proper control measures that redirect storm water to the

supply source area should help alleviate this

tendency. For additional information concerning storm water run-on and runoff control systems, refer to Chapter 6–Protecting

Surface Water.

II. Buffer Zone

Considerations

Many states require buffer zones between

waste management units and other nearby

land uses, such as schools. The size of a

buffer zone often depends on the type of

waste management unit and the land use of

the surrounding areas. You should consult

with state regulatory agencies and local advisory boards about buffer zone requirements

before constructing a new unit or expanding

an existing unit. A summary of state buffer

zone requirements is included in the appendix at the end of this chapter.

Buffer zones provide you with time and

space to mitigate situations where accidental

releases might cause adverse human health or

environmental impacts. The size of the buffer

zone will be directly related to the intended

benefit. These zones provide four primary

benefits: 

• Maintenance of quality of the surrounding ground water.

• Prevention of contaminant migration

off site.

• Protection of drinking water supplies.

• Minimization of nuisance conditions

perceived in surrounding areas.

Protection of ground water will likely be

the primary concern for all involved parties.

You should ensure that materials processed

and disposed at your unit are isolated from

ground-water resources. Placing your unit

further from the water table and potential

receptors, and increasing the number of

physical barriers between your unit and the

water table and potential receptors, provides

for ground-water protection. It is therefore

advised that, in addition to incorporating a

liner system, where necessary, into a waste

4-20

Getting Started—Considering the Site
management unit’s design, you select a site

where an adequate distance separates the bottom of a unit from the ground-water table.

(See the appendix for a summary of these

minimum separation distances.)16 In the event

of a release, this separation distance will

allow for corrective action and natural attenuation to protect ground water.17

Additionally, in the event of an unplanned

release, an adequate buffer zone will allow

time for remediation activities to control contaminants before they reach sensitive areas.

Buffer zones also provide additional protection for drinking water supplies. Drinking

water supplies include ground water, individual and community wells, lakes, reservoirs,

and municipal water treatment facilities.

Finally, buffer zones help maintain good

relations with the surrounding community by

protecting surrounding areas from any noise,

particulate emissions, and odor associated

with your unit. Buffer zones also help to prevent access by unauthorized people. For units

located near property boundaries, houses, or

historic areas, trees or earthen berms can provide a buffer to reduce noise and odors.

Planting trees around a unit can also improve

the aesthetics of a unit, obstruct any view of

unsightly waste, and help protect property

values in the surrounding community. When

planting trees as a buffer, place them so that

their roots will not damage the unit’s liner or

final cover.

A. Recommended Buffer

Zones

You should check with state and local officials to determine what buffer zones might

apply to your waste management unit. Areas

for which buffer zones are recommended

include property boundaries, drinking water

wells, other sources of water, and adjacent

houses or buildings.

Property boundaries. To minimize

adverse effects on adjacent properties, consider incorporating a buffer zone or separation

distance into unit design. You should consider planting trees or bushes to provide a natural buffer between your unit and adjacent

properties. 

Drinking water wells, surface-water

bodies, and public water supplies. Locating

a unit near or within the recharge area for

sole source aquifers and major aquifers,

coastal areas, surface-water bodies, or public

water supplies, such as a community well or

water treatment facility, also raises concerns.

Releases from a waste management unit can

pose serious threats to human health not only

where water is used for drinking, but also

where surface waters are used for recreation. 

Getting Started—Considering the Site

4-21

16 A detailed discussion of technical considerations concerning the design and installation of liner systems, both in situ soil liners and synthetic liners, is included in Chapter 7, Section B – Designing and

Installing Liners.

17 Natural attenuation can be defined as chemical and biological processes that reduce contaminant concentrations.

Many nearby areas and land uses, such as

schools, call for consideration of buffer zones.
4-22

18 For the full text of the Endangered Species Act, visit the U.S. House of Representatives Internet Law

Library Web site at <uscode.house.gov/download.htm>, under Title 16, Chapter 35.

Getting Started—Considering the Site

Houses or buildings. Waste management

units can present noise, odor, and dust problems for residents or businesses located on

adjacent property, thereby diminishing property values. Additionally, proximity to property boundaries can invite increased

trespassing, vandalism, and scavenging.

B. Additional Buffer Zones

There are several other areas for which to

consider establishing buffer zones, including

critical habitats, park lands, public roads, and

historic or archaeological sites.

Critical habitats. These are geographical

areas occupied by endangered or threatened

species. These areas contain physical or biological features essential to the proliferation of

the species. When designing a unit near a

critical habitat, it is imperative that the critical habitat be conserved. A buffer zone can

help prevent the destruction or adverse modification of a critical habitat and minimize

harm to endangered or threatened species.18

Park lands. A buffer between your unit

and park boundaries helps maintain the aesthetics of the park land. Park lands provide

recreational opportunities and a natural

refuge for wildlife. Locating a unit too close

to these areas can disrupt recreational qualities and natural wildlife patterns.

Public roads. A buffer zone will help

reduce unauthorized access to the unit,

reduce potential odor concerns, and improve

aesthetics for travelers on the nearby road.

Historic or archaeological sites. A waste

management unit located in close proximity

to one of these sites can adversely impact the

aesthetic quality of the site. These areas

include historic settlements, battlegrounds,

cemeteries, and Indian burial grounds. Also

check whether a prospective site itself has

historical or archaeological significance.

In summary, it is important to check with

local authorities to ensure that placement of

a new waste management unit or lateral

expansion of an existing unit will not conflict

with any local buffer zone criteria. You

should also review any relevant state or tribal

Buffer zones can help protect endangered

species and their habitats.

Historic sites call for careful consideration

of buffer zones.
regulations that specify buffer zones for your

unit. For units located near any sensitive

areas as described in this section, consider

measures to minimize any possible health,

environmental, and nuisance impacts.

III. Local Land Use

and Zoning

Considerations

In addition to location and buffer zone

considerations, become familiar with any

local land use and zoning requirements. Local

governments often classify the land within

their communities into areas, districts, or

zones. These zones can represent different

use categories, such as residential, commercial, industrial, or agricultural. You should

consider the compatibility of a planned new

unit or a planned lateral expansion with nearby existing and future land use, and contact

local authorities early in the siting process.

Local planning, zoning, or public works officials can discuss with you the development of

a unit, compliance with local regulations, and

available options. Local authorities might

impose conditions for protecting adjacent

properties from potential adverse impacts

from the unit.

Addressing local land use and zoning

issues during the siting process can prevent

these issues from becoming prominent concerns later. Land use and zoning restrictions

often address impacts on community and

recreational areas, historical areas, and other

critical areas. You should consider the proximity of a new unit or lateral expansion to

such areas and evaluate any potential adverse

effects it might have on these areas. For

example, noise, dust, fumes, and odors from

construction and operation of a unit could be

considered a nuisance and legal action could

be brought by local authorities or nearby

property owners.

In situations where land use and zoning

restrictions might cause difficulties in expanding or siting a unit, work closely with local

authorities to learn about local land use and

zoning restrictions and minimize potential

problems. Misinterpreting or ignoring such

restrictions can cause complications with

intended development schedules or designs.

In many cases, the use of vegetation, fences,

or walls to screen your activities can reduce

impacts on nearby properties. In addition, it

might be possible to request amendments,

rezonings, special exceptions, or variances to

restrictions. These administrative mechanisms

allow for flexibility in use and development of

land. Learning about local requirements as

early as possible in the process will maximize

the time available to apply for variances or

rezoning permits, or to incorporate screening

into the plans for your unit.

IV. Environmental

Justice

Considerations

In the past several years, there has been

growing recognition from communities and

federal and state governments that some

socioeconomic and racial groups might bear a

disproportionate burden of adverse environmental effects from waste management activities. President Clinton issued Executive Order

12898, Federal Actions to Address

Environmental Justice in Minority

Populations and Low-Income Populations, on

February 11, 1994.19 To be consistent with

the definition of environmental justice in this

executive order, you should identify and

address, as appropriate, disproportionately

high and adverse human health or environmental effects of waste management proGetting Started—Considering the Site

4-23

19 For the full text of Presidential Executive Order No. 12898 and additional information concerning

environmental justice issues go to EPA’s Web site at <es.epa.gov/program/iniative/justice/

justice.html>.
grams, policies, and activities on minority

and low-income populations.

One of the criticisms made by advocates of

environmental justice is that local communities endure the potential health and safety

risks associated with waste management

units without enjoying any of the economic

benefits. During unit siting or expansion,

address environmental justice concerns in a

manner that is most appropriate for the operations, the community, and the state or tribal

government. 

You should look for opportunities to minimize environmental impacts, improve the

surrounding environment, and pursue

opportunities to make the waste management

facility an asset to the community. When

planning these opportunities, it is beneficial

to maintain a relationship with all involved

parties based on honesty and integrity, utilize

cross-cultural formats and exchanges, and

recognize industry, state, and local knowledge of the issues. It is also important to take

advantage of all potential opportunities for

developing partnerships.

Examples of activities that incorporate

environmental justice issues include tailoring

activities to specific needs; providing interpreters, if appropriate; providing multilingual

materials; and promoting the formation of a

community/state advisory panel.

Tailor the public involvement activities

to the specific needs. Good public involvement programs are site-specific—they take

into account the needs of the facility, neighborhood, and state. There is no such thing

as a “one-size-fits-all” public involvement

program. Listening to each other carefully

will identify the specific environmental justice concerns and determine the involvement activities most appropriate to address

those needs.

Provide interpreters for public meetings.

Interpreters can be used to ensure the information is exchanged. Provide interpreters, as

needed, for the hearing impaired and for any

languages, other than English, spoken by a

significant percentage of the audience.

Provide multilingual fact sheets and

other information. Public notices and fact

sheets should be distributed in as many languages as necessary to ensure that all interested parties receive necessary information.

Fact sheets should be available for the visually impaired in the community on tape, in

large print, or braille.

Promote the formation of a community/

state advisory panel to serve as the voice of

the community. The Louisiana Department

of Environmental Quality, for example,

encourages the creation of environmental justice panels comprised of community members, industry, and state representatives. The

panels meet monthly to discuss environmental justice issues and find solutions to any

concerns identified by the group.

4-24

Getting Started—Considering the Site
Getting Started—Considering the Site

4-25

General Siting Considerations

■ Check to see if the proposed unit site is:

— In a 100-year floodplain.

— In or near a wetland area.

— Within 200 feet of an active fault.

— In a seismic impact zone.

— In an unstable area.

— Close to an airport.

— Within a wellhead protection area.

■ If the proposed unit site is in any of these areas:

— Design the unit to account for the area’s characteristics and minimize the unit’s impacts on

such areas.

— Consider siting the unit elsewhere.

Buffer Zone Considerations

(Note that many states require buffer zones between waste management units and other nearby land

uses.)

■ Check to see if the proposed unit site is near:

— The ground-water table.

— A property boundary.

— A drinking water well.

— A public water supply, such as a community well, reservoir, or water treatment facility.

— A surface-water body, such as a lake, stream, river, or pond.

— Houses or other buildings.

— Critical habitats for endangered or threatened species.

— Park lands.

— A public road.

— Historic or archaeological sites.

■ If the proposed unit site is near any of these areas or land uses, determine how large a buffer zone,

if any, is appropriate between the unit and the area or land use.

Considering the Site Activity List
4-26

Getting Started—Considering the Site

Local Land Use and Zoning Considerations

■ Contact local planning, zoning, and public works agencies to discuss restrictions that apply to the

unit.

■ Comply with any applicable restrictions, or obtain the necessary variances or special exceptions.

Environmental Justice Considerations

■ Determine whether minority or low-income populations would bear a disproportionate burden of

any environmental effects of the unit’s waste management activities.

■ Work with the local community to devise strategies to minimize any potentially disproportionate

burdens.

Considering the Site Activity List (cont.)
Getting Started—Considering the Site

4-27

Bagchi, A. 1994. Design, Construction, and Monitoring of Landfills. John Wiley & Sons Inc.

Das, B. M. 1990. Principles of Geotechnical Engineering. 2nd ed. Boston: PWS-Kent Publishing Co.

Federal Emergency Management Agency. How to Read a Flood Insurance Map. Web Site:

<www.fema.gov/nfip/readmap.htm>

Federal Emergency Management Agency. The National Flood Insurance Program Community Status Book.

Web Site: <www.fema.gov/nfip/>

Federal Emergency Management Agency. 1995. The Zone A Manual: Managing Floodplain Development in

Approximate Zone A Areas. FEMA 265.

Illinois Department of Energy and Natural Resources. 1990. Municipal Solid Waste Management Options:

Volume II: Landfills. 

Law, J., C. Leung, P. Mandeville, and A. H. Wu. 1996. A Case Study of Determining Liquefaction Potential of

a New Landfill Site in Virginia by Using Computer Modeling. Presented at WasteTech ’95, New Orleans, LA

(January).

Noble, George. 1992. Siting Landfills and Other LULUs. Technomic Publications.

Oregon Department of Environmental Quality. 1996. Wellhead Protection Facts. Web Site:

<www.deq.state.or.us/wq/groundwa/gwwell.htm>.

Terrene Institute.1996. American Wetlands: A Reason to Celebrate.

Texas Natural Resource Conservation Commission. 1983. Industrial Solid Waste Landfill Site Selection.

U.S. Army Corps of Engineers. 1995. Engineering and Design: Design and Construction of Conventionally

Reinforced Ribbed Mat Slabs (RRMS). ETL 1110-3-471.

U.S. Army Corps of Engineers. 1995. Engineering and Design: Geomembranes for Waste Containment

Applications. ETL 1110-1-172.

U.S. Army Corps of Engineers. 1992. Engineering and Design: Bearing Capacity of Soils. EM 1110-1-1905.

U.S. Army Corps of Engineers. 1992. Engineering and Design: Design and Construction of Grouted Riprap.

ETL 1110-2-334.

Resources
4-28

Getting Started—Considering the Site

U.S. Army Corps of Engineers. 1991. 1987 U.S. Army Corps of Engineers Wetlands Delineation Manual.

HQUSACE.

U.S. Army Corps of Engineers. 1984. Engineering and Design: Use of Geotextiles Under Riprap. ETL

1110-2-286.

U.S. EPA. 2000a. Social Aspects of Siting RCRA Hazardous Waste Facilities. EPA530-K-00-005.

U.S. EPA. 2000b. Siting of Hazardous Waste Management Facilities and Public Opposition. EPAOSW-0-00-809.

U.S. EPA. 1997. Sensitive Environments and the Siting of Hazardous Waste Management Facilities.

EPA530-K-97-003.

U.S. EPA. 1995a. OSWER Environmental Justice Action Agenda. EPA540-R-95-023.

U.S. EPA. 1995b. Decision-Maker’s Guide to Solid Waste Management, 2nd Ed. EPA530-R-95-023.

U.S. EPA. 1995c. RCRA Subtitle D (258) Seismic Design Guidance for Municipal Solid Waste Landfill

Facilities. EPA600-R-95-051.

U.S. EPA. 1995d. Why Do Wellhead Protection? Issues and Answers in Protecting Public Drinking Water

Supply Systems. EPA813-K-95-001.

U. S. EPA. 1994. Handbook: Ground Water and Wellhead Protection. EPA625-R-94-001.

U. S. EPA. 1993a. Guidelines for Delineation of Wellhead Protection Areas. EPA440-5-93-001.

U.S. EPA. 1993b. Solid Waste Disposal Facility Criteria: Technical Manual. EPA530-R-93-017.

U. S. EPA. 1992. Final Comprehensive State Ground-Water Protection Program Guidance. EPA100-R-93-001.

U. S. EPA. 1991. Protecting Local Ground-Water Supplies Through Wellhead Protection. EPA570-09-91-007.

U. S. EPA. 1988. Developing a State Wellhead Protection Program: A User’s Guide to Assist State Agencies

Under the Safe Drinking Water Act. EPA440-6-88-003.

U.S. Geological Survey. Preliminary Young Fault Maps, Miscellaneous Field Investigation 916. 

Resources (cont.)
Getting Started—Considering the Site

4-29

U.S. Geological Survey. Probabilistic Acceleration and Velocity Maps for the United States and Puerto Rico.

Map Series MF-2120.

U.S. House of Representatives. 1996. Endangered Species Act. Internet Law Library. Web Site:

<uscode.house.gov/title_16.htm>.

University of Illinois Center for Solid Waste Management and Research, Office of Technology Transfer. 1990.

Municipal solid waste landfills: Volume II: Technical issues. 

University of Illinois Center for Solid Waste Management and Research, Office of Technology Transfer. 1989.

Municipal Solid Waste Landfills: Vol. I: General Issues.

White House. Executive Order 12898 Federal Actions to Address Environmental Justice in Minority

Populations and Low-Income Populations.

Resources (cont.)
The universe of industrial wastes and unit types is broad and diverse. States have established

various approaches to address location considerations for the variety of wastes and units in

their states. The tables below summarize the range of buffer zone restrictions and most common buffer zone values specified for each unit type by some states to address their local concerns. The numbers in the tables are not meant to advocate the adoption of a buffer zone of

any particular distance; rather, they serve only as examples of restrictions states have individually developed.

• Surface impoundments. Restrictions with respect to buffer zones vary among states.

In addition, states allow exemptions or variances to these buffer zone restrictions on a

case-by-case basis. Table 1 presents the range of values and the most common value

used by states for each buffer zone category.

Table 1

State Buffer Zone Restrictions for Surface Impoundments

Buffer Zone Category Range of Values—minimum Most Common Value (number of distance (number of states states with this common value)

with this common value)

Groundwater Table 1 to 15 feet (4) 5 feet (2)

Property Boundaries 100 to 200 feet (4) 100 feet (2)

Drinking Water Wells 1,200 to 1,320 feet (2) 1,200 feet (1)

1,320 feet (1)

Public Water Supply 500 to 1,320 feet (4) 1,320 feet (2)

Surface Water Body 100 to 1,320 feet (4) 100 feet (2)

Houses or Buildings 300 to 1,320 feet (4) 1,320 feet (2)

Roads 1,000 feet (1) 1,000 feet (1)

4-30

Getting Started—Considering the Site

Appendix: State Buffer Zone Considerations
Getting Started—Considering the Site

4-31

• Landfills. Table 2 presents the range of values and the most common state buffer zone

restrictions for landfills.

Table 2

State Buffer Zone Restrictions for Landfills

Buffer Zone Category Range of Values—minimum Most Common Value (number of distance (number of states with states with this common value)

this common value)

Groundwater Table 1 to 15 feet (12) 5 feet (4)

Property Boundaries 20 to 600 feet (14) 100 feet (7)

Drinking Water Wells 500 to 1,320 feet (9) 500 feet (2)

600 feet (2)

1,200 feet (2)

Public Water Supply 400 to 5,280 feet (13) 1,200 feet (3)

Surface Water Body 100 to 2,000 feet (20) 100 feet (5)

1,000 feet (5)

Houses or Buildings 200 to 1,320 feet (14) 500 feet (7)

Roads 50 to 1,000 feet (8) 1,000 feet (5)

Park Land 1,000 to 5,280 feet (7) 1,000 feet (4)

Fault Areas 200 feet (2) 200 feet (2)
• Waste Piles. Table 3 presents the state buffer zone restrictions for waste piles. Of the

four states with buffer zone restrictions, only two states specified minimum distances.

Table 3

State Buffer Zone Restrictions for Waste Piles

Buffer Zone Category Range of Values-minimum Most Common Value (number of distance (number of states states with this common value)

with this common value)

Groundwater Table 4 feet* (1) 4 feet* (1)

Property Boundaries 50 feet (1) 50 feet (1)

Surface Water Body 50 feet (1) 50 feet (1)

Houses or Buildings or 200 feet (1) 200 feet (1)

Recreational Area

Historic Archeological Site Minimum distance (1) Minimum distance (1)

or Critical Habitat not specified not specified

* If no liner or storage pad is used, then this state requires four feet between the waste and

the seasonal high water table. 

4-32

Getting Started—Considering the Site
Getting Started—Considering the Site

4-33

• Land Application.20 Table 4 presents the range of values and the most common state

buffer zone restrictions for land application.

Table 4

State Buffer Zone Restrictions for Land Application 

Buffer Zone Category Range of Values-minimum Most Common Value (number of distance (number of states with states with this common value)

this common value)

Groundwater Table 4 to 5 feet (3) 4 feet (1)

5 feet (1)

Property Boundaries 50 to 200 feet (4) 50 feet (2)

Drinking Water Wells 200 to 500 feet (2) 200 feet (1)

500 feet (1)

Public Water Supply 300 to 5,280 feet (3) 300 feet (1)

1,000 feet (1)

5,280 feet (1)

Surface Water Body 100 to 1,000 feet (5) 100 feet (2)

Houses or Buildings 200 to 3,000 feet (6) 300 feet (2)

500 feet (2)

Park Land 2,640 feet (1) 2,640 feet (1)

Fault Areas 200 feet (1) 200 feet (1)

Max. Depth of Treatment 5 feet (1) 5 feet (1)

Pipelines 25 feet (1) 25 feet (1)

Critical Habitat No minimum distance set (2) No minimum distance set (2)

Soil Conditions Not on frozen, ice or snow (1) Not on frozen, ice or snow (1)

covered, or water saturated soils covered, or water saturated soils 

20 In the review of state regulations performed to develop Table 5, it was not possible to distinguish

between units used for treatment and units where wastes are added as a soil amendment. It is recommended that you consult applicable state agencies to determine which buffer zone restrictions are relevant to your land application unit.
Based on the review of state requirements, Table 5 presents the most common buffer zones

restrictions across all four unit types.

Table 5

Common Buffer Zone Restrictions Across All Four Unit Types

Buffer Zone Category Most Common Values

(total number of states for all unit types) (number of states with this common value)

Groundwater Table (20) 4 feet (4)

5 feet (4)

Property Boundaries (23) 50 feet (8)

100 feet (5)

Drinking Water Wells (13) 500 feet (3)

Public Water Supply (20) 1,000 feet (3)

1,200 feet (3)

5,280 feet (3)

Surface Water Body (30) 100 feet (5)

200 feet (5)

1,000 feet (7)

Houses or Buildings (25) 500 feet (9)

4-34

Getting Started—Considering the Site
Part II 

Protecting Air Quality

Chapter 5

Protecting Air Quality
Contents

I. Federal Airborne Emission Control Programs ..........................................................................................5-3

A. National Ambient Air Quality Standards..................................................................................................5-3

B. New Source Performance Standards ........................................................................................................5-3

C. National Emission Standards for Hazardous Air Pollutants ......................................................................5-4

D. Title V Operating Permits ......................................................................................................................5-10

E. Federal Airborne Emission Regulations for Solid Waste Management Activities ....................................5-10

1. Hazardous Waste Management Unit Airborne Emission Regulations ................................................5-10

2. Municipal Solid Waste Landfill Airborne Emission Regulations ........................................................5-10

3. Offsite Waste and Recovery Operations NESHAP ..............................................................................5-11

F. A Decision Guide to Applicable CAA Requirements ..............................................................................5-12

1. Determine Emissions from the Unit ..................................................................................................5-12

2. Is the Waste Management Unit Part of an Industrial Facility Which Is Subject to a CAA

Title V Opening Permit? ....................................................................................................................5-14

3. Conduct a Risk Evaluation Using One of the Following Options:......................................................5-17

II. Assessing Risk ........................................................................................................................................5-17

A. Assessing Risks Associated with Inhalation of Ambient Air ..................................................................5-17

B. IWAIR Model ........................................................................................................................................5-21

1. Emissions Model................................................................................................................................5-21

2. Dispersion Model ..............................................................................................................................5-21

3. Risk Model ........................................................................................................................................5-23

4. Estimation Process ............................................................................................................................5-23

5. Capabilities and Limitations of the Model..........................................................................................5-27

C. Site-specific Risk Analysis ......................................................................................................................5-28

III. Emission Control Techniques..................................................................................................................5-32

A. Controlling Particulate Matter ................................................................................................................5-32

1. Vehicular Operations ........................................................................................................................5-32

2. Waste Placement and Handling ........................................................................................................5-33

3. Wind Erosion ....................................................................................................................................5-35

B. VOC Emission Control Techniques........................................................................................................5-36

1. Choosing a Site to Minimize Airborne Emission Problems ................................................................5-36

2. Pretreatment of Waste........................................................................................................................5-36

3. Enclosure of Units ............................................................................................................................5-36

4. Treatment of Captured VOCs ............................................................................................................5-37

5. Special Considerations for Land Application Units ............................................................................5-38

Protecting Air Activity List ............................................................................................................................5-39
Contents

Resources ......................................................................................................................................................5-40

Figures:

Figure 1. Evaluating VOC Emission Risk ..................................................................................................5-13

Figure 2. Conceptual Site Diagram ............................................................................................................5-18

Figure 3. Emissions from WMU ................................................................................................................5-19

Figure 4. Forces That Affect Contaminant Plumes......................................................................................5-20

Figure 5. IWAIR Approach for Developing Risk or Protective Waste Concentrations ................................5-24

Figure 6. Screen 1, Method, Met Station, WMU ........................................................................................5-25

Figure 7. Screen 2, Wastes Managed ..........................................................................................................5-25

Tables:

Table 1. Industries for Which NSPSs Have Been Established ......................................................................5-5

Table 2. HAPs Defined in Section 112 of the CAA Amendments of 1990 ....................................................5-6

Table 3. Source Categories With MACT Standards ......................................................................................5-8

Table 4. Major Source Determination in Nonattainment Areas ..................................................................5-15

Table 5. Constituents Included in IWAIR ..................................................................................................5-22

Table 6. Source Characterization Models....................................................................................................5-29

Table 7. Example List of Chemical Suppressants........................................................................................5-34 
Protecting Air Quality—Protecting Air Quality

5-1

Health effects from airborne pollutants can be minor and

reversible (such as eye irritation), debilitating (such as

asthma), or chronic and potentially fatal (such as cancer). Potential health

impacts depend on many factors, including

the quantity of air pollution to which people

are exposed, the duration of exposures, and

the toxicity associated with specific pollutants. An air risk assessment takes these factors into account to predict the risk or

hazards posed at a particular site or facility.

Air releases from waste management units

include particulates or wind-blown dust and

gaseous emissions from volatile compounds

It is recommended that every facility

implement controls to address emissions of

airborne particulates. Particulates have immediate and highly visible impacts on surrounding neighborhoods. They can affect human

health and can carry constituents off site as

well. Generally, controls are achieved through

good operating practices.

For air releases from industrial waste management units, you need to know what regulatory requirements under the Clean Air Act

(CAA) apply to your facility, and whether those

requirements address waste management units.

The followup question for facilities whose

waste management units are not addressed by

CAA requirements, is “are there risks from air

releases that should be controlled?”

This Guide provides two tools to help you

answer these questions. First, this chapter

includes an overview of the major emission

control requirements under the CAA and a

decision guide to evaluate which of these

Protecting Air Quality

This chapter will help you address:

• Airborne particulates and air emissions that can cause human health

risks and damage the environment by adopting controls to minimize

particulate emissions. 

• Assessing risks associated with air emissions and implementing pollution prevention, treatment, or controls as needed to reduce risks

for a facility’s waste management units not addressed by requirements under the Clean Air Act.

• Using a Clean Air Act Title V permit, at facilities that must obtain

one, as a vehicle for addressing air emissions from certain waste

management units.

This chapter will help you address the following questions.

• Is a particular facility subject to CAA

requirements?

• What is an air risk assessment?

• Do waste management units pose risks

from volatile air emissions?

• What controls will reduce particulate

and volatile emissions from a facility?
5-2

Protecting Air Quality—Protecting Air Quality

might apply to a facility. The steps of the decision guide are summarized in Figure 1. Each

facility subject to any of these requirements

will most likely be required to obtain a CAA

Title V operating permit. The decision guide

will help you clarify some of the key facility

information you need to identify applicable

CAA requirements. 

If your answers in the decision guide indicate that the facility is or might be subject to

specific regulatory obligations, the next step is

to consult with EPA, state, or local air quality

program staff. Some CAA regulations are

industry-specific and operation-specific within

an industry, while others are pollutant specific

or specific to a geographic area. EPA, state, or

local air quality managers can help you precisely determine applicable requirements and

whether waste management units are

addressed by those requirements.

You might find that waste management

units are not addressed or that a specific facility clearly does not fit into any regulatory category under the CAA. It is then prudent to

look beyond immediate permit requirements

to assess risks associated with volatile organic

compounds (VOCs) released from the unit. A

two-tiered approach to this assessment is recommended, depending on the complexity and

amount of site specific data you have.

Limited Site-Specific Air Assessment:

The CD-ROM version of the Guide contains

the Industrial Waste Air Model (IWAIR). If a

waste contains any of the 95 constituents

included in the model, you can use this risk

model to assess whether VOC emissions pose

a risk that warrants additional emission controls or that could be addressed more effectively with pollution prevention or waste

treatment before placement in the waste management unit. The IWAIR model allows users

to supply inputs for an emission estimate and

for a dispersion factor for the unit.

Comprehensive Risk Assessment: This

assessment relies on a comprehensive analysis

of waste and site-specific data and use of models designed to assess multi-pathway exposures

to airborne contaminants. There are a number

of modeling tools available for this analysis.

You should consult closely with your air quality management agency as you proceed.

Airborne emissions are responsible for the loss of visibility between the left and right photographs of the Grand Canyon. Source: National Park Service, Air Resources Division.
Protecting Air Quality—Protecting Air Quality

5-3

1 42 U.S.C. § 7409

2 For a discussion of the history of the litigation over the revised ozone standard and EPA’s plan for

implementing it, including possible revisions to 40 CFR 50.9(b), see 67 FR 48896 (July 26, 2002).

I. Federal Airborne

Emission Control

Programs

Four major federal programs address airborne emissions that can degrade air quality.

For more information about the CAA and

EPA’s implementation of it, visit the

Technology Transfer Network, EPA’s premier

technical Web site for information transfer

and sharing related to air pollution topics, at

<www.epa.gov/ttn>.

If the facility is a major source or otherwise subject to Title V of the CAA, the owner

must obtain a Title V operating permit. These

permits are typically issued by the state air

permitting authority. As part of the permitting

process, you will be required to develop an

emissions inventory for the facility. Some

states have additional permitting requirements. Whether or not emissions from a

waste management unit will be specifically

addressed through the permit process

depends on a number of factors, including

the type of facility and state permitting

resources and priorities. It is prudent, however, where there are no applicable air permit

requirements to assess whether there might

be risks associated with waste management

units and to address these risks. 

A. National Ambient Air

Quality Standards

The CAA authorizes EPA to establish emission limits to achieve National Ambient Air

Quality Standards (NAAQS).1 EPA has designated NAAQS for the following criteria pollutants: ozone, sulfur dioxide, nitrogen dioxide,

lead, particulate matter (PM), and carbon

monoxide. The NAAQS establish individual

pollutant concentration ceilings that should

be rarely exceeded in a predetermined geographical area (National Ambient Air Quality

District). NAAQS are not enforced directly by

EPA. Instead, each state must submit a State

Implementation Plan (SIP) describing how it

will achieve or maintain NAAQS. Many SIPs

call for airborne emission limits on industrial

facilities.

If a waste emits VOCs, some of which are

precursors to ozone, the waste management

unit could be affected by EPA’s NAAQS for

ground-level ozone. Currently, states are

implementing an ozone standard of 0.12

parts per million (ppm) as measured over a

1-hour period. In 1997, EPA promulgated a

revised standard of 0.08 ppm with an 8-hour

averaging time to protect public health and

the environment over longer exposure periods2 (see 62 FR 38856, July 18, 1997). EPA is

currently developing regulations and guidance for implementing the 8-hour ozone

standard. EPA expects to designate areas as

attaining or not attaining the standard in

2004. At that time, areas not attaining the

standard will need to develop plans to control

emissions and to demonstrate how they will

reach attainment. Consult with your state to

determine whether efforts to comply with the

ozone NAAQS involve VOC emission limits

that apply to a specific facility. General questions about the 8-hour standard should be

directed to EPA’s Office of Air Quality

Planning and Standards, Air Quality

Strategies and Standards Division, Ozone

Policy and Strategies Group, MD-15,

Research Triangle Park, NC 27711, telephone

919 541-5244.

B. New Source

Performance Standards

New Source Performance Standards

(NSPSs) are issued for categories of sources

that cause or contribute significant air pollu-
5-4

Protecting Air Quality—Protecting Air Quality

tion that can reasonably be anticipated to

endanger public health or welfare. For industry categories, NSPSs establish national technology-based emission limits for air pollutants,

such as particulate matter (PM) or VOCs.

States have primary responsibility for assuring

that the NSPSs are followed. These standards

are distinct from NAAQS because they establish direct national emission limits for specified sources, while NAAQS establish air

quality targets that states meet using a variety

of measures that include emission limits. Table

1 lists industries for which NSPSs have been

established and locations of the NSPSs in the

Code of Federal Regulations. You should

check to see if any of the 74 New Source

Performance Standards (NSPSs)3 apply to the

facility.4 Any facility subject to a NSPS must

obtain a Title V permit (see Section D below.).

C. National Emission

Standards for Hazardous

Air Pollutants

Section 112 of the CAA Amendments of

19905 requires EPA to establish national standards to reduce emissions from a set of certain

pollutants called hazardous air pollutants

(HAPs). Section 112(b) contains a list of 188

HAPs (see Table 2) to be regulated by National

Emission Standards for Hazardous Air

Pollutants (NESHAPs) referred to as Maximum

Achievable Control Technology (MACT) standards, that are generally set on an industry-byindustry basis.

MACT standards typically apply to major

sources in specified industries; however, in

some instances, non-major sources also can be

subject to MACT standards. A major source is

defined as any stationary source or group of

stationary sources that (1) is located within a

contiguous area and under common control,

and (2) emits or has the potential to emit at

least 10 tons per year (tpy) of any single HAP

or at least 25 tpy of any combination of HAPs.

All fugitive emissions of HAPs, including emissions from waste management units, are to be

taken into account in determining whether a

stationary source is a major source. Each

MACT standard might limit specific operations, processes, or wastes that are covered.

Some MACT standards specifically cover waste

management units, while others do not. If a

facility is covered by a MACT standard, it

must be permitted under Title V (see below).

EPA has identified approximately 170 industrial categories and subcategories that are or will

be subject to MACT standards. Table 3 lists the

categories for which standards have been finalized, proposed, or are expected. The CAA calls

for EPA to promulgate the standards in four

phases. EPA is currently in the fourth and final

phase of developing proposed regulations.

CAA also requires EPA to assess the risk to

public health remaining after the implementation of NESHAPs and MACT standards. EPA

must determine if more stringent standards are

necessary to protect public health with an

ample margin of safety or to prevent an

adverse environmental effect. As a first step in

this process the CAA requires EPA to submit a

Report to Congress on its methods for making

the health risks from residual emissions determination. The final report, Residual Risk

Report to Congress (U.S. EPA, 1997b), was

signed on March 3, 1999 and is available from

EPA’s Web site at <www.epa.gov/ttn/oarpg/

t3/reports/risk_rep.pdf>. If significant residual risk exists after application of a MACT,

EPA must promulgate health-based standards

for that source category to further reduce HAP

emissions. EPA must set residual risk standards within 8 years after promulgation of

each NESHAP.

3 40 CFR Part 60.

4 While NSPSs apply to new facilities, EPA also established emission guidelines for existing facilities. 

5 42 U.S.C. § 7412.
Protecting Air Quality—Protecting Air Quality

5-5

Facility 40 CFR Part

60 subpart

Ammonium Sulfate Manufacture PP

Asphalt Processing & Asphalt Roofing Manufacture UU

Auto/ld Truck Surface Coating Operations MM

Basic Oxygen Process Furnaces after 6/11/73 N

Beverage Can Surface Coating Industry WW

Bulk Gasoline Terminals XX

Calciners and Dryers in Mineral Industry UUU

Coal Preparation Plants Y

Commercial & Industrial SW Incinerator Units CCCC

Electric Utility Steam Generating Units after 9/18/78 DA

Equipment Leaks of VOC in Petroleum Refineries GGG

Equipment Leaks of VOC in SOCMI VV

Ferroalloy Production Facilities Z

Flexible Vinyl & Urethane Coating & Printing FFF

Fossil-fuel Fired Steam Generators after 8/17/71 D

Glass Manufacturing Plants CC

Grain Elevators DD

Graphic Arts: Publication Rotogravure Printing QQ

Hot Mix Asphalt Facilities I

Incinerators E

Industrial Surface Coating, Plastic Parts TTT

Industrial Surface Coating-Large Appliances SS 

Industrial-Commercial-Institutional Steam Generation Unit DB

Kraft Pulp Mills BB

Large Municipal Waste Combustors after 9/20/94 EB

Lead-Acid Battery Manufacturing Plants KK

Lime Manufacturing HH

Magnetic Tape Coating Facilities SSS

Medical Waste Incinerators (MWI) after 6/20/96 EC

Metal Coil Surface Coating TT

Metallic Mineral Processing Plants LL

Municipal Solid Waste Landfills after 5/30/91 WWW

Municipal Waste Combustors (MWC) EA

New Residential Wood Heaters AAA

Nitric Acid Plants G

Nonmetallic Mineral Processing Plants OOO

Onshore Natural Gas Processing Plants, VOC Leaks KKK

Onshore Natural Gas Processing: SO2 Emissions LLL

Facility 40 CFR Part

60 subpart

Petroleum Dry Cleaners, Rated Capacity 84 Lb JJJ

Petroleum Refineries J

Petroleum Refinery Wastewater Systems QQQ

Phosphate Fertilizer-Wet Process Phosphoric Acid T

Phosphate Fertilizer-Superphosphoric Acid U

Phosphate Fertilizer-Diammonium Phosphate V

Phosphate Fertilizer-Triple Superphosphate W

Phosphate Fertilizers: GTSP Storage Facilities X

Phosphate Rock Plants NN

Polymer Manufacturing Industry DDD

Polymeric Coating of Supporting Substrates Fac. VVV

Portland Cement Plants F

Pressure Sensitive Tape & Label Surface Coating RR

Primary Aluminum Reduction Plants S

Primary Copper Smelters P

Primary Lead Smelters R

Primary Zinc Smelters Q

Rubber Tire Manufacturing Industry BBB

Secondary Brass and Bronze Production Plants M

Secondary Lead Smelters L

Sewage Treatment Plants O

Small Indust./Comm./Institut. Steam Generating Units DC

Small Municipal Waste Combustion Units AAAA

SOCMI - Air Oxidation Processes III

SOCMI - Distillation Operations NNN

SOCMI Reactors RRR

SOCMI Wastewater YYY

Stationary Gas Turbines GG

Steel Plants: Elec. Arc Furnaces after 08/17/83 AAA

Steel Plants: Electric Arc Furnaces AA

Storage Vessels for Petroleum Liquids (6/73–5/78) K

Storage Vessels for Petroleum Liquids (5/78–6/84) KA

Sulfuric Acid Plants H

Surface Coating of Metal Furniture EE

Synthetic Fiber Production Facilities HHH

Volatile Storage Vessel (Incl. Petroleum) after 7/23/84 KB

Wool Fiberglass Insulation Manufacturing Plants PPP

Table 1. Industries for Which NSPSs Have Been Established

For electronic versions of the 40 CFR Part 60 subparts referenced below, visit

<www.access.gpo.gov/nara/cfr>. Be sure to check the Federal Register for updates that have

been published since publication of this Guide.
CAS# CHEMICAL NAME CAS# CHEMICAL NAME CAS# CHEMICAL NAME

75-07-0 Acetaldehyde

60-35-5 Acetamide

75-05-8 Acetonitrile

98-86-2 Acetophenone

53-96-3 2-Acetylaminofluorene

107-02-8 Acrolein

79-06-1 Acrylamide

79-10-7 Acrylic acid

107-13-1 Acrylonitrile

107-05-1 Allyl chloride

92-67-1 4-Aminobiphenyl

62-53-3 Aniline

90-04-0 o-Anisidine

1332-21-4 Asbestos

71-43-2 Benzene (including benzene

from gasoline)

92-87-5 Benzidine

98-07-7 Benzotrichloride

100-44-7 Benzyl chloride

92-52-4 Biphenyl

117-81-7 Bis(2-ethylhexyl) phthalate

(DEHP)

542-88-1 Bis(chloromethyl)ether

75-25-2 Bromoform

106-99-0 1,3-Butadiene

156-62-7 Calcium cyanamide

133-06-2 Captan

63-25-2 Carbaryl

75-15-0 Carbon disulfide

56-23-5 Carbon tetrachloride

463-58-1 Carbonyl sulfide

120-80-9 Catechol

133-90-4 Chloramben

57-74-9 Chlordane

7782-50-5 Chlorine

79-11-8 Chloroacetic acid

532-27-4 2-Chloroacetophenone

108-90-7 Chlorobenzene

510-15-6 Chlorobenzilate

67-66-3 Chloroform

107-30-2 Chloromethyl methyl ether

126-99-8 Chloroprene

1319-77-3 Cresols/Cresylic acid (isomers

and mixture)

95-48-7 o-Cresol

108-39-4 m-Cresol

106-44-5 p-Cresol

98-82-8 Cumene

94-75-7 2,4-D, salts and esters

72-55-9 DDE

334-88-3 Diazomethane

132-64-9 Dibenzofurans

96-12-8 1,2-Dibromo-3-chloropropane

84-74-2 Dibutylphthalate

106-46-7 1,4-Dichlorobenzene(p)

91-94-1 3,3-Dichlorobenzidene

111-44-4 Dichloroethyl ether (Bis(2-

chloroethyl)ether)

542-75-6 1,3-Dichloropropene

62-73-7 Dichlorvos

111-42-2 Diethanolamine

121-69-7 N,N-Diethyl aniline (N,NDimethylaniline)

64-67-5 Diethyl sulfate

119-90-4 3,3-Dimethoxybenzidine

60-11-7 Dimethyl aminoazobenzene

119-93-7 3,3’-Dimethyl benzidine

79-44-7 Dimethyl carbamoyl chloride

68-12-2 Dimethyl formamide

57-14-7 1,1-Dimethyl hydrazine

131-11-3 Dimethyl phthalate

77-78-1 Dimethyl sulfate

534-52-1 4,6-Dinitro-o-cresol, and salts

51-28-5 2,4-Dinitrophenol

121-14-2 2,4-Dinitrotoluene

123-91-1 1,4-Dioxane (1,4-

Diethyleneoxide)

122-66-7 1,2-Diphenylhydrazine

106-89-8 Epichlorohydrin (l-Chloro- 2,3-

epoxypropane)

106-88-7 1,2-Epoxybutane

140-88-5 Ethyl acrylate

100-41-4 Ethyl benzene

51-79-6 Ethyl carbamate (Urethane)

75-00-3 Ethyl chloride (Chloroethane)

106-93-4 Ethylene dibromide

(Dibromoethane)

107-06-2 Ethylene dichloride (1,2-

Dichloroethane)

107-21-1 Ethylene glycol

151-56-4 Ethylene imine (Aziridine)

75-21-8 Ethylene oxide

96-45-7 Ethylene thiourea

75-34-3 Ethylidene dichloride (1,1-

Dichloroethane)

50-00-0 Formaldehyde

76-44-8 Heptachlor

118-74-1 Hexachlorobenzene

87-68-3 Hexachlorobutadiene

77-47-4 Hexachlorocyclopenta-diene

67-72-1 Hexachloroethane

822-06-0 Hexamethylene-1,6-diisocyanate

680-31-9 Hexamethylphosphor-amide

110-54-3 Hexane

302-01-2 Hydrazine

7647-01-0 Hydrochloric acid

7664-39-3 Hydrogen fluoride

(Hydrofluoric acid)

123-31-9 Hydroquinone

78-59-1 Isophorone

58-89-9 Lindane (all isomers)

108-31-6 Maleic anhydride

67-56-1 Methanol

72-43-5 Methoxychlor

74-83-9 Methyl bromide

(Bromomethane)

74-87-3 Methyl chloride

(Chloromethane)

71-55-6 Methyl chloroform (1,1,1-

Trichloroethane)

78-93-3 Methyl ethyl ketone (2-

Butanone)

60-34-4 Methyl hydrazine

74-88-4 Methyl iodide (Iodomethane)

108-10-1 Methyl isobutyl ketone

(Hexone)

624-83-9 Methyl isocyanate

80-62-6 Methyl methacrylate

1634-04-4 Methyl tert butyl ether

101-14-4 4,4-Methylene bis(2-chloroaniline)

75-09-2 Methylene chloride

(Dichloromethane)

101-68-8 Methylene diphenyl diisocyanate (MDI)

101779 4,4’-Methylenedianiline

91-20-3 Naphthalene

98-95-3 Nitrobenzene

92-93-3 4-Nitrobiphenyl

100-02-7 4-Nitrophenol

79-46-9 2-Nitropropane

684-93-5 N-Nitroso-N-methylurea

62-75-9 N-Nitrosodimethylamine

59-89-2 N-Nitrosomorpholine

56-38-2 Parathion

82-68-8 Pentachloronitrobenzene

(Quintobenzene)

87-86-5 Pentachlorophenol

108-95-2 Phenol

106-50-3 p-Phenylenediamine

75-44-5 Phosgene

7803-51-2 Phosphine

Protecting Air Quality—Protecting Air Quality

5-6

Table 2

HAPs Defined in Section 112 of the CAA Amendments of 1990
Protecting Air Quality—Protecting Air Quality

5-7

CAS# CHEMICAL NAME CAS# CHEMICAL NAME CAS# CHEMICAL NAME

Table 2

HAPs Defined in Section 112 of the CAA Amendments of 1990 (cont)

7723-14-0 Phosphorus

85-44-9 Phthalic anhydride

1336-36-3 Polychlorinated biphenyls

(Aroclors)

1120-71-4 1,3-Propane sultone

57-57-8 beta-Propiolactone

123-38-6 Propionaldehyde

114-26-1 Propoxur (Baygon)

78-87-5 Propylene dichloride (1,2-

Dichloropropane)

75-56-9 Propylene oxide

75-55-8 1,2-Propylenimine (2-Methyl

aziridine)

91-22-5 Quinoline

106-51-4 Quinone (p-Benzoquinone)

100-42-5 Styrene

96-09-3 Styrene oxide

1746-01-6 2,3,7,8-Tetrachlorodi-benzo-pdioxin

79-34-5 1,1,2,2-Tetrachloroethane

127-18-4 Tetrachloroethylene

(Perchloroethylene)

7550-45-0 Titanium tetrachloride

108-88-3 Toluene

95-80-7 2,4-Toluene diamine

584-84-9 2,4-Toluene diisocyanate

95-53-4 o-Toluidine

8001-35-2 Toxaphene (chlorinated camphene)

120-82-1 1,2,4-Trichlorobenzene

79-00-5 1,1,2-Trichloroethane

79-01-6 Trichloroethylene

95-95-4 2,4,5-Trichlorophenol

88-06-2 2,4,6-Trichlorophenol

121-44-8 Triethylamine

1582-09-8 Trifluralin

540-84-1 2,2,4-Trimethylpentane

108-05-4 Vinyl acetate

593-60-2 Vinyl bromide

75-01-4 Vinyl chloride

75-35-4 Vinylidene chloride (1,1-

Dichloroethylene)

1330-20-7 Xylenes (mixed isomers)

95-47-6 o-Xylenes

108-38-3 m-Xylenes

106-42-3 p-Xylenes

[none] Antimony Compounds

[none] Arsenic Compounds (inorganic

including arsine)

[none] Beryllium Compounds

[none] Cadmium Compounds

[none] Chromium Compounds

[none] Cobalt Compounds

[none] Coke Oven Emissions

[none] Cyanide Compoundsa

[none] Glycol ethersb

[none] Lead Compounds

[none] Manganese Compounds

[none] Mercury Compounds

[none] Fine mineral fibersc

[none] Nickel Compounds

[none] Polycylic Organic Matterd

[none] Radionuclides (including

radon)e

[none] Selenium Compounds

NOTE: For all listings above which contain the word “compounds” and for glycol ethers, the following applies: Unless otherwise specified,

these listings are defined as including any unique chemical substance that contains the named chemical (i.e., antimony, arsenic, etc.) as part

of that chemical’s infrastructure.

a X’CN where X = H’ or any other group where a formal dissociation can occur. For example KCN or Ca(CN)2.

b On January 12, 1999 (64 FR 1780), EPA proposed to modify the definition of glycol ethers to exclude surfactant alcohol ethoxylates and

their derivatives (SAED). On August 2, 2000 (65 FR 47342), EPA published the final action. This action deletes each individual compound in a group called the surfactant alcohol ethoxylates and their derivatives (SAED) from the glycol ethers category in the list of hazardous air pollutants (HAP) established by section 112(b)(1) of the Clean Air Act (CAA). EPA also made conforming changes in the

definition of glycol ethers with respect to the designation of hazardous substances under the Comprehensive Environmental Response,

Compensation, and Liability Act (CERCLA).

“The following definition of the glycol ethers category of hazardous air pollutants applies instead of the definition set forth in 42 U.S.C.

7412(b)(1), footnote 2: Glycol ethers include mono- and di-ethers of ethylene glycol, diethylene glycol, and triethylene glycol R-

(OCH2CH2)n-OR’

Where:

n= 1, 2, or 3

R= alkyl C7 or less, or phenyl or alkyl substituted phenyl

R’= H, or alkyl C7 or less, or carboxylic acid ester, sulfate, phosphate, nitrate, or sulfonate.

c Includes mineral fiber emissions from facilities manufacturing or processing glass, rock, or slag fibers (or other mineral derived fibers) of

average diameter 1 micrometer or less. (Currently under review.)

d Includes organic compounds with more than one benzene ring, and which have a boiling point greater than or equal to 100°C.

(Currently under review.)

e A type of atom which spontaneously undergoes radioactive decay.
Protecting Air Quality—Protecting Air Quality

5-8

Source Category Federal Register Citation 

Fuel Combustion

Coal- and Oil-fired Electric Utility Steam 

Generating Units 65 FR 79825(N) 12/20/00

Combustion Turbines *

Engine Test Facilities *

Industrial Boilers *

Institutional/Commercial Boilers *

Process Heaters *

Reciprocating Internal Combustion Engines*

Rocket Testing Facilities *

Non-Ferrous Metals Processing

Primary Aluminum Production 62 FR 52383(F) 10/7/97

Primary Copper Smelting 63 FR 19582(P) 4/20/98

Primary Lead Smelting 64 FR 30194(F) 6/4/99

Primary Magnesium Refining *

Secondary Aluminum Production 65 FR 15689(F) 3/23/00

Secondary Lead Smelting 60 FR 32587(F) 6/23/95

Ferrous Metals Processing

Coke Ovens: Charging, Top Side, and 

Door Leaks 58 FR 57898(F) 10/27/93

Coke Ovens: Pushing, Quenching and 

Battery Stacks 66 FR 35327(P) 7/3/01

Ferroalloys Production

Silicomanganese and Ferromanganese 64 FR 27450(F) 5/20/00

Integrated Iron and Steel Manufacturing 66 FR 36835(P) 7/13/01

Iron Foundries *

Steel Foundries *

Steel Pickling–HCl Process Facilities and 

Hydrochloric Acid Regeneration Plants 64 FR 33202(F) 6/22/99

Mineral Products Processing

Asphalt Processing *

Asphalt Roofing Manufacturing *

Asphalt/Coal Tar Application–Metal Pipes *

Clay Products Manufacturing *

Lime Manufacturing *

Mineral Wool Production. 64 FR 29490(F) 6/1/99

Portland Cement Manufacturing 64 FR 31897(F) 6/14/99

Refractories Manufacturing *

Taconite Iron Ore Processing *

Wool Fiberglass Manufacturing 64 FR 31695(F) 6/14/99

Petroleum and Natural Gas Production and Refining

Oil and Natural Gas Production 64 FR 32610(F) 6/17/99

Natural Gas Transmission and Storage 64 FR 32610(F) 6/17/99

Petroleum Refineries–Catalytic Cracking 

Units, Catalytic Reforming Units, and 

Sulfur Recovery Units 63 FR 48890(P) 9/11/98

Petroleum Refineries–Other Sources Not 

Distinctly Listed 60 FR 43244(F) 8/18/95

Liquids Distribution

Gasoline Distribution (Stage 1) 59 FR 64303(F) 12/14/94

Source Category Federal Register Citation

Marine Vessel Loading Operations 60 FR 48399(F) 9/19/95

Organic Liquids Distribution 

(Non-Gasoline) *

Surface Coating Processes

Aerospace Industries 60 FR 45956(F) 9/1/15

Auto and Light Duty Truck *

Flat Wood Paneling 64 FR 63025(N) 11/18/99

Large Appliance 65 FR 81134(P) 12/22/00

Magnetic Tapes 59 FR 64580(F) 12/15/94

Manufacture of Paints, Coatings, and 

Adhesives *

Metal Can *

Metal Coil 65 FR 44616(P) 7/18/00

Metal Furniture *

Miscellaneous Metal Parts and Products *

Paper and Other Webs 65 FR 55332(P) 9/13/00

Plastic Parts and Products *

Printing, Coating, and Dyeing of Fabrics *

Printing/Publishing 61 FR 27132(F) 5/30/96

Shipbuilding and Ship Repair 60 FR 64330(F) 12/16/96

Wood Building Products *

Wood Furniture 60 FR 62930(F) 12/7/95

Waste Treatment and Disposal

Hazardous Waste Incineration 64 FR 52828(F) 9/30/99

Municipal Solid Waste Landfills 65 FR 66672(P) 11/7/00

Off-Site Waste and Recovery Operations 61 FR 34140(F) 7/1/96

Publicly Owned Treatment Works 64 FR 57572(F) 10/26/99

Site Remediation *

Agricultural Chemicals Production

Pesticide Active Ingredient Production 64 FR 33549(F) 6/23/99

Fibers Production Processes

Acrylic Fibers/Modacrylic Fibers 64 FR 34853(F) 6/30/99

Spandex Production 65 FR 76408(P) 12/6/00

Food and Agriculture Processes

Manufacturing of Nutritional Yeast 66 FR 27876(F) 5/21/01

Solvent Extraction for Vegetable Oil 

Production 66 FR 19006(F) 4/12/01

Vegetable Oil Production 66 FR 8220(N) 1/30/01

Pharmaceutical Production Processes

Pharmaceuticals Production 66 FR 40121(F) 6/1/99

Polymers and Resins Production

Acetal Resins Production 64 FR 34853(F) 6/30/99

Acrylonitrile-Butadiene-Styrene Production 61 FR 48208(F) 9/12/96

Alkyd Resins Production *

Amino Resins Production 65 FR 3275(F) 1/20/00

Boat Manufacturing 66 FR 44218(F) 8/22/01

Butyl Rubber Production 61 FR 46906(F) 9/5/96

Cellulose Ethers Production 65 FR 52166(P) 8/28/00

Epichlorohydrin Elastomers Production 61 FR 46906(F) 9/5/96

Table 3

Source Categories With MACT Standards
Protecting Air Quality—Protecting Air Quality

5-9

This table contains final rules (F), proposed rules (P), and notices (N) promulgated as of February 2002. It does

not identify corrections or clarifications to rules. An * denotes sources required by Section 112 of the CAA to have

MACT standards by 11/15/00 for which proposed rules are being prepared but have not yet been published.

Table 3

Source Categories With MACT Standards (cont.)

Source Category Federal Register Citation

Epoxy Resins Production 60 FR 12670(F) 3/8/95

Ethylene-Propylene Rubber Production 61 FR 46906(F) 9/5/96

Flexible Polyurethane Foam Production 63 FR 53980(F) 10/7/98

Hypalon (tm) Production 61 FR 46906(F) 9/5/96

Maleic Anhydride Copolymers Production *

Methyl Methacrylate-Acrylonitrile 

Butadiene-Styrene Production 61 FR 48208(F) 9/12/96

Methyl Methacrylate-Butadiene-Styrene 

Terpolymers Production 61 FR 48208(F) 9/12/96

Neoprene Production 61 FR 46906(F) 9/5/96

Nitrile Butadiene Rubber Production 61 FR 46906(F) 9/5/96

Nitrile Resins Production 61 FR 48208(F) 9/12/96

Non-Nylon Polyamides Production 60 FR 12670(F) 3/8/95

Phenolic Resins Production 65 FR 3275(F) 1/20/00

Polybutadiene Rubber Production 61 FR 46906(F) 9/5/96

Polycarbonates Production 64 FR 34853(F) 6/30/99

Polyester Resins Production *

Polyether Polyols Production 64 FR 29420(F) 6/1/99

Polyethylene Terephthalate Production 61 FR 48208(F) 9/12/96 

Polymerized Vinylidene Chloride 

Production *

Polymethyl Methacrylate Resins Production*

Polystyrene Production 61 FR 48208(F) 9/12/96

Polysulfide Rubber Production 61 FR 46906(F) 9/5/96 

Polyvinyl Acetate Emulsions Production *

Polyvinyl Alcohol Production *

Polyvinyl Butyral Production *

Polyvinyl Chloride and Copolymers 

Production 65 FR 76958(P) 12/8/00

Reinforced Plastic Composites Production 66 FR 40324(P) 8/2/01

Styrene-Acrylonitrile Production 61 FR 48208(F) 9/12/96

Styrene-Butadiene Rubber and Latex 

Production 61 FR 46906(F) 9/5/96

Production of Inorganic Chemicals

Ammonium Sulfate Production–

Caprolactam By-Product Plants *

Carbon Black Production 65 FR 76408(P) 12/6/00

Chlorine Production *

Cyanide Chemicals Manufacturing 65 FR 76408(P) 12/6/00

Fumed Silica Production 64 FR 63025(N) 11/18/99

Hydrochloric Acid Production *

Hydrogen Fluoride Production 64 FR 34853(F) 6/30/99

Phosphate Fertilizers Production 64 FR 31358(F) 6/10/99

Phosphoric Acid Manufacturing 64 FR 31358(F) 6/10/99

Production of Organic Chemicals

Ethylene Processes 65 FR 76408(P) 12/6/00

Source Category Federal Register Citation

Quaternary Ammonium Compounds 

Production *

Synthetic Organic Chemical 

Manufacturing 59 FR 19402(F) 4/22/94

Miscellaneous Processes

Benzyltrimethylammonium Chloride 

Production *

Carbonyl Sulfide Production *

Chelating Agents Production *

Chlorinated Paraffins Production *

Chromic Acid Anodizing 60 FR 04948(F) 1/25/95

Combustion Sources at Kraft, Soda, and 

Sulfite Pulp and Paper Mills 66 FR 3180(F) 1/12/01

Commercial Dry Cleaning 

(Perchloroethylene)–Transfer Machines 58 FR 49354(F) 9/22/93

Commercial Sterilization Facilities 59 FR 62585(F) 12/6/94

Decorative Chromium Electroplating 60 FR 04948(F) 1/25/95

Ethylidene Norbornene Production *

Explosives Production *

Flexible Polyurethane Foam Fabrication 

Operations 66 FR 41718(P) 8/8/01

Halogenated Solvent Cleaners 59 FR 61801(F) 12/2/94

Hard Chromium Electroplating 60 FR 04948(F) 1/25/95

Hydrazine Production *

Industrial Cleaning (Perchloroethylene)–

Dry-to-Dry machines 58 FR 49354(F) 9/22/93

Industrial Dry Cleaning 

(Perchloroethylene)–Transfer Machines 58 FR 49354(F) 9/22/93

Industrial Process Cooling Towers 59 FR 46339(F) 9/8/94

Leather Finishing Operations 67 FR 9155(F) 2/27/02 

Miscellaneous Viscose Processes 65 FR 52166(F) 8/28/00

OBPA/1,3-Diisocyanate Production *

Paint Stripping Operations *

Photographic Chemicals Production *

Phthalate Plasticizers Production *

Plywood and Composite Wood Products *

Pulp and Paper Production 65 FR 80755(F) 12/22/00

Rubber Chemicals Manufacturing *

Rubber Tire Manufacturing 63 FR 62414(P) 10/18/00

Semiconductor Manufacturing *

Symmetrical Tetrachloropyridine 

Production *

Tetrahydrobenzaldehyde Manufacture 63 FR 26078(F) 5/21/98

Wet-Formed Fiberglass Mat Production 65 FR 34277(P) 5/26/00
Protecting Air Quality—Protecting Air Quality

D. Title V Operating

Permits

For many facilities, the new federal operating permit program established under Title

V of the CAA will cover all sources of airborne emissions.6 Generally, it requires a permit for any facility emitting or having the

potential to emit more than 100 tpy of any

air pollutants though lower thresholds apply

in non-attainment areas.7 Permits are also

required for all sources subject to MACT or

NSPS standards, the Title IV acid rain program, and new source review permits under

Parts C and D of Title V. All airborne emission requirements that apply to an industrial

facility, including emission limitations, operational requirements, monitoring requirements, and reporting requirements, will be

incorporated in its operating permit. A Title

V permit provides a vehicle for ensuring that

existing air quality control requirements are

appropriately applied to facility emission

units.

Under the new program, operating permits

that meet federal requirements will generally

be issued by state agencies. In developing

individual permits, states can determine

whether to explicitly apply emission limitations and controls to waste management

units. See Section F of this chapter (A

Decision Guide to Applicable CAA

Requirements), and consult with federal,

state, and local air program staff to determine

if your waste management unit is subject to

airborne emission limits and controls under

CAA regulations. Listings of EPA regional and

state air pollution control agencies can be

obtained from the States and Territorial Air

Pollution Program Administrators (STAPPA)

& Association of Local Air Pollution Control

Officials (ALAPCO). STAPPA/ALAPCO’s Web

site is <www.cleanairworld.org/scripts/

us_temp.asp?id=307>.

E. Federal Airborne

Emission Regulations for

Solid Waste

Management Activities

While EPA has not established airborne

emission regulations for industrial waste management units under RCRA, standards developed for hazardous waste management units

and municipal solid waste landfills (MSWLFs)

can serve as a guide in evaluating the need for

controls at specific units.

1. Hazardous Waste

Management Unit Airborne

Emission Regulations

Under Section 3004(n) of RCRA, EPA

established standards for the monitoring and

control of airborne emissions from hazardous

waste treatment, storage, and disposal facilities. Subparts AA, BB, and CC of 40 CFR Part

264 address VOC releases from process vents,

equipment leaks, tanks, surface impoundments, and containers. Summaries of

Subparts AA, BB, and CC are provided in the

text box on the next page.

2. Municipal Solid Waste Landfill

Airborne Emission Regulations

On March 12, 1996, EPA promulgated airborne emission regulations for large new and

existing MSWLFs.8 These regulations apply to

all new MSWLFs constructed or modified on

6 Federal Operating Permit Regulations were promulgated as 40 CFR Part 71 on July 1, 1996 and

amended on February 19, 1999 to cover permits in Indian Country and states without fully approved

Title V programs.

7 Under CAA Section 302(g), “air pollutant” is defined as any pollutant agent or combination of agents,

including any physical, chemical, biological, or radioactive substance or matter which is emitted into

or otherwise enters the ambient air.

8 61 FR 9905; March 12, 1996, codified at 40 CFR Subpart WWW and CC (amended 63 FR 32750,

June 16, 1998). 5-10
Protecting Air Quality—Protecting Air Quality

5-11

or after May 30, 1991, and to

existing landfills that have

accepted waste on or after

November 8, 1987. In addition

to methane, MSWLFs potentially

emit non-methane organic compounds (NMOCs) in the gases

generated during waste decomposition, as well as in combustion of the gases in control

devices, and from other sources,

such as dust from vehicle traffic

and emissions from leachate

treatment facilities or maintenance shops. Under the regulations, any affected MSWLF that

emits more than 50 Mg/yr (55

tpy) of NMOCs is required to

install controls.

Best demonstrated technology

requirements for both new and

existing municipal landfills prescribe installation of a welldesigned and well-operated gas

collection system and a control

device. The collection system

should be designed to allow

expansion for new cells that

require controls. The control

device (presumed to be a combustor) must demonstrate either

an NMOC reduction of 98 percent by weight in the collected

gas or an outlet NMOC concentration of no more than 20 parts

per million by volume (ppmv).

3. Offsite Waste and

Recovery

Operations NESHAP

On July 1, 1996, EPA established standards for offsite waste

and recovery operations

Summary of Airborne Emission

Regulations for Hazardous Waste

Management Units

Subpart AA regulates organic emissions from

process vents associated with distillation, fractionation,

thin film evaporation, solvent extraction, and air or

stream stripping operations (40 CFR §§264.1030-

1036). Subpart AA only applies to these types of units

managing hazardous waste streams with organic concentration levels of at least 10 parts per million by

weight (ppmw). Subpart AA regulations require facilities with covered process vents to either reduce total

organic emissions from all affected process vents at the

facility to below 3 lb/h and 3.1 tons/yr, or reduce emissions from all process vents by 95 percent through the

use of a control device, such as a closed-vent system,

vapor recovery unit, flare, or other combustion unit.

Subpart BB sets inspection and maintenance

requirements for equipment, such as valves, pumps,

compressors, pressure relief devices, sampling connection systems, open-ended valves or lines, flanges, or

control devices that contain or contact hazardous

wastes with organic concentrations of at least 10 percent by weight (40 CFR §§264.1050-1065). Subpart

BB does not establish numeric criteria for reducing

emissions, it simply establishes monitoring, leak detection, and repair requirements.

Subpart CC establishes controls on tanks, surface

impoundments, and containers in which hazardous

waste has been placed ( 40 CFR §§264.1080-1091). It

applies only to units containing hazardous waste with

an average organic concentration greater than 500

ppmw. Units managing hazardous waste that has been

treated to reduce the concentrations of organics by 95

percent are exempt. Non-exempt surface impoundments must have either a rigid cover or, if wastes are

not agitated or heated, a floating membrane cover.

Closed vent systems are required to control the emissions from covered surface impoundments. These control systems must achieve the same 95 percent emission

reductions described above under Subpart AA.
(OSWRO) that emit HAPs.9 To be covered by

OSWRO, a facility must emit or have the

potential to emit at least 10 tpy of any single

HAP or at least 25 tpy of any combination of

HAPs. It must receive waste, used oil, or used

solvents from off site that contain one or

more HAPs.10 In addition, the facility must

operate one of the following: a hazardous

waste treatment, storage, or disposal facility;

RCRA-exempt hazardous wastewater treatment operation; nonhazardous wastewater

treatment facility other than a publicly owned

treatment facility; or a RCRA-exempt hazardous waste recycling or reprocessing operation, used solvent recovery operation, or used

oil recovery operation. 

OSWRO contains MACT standards to

reduce HAP emissions from tanks, surface

impoundments, containers, oil-water separators, individual drain systems, other material

conveyance systems, process vents, and

equipment leaks. For example, OSWRO

establishes two levels of air emission controls

for tanks depending on tank design capacity

and the maximum organic HAP vapor pressure of the offsite material in the tank. For

process vents, control devices must achieve a

minimum of 95 percent organic HAP emission control. To control HAP emissions from

equipment leaks, the facility must implement

leak detection and repair work practices and

equipment modifications for those equipment

components containing or contacting offsite

waste having a total organic HAP concentration greater than 10 percent by weight (see

40 CFR 63.683(d) cross ref. to 40 CFR

63.680 (c) (3)).

F. A Decision Guide to

Applicable CAA

Requirements

The following series of questions, summarized in Figure 1, is designed to help you identify CAA requirements that might apply to a

facility. This will not give you definitive

answers, but can provide a useful starting point

for consultation with federal, state, or local permitting authorities to determine which requirements apply to a specific facility and whether

such requirements address waste management

units at the facility. If a facility is clearly not

subject to CAA requirements, assessing potential risks from VOC emissions at a waste management unit using the IWAIR or a site-specific

risk assessment is recommended.

The following steps provide a walk

through of this evaluation process:

1. Determining Emissions From

the Unit

a) Determining VOC’s present in the

waste (waste characterization). Then

assume all the VOC’s are emitted

from the unit, or

b) Estimating emissions using an emissions model. This also requires waste

characterization. The CHEMDAT8

model is a logical model for these

types of waste units. You can use the

EPA version on the Internet or the

one contained in the IWAIR modeling tool for the Guide, or

c) Measuring emissions from the unit.

While this is the most resource intensive alternative, measured data will

provide the most accurate information.

9 61 FR 34139; July 1, 1996, as amended, 64 FR 38970 (July 20, 1999) and 66 FR 1266 (January 8,

2001).

10 OSWRO identified approximately 100 HAPs to be covered. This HAP list is a subset of the CAA

Section 112 list.

Protecting Air Quality—Protecting Air Quality

5-12
Protecting Air Quality—Protecting Air Quality

5-13

Characterize waste for potential air emissions

Conduct a risk evaluation using either:

a. Industrial Waste Air

Model (IWAIR)

b. Site-specific risk

assessment 

You should conduct a more sitespecific risk assessment 

You should operate the unit in accordance with the 

recommendations of this guidance.

You should reduce risk to acceptable levels using treatment, controls, or waste minimization 

Does 

the waste

contain any of the 95 

listed contaminants 

in IWAIR?

Is 

the total 

risk for the unit

acceptable?

No further 

evaluation is 

indicated

Facility is subject

to an air permit.

Consult with

state/local 

permitting 

authority

Is the unit part 

of an industrial facility 

which is subject to a CAA Title V 

operating permit by virtue of being:

a. considered a major source; or 

b. subject to NSPSs; or

c. considered a major source of HAPs and subject to

NESHAP or MACT standards; or 

d. subject to the acid rain program; or 

e. a unit subject to the 

OSWRO NESHAP?

NO

NO

NO

YES

YES

OR

YES

Figure 1. Evaluating VOC Emission Risk
11 EPA can designate additional source categories subject to Title V operating permit requirements.

12 Implementation of air emission controls can generate new residual waste. Ensure that these wastes are

managed appropriately, in compliance with state requirements and consistent with the Guide.

2. Is the Waste Management

Unit Part of an Industrial

Facility That Is Subject to a

CAA Title V Operating

Permit?

A facility is subject to a Title V operating

permit if it is considered a major source of air

pollutants, or is subject to a NSPS, NESHAP,

or Title IV acid rain provision.11 As part of the

permitting process, the facility should develop

an emissions inventory. Some states have

additional permitting requirements. If a facility is subject to a Title V operating permit, all

airborne emission requirements that apply to

an industrial facility, including emission limitations as well as operational, monitoring, and

reporting requirements, will be incorporated

in its operating permit. You should consult

with appropriate federal, state, and local air

program staff to determine whether your

waste management unit is subject to air emission limits and controls.12

If you answer yes to any of the questions

in items a. through e. below, the facility is

subject to a Title V operating permit. Consult

with the appropriate federal, state, and/or

local permitting authority.

Whether or not emissions from waste

management unit(s) will be specifically

addressed through the permit process

depends on a number of factors, including

the type of facility and CAA requirements

and state permitting resources and priorities.

It is prudent, when there are no applicable

air permit requirements, to assess whether

there might be risks associated with waste

management units and to address these

potential risks.

If you answer no to all the questions

below, continue to Step 3.

a. Is the facility considered a major

source?

If the facility meets any of the following

three definitions, it is considered a major

source (under 40 CFR § 70.2) and subject to

Title V operating permit requirements.

i. Any stationary source or group of

stationary sources that emits or has

the potential to emit at least 100 tpy

of any air pollutant.

ii. Any stationary source or group of

stationary sources that emits or has

the potential to emit at least 10 tpy

of any single HAP or at least 25 tpy

of any combination of HAPs.

iii. A stationary source or group of stationary sources subject to the nonattainment area provisions of CAA Title

I that emits, or has the potential to

emit, above the threshold values for

its nonattainment area category. The

nonattainment area category and the

source’s emission levels for VOCs and

NOx, particulate matter (PM-10), and

carbon monoxide (CO) determine

whether the stationary source meets

the definition of a “major source.”

For nonattainment areas, stationary

sources are considered “major

5-14

Protecting Air Quality—Protecting Air Quality

Stationary source is defined as any

building, structure, facility, or installation

that emits or may emit any regulated air

pollutant or any hazardous air pollutant

listed under Section 112 (b) of the Act.

An air pollutant is defined as any air pollution agent or combination of agents,

including a physical, chemical, biological,

radioactive substance or matter which is

emitted into or otherwise enters the ambient air.
sources” if they emit or have the

potential to emit at least the levels

found in Table 4 below.

If yes, the facility is subject to a Title V

operating permit. Consult with the appropriate federal, state, and/or local permitting

authority.

If no, continue to determine whether the

facility is subject to a Title V operating permit.

b. Is the facility subject to NSPSs?

Any stationary source subject to a standard

of performance under 40 CFR Part 60 is subject to NSPS. (A list of NSPSs can be found in

Table 1 above.)

If yes, the facility is subject to a Title V

operating permit. Consult with the appropriate federal, state, and/or local permitting

authority.

If no, continue to determine if the facility

is subject to a Title V operating permit. 

c. Is the facility a major source of

HAPs as defined by Section 112 of

CAA and subject to a NESHAP or

MACT standard?

Under Title V of CAA, an operating permit

is required for all facilities subject to a MACT

standard. NESHAPs or MACT standards are

national standards to reduce HAP emissions.

Each MACT standard specifies particular

operations, processes, and/or wastes that are

covered. EPA has identified approximately

170 source categories and subcategories that

are or will be subject to MACT standards.

(Table 3 above lists the source categories for

which EPA is required to promulgate MACT

standards.) MACT standards have been or

will be promulgated for all major source categories of HAPs and for certain area sources. 

If yes, the facility should be permitted

under CAA Title V. Consult with the appropriate federal, state, and/or local permitting

authority. 

If no, continue to determine if the facility

must obtain a Title V operating permit.

d. Is the facility subject to the acid rain

program under Title IV of CAA?

If a facility, such as a

fossil-fuel fired power

plant, is subject to

emission reduction

requirements or limitations under the acid

rain program, it must

obtain a Title V operating permit (40 CFR §

72.6). The acid rain

program focuses on the

reduction of annual sulfur dioxide and nitrogen oxides emissions.

Protecting Air Quality—Protecting Air Quality

5-15

13 The nonattainment categories are based upon the severity of the area’s pollution problems. The four categories for VOCs and NOx range from Moderate to Extreme. Moderate areas are the closest to meeting the

attainment standard, and require the least amount of action. Nonattainment areas with more serious air

quality problems must implement various control measures. The worse the air quality, the more controls

areas will have to implement. PM-10 and CO have only two categories, Moderate and Serious. 

Nonattainment VOCs or NOx PM-10 CO

Area Category13

Marginal or 100 tpy 100 tpy 100 tpy

Moderate

Serious 50 tpy 70 tpy 50 tpy

Severe 25 tpy — —

Extreme 10 tpy — —

Table 4.

Major Source Determination in Nonattainment Areas
If yes, the facility must obtain a Title V

permit. Consult with the appropriate federal,

state, and/or local permitting authority. 

When you consult with the appropriate

permitting authority, it is important to clarify

whether waste management units at the facility are addressed by the requirements. If

waste management units will not be

addressed through the permit process, you

should evaluate VOC emission risks.

If no, continue to determine if the facility

must obtain a Title V operating permit. 

e. Is the waste management unit

subject to the OSWRO NESHAP?

This is just an example of the types

of questions you will need to

answer to determine whether a

NESHAP or MACT standard covers

your facility. 

To be covered by the OSWRO standards,

your facility must meet all these conditions:

i. Be identified as a major source of

HAP emissions.

ii. Receive waste, used oil, or used solvents (subject to certain exclusions,

40 CFR 63.680 (b) (2)) from off site

that contain one or more HAPs.14

iii. Operate one of the following six

types of waste management or recovery operations (see 40 CFR 63.680

(a) (2)):

• Hazardous waste treatment, storage,

or disposal facility.

• RCRA-exempt hazardous wastewater

treatment operation.

• Nonhazardous wastewater treatment

facility other than a publicly owned

treatment facility.

• RCRA-exempt hazardous waste recycling or reprocessing operation.

• Used solvent recovery operations.

• Used oil recovery operations. 

If yes, the unit should be covered by the

OSWRO standards and Title V permitting.

Consult with the appropriate federal, state,

and/or local permitting authority.

If no, it is highly recommended that you

conduct an air risk evaluation as set out in

step 3.

5-16

Protecting Air Quality—Protecting Air Quality

A major source under Title III is

defined as any stationary source or

group of stationary sources that emits or

has the potential to emit at least 10 tpy

of any single hazardous air pollutant

(HAP) or at least 25 tpy of any combination of HAPs. 

An area source is any stationary

source which is not a major source but

which might be subject to controls. Area

sources represent a collection of facilities

and emission points for a specific geographic area. Most area sources are

small, but the collective volume of large

numbers of facilities can be a concern in

densely developed areas, such as urban

neighborhoods and industrial areas.

Examples of areas sources subject to

MACT standards include chromic acid

anodizing, commercial sterilization facilities, decorative chromium electroplating, hard chromium electroplating,

secondary lead smelting, and halogenated solvent cleaners. 

HAPs are any of the 188 pollutants

listed in Section 112(b) of CAA. (Table 2

above identifies the 188 HAPs.)

14 OSWRO identified approximately 100 HAPs to be covered. This HAP list is a subset of the CAA

Section 112 list.
3. Conducting a Risk Evaluation

Using One of the Following

Options:

a. Using IWAIR included with the

Guide if your unit contains any of the

95 contaminants that are covered in

the model.

b. Initiating a site-specific risk assessment for individual units. Total all

target constituents from all applicable

units and consider emissions from

other sources at the facility as well.

II. Assessing Risk

Air acts as a medium for the transport of

airborne contamination and, therefore, constitutes an exposure pathway of potential

concern. Models that can predict the fate and

transport of chemical emissions in the atmosphere can provide an important tool for evaluating and protecting air quality. The

Industrial Waste Air Model (IWAIR) included

in the Guide was developed to assist facility

managers, regulatory agency staff, and the

public in evaluating inhalation risks from

waste management unit emissions. Although

IWAIR is simple to use, it is still essential to

understand the basic concepts of atmospheric

modeling to be able to interpret the results

and understand the nature of any uncertainties. The purpose of this section is to provide

general information on the atmosphere,

chemical transport in the atmosphere, and

the risks associated with inhalation of chemicals so you can understand important factors

to consider when performing a risk assessment for the air pathway. 

From a risk perspective, because humans

are continuously exposed to air, the presence

of chemicals in air is important to consider in

any type of assessment. If chemicals build up

to high concentrations in a localized area,

human health can be compromised. The concentration of chemicals in a localized area and

the resulting air pollution that can occur in the

atmosphere is dependent upon the quantity

and the rate of the emissions from a source

and the ability of the atmosphere to disperse

the chemicals. Both meteorological and geographic conditions in a local area will influence the emission rate and subsequent

dispersion of a chemical. For example, the

meteorologic stability of the atmosphere, a factor dependent on air temperature, influences

whether the emission stream will rise and mix

with a larger volume of air (resulting in the

dilution of pollutants) or if the emissions

stream will remain close to the ground. Figure

2 is a conceptual diagram of a waste site illustrating potential paths of human exposure

through air.

A. Assessing Risks Associated

with Inhalation of

Ambient Air 

In any type of risk assessment, there are

basic steps that are necessary for gathering

and evaluating data. An overview of some of

these steps is presented in this section to

assist you in understanding conceptually the

information discussed in the IWAIR section

(Section B). The components of a risk assessment that are discussed in this section are:

identification of chemicals of concern, source

characterization, exposure assessment, and

risk characterization. Each of these steps is

described below as it applies specifically to

risk resulting from the inhalation of organic

chemicals emitted from waste management

units to the ambient air.

Identification of Chemicals of Concern

A preliminary step in any risk assessment

is the identification of chemicals of concern.

These are the chemicals present that are

anticipated to have potential health effects as

Protecting Air Quality—Protecting Air Quality

5-17
a result of their concentrations or toxicity

factors. An assessment is performed for a

given source, to evaluate chemical concentrations and toxicity of different chemicals.

Based on these factors along with potential

mechanisms of transport and exposure pathways, the decision is made to include or

exclude chemicals in the risk assessment. 

Source Characterization

In this step, the critical aspects of the

source (e.g., type of WMU, size, chemical

concentrations, location) are necessary to

obtain. When modeling an area source, such

as those included in the Guide, the amount

of a given chemical that volatilizes and disperses from a source is critically dependent

on the total surface area exposed. The source

characterization should include information

on the surface area and elevation of the unit.

The volatilization is also dependent on other

specific attributes related to the waste management practices. Waste management practices of importance include application

frequency in land application units and the

degree of aeration that occurs in a surface

impoundment. Knowledge of the overall content of the waste being deposited in the

WMU is also needed to estimate chemical

volatilization. Depending on its chemical

characteristics, a chemical can bind with the

other constituents in a waste, decreasing its

emissions to the ambient air. Source characterization involves defining each of these key

parameters for the WMU being modeled. The

accuracy of projections concerning volatilization of chemicals from WMUs into ambient

air is improved if more site-specific information is used in characterizing the source.

Exposure Assessment

The goal of an exposure assessment is to

estimate the amount of a chemical that is

available and is taken in by an individual,

typically referred to as a receptor. An exposure assessment is performed in two steps: 1)

the first step uses fate and transport modeling to determine the chemical concentration

in air at a specified receptor location and, 2)

the second step estimates the amount of the

chemical the receptor will intake by identifying life-style activity patterns. The first step,

the fate and transport modeling, uses a combination of an emission and dispersion model

to estimate the amount of chemical that individuals residing or working within the vicini5-18

Protecting Air Quality—Protecting Air Quality

Figure 2. Conceptual Site Diagram
ty of the source are exposed to through

inhalation of ambient air. When a chemical

volatilizes from a WMU into the ambient air,

it is subjected to a number of forces that

result in its diffusion and transport away from

the point of release. 

In modeling the movement of the volatile

chemical away from the WMU, it is often

assumed that the chemical behaves as a

plume (i.e., the chemical is continuously

emitted into the environment) whose movement is modeled to produce estimated air

concentrations at points of interest. This

process is illustrated in Figure 3.

The pattern of diffusion and movement of

chemicals that volatilize from WMUs depends

on a number of interrelated factors. The ultimate concentration and fate of emissions to

the air are most significantly impacted by

three meteorologic conditions: atmospheric

stability, wind speed, and wind direction.

These meteorologic factors interact to determine the ultimate concentration of a pollutant in a localized area. 

• Atmospheric stability: The stability

of the atmosphere is influenced by

the vertical temperature structure of

the air above the emission source. In

a stable environment, there is little or

no movement of air parcels, and,

consequently, little or no movement

and mixing of contaminants. In such

a stable air environment, chemicals

become “trapped” and unable to

move. Conversely, in an unstable

environment there is significant mixing and therefore greater dispersion

and dilution of the plume.15

• Prevailing wind patterns and their

interaction with land features: The

nature of the wind patterns immediately surrounding the WMU can significantly impact the local air

concentrations of airborne chemicals.

Prevailing wind patterns combine

with topographic features such as

hills and buildings to affect the

movement of the plume. Upon

release, the initial direction that emissions will travel is the direction of the

wind. The strength of the wind will

determine how dilute the concentration of the pollutant will be in that

direction. For example, if a strong

wind is present at the time the pollutants are released, it is likely the pollutants will rapidly leave the source

and become dispersed quickly into a

large volume of air. 

Protecting Air Quality—Protecting Air Quality

5-19

15 An example of an unstable air environment is one in which the sun shining on the earth’s surface has

resulted in warmer air at the earth’s surface. This warmer air will tend to rise, displacing any cooler air

that is on top of it. As these air parcels essentially switch places, significant mixing occurs.

Figure 3. Emissions from a WMU
In addition to these factors affecting the

diffusion and transport of a plume away from

its point of release, the concentration of specific chemicals in a plume can also be affected by depletion. As volatile chemicals are

transported away from the WMU, they can

be removed from the ambient air through a

number of depletion mechanisms including

wet deposition (the removal of chemicals due

to precipitation) and dry deposition (the

removal of chemicals due to the forces of

gravity and impacts of the plume on features

such as vegetation). Chemicals can also be

transformed chemically as they come in contact with the sun’s rays (i.e., photochemical

degradation). Figure 4 illustrates the forces

acting to transport and deplete the contaminant plume.

Because the chemicals being considered in

IWAIR are volatiles and semi-volatiles and the

distances of transport being considered are

relatively short, the removal mechanisms

shown in the figure are likely to have a relatively minor effect on plume concentration

(both wet and dry deposition have significantly greater effects on airborne particulates).

Once the constituent’s ambient outdoor

concentration is determined, the receptor’s

extent of contact with the pollutant must be

characterized. This step involves determining

the location and activity patterns relevant to

the receptor being considered. In IWAIR, the

receptors are defined as residents and workers located at fixed distances from the WMU,

and the only route of exposure considered

for these receptors is the inhalation of

volatiles. Typical activity patterns and body

physiology of workers and residents are used

to determine the intake of the constituent.

Intake estimates quantify the extent to which

5-20

Protecting Air Quality—Protecting Air Quality

Figure 4. Forces That Affect Contaminant Plumes.
the individual is exposed to the contaminant

and are a function of the breathing rate,

exposure concentration, exposure duration,

exposure frequency, exposure averaging time

(for carcinogens), and body weight.

Estimated exposures are presented in terms of

the mass of the chemical per kilogram of

receptor body weight per day.

Risk Characterization

The concentrations that an individual takes

into his or her body that were determined during the exposure assessment phase are combined with toxicity values to generate risk

estimates. Toxicity values used in IWAIR

include inhalation-specific cancer slope factors

(CSFs) for carcinogenic effects and reference

concentrations (RfCs) for noncancer effects.

These are explained in the General Risk

Section in Chapter 1—Understanding Risk

and Building Partnerships. Using these toxicity

values, risk estimates are generated for carcinogenic effects and noncancer effects. Risk estimates for carcinogens are summed by IWAIR.

B. IWAIR Model

IWAIR is an interactive computer program

with three main components: an emissions

model; a dispersion model to estimate fate

and transport of constituents through the

atmosphere and determine ambient air concentrations at specified receptor locations;

and a risk model to calculate either the risk

to exposed individuals or the waste constituent concentrations that can be protectively managed in the unit. To operate, the

program requires only a limited amount of

site-specific information, including facility

location, WMU characteristics, waste characteristics, and receptor information. A brief

description of each component follows. The

IWAIR Technical Background Document (U.S.

EPA, 2002a)contains a more detailed explanation of each.

1. Emissions Model

The emissions model uses waste characterization, WMU, and facility information to

estimate emissions for 95 constituents that

are identified in Table 5. The emission model

selected for incorporation into IWAIR is EPA’s

CHEMDAT8 model. The entire CHEMDAT8

model is run as the emission component of

the IWAIR model. CHEMDAT8 has undergone extensive review by both EPA and

industry representatives and is publicly available from EPA’s Web page, <www.epa.gov/

ttnchie1/software/water/water8.html>. 

To facilitate emission modeling with

CHEMDAT8, IWAIR prompts the user to provide the required waste- and unit-specific

data. Once these data are entered, the model

calculates and displays chemical-specific

emission rates. If users decide not to develop

or use the CHEMDAT8 rates, they can enter

their own site-specific emission rates (g/m2

-s).

2. Dispersion Model

IWAIR’s second modeling component estimates dispersion of volatilized contaminants

and determines air concentrations at specified

receptor locations, using default dispersion

factors developed with EPA’s Industrial

Source Complex, Short-Term Model, version

3 (ISCST3). ISCST3 was run to calculate dispersion for a standardized unit emission rate

(1 μg/m2 - s) to obtain a unitized air concentration (UAC), also called a dispersion factor,

which is measured in μ/m3 per μg/m2

-s. The

total air concentration estimates are then

developed by multiplying the constituentspecific emission rates derived from CHEMDAT8 (or from another source) with a

site-specific dispersion factor. Running

ISCST3 to develop a new dispersion factor

for each location/WMU is very time consuming and requires extensive meteorological

data and technical expertise. Therefore

IWAIR incorporates default dispersion factors

Protecting Air Quality—Protecting Air Quality

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5-22

Protecting Air Quality—Protecting Air Quality

75-07-0

67-64-1

75-05-8

107-02-8

79-06-1

79-10-7

107-13-1

107-05-1

62-53-3

71-43-2

92-87-5

50-32-8

75-27-4

106-99-0

75-15-0

56-23-5

108-90-7

124-48-1

67-66-3

95-57-8

126-99-8

1006-10-15

1319-77-3

98-82-8

108-93-0

96-12-8

75-71-8

107-06-2

75-35-4

78-87-5

57-97-6

95-65-8

121-14-2

123-91-1

122-66-7

106-89-8

106-88-7

11-11-59

110-80-5

100-41-4

106-93-4

107-21-1

75-21-8

50-00-0

98-01-1

87-68-3

118-74-1 

Table 5. Constituents Included in IWAIR

Chemical Compound Name Chemical Compound Name

Abstracts Abstracts

(CAS) (CAS)

Number Number 

Acetaldehyde

Acetone

Acetonitrile

Acrolein

Acrylamide

Acrylic acid

Acrylonitrile

Allyl chloide

Aniline

Benzene

Benzidine

Benzo(a)pyrene

Bromodichloromethane

Butadine, 1,3-

Carbon disulfide

Carbon tetrachloride

Chlorobenzene

Chlorodibromomethane

Chloroform

Chloropphenol, 2-

Chloroprene

cis-1,3-Dichloropropylene

Cresols (total)

Cumene

Cyclohexanol

Dibromo-3-chloropropane, 1,2-

Dichlorodifluoromethane

Dichloroethane, 1,2-

Dichloroethylene, 1,1-

Dichloropropane, 1,2-

Dimethylbenz[a]anthracene , 7,12-

Dimethylphenol, 3,4-

Dinitrotoluene, 2,4-

Dioxane, 1,4-

Diphenylhydrazine, 1,2-

Epichlorohydrin

Epoxybutane, 1,2-

Ethoxyethanol acetate, 2-

Ethoxyethanol, 2-

Ethylbenzene

Ethylene dibromide

Ethylene glycol

Ethylene oxide

Formaldehyde

Furfural

Hexachloro-1,3-butadiene

Hexchlorobenzene 

77-47-4

67-72-1

78-59-1

7439-97-6

67-56-1

110-49-6

109-86-4

74-83-9

74-87-3

78-93-3

108-10-1

80-62-6

1634-04-4

56-49-5

75-09-2

68-12-2

91-20-3

110-54-3

98-95-3

79-46-9

55-18-5

924-16-3

930-55-2

95-50-1

95-53-4

106-46-7

108-95-2

85-44-9

75-56-9

110-86-1

100-42-5

1746-01-6

630-20-6

79-34-5

127-18-4

108-88-3

10061-02-6

75-25-2

76-13-1

120-82-1

71-55-6

79-00-5

79-01-6

75-69-4

121-44-8

108-05-4

75-01-4

1330-20-7

Hexachlorocyclopentadine

Hexachloroethane

Isophorone

Mercury

Methanol

Methoxyethanol acetate, 2-

Methoxyethanol, 2-

Methyl bromide

Methyl chloride

Methyl ethyl ketone

Methyl isobutyl ketone

Methyl methacrylate

Methyl tert-butyl ether

Methylcholanthrene, 3-

Methylene chloride

N-N-Dimethyl formamide

Naphthalene

n-Hexane

Nitrobenzene

Nitropropane, 2-

NiNitrosodiethylamine

N-Nitrosodi-n-butylamine

N-Nitrosoyrrolidine

o-Dichlorobenzene

o-Toluidine

p-Dichlorobenzene

Phenol

Phthalic anhydride

Propylene oxide

Pyridine

Stryene

TCDD-2,3,7,8-

Tetrachloroethane, 1,1,1,2-

Tetrachloroethane, 1,1,2,2-

Tetrachloroethylene

Toluene

trans-1,3-Dichloropropylene

Tribromomethane

Freon 113 (Trichloro-1,2,2- 1,1,2- trifluoroethane)

Trichlorobenzene, 1,2,4-

Trichloroethane, 1,1,1-

Trichloroethane, 1,1,2-

Trichloroethylene

Trichlorofluoromethane

Triethylamine

Vinyl acetate

Vinyl chloride

Xylenes
developed by ISCST3 for many separate scenarios designed to cover a broad range of

unit characteristics, including:

• 60 meteorological stations, chosen to

represent the 9 general climate

regions of the continental U.S.

• 4 unit types.

• 17 surface area sizes for landfills,

land application units and surface

impoundments, and 11 surface area

sizes and 7 heights for waste piles.

• 6 receptor distances from the unit

(25, 50, 75, 150, 500, 1000 meters).

• 16 directions in relation to the edge

of the unit.

The default dispersion factors were derived

by modeling many scenarios with various

combinations of parameters, then choosing as

the default the maximum dispersion factor

for each waste management unit/surface

area/meteorological station/receptor distance

combination. 

Based on the size and location of a unit, as

specified by a user, IWAIR selects an appropriate dispersion factor from the default dispersion factors in the model. If the user

specifies a unit surface area that falls between

two of the sizes already modeled, a linear

interpolation method will estimate dispersion

in relation to the two closest unit sizes. 

Alternatively, a user can enter a site-specific dispersion factor developed by conducting

independent modeling with ISCST3 or with a

different model and proceed to the next step,

the risk calculation.

3. Risk Model

The third component to the model combines the constituent’s air concentration with

receptor exposure factors and toxicity benchmarks to calculate either the risk from concentrations managed in the unit or the waste

concentration (Cw) in the unit that should

not be exceeded to protect human health. In

calculating either estimate, the model applies

default values for exposure factors, including

inhalation rate, body weight, exposure duration, and exposure frequency. These default

values are based on data presented in the

Exposure Factors Handbook (U.S. EPA, 1995a)

and represent average exposure conditions.

IWAIR maintains standard health benchmarks

(CSFs for carcinogens and RfCs for noncarcinogens) for 95 constituents. These health

benchmarks are from the Integrated Risk

Information System (IRIS) and the Health

Effects Assessment Summary Tables (HEAST).

IWAIR uses these data to perform either a forward calculation to obtain risk estimates or a

backward calculation to obtain protective

waste concentration estimates. 

4. Estimation Process

Figure 5 provides an overview of the stepwise approach the user follows to calculate

risk or protective waste concentration estimates with IWAIR. The seven steps of the

estimation process are shown down the right

side of the figure, and the user specified

inputs are listed to the left of each step. As

the user provides input data, the program

proceeds to the next step. Each step of the

estimation process is discussed below. 

a. Select Calculation Method. The user

selects one of two calculation methods. Use the forward calculation to

arrive at chemical-specific and cumulative risk estimates if the user knows

the concentrations of constituents in

the waste. Use the backward calculation method to estimate protective

waste concentrations not to be

exceeded in new units. The screen

where this step is performed is shown

in Figure 6.

Protecting Air Quality—Protecting Air Quality

5-23
5-24

Protecting Air Quality—Protecting Air Quality

Figure 5. IWAIR Approach for Developing Risk or Protective Waste Concentrations:

This figure shows the steps in the tool to assist the user in developing risk or 

protective waste concentration estimates.

User Specifies:

Calculation option

User Specifies:

WMU type

WMU information (e.g.,

operating parameters)

User Specifies:

Emission rate option

Facility location for meteorological input

User Specifies:

Dispersion factor option

Receptor information (e.g., distance and type)

Risk calculation

or

Allowable waste concentration

calculation

Select Calculation Method

Identify WMU

Add/modify properties data, as

desired

Define the Waste Managed

Determine Emission Rates

Interpolated from ISCST3 default

dispersion factors

or

User-specified dispersion factors

Determine Dispersion Factors

Calculates ambient air concentrations for

each receptor based on emission and

dispersion data

Calculate Ambient Air Concentrations

 Risk Calculation

1. Chemical-specific carcinogenic risk

2. Chemical-specific noncarcinogenic risk

3. Total cancer risk

 or

 Allowable Waste Concentration

 (Cwaste) Calculation

Cwaste for wastewaters (mg/L)

Cwaste for solid wastes (mg/kg)

Calculate Results

CHEMDAT8

or

User-specified emission rates

User Specifies:

Constituents (choose up to 6)

Concentration for risk calculation

User Specifies:

Risk level for allowable concentration

calculation

Land application unit

Waste pile

Surface impoundment, aerated

and quiescent

Landfill
Protecting Air Quality—Protecting Air Quality

5-25

Figure 6. Screen 1, Method, Met Station, WMU.

A. Select 

calculation 

method

C. Select met 

station search 

option

Enter zip code 

and search for 

met station

Enter latitude 

and longitude 

and search for 

met station

D. View 

selected met 

station

B. Select 

WMU type

E. Select 

emission and 

dispersion 

option

Figure 7. Screen 2, Wastes Managed.

B. Select 

sorting option 

for identifying 

chemicals

C. Identify 

chemicals in 

waste

D. View 

selected 

chemicals

E. Enter waste 

concentrations

A. Add/ 

modify 

chemicals
b. Identify Waste Management Unit.

Four WMU types can be modeled:

surface impoundments (SIs), land

application units (LAUs), active landfills (LFs), and wastepiles (WPs). For

each WMU, you will be asked to

specify some design and operating

parameters such as surface area,

depth for surface impoundments and

landfills, height for wastepiles, and

tilling depth for LAUs. The amount

of unit specific data needed as input

will vary depending on whether the

user elects to develop CHEMDAT8

emission rates. IWAIR provides

default values for several of the operating parameters that the user can

choose, if appropriate.

c. Define Waste Managed. Specify

constituents and concentrations in

the waste if you choose a forward

calculation to arrive at chemical specific risk estimates. If you choose a

backward calculation to estimate protective waste concentrations, then

specify constituents of concern. The

screen where this step is performed

is shown in Figure 7.

d. Determine Emission Rates. You can

elect to develop CHEMDAT8 emission rates or provide your own sitespecific emission rates for use in

calculations. IWAIR will also ask for

facility location information to link

the facility’s location to one of the 60

IWAIR meteorological stations. Data

from the meteorological stations provide wind speed and temperature

information needed to develop emission estimates. In some circumstances the user might already have

emissions information from monitoring or a previous modeling exercise.

As an alternative to using the CHEMDAT8 rates, a user can provide their

own site-specific emission rates

developed with a different model or

based on emission measurements. 

e. Determine Dispersion. The user can

provide site-specific unitized dispersion factors (μg/m3 per μg/m2

-s) or

have the model develop dispersion

factors based on user-specified WMU

information and the IWAIR default

dispersion data. Because a number of

assumptions were made in developing the IWAIR default dispersion

data you can elect to provide sitespecific dispersion factors which can

be developed by conducting independent modeling with ISCST3 or

with a different model. Whether you

use IWAIR or provide dispersion factors from another source, specify distance to the receptor from the edge

of the WMU and the receptor type

(i.e., resident or worker). These data

are used to define points of exposure. 

f. Calculate Ambient Air

Concentration. For each receptor,

the model combines emission rates

and dispersion data to estimate ambient air concentrations for all waste

constituents of concern. 

g. Calculate Results. The model calculates results by combining estimated

ambient air concentrations at a specified exposure point with receptor

exposure factors and toxicity benchmarks. Presentation of results

depends on whether you chose a forward or backward calculation: 

Forward calculation: Results are estimates of

cancer and non-cancer risks from inhalation

exposure to volatilized constituents in the

waste. If risks are too high, options are: 1)

implement unit controls to reduce volatile air

emissions, 2) implement pollution preven5-26

Protecting Air Quality—Protecting Air Quality
tion or treatment to reduce volatile organic

compound (VOC) concentrations before the

waste enters the unit, or 3) conduct a full

site-specific risk assessment to more precisely

characterize risks from the unit.

Backward calculation: Results are estimates of

constituent concentrations in waste that can be

protectively managed in the unit so as not to

exceed a defined risk level (e.g., 1 x 10-6 or

hazard quotient of 1) for specified receptors. A

target risk level for your site can be calculated

based on a number of site-specific factors

including, proximity to potential receptors,

waste characteristics, and waste management

practices. This information should be used to

determine preferred characteristics for wastes

entering the unit. There are several options if it

appears that planned waste concentrations

might be too high: 1) implement pollution

prevention or treatment to reduce VOC concentrations in the waste, 2) modify waste management practices to better control VOCs (for

example, use closed tanks rather than surface

impoundments), or 3) conduct a full site-specific risk assessment to more precisely characterize risks from the unit.

5. Capabilities and Limitations of

the Model

In many cases, IWAIR will provide a reasonable alternative to conducting a full-scale

site-specific risk analysis to determine if a

WMU poses unacceptable risk to human

health. Because the model can accommodate

only a limited amount of site-specific information, however, it is important to understand its capabilities and recognize situations

when it might not be appropriate to use.

Capabilities

• The model provides a reasonable representation of VOC inhalation risks

associated with waste management

units.

• The model is easy-to-use and

requires a minimal amount of data

and expertise.

• The model is flexible and provides

features to meet a variety of user

needs.

• A user can enter emission and/or dispersion factors derived from another

model (perhaps to avoid some of the

limitations below) and still use

IWAIR to conduct a risk evaluation.

• The model can run a forward calculation from the unit or a backward calculation from the receptor point.

• A user can modify health benchmarks (HBNs) and target risk level,

when appropriate and in consultation

with other stakeholders.

Limitations

• Release Mechanisms and Exposure

Routes. The model considers exposures from breathing ambient air. It

does not address potential risks

attributable to particulate releases nor

does it address risks associated with

indirect routes of exposure (i.e, noninhalation routes of exposure).

Additionally, in the absence of userspecified emission rates, volatile

emission estimates are developed

with CHEMDAT8 based on unit- and

waste-specific data. The CHEMDAT8

model was developed to address only

volatile emissions from waste management units. Competing mechanisms that can generate additional

exposures to the constituents in the

waste such as runoff, erosion, and

Protecting Air Quality—Protecting Air Quality

5-27
particulate emissions are not

accounted for in the model. 

• Waste Management Practices. The

user specifies a number of unit-specific parameters that significantly

impact the inhalation pathway (e.g.,

size, type, and location of WMU,

which is important in identifying

meteorological conditions). However,

the model cannot accommodate

information concerning control technologies such as covers that might

influence the degree of volatilization

(e.g., whether a wastepile is covered

immediately after application of new

waste). In this case, it might be advisable to generate site-specific emission

rates and enter those into IWAIR.

• Terrain and Meteorological

Conditions. If a facility is located in

an area of intermediate or complex

terrain or with unusual meteorological conditions, it might be advisable

to either 1) generate site-specific air

dispersion modeling results for the

site and enter those results into the

program, or 2) use a site-specific risk

modeling approach different from

IWAIR. The model will inform the

user which of the 60 meteorological

stations is used for a facility. If the

local meteorological conditions are

very different from the site chosen by

the model, it would be more accurate

to choose a different model.

The terrain type surrounding a facility can impact air dispersion modeling results and ultimately risk

estimates. In performing air dispersion modeling to develop the IWAIR

default dispersion factors, the model

ISCST3 assumes the area around the

WMU is of simple or flat terrain. The

Guideline on Air Quality Models (U.S.

EPA, 1993) can assist users in determining whether a facility is in an

area of simple, intermediate, or complex terrain. 

• Receptor Type and Location.

IWAIR has predetermined adult

worker and resident receptors, six

receptor locations, and predetermined exposure factors. The program

cannot be used to characterize risk

for other possible exposure scenarios.

For example, the model can not evaluate receptors that are closer to the

unit than 25 meters or those that are

further from the unit than 1,000

meters. If the population of concern

for your facility is located beyond the

limits used in IWAIR, consider using

a model that is more appropriate for

the risks posed from your facility.

C. Site-specific Risk

Analysis

IWAIR is not the only model that can be

applicable to a site. In some cases, a site-specific risk assessment might be more advantageous. A site-specific approach can be

tailored to accommodate the individual needs

of a particular WMU. Such an approach

would rely on site-specific data and on the

application of existing fate and transport

models. Table 6 summarizes available emissions and/or dispersion models that can be

applied in a site-specific analysis. Practical

considerations include the source of the

model(s), the ease in obtaining the model(s),

and the nature of the model(s) (i.e., is it proprietary), and the availability of site-specific

data required for use of the model. Finally,

the model selection process should determine

whether or not the model has been verified

against analytical solutions, other models,

and/or field data. Proper models can be

selected based on the physical and chemical

5-28

Protecting Air Quality—Protecting Air Quality
Protecting Air Quality—Protecting Air Quality

5-29

Model Name Summary

Table 6

Source Characterization Models

AP-42 The EPA’s Compilation of Air Pollutant Emission Factors, Volume I: Stationary

Point and Area Sources (AP-42), is a compilation of emission factors for a wide

variety of air emission sources, including fugitive dust sources (Section 13.2).

Emission factors are included for paved roads, unpaved roads, heavy construction operations, aggregate handling and storage piles, industrial wind erosion

(this is the 1988 Cowherd model), and abrasive blasting. These are simple emission factors or equations that relate emissions to inputs (e.g., silt loading or content, moisture content, mean vehicle weight, area, activity level, and wind

speed). Guidance is provided for most inputs, but the more site-specific the

input data used, the more accurate the results.

The entire AP-42 documentation is available at <www.epa.gov/ttn/chief/

efinformation.html>.

CHEMDAT8 The CHEMDAT8 model allows the user to conduct source and chemical specific

emissions modeling. CHEMDAT8 is a Lotus 1-2-3 spreadsheet that includes analytical models to estimate volatile organic compound emissions from treatment,

storage, and disposal facility processes under user-specified input parameters.

CHEMDAT8 calculates the fractions of waste constituents of interest that are distributed among pathways (partition fractions) applicable to the facility under

analysis.

Emissions modeling using CHEMDAT8 is conducted using data entered by the

user for unit-specific parameters. The user can choose to override the default

data and enter their estimates for these unit-specific parameters. Thus, modeling

emissions using CHEMDAT8 can be done with a limited amount of site-specific

information.

Available at <www.epa.gov/ttnchie1/software/water/water8.html>, hotline at

919 541-5610 for more information.

Cowherd The Cowherd model, Rapid Assessment of Exposure to Particulate Emissions

from Surface Contamination Sites, allows the user to calculate particulate emission rates for wind erosion using data on wind speed and various parameters

that describe the surface being eroded. The latest (1988) version of this model is

event-based (i.e., erosion is modeled as occurring in response to specific events

in which the wind speed exceeds levels needed to cause wind erosion). An older

(1985) version of the model is not event-based (i.e., erosion is modeled as a

long-term average, without regard to specific wind speed patterns over time).

The older version is less complicated and requires fewer inputs, but produces

more conservative results (i.e., higher emissions). The documentation on both

models provides guidance on developing all inputs. Both require data on wind

speed (fastest mile for the 1988 version and annual average for the 1985 version), anemometer height, roughness height, and threshold friction velocity. The

1985 version also requires input on vegetative cover. The 1988 version requires

data on number of disturbances per year and, if the source is not a flat surface,

pile shape and orientation to the fastest mile.

The 1985 version of the model is presented in Rapid Assessment of Exposures to

Particulate Emissions from Surface Contamination Sites (U.S. EPA, 1985). Office

of Health and Environmental Assessment, Washington DC.

The 1988 version of the model is available as part of AP-42, Section 13.2.5 (see

above).
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Model Name Summary

Table 6

Source Characterization Models

ISCLT3 The Industrial Source Complex Model-Long Term, ISCLT3, is a steady state

Gaussian plume dispersion model that can be used to model dispersion of continuous emissions from point or area sources over transport distances of less

than 50km. It can estimate air concentration for vapors and particles, and dry

deposition rates for particles (but not vapors), and can produce these outputs

averaged over seasonal, annual, or longer time frames. ISCLT3 inputs include

readily available meteorological data known as STAR (STability ARray) summaries (these are joint frequency distributions of wind speed class by wind

direction sector and stability class, and are available from the National Climate

Data Center in Asheville, North Carolina), and information on source characteristics (such as height, area, emission rate), receptor locations, and a variety of

modeling options (such as rural or urban). Limitations of ISCLT3 include inability to model wet deposition, deposition of vapors, complex terrain, or shorter

averaging times than seasonal, all of which can be modeled by ISCST3. In addition, the area source algorithm used in ISCLT3 is less accurate than the one used

in ISCST3. The runtime for area sources, however, is significantly shorter for

ISCLT3 than for ISCST3.

ISCLT3 is available at <www.epa.gov/scram001/tt22.htm>. 

ISCST3 A steady-state Gaussian plume dispersion model that can estimate concentration,

dry deposition rates (particles only), and wet deposition rates. Is applicable for

continuous emissions, industrial source complexes, rural or urban areas, simple

or complex terrain, transport distances of less than 50 km, and averaging times

from hourly to annual.

Available at <www.epa.gov/scram001/tt22.htm>.

Landfill Air Emissions Estimation Used to estimate emission rates for methane, carbon dioxide, nonmethane 

Model (LAEEM) volatile organic compounds, and other hazardous air pollutants from municipal

solid waste landfills. The mathematical model is based on a first order decay

equation that can be run using site-specific data supplied by the user for the

parameters needed to estimate emissions or, if data are not available, using

default value sets included in the model.

Developed by the Clean Air Technology Center (CATC). Can be used to estimate

emission rates for methane, carbon dioxide, nonmethane organic compounds,

and individual air pollutants from landfills. Can also be used by landfill owners

and operators to determine if a landfill is subject to the control requirements of

the federal New Source Performance Standard (NSPS) for new municipal solid

waste (MSW) landfills (40 CFR 60 Subpart WWW) or the emission guidelines

for existing MSW landfills (40 CFR 60 Subpart CC).

Developed for municipal solid waste landfills; might not be appropriate for all

industrial waste management units.

Available at <www.epa.gov/ttn/chief/software/index.html>. 
Protecting Air Quality—Protecting Air Quality

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Model Name Summary

Table 6

Source Characterization Models

Wastewater Treatment Compound WATER9 is a Windows based computer program and consists of analytical 

Property Processor and Air Emissions expressions for estimating air emissions of individual waste constituents in 

Estimator Program (WATER9) wastewater collection, storage, treatment, and disposal facilities; a database listing many of the organic compounds; and procedures for obtaining reports of

constituent fates, including air emissions and treatment effectiveness.

WATER9 is a significant upgrade of features previously obtained in the computer

programs WATER8, Chem9, and Chemdat8. WATER9 contains a set of model

units that can be used together in a project to provide a model for an entire facility. WATER9 is able to evaluate a full facility that contains multiple wastewater

inlet streams, multiple collection systems, and complex treatment configurations.

It also provides separate emission estimates for each individual compound that is

identified as a constituent of the wastes.

WATER9 has the ability to use site-specific compound property information, and

the ability to estimate missing compound property values. Estimates of the total air

emissions from the wastes are obtained by summing the estimates for the individual compounds. The EPA document Air Emissions Models for Waste and Wastewater

(U.S. EPA, 1994a) includes the equations used in the WATER9 model.

Available at <www.epa.gov/ttnchie1/software/water/water9/index.html>.

Contact the Air Emissions Model Hotline at 919 541-5610 for support or more

information.

Toxic Modeling System Short Term An interactive PC-based system to analyze intermittent emissions from toxic 

(TOXST) sources. Estimates the dispersion of toxic air pollutants from point, area, and

volume sources at a complex industrial site. This system uses a Monte Carlo simulation to allow the estimation of ambient concentration impacts for single and

multiple pollutants from continuous and intermittent sources. In addition, the

model estimates the average annual frequency with which user-specified concentration thresholds are expected to be exceeded at receptor sites around the modeled facility. TOXST requires the use of ISCT3 model input files for physical

source parameters.

Available at <www.epa.gov/rgytgrnj/programs/artd/toxics/arpp/etools.htm>. 

Toxic Screening Model (TSCREEN) TSCREEN, a Model for Screening Toxic Air Pollutant Concentrations, should be

used in conjunction with the “Workbook of Screening Techniques for Assessing

Impacts of Toxic Air Pollutants.” The air toxics dispersion screening models

imbedded in TSCREEN that are used for the various scenarios are SCREEN2,

RVD, PUFF, and the Britter-McQuaid model. Using TSCREEN, a particular

release scenario is selected via input parameters, and TSCREEN model to simulate that scenario. The model to be used and the worst case meteorological conditions are automatically selected based on criteria given in the workbook.

TSCREEN has a front-end control program to the models that also provides, by

use of interactive menus and data entry screen, the same steps as the workbook.
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Protecting Air Quality—Protecting Air Quality

attributes of the site in question. As with all

modeling, however, you should consult with

your state prior to investing significant

resources in a site-specific analysis. The state

might have preferred models or might be able

to help plan the analysis.

III. Emission Control

Techniques

A. Controlling Particulate

Matter

Particulate matter (PM) consists of airborne solid and liquid particles. PM is easily

inhaled and can cause various health problems. PM also impacts the environment by

decreasing visibility and harming plants as

well as transporting constituents off site.

Constituents can sorb to particulate matter

and, therefore, wind blown dust is a potential

pathway for constituents to leave the site. It is

recommended that facilities adopt controls to

address emissions of airborne particulates.

Solid PM that becomes airborne directly or

indirectly as a result of human activity, is

referred to as fugitive dust16 and it can be

generated from a number of different sources.

The most common sources of fugitive dust at

waste management units include vehicular

traffic on unpaved roads and land-based

units, wind erosion from land-based units,

and waste handling procedures. Developing a

fugitive dust control plan is an efficient way

to tackle these problems. The plan should

include a description of all operations conducted at the unit, a map, a list of all fugitive

dust sources at the unit, and a description of

the control measures that will be used to

minimize fugitive dust emissions. OSHA has

established standards for occupational exposure to dust (see 29 CFR § 1910.1000). You

should check to see if your state also has regulations or guidance concerning dust or fugitive emission control.

PM emissions at waste management units

vary with the physical and chemical characteristics of waste streams; the volume of waste

handled; the size of the unit, its location, and

associated climate; and waste transportation

and placement practices. The subsections

below discuss the main PM-generating operations and identify emission control techniques. The waste management units of main

concern for PM emissions include landfills,

waste piles, land application units, and closed

surface impoundments.

1. Vehicular Operations 

Waste and cover material are often transported to units using trucks. If the waste has

the potential for PM to escape to the atmosphere during transport, you should cover the

waste with tarps or place wastes in containers

such as double bags or drums.17

A unit can also use vehicles to construct

lifts in landfills, apply liquids to land application units, or dredge surface impoundments.

Consider using “dedicated” equipment—vehicles that operate only within the unit and are

not routinely removed from the unit to perform other activities. This practice reduces

the likelihood that equipment movement will

spread contaminated PM outside the unit. To

control PM emissions when equipment must

be removed from the landfill unit, such as for

maintenance, a wash station can remove any

contaminated material from the equipment

before it leaves the unit. You should ensure

that this is done in a curbed wash area where

wash water is captured and properly handled.

To minimize PM emissions from all vehicles, it is recommended that you construct

temporary roadways with gravel or other

16 Fugitive emissions are defined as emissions not caught by a capture system and therefore exclude PM

emitted from exhaust stacks with control devices.

17 Containerizing wastes provides highly effective control of PM emissions, but, due to the large volume of

many industrial waste streams, containerizing waste might not always be feasible.
coarse aggregate material to reduce silt content and thus, dust generation. In addition,

consider regularly cleaning paved roads and

other travel surfaces of dust, mud, and contaminated material.

In land application units, the entire application surface is often covered with a soilwaste mix. The most critical preventive

control measure, therefore, involves minimizing contact between the application surface

and waste delivery vehicles. If possible, allow

only dedicated application vehicles on the

surface, restricting delivery vehicles to a staging or loading area where they deposit waste

into application vehicles or holding tanks. If

delivery vehicles must enter the application

area, ensure that mud and waste are not

tracked out and deposited on roadways,

where they can dry and then be dispersed by

wind or passing vehicles.

2. Waste Placement and

Handling

PM emissions from waste placement and

handling activities are less likely if exposed

material has a high moisture content.

Therefore, consider wetting the waste prior to

loadout. Increasing the moisture content,

however, might not be suitable for all waste

streams and can result in an unacceptable

increase in leachate production. To reduce

the need for water or suppressants, cover or

confine freshly exposed material. In addition,

consider increasing the moisture content of

the cover material.

It can also be useful to apply water to unit

surfaces after waste placement. Water is generally applied using a truck with a gravity or

pressure feed. Watering might or might not

be advisable depending on application intensity and frequency, the potential for tracking

of contaminated material off site, and climactic conditions. PM control efficiency generally

increases with application intensity and frequency but also depends on activity levels,

climate, and initial surface conditions.

Infrequent or low-intensity water application

typically will not provide effective control,

while too frequent or high-intensity application can increase leachate volume, which can

strain leachate collection systems and threaten ground water and surface water. Addition

of excess water to bulk waste material or to

unit surfaces also can reduce the structural

integrity of the landfill lifts, increase tracking

of contaminated mud off site, and increase

odor. These undesirable possibilities can have

long-term implications for the proper management of a unit. Before instituting a watering program, therefore, ensure that addition

of water does not produce undesirable

impacts on ground- and surface-water quality.

You should consult with your state agency

with respect to these problems.

Chemical dust suppressants are an alternative to water application. The suppressants are

detergent-like surfactants that increase the

total number of droplets and allow particles to

more easily penetrate the droplets, increasing

the total surface area and contact potential.

Adding a surfactant to a relatively small quantity of water and mixing vigorously produces

small-bubble, high-energy foam in the 100 to

200 μm size range. The foam occupies very

little liquid volume, and when applied to the

surface of the bulk material, wets the fines

Protecting Air Quality—Protecting Air Quality

5-33
more effectively than water. When applied to

a unit, suppressants cement loose material

into a more impervious surface or form a surface which attracts and retains moisture.

Examples of chemical dust suppressants are

provided in Table 7. The degree of control

achieved is a function of the application

intensity and frequency and the dilution ratio.

Chemical dust suppressants tend to require

less frequent application than water, reducing

the potential for leachate generation. Their

efficiency varies, depending on the same factors as water application, as well as spray

nozzle parameters, but generally falls

between 60 and 90 percent reduction in fugitive dust emissions. Suppressant costs, however, can be high. 

At land application units, if wastes contain

considerable moisture, PM can be suppressed

through application of more waste rather

than water or chemical suppressants. This

method, however, is only viable if it would

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* Mention of trade names or commercial products is not intended to constitute endorsement or recommendation for use.

Source: U.S. EPA, 1989.

Protecting Air Quality—Protecting Air Quality

Type Product Manufacturer

Bitumens AMS 2200, 2300® Arco Mine Sciences

Coherex® Witco Chemical

Docal 1002® Douglas Oil Company

Peneprime® Utah Emulsions

Petro Tac P® Syntech Products Corporation

Resinex® Neyra Industries, Inc.

Retain® Dubois Chemical Company

Salts Calcium chloride Allied Chemical Corporation

Dowflake, Liquid Dow® Dow Chemical

DP-10® Wen-Don Corporation

Dust Ban 8806® Nalco Chemical Company

Dustgard® G.S.L. Minerals and Chemical Corporation

Sodium silicate The PQ Corporation

Adhesives Acrylic DLR-MS® Rohm and Haas Company

Bio Cat 300-1® Applied Natural Systems, Inc.

CPB-12® Wen-Don Corporation

Curasol AK® American Hoechst Corporation

DCL-40A, 1801, 1803® Calgon Corporation

DC-859, 875® Betz Laboratories, Inc.

Dust Ban® Nalco Chemical Company

Flambinder® Flambeau Paper Company

Lignosite® Georgia Pacific Corporation

Norlig A, 12® Reed Lignin, Inc.

Orzan Series® Crown Zellerbach Corporation

Soil Gard® Walsh Chemical

Table 7. Example List of Chemical Suppressants*
not cause an exceedence of a design waste

application rate or exceed the capacity of soil

and plants to assimilate waste.

At surface impoundments, the liquid

nature of the waste means PM is not a major

concern while the unit is operational. Inactive

or closed surface impoundments, however,

can emit PM during scraping or bulldozing

operations to remove residual materials. The

uppermost layer of the low permeability soils,

such as compacted clay, which can be used to

line a surface impoundment, contains the

highest contaminant concentrations.

Particulate emissions from this uppermost

layer, therefore, are the chief contributor to

contaminant emissions. When removing

residuals from active units, you should ensure

that equipment scrapes only the residuals,

avoiding the liner below.

3. Wind Erosion

Wind erosion occurs when a dry surface is

exposed to the atmosphere. The effect is most

pronounced with bare surfaces of small particles, such as silty soil; heavier or better

anchored material, such as stones or clumps

of vegetation, has limited erosion potential

and requires higher wind speeds before erosion can begin.

Compacted clay and in-situ soil liners tend

to form crusts as their surfaces dry. Crusted

surfaces usually have little or no erosion

potential. Examine the crust thickness and

strength during site inspections. If the crust

does not crumble easily the erosion potential

might be minimal.

Wind fences or barriers are effective means

by which to control fugitive dust emissions

from open dust sources. The wind fence or

barrier reduces wind velocity and turbulence

in an area whose length is many times the

height of the fence. This allows settling of

large particles and reduces emissions from

the exposed surface. It can also shelter materials handling operations to reduce entrainment during load-in and loadout. Wind

fences or barriers can be portable and either

man-made structures or vegetative barriers,

such as trees. A number of studies have

attempted to determine the effectiveness of

wind fences or barriers for the control of

windblown dust under field conditions.

Several of these studies have shown a

decrease in wind velocity, however, the

degree of emissions reduction varies significantly from study to study depending on test

conditions.

Other wind erosion control measures

include passive enclosures such as threesided bunkers for the storage of bulk materials, storage silos for various types of aggregate

material, and open-ended buildings. Such

enclosures are most easily used with small,

temporary waste piles. At land application

units that use spray application, further wind

erosion control can be achieved simply by

not spraying waste on windy days.

Windblown PM emissions from a waste

pile depend on how frequently the pile is disturbed, the moisture content of the waste, the

proportion of aggregate fines, and the height

of the pile. When small-particle wastes are

loaded onto a waste pile, the potential for

dust emissions is at a maximum, as small

particles are easily disaggregated and picked

up by wind. This tends to occur when material is either added to or removed from the

pile or when the pile is otherwise reshaped.

On the other hand, when the waste remains

undisturbed for long periods and is weathered, its potential for dust emissions can be

greatly reduced. This occurs when moisture

from precipitation and condensation causes

aggregation and cementation of fine particles

to the surface of larger particles, and when

vegetation grows on the pile, shielding the

surface and strengthening it with roots.

Protecting Air Quality—Protecting Air Quality

5-35
Finally, limiting the height of the pile can

reduce PM emissions, as wind velocities generally increase with distance from the

ground.

B. VOC Emission Control

Techniques

If air modeling indicates that VOC emissions are a concern, you should consider pollution prevention and treatment options to

reduce risk. There are several control techniques you can use. Some are applied before

the waste is placed in the unit, reducing

emissions; others contain emissions that

occur after waste placement; still others

process the captured emissions.

1. Choosing a Site to Minimize

Airborne Emission Problems

Careful site choice can reduce VOC emissions. Locations that are sheltered from wind

by trees or other natural features are preferable. Knowing the direction of prevailing

winds and determining whether the unit

would be upwind from existing and expected

future residences, businesses, or other population centers can result in better siting of

units. After a unit is sited, observe wind

direction during waste placement, and plan

or move work areas accordingly to reduce

airborne emission impacts on neighbors. 

2. Pretreatment of Waste

Pretreating waste can remove organic compounds and possibly eliminate the need for

further air emission controls. Organic

removal or pretreatment is feasible for a variety of wastes. These processes, which include

steam or air stripping, thin-film evaporation,

solvent extraction, and distillation, can sometimes remove essentially all of the highly

volatile compounds from your waste.

Removal of the volatiles near the point of

generation can obviate the need for controls

on your subsequent process units and can

facilitate recycling the recovered organics

back to the process.

The control efficiency of organic removal

depends on many factors, such as emissions

from the removal system, and the uncontrolled emissions from management units

before the removal device was installed.

Generally, overall organic removal efficiencies

of 98 to over 99 percent can be achieved.

3. Enclosure of Units

You might be able to control VOC emissions from your landfill or waste pile by

installing a flexible membrane cover, enclosing the unit in a rigid structure, or using an

air-supported structure. Fans maintain positive pressure to inflate an air-supported structure. Some of the air-supported covers that

have been used consist of PVC-coated polyester with a polyvinyl fluoride film backing.

The efficiency of air-supported structures

depends primarily on how well the structure

prevents leaks and how quickly any leaks

that do occur are detected. For effective control, the air vented from the structure should

be sent to a control device, such as a carbon

adsorber. Worker safety issues related to

access to the interior of any flexible membrane cover or other pollutant concentration

system should also be considered.

Wind fences or barriers can also aid in

reducing organic emissions by reducing air

mixing on the leeward side of the screen. In

addition, wind fences reduce soil moisture

loss due to wind, which can in turn result in

decreased VOC emissions.

Floating membrane covers provide control

on various types of surface impoundments,

including water reservoirs in the western

United States. For successful control of

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Protecting Air Quality—Protecting Air Quality
organic compounds, the membrane must

provide a seal at the edge of the impoundment and rainwater must be removed. If gas

is generated under the cover, vents and a

control device might also be needed.

Emission control depends primarily on the

type of membrane, its thickness, and the

nature of the organic compounds in the

waste. Again, we recommend that you consult with your state or local air quality agency

to identify the most appropriate emission

control for your impoundment.

4. Treatment of Captured VOCs

In some cases, waste will still emit some

VOCs despite waste reduction or pretreatment efforts. Enclosing the unit serves to prevent the immediate escape of these VOCs to

the atmosphere. To avoid eventually releasing

VOCs through an enclosure’s ventilation system, a treatment system is necessary. Some of

the better-known treatment methods are discussed below; others also are be available.

a. Adsorption

Adsorption is the adherence of particles of

one substance, in this case VOCs, to the surface of another substance, in this case a filtration or treatment matrix. The matrix can be

replaced or flushed when its surface becomes

saturated with the collected VOCs.

Carbon Adsorption. In carbon adsorption, organics are selectively collected on the

surface of a porous solid. Activated carbon is

a common adsorbent because of its high

internal surface area: 1 gram of carbon can

have a surface area equal to that of a football

field and can typically adsorb up to half its

weight in organics. For adsorption to be

effective, replace, regenerate, or recharge the

carbon when treatment efficiency begins to

decline. In addition, any emissions from the

disposal or regeneration of the carbon should

be controlled. Control efficiencies of 97 to 99

percent have been demonstrated for carbon

adsorbers in many applications.

Biofiltration. While covering odorous

materials with soil is a longstanding odor

control practice, the commercial use of biofiltration is a relatively recent development.

Biofilters reproduce and improve upon the

soil cover concept used in landfills. In a

biofilter, gas emissions containing biodegradable VOCs pass through a bed packed with

damp, porous organic particles. The biologically active filter bed then adsorbs the VOCs.

Microorganisms attached to the wetted filter

material aerobically degrade the adsorbed

chemical compounds. Biofiltration can be a

highly effective and low-cost alternative to

other, more conventional, air pollution control technologies such as thermal oxidation,

catalytic incineration, condensation, carbon

adsorption, and absorption. Successful commercial biofilter applications include treatment of gas emissions from composting

operations, rendering plants, food and tobacco processing, chemical manufacturing,

foundries, and other industrial facilities.18

b. Condensation

Condensers work by cooling the vented

vapors to their dew point and removing the

organics as liquids. The efficiency of a condenser is determined by the vapor phase concentration of the specific organics and the

condenser temperature. Two common types

of condensers are contact condensers and

surface condensers.

c. Absorption

In absorption, the organics in the vent gas

dissolve in a liquid. The contact between the

absorbing liquid and the vent gas is accomplished in spray towers, scrubbers, or packed

or plate columns. Some common solvents

that might be useful for volatile organics

Protecting Air Quality—Protecting Air Quality

5-37

18 Mycock, J.C., J.D. McKenna, and L. Theodore. 1995. Handbook of Air Pollution Control Engineering

and Technology.
include water, mineral oils, or other nonvolatile petroleum oils. Absorption efficiencies of 60 to 96 percent have been reported

for organics. The material removed from the

absorber can present a disposal or separation

problem. For example, organics must be

removed from the water or nonvolatile oil

without losing them as emissions during the

solvent recovery or treatment process.

d. Vapor Combustion

Vapor combustion is another control technique for vented vapors. The destruction of

organics can be accomplished in flares; thermal oxidizers, such as incinerators, boilers,

or process heaters; and in catalytic oxidizers.

Flares are an open combustion process in

which oxygen is supplied by the air surrounding the flame. Flares are either operated

at ground level or elevated. Properly operated

flares can achieve destruction efficiencies of

at least 98 percent. Thermal vapor incinerators can also achieve destruction efficiencies

of at least 98 percent with adequately high

temperature, good mixing, sufficient oxygen,

and an adequate residence time. Catalytic

incinerators provide oxidation at temperatures lower than those required by thermal

incinerators. Design considerations are

important because the catalyst can be

adversely affected by high temperatures, high

concentrations of organics, fouling from particulate matter or polymers, and deactivation

by halogens or certain metals.

5. Special Considerations for

Land Application Units

Since spraying wastes increases contact

between waste and air and promotes VOC

emissions, if the waste contains volatile

organics you might want to choose another

application method, such as subsurface injection. During subsurface injection, waste is

supplied to the injection unit directly from a

remote holding tank and injected approximately 6 inches into the soil; hence, the

waste is not exposed to the atmosphere. In

addition, you should consider pretreating the

waste to remove the organics before placing

it in the land application unit.

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Protecting Air Quality—Protecting Air Quality
Protecting Air Quality—Protecting Air Quality

5-39

We recommend that you consider the following issues when evaluating and controlling air

emissions from industrial waste management units:

■ Understand air pollution laws and regulations, and determine whether and how they

apply to a unit.

■ Evaluate waste management units to identify possible sources of volatile organic

emissions.

■ Work with your state agency to evaluate and implement appropriate emission control

techniques, as necessary.

Protecting Air Activity List
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Protecting Air Quality—Protecting Air Quality

American Conference of Governmental Industrial Hygienists. 1997. Threshold Limit Values for Chemical

Substances and Physical Agents and Biological Exposure Indices.

Christensen, T.H., R. Cossu, and R. Stegmann. 1995. Siting, Lining Drainage & Landfill Mechanics,

Proceeding from Sardinia 95 Fifth International Landfill Symposium, Volume II. 

Finn, L., and R. Spencer. 1987. Managing Biofilters for Consistent Odor and VOC Treatment. BioCycle.

January.

Hazardous Waste Treatment, Storage and Disposal Facilities and Hazardous Waste Generators; Organic Air

Emission Standards for Tanks, Surface Impoundments, and Containers; Final Rule. Federal Register. Volume

59, Number 233, December 6, 1994. pp. 62896 - 62953.

Mycock, J.C., J.D. McKenna, and L. Theodore. 1995. Handbook of Air Pollution Control Engineering and

Technology. 

National Ambient Air Quality Standards for Particulate Matter. Federal Register. Volume 62, Number 138, July

18, 1997. pp. 38651 - 38701.

Orlemann, J.A., T.J. Kalman, J.A. Cummings, E.Y. Lin. 1983. Fugitive Dust Control Technology.

Robinson, W. 1986. The Solid Waste Handbook: A Practical Guide. 

Texas Center for Policy Studies. 1995. Texas Environmental Almanac, Chapter 6, Air Quality. <www.tec.org>

U.S. EPA. 2002a. Industrial Waste Air Model Technical Background Document. EPA530-R-02-010.

U.S. EPA. 2002b. Industrial Waste Air Model (IWAIR) User’s Guide. EPA530-R-02-011.

U.S. EPA. 1998. Taking Toxics out of the Air: Progress in Setting “Maximum Achievable Control Technology”

Standards Under the Clean Air Act. EPA451-K-98-001.

U.S. EPA. 1997a. Best Management Practices (BMPs) for Soil Treatment Technologies: Suggested Operational

Guidelines to Prevent Cross-Media Transfer of Contaminants During Clean-Up Activities. EPA530-R-97-007.

U.S. EPA. 1997b. Residual Risk Report to Congress. EPA453-R-97-001.

U.S. EPA. 1996. Test Methods for Evaluating Solid Waste Physical/Chemical Methods—SW846. Third

Edition.

Resources
Protecting Air Quality—Protecting Air Quality

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U.S. EPA. 1995a. Exposure Factors Handbook: Volumes 1-3. EPA600-P-95-002FA-C.

U.S. EPA. 1995b. Survey of Control Technologies for Low Concentration Organic Vapor Gas Streams.

EPA456-R-95-003.

U.S. EPA. 1995c. User’s Guide for the Industrial Source Complex (ISC3) Dispersion Models: Volume I.

EPA454-B-95-003a.

U.S. EPA. 1995d. User’s Guide for the Industrial Source Complex (ISC3) Dispersion Models: Volume IIDescription of Model Algorithms. EPA454-B-95-003b.

U.S. EPA. 1994a. Air Emissions Models for Waste and Wastewater. EPA453-R-94-080A.

U.S. EPA. 1994b. Handbook: Control Techniques for Fugitive VOC Emissions from Chemical Process

Facilities. EPA625-R-93-005.

U.S. EPA. 1994c. Toxic Modeling System Short-Term (TOXST) User’s Guide: Volume I. EPA454-R-94-058A.

U.S. EPA. 1993. Guideline on Air Quality Models. EPA450-2-78-027R-C

U.S. EPA. 1992a. Control of Air Emissions from Superfund Sites. EPA625-R-92-012.

U.S. EPA. 1992b. Protocol for Determining the Best Performing Model. EPA454-R-92-025. 

U.S. EPA. 1992c. Seminar Publication: Organic Air Emissions from Waste Management Facilities. EPA625-

R-92-003.

U.S. EPA. 1991. Control Technologies for Hazardous Air Pollutants. EPA625-6-91-014.

U.S. EPA. 1989. Hazardous Waste TSDF—Fugitive Particulate Matter Air Emissions Guidance Document.

EPA450-3-89-019.

U.S. EPA. 1988. Compilation of Air Pollution Emission Factors. AP-42.

U.S. EPA. 1985. Rapid Assessment of Exposures to Particulate Emissions form Surface Contamination

Sites.

Viessman, W., and M. Hammer. 1985. Water Supply and Pollution Control.

Resources (cont.)
Part III

Protecting Surface Water

Chapter 6

Protecting Surface Water
Contents

I. Determining the Quality and Health of Surface Waters ..........................................................................6 - 1

A. Water Quality Criteria............................................................................................................................6 - 2

B. Water Quality Standards ........................................................................................................................6 - 2

C. Total Maximum Daily Load (TMDL) Program........................................................................................6 - 3

II. Surface-Water Protection Programs Applicable to Waste Management Units ..........................................6 - 4

A. National Pollutant Discharge Elimination System (NPDES) Permit Program..........................................6 - 4

1. Storm-Water Discharges ....................................................................................................................6 - 5

2. Discharges to Surface Waters ............................................................................................................6 - 6

B. National Pretreatment Program..............................................................................................................6 - 6

1. Description of the National Pretreatment Program ............................................................................6 - 6

2. Treatment of Waste at POTW Plants..................................................................................................6 - 8

III. Understanding Fate and Transport of Pollutants ..................................................................................6 - 10

A. How Do Pollutants Move From Waste Management Units To Surface Water?......................................6 - 10

1. Overland Flow ................................................................................................................................6 - 10

2. Ground Water to Surface Water ......................................................................................................6 - 11

3. Air to Surface Water ........................................................................................................................6 - 11

B. What Happens When Pollutants Enter Surface Water? ........................................................................6 - 12

C. Pollutants Of Concern ........................................................................................................................6 - 13

IV. Protecting Surface Waters ....................................................................................................................6 - 13

A. Controls to Address Surface-Water Contamination from Overland Flow ............................................6 - 13

1. Baseline BMPs..................................................................................................................................6 - 18

2. Activity-Specific BMPs ....................................................................................................................6 - 18

3. Site-Specific BMPs ..........................................................................................................................6 - 19

B. Controls to Address Surface-water Contamination from Ground Water to Surface Water....................6 - 29

C. Controls to Address Surface-water Contamination from Air to Surface Water......................................6 - 29

V. Methods of Calculating Run-on and Runoff Rates ................................................................................6 - 30

Protecting Surface Water Activity List..........................................................................................................6 - 33

Resources ....................................................................................................................................................6 - 34

Figures:

Figure 1. BMP Identification and Selection Flow Chart............................................................................6 - 17

Figure 2. Coverings..................................................................................................................................6 - 22

Figure 3. Silt Fence ..................................................................................................................................6 - 24
Contents (cont.)

Figure 4. Straw Bale ................................................................................................................................6 - 24

Figure 5. Storm Drain Inlet Protection ....................................................................................................6 - 25

Figure 6. Collection and Sedimentation Basin..........................................................................................6 - 26

Figure 7. Outlet Protection ......................................................................................................................6 - 27

Figure 8. Infiltration Trench ....................................................................................................................6 - 28

Figure 9. Typical Intensity-Duration-Frequency Curves ..........................................................................6 - 31

Tables:

Table 1. Biological and Chemical Processes Occurring in Surface Water Bodies ......................................6 - 14

Table 2. Priority Pollutants ......................................................................................................................6 - 15
Protecting Surface Water—Protecting Surface Water

6-1

Over 70 percent of the Earth’s

surface is water. Of all the

Earth’s water, 97 percent is

found in the oceans and seas,

while 3 percent is fresh water.

This fresh water is found in glaciers, lakes,

ground water, wetlands, and rivers. Because

water is such a valuable commodity, the protection of our surface waters should be everyone’s goal. Pollutants1 associated with waste

management units and storm-water discharges must be controlled.

This chapter summarizes how EPA and

states determine the quality of surface waters

and subsequently describes the existing surface-water protection programs for ensuring

the health and integrity of waterbodies. The

fate and transport of pollutants in the surfacewater environment is also discussed. Finally,

various methods that are used to control pollutant discharges to surface waters are described.

I. Determining the

Quality and

Health of

Surface Waters

The protection of aquatic resources is governed by the Clean Water Act (CWA). The

objective of the CWA is to “restore and maintain the chemical, physical, and biological

1 To be consistent with the terminology used in the Clean Water Act, the term pollutant is used in this

chapter in place of the term constituent. In this chapter, pollutant means an effluent or condition introduced to surface waters that results in degradation. Water pollutants include human and animal wastes,

nutrients, soil and sediments, toxics, sewage, garbage, chemical wastes, and heat.

Protecting Surface Water

This chapter will help you:

• Protect surface waters by limiting the discharge of pollutants into

the waters of the United States. 

• Guard against inappropriate discharges of pollutants associated

with process wastewaters and storm water to ensure the safety of

the nation’s surface waters. 

• Reduce storm-water discharges by complying with applicable regulations, implementing available storm-water controls, and identifying

best management practices (BMPs) to control storm water.

This chapter will help you address the

following questions:

• What surface-water protection programs are applicable to my waste

management unit?

• What are the objectives of run-on and

runoff control systems?

• What should be considered in designing surface-water protection systems?

• What BMPs should be implemented

to protect surface waters from pollutants associated with waste management units?

• What are some of the engineering and

physical mechanisms available to control storm water?
6-2

Protecting Surface Water—Protecting Surface Water

integrity of the nation’s waters” (Section

101(a)). Section 304(a) of the CWA authorizes

EPA to publish recommended water quality

criteria that provide guidance for states to use

in adopting water quality standards under

Section 303(c). Section 303 of the CWA also

establishes the Total Maximum Daily Load

(TMDL) Program which requires EPA and the

states to identify waters not meeting water

quality standards and to establish TMDLs for

those waters.

A. Water Quality Criteria

Under authority of Section 304 of the

CWA, EPA publishes water quality “criteria”

that reflect available scientific information on

the maximum acceptable concentration levels

of specific chemicals in water that will protect

aquatic life, human health, and drinking

water. EPA has also established nutrient criteria (e.g., phosphorus and nitrogen) and biological criteria (i.e., biointegrity values). These

criteria are used by the states for developing

enforceable water quality standards and identifying problem areas.

Water quality criteria are developed from

toxicity studies conducted on different organisms and from studies of the effects of toxic

compounds on humans. Federal water quality

criteria specify the maximum exposure concentrations that will provide protection of

aquatic life and human health. Generally,

however, the water quality criteria describe

the quality of water that will support a particular use of the water body. For the protection

of aquatic life a two-value criterion has been

established to account for acute and chronic

toxicity of pollutants. The human health criterion specifies the risk incurred with exposure

to the toxic compounds at a specified concentration. The human health criterion is associated with the increased risk of contracting a

debilitating disease, such as cancer.

B. Water Quality Standards

Water quality standards are laws or regulations that states (and authorized tribes) adopt

to enhance and maintain the quality of water

and protect public health. States have the primary responsibility for developing and implementing these standards. Water quality

standards consist of three elements: 1) the

“designated beneficial use” or “uses” of a

waterbody or segment of a waterbody, 2) the

water quality “criteria” necessary to protect

the uses of that particular waterbody, and 3)

an antidegradation policy. “Designated use” is

a term that is specified in water quality standards for a body of water or a segment of a

body of water (e.g., a particular branch of a

river). Typical uses include public water supply, propagation of fish and wildlife, and

recreational, agricultural, industrial, and navigational purposes. Each state develops its own

use classification system based on the generic

What is water quality?

Water quality reflects the composition of

water as affected by natural causes and

human activities, expressed in terms of

measurable quantities and related to

intended water use. Water quality is determined by comparing physical, chemical,

biological, microbiological, and radiological quantities and parameters to a set of

standards and criteria. Water quality is

perceived differently by different people.

For example, a public health official might

be concerned with the bacterial and viral

safety of water used for drinking and

bathing, while fishermen might be concerned that the quality of water be sufficient to provide the best habitat for fish.

For each intended use and water quality

benefit, different parameters can be used

to express water quality. 
Protecting Surface Water—Protecting Surface Water

6-3

uses cited in the CWA. The states may differentiate and subcategorize the types of uses

that are to be protected, such as cold-water or

warm-water fisheries, or specific species that

are to be protected (e.g., trout, salmon, bass).

States may also designate special uses to protect sensitive or valuable aquatic life or habitat. In addition, the water quality criteria

adopted into a state water quality standard

may or may not be the same number published by EPA under section 304. States have

the discretion to adjust the EPA’s criteria to

reflect local environmental conditions and

human exposure patterns.

The CWA requires that the states review

their standards at least once every three years

and submit the results to EPA for review. EPA

is required to either approve or disapprove

the standards, depending on whether they

meet the requirements of the CWA. When

EPA disapproves a standard, and the state

does not revise the standard to meet EPA’s

objection, the CWA requires the Agency to

propose substitute federal standards. 

C. Total Maximum Daily

Load (TMDL) Program

Lasting solutions to water quality problems

and pollution control can be best achieved by

looking at the fate of all pollutants in a watershed. The CWA requires EPA to administer

the total maximum daily load (TMDL) program, under which the states establish the

allowable pollutant loadings for impaired

waterbodies (i.e., waterbodies not meeting

state water quality standards) based on their

“waste assimilative capacity.” EPA must

approve or disapprove TMDLs established by

the states. If EPA disapproves a state TMDL,

EPA must establish a federal TMDL.

A TMDL is a calculation of the maximum

amount of a pollutant that a waterbody can

receive and still meet water quality standards.

The calculation must include a margin of

safety to ensure that the waterbody can be

used for the purposes the state has designated. The calculation must also account for seasonal variation in water quality.

The quantity of pollutants that can be discharged into a surface-water body without

use impairment (also taking into account natural inputs such as erosion) is known as the

“assimilative capacity.” The assimilative capacity is the range of concentrations of a substance or a mixture of substances that will

not impair attainment of water quality standards. Typically, the assimilative capacity of

surface-water bodies might be higher for

biodegradable organic matter, but it can be

very low for some toxic chemicals that accumulative in the tissues of aquatic organisms

and become injurious to animals and people

using them as food.

U.S. EPA Selected Water Quality Criteria in Micrograms per Liter

Aquatic Life Human Health 10-6 Risk

Freshwater Marine Water and Fish Fish Ingestion

Chemical Acute Chronic Acute Chronic Ingestion Only

Benzene 5300 — 5100 700 0.66 40

Cadmium — — 43 9.3 10 —

DDT 1.1 0.001 0.13 0.001 0.000024 0.000024

PCBs 2 0.014 10 0.03 0.000079 0.000079
6-4

Protecting Surface Water—Protecting Surface Water

II. Surface-Water

Protection

Programs

Applicable to

Waste

Management

Units

To ensure that a state’s water quality standards and TMDLs are being met, discharges of

pollutants are regulated through the National

Pollutant Discharge Elimination System

(NPDES) Permit Program and the National

Pretreatment Program. These permitting programs are implemented and enforced at the

state or local level.

A. National Pollutant

Discharge Elimination

System (NPDES) Permit

Program

The CWA requires most “point sources”

(i.e., entities that discharge pollutants of any

kind into waters of the United States) to have

a permit establishing pollution limits, and

specifying monitoring and reporting requirements. This permitting process is known as

the National Pollutant Discharge Elimination

System (NPDES). Permits are issued for three

types of wastes that are collected in sewers

and treated at municipal wastewater treatment plants or that discharge directly into

receiving waters: process wastewater, nonprocess wastewater, and storm water. Most

discharges of municipal and industrial storm

water require NPDES permits, but some

other storm water discharges do not require

permits. To protect public health and aquatic

life and assure that every facility treats wastewater, NPDES permits include the following

terms and conditions. 

• Site-specific effluent (or discharge)

limitations.

• Standard and site-specific compliance

monitoring and reporting requirements.

• Monitoring, reporting, and compliance

schedules that must be met.

There are various methods used to monitor

NPDES permit conditions. The permit will

require the facility to sample its discharges and

notify EPA and the state regulatory agency of

these results. In addition, the permit will

require the facility to notify EPA and the state

regulatory agency when the facility determines

it is not in compliance with the requirements

of a permit. EPA and state regulatory agencies

also send inspectors to facilities in order to

What is a watershed?

Watersheds are areas of land that drain to

surface-waterbodies. A watershed generally includes lakes, rivers, estuaries, wetlands, streams, and the surrounding

landscape. Ground-water recharge areas

are also considered part of a watershed.

Because watersheds are defined by natural hydrology, they represent the most logical basis for managing surface-water

resources. Managing the watershed as a

whole allows state and local authorities to

gain a more complete understanding of

overall conditions in an area and the

cumulative stressors which affect the surface-water body. Information on EPA’s

strategy to protect and restore water quality and aquatic ecosystems at the watershed level can be found at <www.epa.

gov/owow/watershed/index2.html>
Protecting Surface Water—Protecting Surface Water

6-5

2 Initially, a group application option was available for facilities with similar activities to jointly submit a

single application for permit coverage. A multi-sector general permit was then issued based upon information provided in the group applications. The group application option was only used during the initial stages of the program and is no longer available.

determine if they are in compliance with the

conditions imposed under their permits. 

NPDES permits typically establish specific

“effluent limitations” relating to the type of

discharge. For process wastewaters, the permit incorporates the more stringent of technology-based limitations (either at 40 CFR

Parts 405 through 471 or developed on a

case-by-case basis according to the permit

writer’s best professional judgement) or water

quality-based effluent limits (WQBELs).

Some waste management units, such as surface impoundments, might have an NPDES

permit to discharge wastewaters directly to

surface waters. Other units might need an

NPDES permit for storm-water discharges.

NPDES permits are issued by EPA or states

with NPDES permitting authority. If you are

located in a state with NPDES authority, you

should contact the state directly to determine

the requirements for your discharges. EPA’s

Office of Wastewater Management’s Web page

contains a complete, updated list of the states

with approved NPDES permit programs, as

well as a fact sheet and frequently asked

questions about the NPDES permit program

at <cfpub.epa.gov/npdes>. If a state does not

have NPDES permitting authority, you should

follow any state requirements for discharges

and contact EPA to determine the applicable

federal requirements for discharges.

1. Storm-Water Discharges

EPA has defined 11 categories of “stormwater discharges associated with industrial

activity” that require a permit to discharge to

navigable waters (40 CFR Part 122.26 (b)

(14)). These 11 categories are: 1) facilities

subject to storm-water effluent limitations

guidelines, new source performance standards (NSPS), or toxic pollutant effluent standards under 40 CFR Part 129 (specifies

manufacturers of 6 specific pesticides), 2)

“heavy” manufacturing facilities, 3) mining

and oil and gas operations with “contaminated” storm-water discharges, 4) hazardous

waste treatment, storage, or disposal facilities,

5) landfills, land application sites, and open

dumps, 6) recycling facilities, 7) steam electric generating facilities, 8) transportation

facilities, 9) sewage treatment plants, 10)

construction operations disturbing five or

more acres, and 11) other industrial facilities

where materials are exposed to storm water.

Nonhazardous waste landfills, waste piles,

and land application units are included in

category 5. Under a new Section 122.26(b)

(15), storm water discharges from construction operations disturbing between one and

five acres will be required to obtain a NPDES

permit effective in March 2003. There will

be, however, some waivers from permit

requirements available.

To provide flexibility for the regulated

community in acquiring NPDES storm-water

discharge permits, EPA has two NPDES permit application options: individual permits

and general permits.2 Applications for indiWhen is an NPDES permit

needed?

To answer questions about whether or

not a facility needs to seek NPDES permit coverage, or to determine whether a

particular program is administered by

EPA or a state agency, contact your state

or EPA regional storm-water office.

Currently, 44 states and the U.S. Virgin

Islands have federally-approved state

NPDES permit programs. The following

6 states do not have final EPA approval:

Alaska, Arizona, Idaho, Massachusetts,

New Hampshire, and New Mexico.

(As of March 2001)
Protecting Surface Water—Protecting Surface Water

vidual permits require the submission of a

site drainage map, a narrative description of

the site that identifies potential pollutant

sources, and quantitative testing data for specific parameters. General permits usually

involve the submission of a Notice of Intent

(NOI) that includes only general information,

which is neither industry-specific or pollutant-specific and typically do not require the

collection of monitoring data. NPDES general

storm-water permits typically require the

development and implementation of stormwater pollution prevention plans and BMPs

to limit pollutants in storm-water discharges. 

The EPA has also issued the Multi-Sector

General Permit (60 FR 50803; September 29,

1995) which covers 29 different industry sectors. The Agency reviewed, on a sector-bysector basis, information concerning industrial activities, BMPs, materials stored outdoors,

and end-of-pipe storm-water sampling data.

Based on this review, EPA identified pollutants of concern in each industry sector, the

sources of these pollutants, and the BMPs

used to control them. The Multi-Sector

General Permit requires the submission of an

NOI, as well as development and implementation of a site-specific pollution prevention

plan, as the basic storm-water control strategy

for each industry sector. 

2. Discharges to Surface Waters

Most surface impoundments that are

addressed by the Guide are part of a facility’s

wastewater treatment process that results in

an NPDES-permitted discharge to surface

waters. The NPDES permit only sets pollution limits for the final discharge of treated

wastewater. Generally, the NPDES permit

would not establish any regulatory requirements regarding the design or operation of

the surface impoundments that are part of

the treatment process except that, once

designed and constructed, a provision

requires use of those treatment processes

except in limited circumstances. Individual

state environmental agencies, under their

own statutory authorities, can impose

requirements on surface impoundment

design and operation.

B. National Pretreatment

Program

1. Description of the National

Pretreatment Program

For industrial facilities that discharge

wastewaters to publicly owned treatment

works (POTW) through domestic sewer lines,

pretreatment of the wastewater may be

required (40 CFR Part 403). Under the

6-6

What types of pollutants

are regulated by NPDES? 

Conventional pollutants are contained

in the sanitary wastes of households,

businesses, and industries. These pollutants include human wastes, ground-up

food from sink disposals, and laundry

and bath waters. Conventional pollutants

include fecal coliform, oil and grease,

total suspended solids (TSS), biochemical

oxygen demand (BOD), and pH.

Toxic pollutants are particularly harmful to animal or plant life. They are primarily grouped into organics (including

pesticides, solvents, polychlorinated

biphenyls (PCBs), and dioxins) and metals

(including lead, silver, mercury, copper,

chromium, zinc, nickel, and cadmium).

Nonconventional pollutants are any

additional substances that are not considered conventional or toxic that may

require regulation. These include nutrients such as nitrogen and phosphorus.
Protecting Surface Water—Protecting Surface Water

6-7

National Pretreatment Program, EPA, states,

and local regulatory agencies establish discharge limits to reduce the level of pollutants

discharged by industry into municipal sewer

systems. These limits control the pollutant

levels reaching a POTW, improve the quality

of the effluent and sludges produced by the

POTW, and increase the opportunity for beneficial use of the end products (e.g., effluents,

sludges, etc). Further information about

industrial pretreatment and the National

Pretreatment Program is available on the

Office of Wastewater Management’s Web page

at <cfpub.epa.gov/npdes/home.cfm?

program_id=3>.

POTWs are designed to treat domestic

wastes and biodegradable commercial and

industrial wastes. The CWA and EPA define

the pollutants from these sources as “conventional pollutants” which includes those specific pollutants that are expected to be

present in domestic discharges to POTWs.

Commercial and industrial facilities can,

however, discharge toxic pollutants that a

treatment plant is neither designed nor able

to remove. Such discharges, from both industrial and commercial sources, can cause serious problems at POTWs. The undesirable

outcome of these discharges can be prevented

by using treatment techniques or management practices to reduce or eliminate the discharge of these pollutants. 

The act of treating wastewater prior to discharge to a POTW is commonly referred to as

“pretreatment.” The National Pretreatment

Program provides the statutory and regulatory

basis to require non-domestic dischargers to

comply with pretreatment standards to ensure

that the goals of the CWA are attained. The

objectives of the National Pretreatment

Program are to:

• Prevent the introduction of pollutants

into POTWs which will interfere with

the operation of a POTW, including

interference with the disposal of

municipal sludge.

• Prevent the introduction of pollutants

into POTWs which will pass through

the treatment works or otherwise be

incompatible with such works.

• Improve opportunities to recycle and

reclaim municipal and industrial

wastewaters and sludges.

To help accomplish these objectives, the

National Pretreatment Program is charged

with controlling 126 priority pollutants from

industries that discharge into sewer systems

as described in the CWA, Section 307(a), and

listed in 40 CFR Part 423 Appendix A. These

priority pollutants fall into two categories,

metals and toxic organics.

• The metals include lead, mercury,

chromium, and cadmium. Such toxic

metals cannot be destroyed or broken

down through treatment or environmental degradation. They can cause

various human health problems such

as lead poisoning and cancer.

• The toxic organics include solvents,

pesticides, dioxins, and polychlorinated biphenyls (PCBs). These can be

cancer-causing and lead to other serious ailments, such as kidney and liver

damage, anemia, and heart failure.

The objectives of the National

Pretreatment Program are achieved by applying and enforcing three types of discharge

standards: 1) prohibited discharge standards

(provide for overall protection of POTWs), 2)

categorical standards applicable to specific

point source categories (provide for general

protection of POTWs), and 3) local limits

(address the water quality and other concerns

at specific POTWs).

Prohibited Discharge Standards. All

industrials users (IUs), whether or not subject

to any other federal, state, or local pretreat-
Protecting Surface Water—Protecting Surface Water

ment requirements, are subject to the general

and specific prohibitions identified in 40 CFR

Part 403.5 (a) and (b), respectively. General

prohibitions forbid the discharge of any pollutant to a POTW that can pass through or

cause interference. Specific prohibitions forbid the discharge of pollutants that pose fire

or explosion hazards; corrosives; solid or viscous pollutants in amounts that will obstruct

system flows; quantities of pollutants that will

interfere with POTW operations; heat that

inhibits biological activity; specific oils; pollutants that can cause the release of toxic gases;

and pollutants that are hauled to the POTW

(except as authorized by the POTW).

Categorical Standards. Categorical pretreatment standards are national, uniform,

technology-based standards that apply to discharges to POTWs from specific industrial

categories (e.g., battery manufacturing, coil

coating, grain mills, metal finishing, petroleum refining, rubber manufacturing) and limit

the discharge of specific pollutants. These

standards are described in 40 CFR Parts 405

through 471.

Categorical pretreatment standards can be

concentration-based or mass-based.

Concentration- based standards are expressed

as milligrams of pollutant allowed per liter of

wastewater discharged (mg/l) and are issued

where production rates for the particular

industrial category do not necessarily correlate with pollutant discharges. Mass-based

standards are generally expressed as a mass

per unit of production (e.g., milligrams of

pollutant per kilogram of product produced)

and are issued where production rates do

correlate with pollutant discharges. Thus,

limiting the amount of water discharge (i.e.,

water conservation) is important to reducing

the pollutant load to the POTW. For a few

categories where reducing a facility’s flow volume does not provide a significant difference

in the pollutant load discharged, EPA has

established both mass- and concentrationbased standards. Generally, both a daily maximum limitation and a long-term average

limitation (e.g., average daily values in a calendar month) are established for each regulated pollutant.

Local Limits. Federal regulations located

at 40 CFR Parts 403.8 (f) (4) and 122.21 (j)

(4) require authorities to evaluate the need

for local limits and, if necessary, implement

and enforce specific limits protective of that

POTW. Local limits might be developed for

pollutants such as metals, cyanide, BOD, TSS,

oil & grease, and organics that can interfere

with or pass through the treatment works,

cause sludge contamination, or cause worker

health and safety problems if discharged at

excess levels.

All POTWs designed to accommodate

flows of more than 5 million gallons per day

and smaller POTWs with significant industrial discharges are required to establish pretreatment programs. The EPA Regions and

states with approved pretreatment programs

serve as approval authorities for the National

Pretreatment Program. In that capacity, they

review and approve requests for POTW pretreatment program approval or modification,

oversee POTW program implementation,

review requested modifications to categorical

pretreatment standards, provide technical

guidance to POTWs and IUs, and initiate

enforcement actions against noncompliant

POTWs and IUs.

2. Treatment of Waste at POTW

Plants

A waste treatment works’ basic function is

to speed up the natural processes by which

water is purified and returned to receiving

lakes and streams. There are two basic stages

in the treatment of wastes, primary and secondary. In the primary stage, solids are

6-8
Protecting Surface Water—Protecting Surface Water

6-9

allowed to settle and are removed from

wastewater. The secondary stage uses biological processes to further purify wastewater.

Sometimes, these stages are combined into

one operation. POTWs can also perform

other “advanced treatment” operations to

remove ammonia, phosphorus, pathogens

and other pollutants in order to meet effluent

discharge requirements.

Primary treatment. As sewage enters a

plant for treatment, it flows through a screen,

which removes large floating objects such as

rags and sticks that can clog pipes or damage

equipment. After sewage has been screened, it

passes into a grit chamber, where cinders,

sand, and small stones settle to the bottom. At

this point, the sewage still contains organic

and inorganic matter along with other suspended solids. These solids are minute particles that can be removed from sewage by

treatment in a sedimentation tank. When the

speed of the flow of sewage through one of

these tanks is reduced, the suspended solids

will gradually sink to the bottom, where they

form a mass of solids called raw primary

sludge. Sludge is usually removed from tanks

by pumping, after which it can be further

treated for use as fertilizer, or disposed of

through incineration if necessary. To complete

primary treatment, effluent from the sedimentation tank is usually disinfected with chlorine

before being discharged into receiving waters.

Sometimes chlorine is fed into the water to

kill pathogenic bacteria and to reduce

unpleasant odors.

Secondary treatment. The secondary stage

of treatment removes about 85 percent of the

organic matter in sewage by making use of the

bacteria in it. The two principal techniques

used in secondary treatment are trickling filters and the activated sludge process.

Trickling filters. A trickling filter is a bed of

stones from three to six feet deep through

which the sewage passes. More recently, interlocking pieces of corrugated plastic or other

synthetic media have also been used in trickling beds. Bacteria gather and multiply on

these stones until they can consume most of

the organic matter in the sewage. The cleaner

water trickles out through pipes for further

treatment. From a trickling filter, the sewage

flows to another sedimentation tank to

remove excess bacteria. Disinfection of the

effluent with chlorine is generally used to

complete the secondary stage. Ultraviolet

light or ozone are also sometimes used in situations where residual chlorine would be

harmful to fish and other aquatic life. 

Activated sludge. The activated sludge treatment process speeds up the work of the bacteria by bringing air and sludge, heavily laden

with bacteria, into close contact with sewage.

After the sewage leaves the settling tank in

the primary stage, it is pumped into an aeration tank, where it is mixed with air and

sludge loaded with bacteria and allowed to

remain for several hours. During this time,

the bacteria break down the organic matter

into harmless by-products. The sludge, now

activated with additional millions of bacteria

and other tiny organisms, can be used again

by returning it to the aeration tank for mixing

with new sewage and ample amounts of air.

From the aeration tank, the sewage flows to

another sedimentation tank to remove excess

bacteria. The final step is generally the addition of chlorine to the effluent.

Advanced treatment. New pollution

problems have created additional treatment

needs on wastewater treatment systems. Some

pollutants can be more difficult to remove

from water. Increased demands on the water

supply only aggravate the problem. These

challenges are being met through better and

more complete methods of removing pollutants at treatment plants, or through prevention of pollution at the source (refer to
Protecting Surface Water—Protecting Surface Water

Chapter 3 – Integrating Pollution Prevention

for more information). Advanced waste treatment techniques in use or under development range from biological treatment capable

of removing nitrogen and phosphorus to

physical-chemical separation techniques such

as filtration, carbon adsorption, distillation,

and reverse osmosis. These wastewater treatment processes, alone or in combination, can

achieve almost any degree of pollution control desired. As waste effluents are purified to

higher degrees by such treatment, the effluent

water can be used for industrial, agricultural,

or recreational purposes, or even as drinking

water supplies.

III. Understanding

Fate and

Transport of

Pollutants

A. How Do Pollutants

Move From Waste

Management Units To

Surface Water?

1. Overland Flow

The primary means by which pollutants

are transported to surface-water bodies is via

overland flow or “runoff.” Runoff to surface

water is the amount of precipitation after all

“losses” have been subtracted. Losses include

infiltration into soils, interception by vegetation, depression storage and ponding, and

evapotranspiration (i.e., evaporation from the

soil and transpiration by plants).

There is a correlation between the pollutant loadings to surface water and the amount

of precipitation (rainfall, snow, etc.) that falls

on the watershed in which a waste management unit is located. In addition, the characteristics of the soil at a facility also influence

pollutant loading to surface water. If, for

example, the overland flow is diminished due

to high soil infiltration, so is the transport of

particulate pollutants to surface water. Also, if

wastes are land applied and surface overland

flow is generated by a rainfall event, a significant portion of pollutants can be moved over

land into adjacent surface water. 

A diagram representing rainfall transformation into runoff and other components of the

hydrologic cycle is shown in Chapter 7:

Section A–Assessing Risk. The first stage of

runoff formation is condensation of atmospheric moisture into rain droplets or

snowflakes. During this process, water comes

in contact with atmospheric pollutants. The

pollution content of rainwater can therefore

reach high levels. In addition, rain water dis6-10

What is “runoff?”

Runoff is water or leachate that drains

or flows over the land from any part of a

waste management unit.

What is “run-on?”

Run-on is water from outside a waste

management unit that flows into the

unit. Run-on includes storm water from

rainfall or the melting of snow or ice

that falls directly on the unit, as well as

the water that drains from adjoining

areas.
solves atmospheric carbon dioxide and sulfur

and nitrogen oxides, and acts as a weak acid

after it hits the ground, reacting with soil and

limestone formations. Overland flow begins

after rain particles reach the earth’s surface

(note that during winter months runoff formation can be delayed by snowpack formation and subsequent melting). Rain hitting an

exposed waste management unit will liberate

and pick up particulates and pollutants from

the unit and can also dissolve other chemicals

it comes in contact with. Precipitation that

flows into a waste management unit, called

“run-on,” can also free-up and subsequently

transport pollutants out of the unit. Runoff

carries the pollutants from the waste management unit as it flows downgradient following

the natural contours of the watershed to

nearby lakes, rivers, or wetland areas. 

2. Ground Water to Surface

Water

Ground water and surface water are fundamentally interconnected. In fact, it is often

difficult to separate the two because they

“feed” each other. As a result, pollutants can

move from one media to another. Shallow

water table aquifers interact closely with

streams, sometimes discharging water into a

stream or lake and sometimes receiving water

from the stream or lake. Many rivers, lakes,

and wetlands rely heavily on ground-water

discharge as a source of water. During times

of low precipitation, some bodies of water

would not contain any water at all if it were

not for ground-water discharge.

An unconfined aquifer that feeds a stream

is said to provide the stream’s “baseflow.”

Gravity is the dominant driving force in

ground-water movement in unconfined

aquifers. As such, under natural conditions,

ground water moves “downhill” until it

reaches the land surface at a spring or

through a seep in the side or bottom of a

river bed, lake, wetland, or other surfacewater body. Ground water can also leave the

aquifer via the pumping of a well. The

process of ground water outflowing into a

surface-water body or leaving the aquifer

through pumping is called discharge. 

Discharge from confined aquifers occurs in

much the same way except that pressure,

rather than gravity, is the driving force in

moving ground water to the surface. When

the intersection between the aquifer and the

land’s surface is natural, the pathway is called

a spring. If discharge occurs through a well,

that well is a “flowing artesian well.” 

3. Air to Surface Water

Pollutants released into the air are carried

by wind patterns away from their place of

origin. Depending on weather conditions and

the chemical and physical properties of the

pollutants, pollutants can be carried significant distances from their source and can

undergo physical and chemical changes as

they travel. Some of these chemical changes

include the formation of new pollutants such

as ozone, which is formed from nitrogen

oxides (NOx) and hydrocarbons. 

Atmospheric deposition occurs when pollutants in the air fall on the land or surface

waters. When pollutants are deposited in

snow, fog, or rain, the process is called wet

deposition, while the deposition of pollutants

as dry particles or gases is called dry deposition. Pollutants can be deposited into water

bodies either directly from the air onto the

surface of the water, or through indirect

deposition, where the pollutants settle on the

land and are then carried into a water body

by runoff. 

Protecting Surface Water—Protecting Surface Water

6-11
Protecting Surface Water—Protecting Surface Water

Any pollutant that is emitted into the air

can become a surface-water problem due to

deposition. Some of the common pollutants

that can be transported to surface-water bodies via air include different forms of nitrogen,

mercury, copper, polychlorinated biphenols

(PCBs), polycyclic aromatic hydrocarbons

(PAHs), chlordane, dieldrin, lead, lindane,

polycyclic organic matter (POM), dioxins,

and furans.

B. What Happens When

Pollutants Enter Surface

Water?

All pollutants entering surface water via

runoff, ground-water infiltration, or air transport have an effect on the aquatic ecosystem.

Additive and synergistic effects are also factors because many different pollutants can

enter a surface-water body from diverse

sources and activities. As such, solutions to

water quality problems are best achieved by

looking at all activities and inputs to surface

water in a watershed.

Surface-water ecosystems (i.e., rivers,

lakes, wetlands, estuaries) are considered to

be in a dynamic equilibrium with their inputs

and surroundings. These ecosystems can be

divided into two components, the biotic (living) and abiotic (nonliving). Pollutants are

continually moving between the two. For

example, pollutants can move from the abiotic environment (i.e., the water column) into

aquatic organisms, such as fish. The intake of

the pollutant can occur as water moves across

the gills or directly through the skin. Toxic

pollutants can accumulate in fish (known as

bioaccumulation), as the fish uptakes more of

the pollutant than it can metabolize or

excrete. Pollutants can eventually concentrate

in an organism to a level where death results.

At that point, the pollutants will be released

back into the abiotic environment as the

organism decays.

Pollutants can also move within the abiotic

environment, as for example, between water

and its bottom sediments. Pollutants that are

attached to soil particles being carried downThe Dissolved Oxygen

Problem

The dissolved oxygen balance is an

important water quality consideration

for streams and estuaries. Dissolved oxygen is the most important parameter for

protecting fish and other aquatic organisms. Runoff with a high concentration

of biodegradable organics (organic matter) can have a serious effect on the

amount of dissolved oxygen in the

water. Low dissolved oxygen levels can

be very detrimental to fish. The content

of organic matter in waste discharges is

commonly expressed as the biochemical

oxygen demand (BOD) load. Organic

matter can come from a variety of

sources, including waste management

units. When runoff containing organic

matter is introduced into receiving

waters, decomposers immediately begin

to breakdown the organic matter using

dissolved oxygen to do so. Further, if

there are numerous inputs of organic

matter into a single water body, for

example a stream, the effects will be

additive (i.e., more and more dissolved

oxygen will be removed from the stream

as organic matter is added along the

stream reach and decomposes). This is

also an example of how an input that

might not be considered a pollutant

(i.e., organic matter) can lead to harmful

effects due to the naturally occurring

process within a surface-water body.

6-12
stream will be deposited on the bottom of the

streambed as the particles fall out of the

water column. In this manner, pollutants can

accumulate in areas of low flow. Thus, it is

obvious that the hydrodynamical, biological,

and chemical processes in aquatic systems

cannot be separated and must be addressed

simultaneously when considering pollutant

loads and impacts to surface water. Table 1

presents some additional information on the

biological and chemical processes that occur

in water bodies.

C. Pollutants Of Concern

As you assess the different types of best

management practices (BMPs) that can be

used at waste management units to protect

surface waters (discussed in Section IV of this

chapter), you should also identify the pollutants in the unit that pose the greatest threats

to surface water. Factors to consider include

the solubility of the constituents in the waste

management unit, how easily these potential

pollutants can be mobilized, degradation

rates, vapor pressures, and biochemical decay

coefficients of the pollutants and any other

factors that could encourage their release into

the environment.

While all pollutants can become toxic at

high enough levels, there are a number of

compounds that are toxic at relatively low

levels. These pollutants have been designated

by the EPA as priority pollutants. The list of

priority pollutants is included in Table 2. The

list of priority pollutants is continuously

under review by EPA and is periodically

updated. The majority of pollutants on the

list are classified as organic chemicals. Others

are heavy metals which are being mobilized

into the environment by human activities at

rates greatly exceeding those of natural geological processes. Several of the priority pollutants are also considered carcinogenic (i.e.,

they can increase the risk of cancer to the

human population or to aquatic organisms,

such as fish). Priority pollutants of particular

concern for surface-water bodies include: 

• Metals, such as cadmium, copper,

chromium, lead, mercury, nickel, and

zinc, that arise from industrial operations, mining, transportation, and

agricultural use.

• Organic compounds, such as pesticides, PCBs, solvents, petroleum

hydrocarbons, organometallic compounds, phenols, formaldehyde, and

biochemical methylation of metals in

aquatic sediments.

• Dissolved gases, such as chlorine and

ammonium.

• Anions, such as cyanides, fluorides,

sulfides, and sulphates.

• Acids and alkalis.

IV. Protecting

Surface Waters

A. Controls to Address

Surface-Water

Contamination from

Overland Flow

Protecting surface water entails preventing

storm-water contamination during both the

construction of a waste management unit and

the operational life of the unit. During construction the primary concern is sediment

eroding from exposed soil surfaces.

Temporary sediment and erosion control

measures, such as silt fences around construction perimeters, straw bales around

storm-water inlets, and seeding or straw covering of exposed slopes, are typically used to

limit and manage erosion. States or local

Protecting Surface Water—Protecting Surface Water

6-13
6-14

Protecting Surface Water—Protecting Surface Water

Table 1. Biological and Chemical Processes Occurring in Surface-Water Bodies

After pollutants are transported to lakes, rivers, and other water bodies, they can be subject to a

variety of biological and chemical processes that affect how they will interact and impact the aquatic ecosystem. These processes determine how pollutants are mobilized, degraded, or released into

the biotic and abiotic environments.

Metabolism of a toxicant consists of a series of chemical transformations that take place within

an organism. A wide range of enzymes act on toxicants, that can increase water solubility, and facilitate elimination from the organism. In some cases, however, metabolites can be more toxic than

their parent compound. Sullivan. 1993. Environmental Regulatory Glossary, 6th Ed. Government

Institutes.

Bioaccumulation is the uptake and sequestration of pollutants by organisms from their ambient

environment. Typically, the concentration of the substance in the organism exceeds the concentration in the environment since the organism will store the substance and not excrete it. Phillips.

1993. In: Calow (ed), Handbook of Ecotoxicology, Volume One. Blackwell Scientific Publications.

Biomagnification is the concentration of certain substances up a food chain. It is a very important mechanism in concentrating pesticides and heavy metals in organisms such as fish. Certain

substances such as pesticides and heavy metals move up the food chain, work their way into a river

or lake and are eaten by large birds, other animals, or humans. The substances become concentrated in tissues or internal organs as they move up the chain. Sullivan. 1993. Environmental Regulatory

Glossary, 6th Ed. Government Institutes.

Biological degradation is the decomposition of a substance into more elementary compounds

by action of microorganisms such as bacteria. Sullivan. 1993. Environmental Regulatory Glossary, 6th

Ed. Government Institutes.

Hydrolysis is a chemical process of decomposition in which the elements of water react with

another substance to yield one or more new substances. This transformation process changes the

chemical structure of the substance. Sullivan. 1993. Environmental Regulatory Glossary, 6th Ed.

Government Institutes.

Precipitation is a chemical or physical change whereby a pollutant moves from a dissolved form

in a solution to a solid or insoluble form and subsequently drops out of the solution. Precipitation

reduces the mobility of constituents, such as metals and is not generally reversible. Boulding. 1995.

Soil, Vadose Zone, and Ground-Water Contamination: Assessment, Prevention, and Remediation.

Oxidation/Reduction (Redox) process is a complex of biochemical reactions in sediment that

influences the valence state of elements (and their ions) found in sediments. Under anaerobic conditions the overall process shifts to a reducing condition. The chemical properties for elements can

change substantially with changes in the oxidation state. Sullivan. 1993. Environmental Regulatory

Glossary, 6th Ed. Government Institutes. 

Photochemical process is the chemical changes brought about by the radiant energy of the sun

acting upon various polluting substances. Sullivan. 1993. Environmental Regulatory Glossary, 6th Ed.

Government Institutes.
001 Acenaphthene

002 Acrolein

003 Acrylonitrile

004 Benzene

005 Benzidine

006 Carbon tetrachloride

007 Chlorobenzene

008 1,2,4-trichlorobenzene

009 Hexachlorobenzene

010 1,2-dichloroethane

011 1,1,1-trichloreothane

012 Hexachloroethane

013 1,1-dichloroethane

014 1,1,2-trichloroethane

015 1,1,2,2-tetrachloroethane

016 Chloroethane

017 Bis(2-chloroethyl) ether

018 2-chloroethyl vinyl ethers

019 2-chloronaphthalene

020 2,4,6-trichlorophenol

021 Parachlorometa cresol

022 Chloroform

023 2-chlorophenol

024 1,2-dichlorobenzene

025 1,3-dichlorobenzene

026 1,4-dichlorobenzene

027 3,3-dichlorobenzidine

028 1,1-dichloroethylene

029 1,2-trans-dichloroethylene

030 2,4-dichlorophenol

031 1,2-dichloropropane

032 1,2-dichloropropylene

033 2,4-dimethylphenol

034 2,4-dinitrotoluene

035 2,6-dinitrotoluene

036 1,2-diphenylhydrazine

037 Ethylbenzene

038 Fluoranthene

039 4-chlorophenyl phenyl ether

040 4-bromophenyl phenyl ether

041 Bis(2-chloroisopropyl) ether

042 Bis(2-chloroethoxy) methane 

043 Methylene chloride

044 Methyl chloride

045 Methyl bromide

046 Bromoform

047 Dichlorobromomethane

048 Chlorodibromomethane

049 Hexachlorobutadiene

050 Hexachlorocyclopentadiene

051 Isophorone

052 Naphthalene

053 Nitrobenzene

054 2-nitrophenol

055 4-nitrophenol

056 2,4-dinitrophenol

057 4,6-dinitro-o-cresol

058 N-nitrosodimethylamine

059 N-nitrosodiphenylamine

060 N-nitrosodi-n-propylamine

061 Pentachlorophenol

062 Phenol

063 Bis(2-ethylhexyl) phthalate

064 Butyl benzyl phthalate

065 Di-N-Butyl Phthalate

066 Di-n-octyl phthalate

067 Diethyl Phthalate

068 Dimethyl phthalate

069 Benzo(a) anthracene

070 Benzo(a)pyrene

071 Benzo(b) fluoranthene

072 Benzo(b) fluoranthene

073 Chrysene

074 Acenaphthylene

075 Anthracene

076 Benzo(ghi) perylene

077 Fluorene

078 Phenanthrene

079 Dibenzo(,h) anthracene

080 Indeno (1,2,3-cd) pyrene

081 Pyrene

082 Tetrachloroethylene

083 Toluene

084 Trichloroethylene 

085 Vinyl chloride

086 Aldrin

087 Dieldrin

088 Chlordane

089 4,4-DDT

090 4,4-DDE

091 4,4-DDD

092 Alpha-endosulfan

093 Beta-endosulfan

094 Endosulfan sulfate

095 Endrin

096 Endrin aldehyde

097 Heptachlor

098 Heptachlor epoxide

099 Alpha-BHC

100 Beta-BHC

101 Gamma-BHC

102 Delta-BHC

103 PCB–1242

104 PCB–1254

105 PCB–1221

106 PCB–1232

107 PCB–1248

108 PCB–1260

109 PCB–1016

110 Toxaphene

111 Antimony

112 Arsenic

113 Asbestos

114 Beryllium

115 Cadmium

116 Chromium

117 Copper

118 Cyanide, Total

119 Lead

120 Mercury

121 Nickel

122 Selenium

123 Silver

124 Thallium

125 Zinc

126 2,3,7,8-TCDD

Protecting Surface Water—Protecting Surface Water

6-15

3 The list of pollutants is current as of the Federal Register dated April 2, 2001.

Table 2. Priority Pollutants3
municipalities often require the use of sediment and erosion controls at any construction site disturbing greater than a certain

number of acres, and can have additional

requirements in especially sensitive watersheds. You should consult with the state and

local regulatory agencies to determine the

sediment and erosion control requirements

for construction.

Once a waste management unit has been

constructed, permanent run-on and runoff

controls are necessary to protect surface

water. Run-on controls are designed to prevent storm water from entering the active

areas of units. If run-on is not prevented

from entering active areas, it can seep into

the waste and increase the amount of

leachate that must be managed. It can also

deposit pollutants from nearby sites, such as

pesticides from adjoining farms, further burdening treatment systems. Excessive run-on

can also damage earthen containment systems, such as dikes and berms. Run-on that

contacts the waste can carry pollutants into

receiving waters through overland runoff or

into ground water through infiltration. You

can divert run-on to the waste management

unit by taking advantage of natural contours

in the land or by constructing ditches or

berms designed to intercept and drain storm

water away from the unit. Run-on diversion

systems should be designed to handle the

peak discharge of a design storm event (e.g.,

a 24-hour, 25-year storm4

). Also note that

surface impoundments should be designed

with sufficient freeboard and adequate capacity to accommodate not only waste, but also

precipitation and run-on. 

Runoff controls can channel, divert, and

convey storm water to treatment facilities or,

if appropriate, to other intended discharge

points. Runoff from landfills, land treatment

units, or waste piles should be managed as a

potentially contaminated material. The runoff

from active areas of a landfill or waste pile

should be managed as leachate. You should

design a leachate collection and removal system to handle the potentially contaminated

runoff, in addition to the leachate that might

be generated by the unit. You should segregate noncontact runoff to reduce the volume

that will need to be treated as leachate. The

Multi-Sector General Permit does not authorize discharges of leachate which includes

storm water that comes in contact with

waste. The discharge of leachate would be

regulated under either an individually drafted

NPDES permit with site- specific discharge

limitations, or an alternative NPDES general

permit if one is available. Note that for land

application sites, runoff from the site can also

adversely affect nearby surface water if pollutants are picked up and carried overland. 

BMPs are measures used to reduce or

eliminate pollutant releases to surface waters

via overland flow. They fall into three categories, baseline, activity-specific, and sitespecific, and can take the form of a process,

activity, or physical structure. The use of

6-16

4 This discharge is the amount of water resulting from a 24-hour rainfall event of a magnitude with a 4

percent statistical likelihood of occurring in any given year (i.e, once every 25 years). Such an event

might not occur in a given 25-year period, or might occur more than once during a single year.

Protecting Surface Water—Protecting Surface Water

Why are “run-on” controls necessary?

Run-on controls are designed to prevent: 1) contamination of storm water,

2) erosion that can damage the physical

structure of units, 3) surface discharge

of waste constituents, 4) creation of

leachate, and 5) already contaminated

surface water from entering the unit.

What is the purpose of a “runoff”

control system?

Runoff control systems are designed

to collect and control at a minimum the

water flow resulting from a storm event

of a specified duration, such as a 24-

hour, 25-year storm event.
BMPs to protect surface water should be considered in both the design and operation of a

waste management unit. Before identifying

and implementing BMPs, you should assess

the potential sources of storm-water contamination including possible erosion and sediment discharges caused by storm events. A

thorough assessment of a waste management

unit involves several steps including creating

a map of the waste management

unit area; considering the design

of the unit; identifying areas

where spills, leaks, or discharges

could or do occur; inventorying

the types of wastes contained in

the unit; and reviewing current

operating practices (refer to

Chapter 8–Operating the Waste

Management System for more

information). Figure 1 illustrates

the process of identifying and

selecting the most appropriate

BMPs. 

Designing a storm-water

management system to protect

surface water involves knowledge of local precipitation patterns, surrounding topographic

features, and geologic conditions. You should consider sampling runoff to ascertain the

quantity and concentration of

pollutants being discharged.

(Refer to the Chapter 9–

Monitoring Performance for

more information). Collecting

and evaluating this type of information can help you to select

the most appropriate BMPs to

prevent or control pollutant discharges. The same considerations (e.g., types of wastes to be

contained in the unit, precipitation patterns, local topography

and geology) should be made

while designing and constructing a new waste

management unit to ensure that the proper

baseline, activity-specific, and site-specific

BMPs are implemented and installed from the

start of operations. After assessing the potential and existing sources of storm-water contamination, the next step is to select appropriate

BMPs to address these contamination sources. 

Protecting Surface Water—Protecting Surface Water

6-17

Figure 1. BMP Identification and Selection Flow Chart

Recommended Steps

Adapted from U.S. EPA, 1992e.

Assessment Phase 

Develop a site map

Inventory and describe exposed materials 

List significant spills and leaks 

Identify areas associated with industrial activity 

Test for nonstorm-water discharges

Evaluate monitoring/sampling data if appropriate 

(see Chapter 9–Monitoring Performance)

BMP Identification Phase 

Operational BMPs

Source control BMPs

Erosion and sediment control BMPs

Treatment BMPs

Innovative BMPs

Implementation Phase 

Implement BMPs

Train employees

Evaluation/Monitoring Phase 

Conduct semiannual inspection/BMP evaluation (see 

Chapter 8–Operating the Waste Management System)

Conduct recordkeeping 

Monitor surface water if appropriate 

Review and revise plan
1. Baseline BMPs

These practices are, for the most part,

inexpensive and relatively simple. They focus

on preventing circumstances that could lead

to surface-water contamination before it can

occur. Many industrial facilities already have

these measures in place for product loss prevention, accident and fire prevention, worker

health and safety, or compliance with other

regulations (refer to Chapter 8–Operating the

Waste Management System for more information). Baseline BMPs include the measures

summarized below.

Good housekeeping. A clean and orderly

work environment is an effective first step

toward preventing contamination of run-on

and runoff. You should conduct an inventory

of all materials and store them so as to prevent leaks and spills and, if appropriate,

maintain them in areas protected from precipitation and other elements.

Preventive maintenance. A maintenance

program should be in place and should

include inspection, upkeep, and repair of the

waste management unit and any measures

specifically designed to protect surface water.

Visual inspections. Inspections of surface-water protection measures and waste

management unit areas should be conducted

to uncover potential problems and identify

necessary changes. Areas deserving close

attention include previous spill locations;

material storage, handling, and transfer areas;

and waste storage, treatment, and disposal

areas. Any problems such as leaks or spills

that could lead to surface-water contamination should be corrected as soon as practical.

Spill prevention and response. General

operating practices for safety and spill prevention should be established to reduce accidental releases that could contaminate

run-on and runoff. Spill response plans

should be developed to prevent any accidental releases from reaching surface water.

Mitigation practices. These practices contain, clean-up, or recover spilled, leaked, or

loose material before it can reach surface

water and cause contamination. Other BMPs

should be considered and implemented to

avoid releases, but procedures for mitigation

should be devised so that unit personnel can

react quickly and effectively to any releases

that do occur. Mitigation practices include

sweeping or shoveling loose waste into

appropriate areas of the unit; vacuuming or

pumping spilled materials into appropriate

treatment or handling systems; cleaning up

liquid waste or leachate using sorbents such

as sawdust; and applying gelling agents to

prevent spilled liquid from flowing towards

surface water.

Training employees to operate, inspect,

and maintain surface-water protection measures is itself considered a BMP, as is keeping

records of installation, inspection, maintenance, and performance of surface-water protection measures. For more information on

employee training and record keeping, refer

to Chapter 8–Operating the Waste

Management System.

2. Activity-Specific BMPs

After assessment and implementation of

baseline BMPs, you should also consider

planning for activity-specific BMPs. Like

baseline BMPs, they are often procedural

rather than structural or physical measures,

and they are often inexpensive and easy to

implement. In the BMP manual for industrial

facilities, Storm Water Management for

Industrial Activities: Developing Pollution

Prevention Plans and Best Management Practices

(U.S. EPA, 1992f), EPA developed activityspecific BMPs for nine industrial activities,

including waste management. The BMPs that

6-18

Protecting Surface Water—Protecting Surface Water
are relevant to waste management are summarized below. 

Preventing waste leaks and dust emissions due to vehicular travel. To prevent

leaks, you should ensure that trucks moving

waste into and around a waste management

unit have baffles (if they carry liquid waste)

or sealed gates, spill guards, or tarpaulin covers (if the waste is solid or semisolid). To

minimize tracking dust off site where it can

be picked up by storm water, wash trucks in

a curbed truck wash area where wash water

is captured and properly handled. For more

information on these topics, consult Chapter

8–Operating the Waste Management System .

You should be aware that washwater from

vehicle and equipment cleaning is considered

to be “process wastewater,” and is not eligible

for discharge under the Multi-Sector General

Permit program for industrial storm-water

discharges. Such discharges would require

coverage under either a site-specific individual NPDES permit or an NPDES general

storm-water permit.

For land application, choosing appropriate slopes. You should minimize runoff by

designing a waste management unit site with

slopes less than six percent. Moderate slopes

help reduce storm-water runoff velocity

which encourages infiltration and reduces

erosion and sedimentation. Note that stormwater discharges from land application units

are regulated under the Multi-Sector General

Permit program.

3. Site-Specific BMPs

In addition to baseline and activity-specific

BMPs, you should also consider site-specific

BMPs, which are more advanced measures

tailored to specific pollutant sources at a particular waste management unit and usually

consist of the installation of structural or

physical measures. These site-specific BMPs

can be grouped into five areas: flow diversion, exposure minimization, erosion and

sedimentation prevention, infiltration, and

other prevention practices. For many of the

surface-water protection measures described

in this section, it is important to design for an

appropriate storm event (i.e., structures that

control run-on and runoff should be designed

for the discharge of a 24-hour, 25-year storm

event). 

When selecting and designing surfacewater protection measures or systems, you

should consult state, regional, and local

watershed management organizations. Some

of these organizations maintain management

plans devised at the overall watershed level

that address storm-water control. Thus, these

agencies might be able to offer guidance in

developing surface-water protection systems

for optimal coordination with other discharges in the watershed. Again, after sitespecific BMPs have been installed, you should

evaluate the effectiveness of the selected

BMPs on a regular basis to ensure that they

are functioning properly .

Protecting Surface Water—Protecting Surface Water

6-19

BMP Maintenance

BMPs must be maintained on a regular basis to ensure adequate surfacewater protection. Maintenance is

important because storms can damage

surface-water protection measures such

as storage basin embankments or spillways. Runoff can also cause sediments

to settle in storage basins or ditches and

can carry floatables (i.e., tree branches,

lumber, leaves, litter) to the basin.

Facilities might need to repair stormwater controls and periodically remove

sediment and floatables.
6-20

Protecting Surface Water—Protecting Surface Water

a. Flow Diversion

Flow diversion can be used to protect surface water in two ways. First, it can channel

storm water away from waste management

units to minimize contact of storm water

with waste. Second, it can carry polluted or

potentially polluted materials to treatment

facilities. Flow diversion mechanisms include

storm-water conveyances and diversion

dikes.

Storm-Water Conveyances (Channels, Gutters,

Drains, and Sewers)

Storm-water conveyances, such as channels, gutters, drains, and sewers, can prevent

storm-water run-on from entering a waste

management unit or runoff from leaving a

unit untreated. Some conveyances collect

storm water and route it around waste management units or other waste containment

areas to prevent contact with the waste,

which might otherwise contaminate storm

water with pollutants. Other conveyances

collect water that potentially came into contact with the waste management unit and

carry it to a treatment plant (or possibly back

to the unit for reapplication in the case of

land application units, some surface

impoundments, and leachate-recirculating

landfills). Conveyances should not mix the

stream of storm water diverted around the

unit with that of water that might have contacted waste. Remember, storm water that

contacts waste is considered leachate and can

only be discharged in accordance with an

NPDES permit other than the Multi-Sector

General Permit.

Storm-water conveyances can be constructed of or lined with materials such as

concrete, clay tile, asphalt, plastic, metal,

riprap, compacted soil, and vegetation. The

material used will vary depending on the use

of the conveyance and the expected intensity

of storm-water flow. Storm-water conveyances should be designed with a capacity

to accept the estimated storm-water flow

associated with the selected design storm

event. Section V of this chapter discusses

methods for determining storm water flow.

Diversion Dikes

Diversion dikes, often made with compacted soil, direct run-on away from a waste management unit. Dikes are built uphill from a

unit and usually work with storm-water conveyances to divert storm water from the unit.

To minimize the potential for erosion, diversion dikes are often constructed to redirect

runoff at a shallow slope to minimize its

velocity. A similar means of flow diversion is

grading the area around the waste management unit to keep storm water away from the

area, instead of or in addition to using diversion dikes to redirect water that would otherwise flow into these areas. In planning for the

installation of dikes, you should consider the

slope of the drainage area, the height of the

dike, the size of the flow it will need to divert,

What are some advantages of

conveyances?

Conveyances direct storm-water flows

around industrial areas, waste management units, or other waste containment

areas to prevent temporary flooding;

require little maintenance; and provide

long-term control of storm-water flows.

What are some disadvantages of

conveyances?

Conveyances require routing through

stabilized structures to minimize erosion.

They also can increase flow rates, might

be impractical if there are space limitations, and might not be economical.
and the type of conveyance that will be used

with the dike.

b. Exposure Minimization

Like flow diversion, exposure minimization practices, such as curbing, diking, and

covering can reduce contact of storm water

with waste. They often are small structures

immediately covering or surrounding a higher risk area, while flow diversion practices

operate on the scale of an entire waste management unit.

Curbing and Diking

These are raised borders enclosing areas

where liquid spills can occur. Such areas

could include waste transfer points in land

application, truck washes, and leachate management areas at landfills and waste piles.

The raised dikes or curbs prevent spilled liquids from flowing to surface waters, enabling

prompt cleanup of only a small area.

Covering

Erecting a roof, tarpaulin, or other permanent or temporary covering (see Figure 2)

over the active area of a landfill or waste

transfer location can keep precipitation from

falling directly on waste materials and prevent run-on from occurring. If temporary

coverings are used, you should ensure that

sufficient weight is attached to prevent wind

from moving the cover, and to repair or

replace the cover material if holes or leaks

develop.

c. Erosion and Sedimentation

Prevention

Erosion and sedimentation practices serve to

limit erosion (the weathering of soil or rock

particles from the ground by wind, water, or

human activity) and to prevent particles that

are eroded from reaching surface waters as sediment. Erosion and sedimentation can threaten

aquatic life, increase treatment costs for downstream water treatment plants, and impede

recreational and navigational uses of waterways. Erosion and sedimentation are of particular concern at waste management units because

the sediment can be contaminated with waste

constituents and because erosion can undercut

or otherwise weaken waste containment structures. Practices such as vegetation, interceptor

dikes, pipe slope drains, silt fences, storm drain

inlet protection, collection and sedimentation

basins, check dams, terraces and benches, and

outlet protection can help limit erosion and

sedimentation.

Vegetation

Erosion and sedimentation can be reduced

by ensuring that areas where storm water is

likely to flow are vegetated. Vegetation slows

erosion and sedimentation by shielding soil

surfaces from rainfall, improving the soil’s

water storage capacity, holding soil in place,

slowing runoff, and filtering out sediment.

One method of providing vegetation is to preserve natural growth. This is achieved by

Protecting Surface Water—Protecting Surface Water

6-21

What are some advantages of

diversion dikes?

Diversion dikes limit storm-water

flows over industrial site areas; can be

economical, temporary structures when

built from soil onsite; and can be converted from temporary to permanent at

any time.

What are some disadvantages of

diversion dikes?

Diversion dikes are not suitable for

large drainage areas unless there is a

gentle slope and might require maintenance after heavy rains.
managing the construction of the waste management unit to minimize disturbance of surrounding grass and plants. If it is not possible

to leave all areas surrounding a unit undisturbed, preserve strips of existing vegetation

as buffer zones in strategically chosen areas of

the site where erosion and sediment control is

most needed, such as on steep slopes uphill

of the unit and along stream banks downhill

from the unit. If it is not possible to leave sufficient buffer zones of existing vegetation, you

should create buffer zones by planting such

areas with new vegetation.

Temporary or permanent seeding of erodible areas is another means of controlling erosion and sedimentation using vegetation.

Permanent seeding, often of grass, is appropriate for establishing long-term ground

cover after construction and other land-disturbing activities are complete. Temporary

seeding can help prevent erosion and sedimentation in areas that are exposed but will

not be disturbed again for a considerable

time. These areas include soil stockpiles,

temporary roadbanks, and dikes. Local regulations might require temporary seeding of

areas that would otherwise remain exposed

beyond a certain period of time. You should

consult local officials to determine whether

such requirements apply. Seeding might not

be feasible for quickly establishing cover in

arid climates or during nongrowing seasons

in other climates. Sod, although more expensive, can be more tolerant of these conditions

than seed and establish a denser grass cover

more quickly. Compost used in combination

with seeding can also be used effectively to

establish vegetation on slopes.

Physical and chemical stabilization, and

various methods of providing cover are also

often considered in conjunction with vegetative measures or when vegetative measures

cannot be used. Physical stabilization is

appropriate where stream flow might be

increased due to construction or other activities associated with the waste management

unit and where vegetative measures are not

practical. Stream-bank stabilization might

involve the reinforcement of stream banks

with stones, concrete or asphalt, logs, or

gabions (i.e., structures formed from crushed

rock encased in wire mesh). Methods of providing cover such as mulching, compost, matting, and netting can be used to cover

surfaces that are steep, arid, or otherwise

unsuitable for planting. These methods also

can work in conjunction with planting to stabilize and protect seeds. (Mattings are sheets

of mulch that are more stable than loose

mulch chips. Netting is a mesh of jute, wood

fiber, plastic, paper, or cotton that can hold

mulch on the ground or stabilize soils. These

measures are sometimes used with seeding to

provide insulation, protect against birds, and

hold seeds and soil in place.) Chemical stabilization (also known as chemical mulch, soil

6-22

Protecting Surface Water—Protecting Surface Water

Figure 2. Coverings 

Roof, overhang, or other 

permanent structure 

Tarp or other covering

From U.S. EPA, 1992e.
binder, or soil palliative) can hold the soil in

place and protect against erosion by spraying

vinyl, asphalt, or rubber onto soil surfaces.

Erosion and sediment control is immediate

upon spraying and does not depend on climate or season. Stabilizer should be applied

according to manufacturer’s instructions to

ensure that water quality is not affected.

Coating large areas with thick layers of stabilizer, however, can create an impervious surface and speed runoff to downgradient areas

and should be avoided.

Interceptor Dikes and Swales

Dikes (ridges of compacted soil) and

swales (excavated depressions in which storm

water flows) work together to prevent entry

of run-on into erodible areas. A dike is built

across a slope upgradient of an area to be

protected, such as a waste management unit,

with a swale just above the dike. Water flows

down the slope, accumulates in the swale,

and is blocked from exiting it by the dike.

The swale is graded to direct water slowly

downhill across the slope to a stabilized outlet structure. Since flows are concentrated in

the swale, it is important to vegetate the

swale to prevent erosion of its channel and to

grade it so that predicted flows will not damage the vegetation.

Pipe Slope Drains

Pipe slope drains are flexible pipes or

hoses used to traverse a slope that is already

damaged or at high risk of erosion. They are

often used in conjunction with some means

of blocking water flow on the slope, such as a

dike. Water collects against the dike and is

then channeled to one point along the dike

where it enters the pipe, which conveys it

downhill to a stabilized (usually riprap-lined)

outlet area at the bottom of the slope. You

should ensure that pipes are of adequate size

to accommodate the design storm event and

are kept clear of clogs.

Silt Fences, Straw Bales, and Brush Barriers

Silt fences and straw bales (see Figures 3

and 4) are temporary measures designed to

capture sediment that has already eroded and

reduce the velocity of storm water. Silt fences

and straw bales should not be considered

permanent measures unless fences are maintained on a routine basis and straw bales are

replaced regularly. They could be used, for

example, during construction of a waste management unit or on a final cover before permanent grass growth is established. 

Silt fences consist of geotextile fabric supported by wooden posts. These fences slow

the flow of storm water and retain sediment as

the water filters through the fabric. If properly

installed, straw bales perform a similar function. Straw bales should be placed end to end

(with no gaps in between) in a shallow, excavated trench and staked into place. Silt fences

and straw bales limit sediment from entering

receiving waters if properly maintained. Both

measures require frequent inspection and

maintenance, including checking for channels

eroded beneath the fence or bales, removing

Protecting Surface Water—Protecting Surface Water

6-23

What are some advantages of silt

fences, straw bales, and brush barriers?

They prevent eroded materials from

reaching surface waters and prevent

downstream damage from sediment

deposits at minimal cost.

What are some disadvantages of silt

fences, straw bales, and brush barriers?

These measures are not appropriate

for streams or large swales and pose a

risk of washouts if improperly installed.
accumulated sediment, and replacing damaged or deteriorated sections.

Brush barriers work like silt fences and

straw bales but are constructed of readily

available materials. They consist of brush and

other vegetative debris piled in a row and are

often covered with filter fabric to hold them

in place and increase sediment interception.

Brush barriers are inexpensive due to their

reuse of material that is likely available from

clearing the site. New vegetation often grows

in the organic material of a brush barrier,

helping anchor the barrier with roots.

Depending on the material used, it might be

possible to leave a former brush barrier in

place and allow it to biodegrade, rather than

remove it.

Storm Drain Inlet Protection

Filtering measures placed around inlets or

drains to trap sediment are known as inlet

protection (see Figure 5). These measures

prevent sediment from entering inlets or

drains and possibly making their way to the

receiving waters into which the storm

drainage system discharges. Keeping sediment

out of storm-water drainage systems also

serves to prevent clogging, loss of capacity,

and other problems associated with siltation

of drainage structures. Inlet protection methods include sod, excavated areas for settlement of sediment, straw bales or filter fences,

and gravel or stone with wire mesh. These

measures are appropriate for inlets draining

small areas where soil will be disturbed. Some

state or local jurisdictions require installation

of these measures before disturbance of more

than a certain acreage of land begins. Regular

maintenance to remove accumulated sediment is important for proper operation. 

Collection and Sedimentation Basins

A collection or sedimentation basin (see

Figure 6) is an area that retains runoff long

enough to allow most of the sediment to settle out and accumulate on the bottom of the

basin. Since many pollutants are attached to

suspended solids, they will also settle out in

the basin with the sediment. The quantity of

sediment removed will depend on basin volume, inlet and outlet configuration, basin

depth and shape, and retention time. Regular

maintenance and dredging to remove accu6-24

Protecting Surface Water—Protecting Surface Water

Figure 3. Silt Fence

Bottom: Perspective of silt fence. Top: Crosssection detail of base of silt fence.

From U.S. EPA, 1992e.

Figure 4. Straw Bale

From U.S. EPA, 1992e.
mulated sediment and to minimize growth of

aquatic plants that can reduce effectiveness is

critical to the operation of basins. All dredged

materials, whether they are disposed or

reused, should be managed appropriately.

Basins can also present a safety hazard.

Fences or other measures to prevent unwanted public access to the basins and their associated inlet and outlet structures are prudent

safety precautions. In designing collection or

sedimentation basins (a form of surface

impoundment), consider storm- water flow,

sediment and pollutant loadings, and the

characteristics of expected pollutants. In the

case of certain pollutants, it might be appropriate to line the basins to protect the ground

water below. Lining a basin with concrete also

facilitates maintenance by allowing dredging

vehicles to drive into a drained basin and

remove accumulated sediment. Poor implementation of baseline and activity-specific

BMPs can result in high sediment and pollutant loads, leading to unusually frequent

dredging of settled materials. For this reason,

when operating sedimentation basins, it is

important that baseline and activity-specific

BMPs are being implemented properly. We

recommend that construction of these basins

be supervised by a qualified engineer familiar

with state and local storm-water requirements.

Check Dams

Small rock or log

dams erected across a

ditch, swale, or channel

can reduce the speed of

water flow in the conveyance. This reduces

erosion and also allows

sediment to settle out

along the channel. Check

dams are especially useful in steep, fast-flowing

swales where vegetation

cannot be established.

For best results, it is recommended that you

place check dams along

the swale so that the crest

of each check dam is at

the same elevation as the

toe (lowest point) of the

Protecting Surface Water—Protecting Surface Water

6-25

Figure 5. Storm Drain Inlet Protection

From U.S. EPA, 1992e.

What are some advantages of

sedimentation basins?

They protect downstream areas against

clogging or damage and contain smaller

sediment particles than sediment traps

can due to their longer retention time.

What are some disadvantages?

Sedimentation basins are generally

not suitable for large areas, require regular maintenance and cleaning, and will

not remove very fine silts and clays

unless used with other measures.
previous (upstream) check dam. Check dams

work best in conveyances draining small

areas and should be installed only in manmade conveyances. Placement of check dams

in streams is not recommended and might

require a permit.

Terraces and Benches

Terraces and benches are earthen embankments with flat tops or ridge-and-channels.

Terraces and benches hold moisture and

minimize sediment loading in runoff. They

can be used on land with no vegetation or

where it is anticipated that erosion will be a

problem. Terraces and benches reduce erosion damage by capturing storm-water runoff

and directing it to an area where the runoff

will not cause erosion or damage. For best

results, this area should be a grassy waterway,

vegetated area, or tiled outlet. Terraces and

benches might not be appropriate for use on

sandy or rocky slopes.

Outlet Protection

Stone, riprap, pavement, or other stabilized surfaces placed at a storm-water conveyance outlet are known as outlet protection

(see Figure 7). Outlet protection reduces the

speed of concentrated storm-water flows exiting the outlet, lessening erosion and scouring

of channels downstream. It also removes sediment by acting as a filter medium. It is recommended that you consider installing outlet

protection wherever predicted outflow velocities might cause erosion.

d. Infiltration

Infiltration measures such as vegetated filter strips, grassed swales, and infiltration

trenches encourage quick infiltration of

storm water into the ground rather than

allowing it to remain as overland flow.

Infiltration not only reduces runoff velocity,

but can also provide some treatment of

runoff, preserve natural stream flow, and

recharge ground water. Infiltration measures

can be inappropriate on unstable slopes or in

cases where runoff might be contaminated,

6-26

Protecting Surface Water—Protecting Surface Water

Figure 6. 

Collection and Sedimentation Basin

From U.S. EPA, 1992e.

What are some advantages of terraces

and benches?

Terraces and benches reduce runoff

speed and increase the distance of overland runoff flow. In addition, they hold

moisture better than do smooth slopes

and minimize sediment loading in runoff.

What are some disadvantages of

terraces and benches?

Terraces and benches can significantly

increase cut and fill costs and cause

sloughing if excess water infiltrates the

soil. They are not practical for sandy,

steep, or shallow soils.
or where wells, foundations, or septic fields

are nearby.

Vegetated Filter Strips and Grassed Swales

Vegetated filter strips are gently sloped

areas of natural or planted vegetation. They

allow water to pass over them in sheetflow

(runoff that flows in a thin, even layer), infiltrate the soil, and drop sediment. Vegetated

filter strips are appropriate where soils are

well draining and the ground-water table is

deep below the surface. They will not work

effectively on slopes of 15 percent or more

due to high runoff velocity. Strips should be

at least 20 feet wide and 50 to 75 feet long in

general, and longer on steeper slopes. If possible, it is best to leave existing natural vegetation in place as filter strips, rather than

planting new vegetation, which will not function to capture eroded particles until it

becomes established.

Grassed swales function similarly to nonvegetated swales (discussed earlier in this

chapter) except that grass planted along the

swale bottom and sides will slow water flow

and filter out sediment. Permeable soil in

which the swale is cut encourages reduction

of water volume through infiltration. Check

dams (discussed earlier in this chapter) are

sometimes provided in grassed swales to further slow runoff velocity, increasing the rate

of infiltration.

To optimize swale performance, it is best

to use a soil which is permeable but not

excessively so; very sandy soils will not hold

vegetation well and will not form a stable

channel structure. It is also recommended

that you grade the swale to a very gentle

slope to maximize infiltration.

Infiltration Trenches

An infiltration trench (see Figure 8) is a

long, narrow excavation ranging from 3 to 12

feet deep. It is filled with stone to allow for

temporary storage of storm water in the open

spaces between the stones. The water eventually infiltrates the surrounding soil or is collected by perforated pipes in the bottom of

the trench and conveyed to an outflow point.

Such trenches can remove fine sediments and

Protecting Surface Water—Protecting Surface Water

6-27

Figure 7. Outlet Protection 

From U.S. EPA, 1992e.
soluble pollutants. They should not be built

in relatively impervious soils, such as clay,

that would prevent water from draining from

the bottom of the trench; less than 3 feet

above the water table; in soil that is subject

to deep frost penetration; or at the foot of

slopes steeper than 5 percent. Infiltration

trenches should not be used to handle contaminated runoff. Runoff can be pretreated

using a grass buffer/filter strip or treated in

the trench with filter fabric.

e. Other Practices

Additional practices exist that can help

prevent contamination of surface water such

as preventive monitoring, dust control, vehicle washing, and discharge to wetlands.

Many of these practices are simple and inexpensive to implement while others, such as

monitoring, can require more resources.

Preventive Monitoring

Preventive monitoring includes automatic

and control systems, monitoring of operations by waste management unit personnel,

and testing of equipment. These processes

can help to ensure that equipment functions

as designed and is in good repair so that

spills and leaks, which could contaminate

adjacent surface waters, are minimized and

do not go undetected when they do occur.

Some automatic monitoring equipment, such

as pressure gauges coupled with pressure

relief devices, can correct problems without

human intervention, preventing leaks or

spills that could contaminate surface water if

allowed to occur. Other monitoring equipment can provide early warning of problems

so that personnel can intervene before leaks

or spills occur. Systems that could contaminate surface water if they failed and that

could benefit from automatic monitoring or

early warning devices include leachate

pumping and treatment systems, liquid waste

distribution and storage systems at land

application units, and contaminated runoff

conveyances.

Dust Control

In addition to being an airborne pollutant,

dust can settle in areas where it can be

picked up by runoff or can be transported by

air and deposited directly into surface waters.

Dust particles can carry pollutants and can

also result in sedimentation of waterbodies.

Several methods of dust control are available

to prevent this. These include irrigation,

chemical treatments, minimization of

exposed soil areas, wind breaks, tillage, and

sweeping. For further information on dust

control, consult Chapter 8–Operating the

Waste Management System.

Vehicle Washing

Materials that accumulate on tires and other

vehicle surfaces and then disperse across a

facility are an important source of surfacewater contamination. Vehicle washing removes

materials such as dust and waste. Washing stations can be located near waste transfer areas

or near the waste management site exit.

Pressurized water spray is usually sufficient to

remove dust. Waste water from vehicle washing operations should be contained and han6-28

Protecting Surface Water—Protecting Surface Water

Figure 8. Infiltration Trench 

From U.S. EPA, 1992e.
dled appropriately. Discharge of such waste

water requires an NPDES permit other than

the Multi-Sector General Permit.

Discharges to Wetlands

Discharge to constructed wetlands is a

method less frequently used and can involve

complicated designs. The discharge of storm

water into natural wetlands, or the modification of wetlands to improve their treatment

capacity, can damage a wetland ecosystem

and, therefore, is subject to federal, state, and

local regulations.

Constructed wetlands provide an alternative to natural wetlands. A specially designed

pond or basin, which is lined in some cases,

is stocked with wetland plants that can control sedimentation and manage pollutants

through biological uptake, microbial action,

and other mechanisms. Together, these

processes often result in better pollutant

removal than would be expected from sedimentation alone. When designing constructed wetlands, you should consider 1) that

maintenance might include dredging, similar

to that required for sedimentation basins, 2)

provisions for a dry-weather flow to maintain

the wetlands, 3) measures to limit mosquito

breeding, 4) structures to prevent escape of

floating wetland plants (such as water

hyacinths) into downstream areas where they

are undesirable, and 5) a program of harvesting and replacing plants.

B. Controls to Address

Surface-water

Contamination from

Ground Water to

Surface Water

Generally, the use of liners and groundwater monitoring systems will reduce potential contamination from ground water to

surface water. For more information on protecting ground water, refer to Chapter 7:

Sections A–Assessing Risk, Section

B–Designing and Installing Liners, and

Section C–Designing a Land Application

Program.

C. Controls to Address

Surface-water

Contamination from Air

to Surface Water

Emission control techniques for volatile

organic compounds (VOC) and particulates

can assist in reducing potential contamination

of surface water from air. Refer to Chapter

5–Protecting Air Quality, for more information on air emission control techniques.

Protecting Surface Water—Protecting Surface Water

6-29

What are some advantages of

constructed wetlands?

Provide aesthetic as well as water quality benefits and areas for wildlife habitat.

What are some disadvantages of

constructed wetlands?

Discharges to wetlands might be subject to multiple federal, state, and local

regulations. In addition, constructed

wetlands might not be feasible if land is

not available and might not be effective

as a storm-water control measure until

time has been allowed for substantial

plant growth.
V. Methods of

Calculating 

Run-on and

Runoff Rates

The design and operation of surface-water

protection systems will be driven by anticipated storm-water flow. Run-on and runoff

flow rates for the chosen design storm event

should be calculated in order to: 1) choose

the proper type of storm-water controls to

install, and 2) properly design the controls

and size the chosen control measures to minimize impacts to surface water. Controls

based on too small a design storm event, or

sized without calculating flows will not function properly and can result in releases of

contaminated storm water. Similarly, systems

can also be designed for too large a flow,

resulting in unnecessary control and excessive costs.

The usual approach for sizing surfacewater protection systems relies on the use of

standardized “design storms.” A design storm

is, in theory, representative of many recorded

storms and reflects the intensity, volume, and

duration of a storm predicted to occur once

in a given number of years. In general, surface-water protection structures should be

designed to handle the discharge from a 24-

hour, 25-year storm event (i.e., a rainfall

event of 24 hours duration and of such a

magnitude that it has a 4 percent statistical

likelihood of occurring in any given year).

Figure 9 presents a typical intensity-durationfrequency curve for rainfall events.

The Hydrometeorological Design Studies

Center (HDSC) at the National Weather

Service has prepared Technical Paper 40,

Rainfall Frequency Atlas of the United States for

Durations From 30 Minutes to 24 Hours and

Return Periods From 1 to 100 Years (published

6-30

Protecting Surface Water—Protecting Surface Water

Rational Method for

Calculating Storm-Water

Runoff Flow

Q = cia

where,

Q = peak flow rate (runoff), expressed in

cubic feet per second (cfs)*

c = runoff coefficient, unitless. The coefficient c is not directly calculable, so

average values based on experience

are used. Values of c range from 0 (all

infiltration, no runoff) to 1 (all

runoff, no infiltration). For example,

flat lawns with sandy soil have a c

value of 0.05 to 0.10, while concrete

streets have a c value of 0.80 to 0.95.

i = average rainfall intensity, expressed

in inches per hour, for the time of

concentration, tc, which is a calculable flow time from the most distant

point in the drainage area to the

point at which Q is being calculated.

Once tc is calculated and a design

storm event frequency is selected, i

can be obtained from rainfall intensity-duration-frequency graphs (see

Figure 9).

a = drainage area, expressed in acres.

The drainage area is the expanse in

which all runoff flows to the point

at which Q is being calculated.

* Examining the units of i and a would

indicate that Q should be in units of

ac-in/hr. However, since 1 ac-in/hr =

1.008 cfs, the units are interchangeable

with a negligible loss of accuracy. Units

of cfs are usually desired for subsequent calculations.
in 1961). This document contains rainfall

intensity information for the entire United

States. Another HDSC document, NOAA Atlas

2, Precipitation Frequency Atlas of the Western

United States (published in 1973) comes in 11

volumes, one for each of the 11 westernmost

of the contiguous 48 states. Precipitation frequency maps for the eleven western most

states are available on the Western Regional

Climate Center’s Web page at <www.wrcc.

sage.dri.edu/ pcpnfreq.html>. HDSC is currently assembling more recent data for some

areas. Your state or local regulatory agency

might be able to provide data for your area.

Several methods are available to help you

calculate storm-water flows. The Rational

Method can be used for calculating runoff for

areas of less than 200 acres. Another useful

tool for estimating storm-water flows is the

Natural Resource Conservation Service’s TR55 software.5 TR-55 estimates runoff volume

from accumulated rainfall and then applies

the runoff volume to a simplified hydrograph

for peak discharge total runoff estimations.

Computer models are also available to aid

in the design of storm-water control systems.

For example, EPA’s Storm Water

Management Model (SWMM) is a comprehensive model capable of simulating the

movement of precipitation and pollutants

from the ground surface through pipe and

channel networks, storage treatment units,

and finally to receiving water bodies. Using

SWMM, it might be possible to perform both

single-event and continuous simulation on

catchments having storm sewers and natural

drainage, for prediction of flows, stages, and

pollutant concentrations.

Some models, including SWMM, were

developed for purposes of urban storm-water

control system design, so it is important to

ensure that their methodology is applicable to

the design of industrial waste management

units. As with all computer models, these

should be used as part of the array of design

tools, rather than as a substitute for careful

consideration of the unit’s design by qualified

professionals.

Protecting Surface Water—Protecting Surface Water

6-31

5 TR-55, Urban Hydrology for Small Watersheds Technical Release 55, presents simplified procedures to

calculate storm runoff volume, peak rate of discharge, hydrographs, and storage volumes required for

floodwater reservoirs. This software is suited for use in small and especially urbanizing watersheds. TR55 can be downloaded from the National Resource Conservation Service at

<www.wcc.nrcs.usda.gov/water/quality/common/tr55/tr55.html>.

Figure 9. Typical Intensity-DurationFrequency Curves

From WATER SUPPLY AND POLLUTION CONTROL, 5th Edition, by Warren Viessman, Jr. and

Mark J. Hammer; Copyright (©) 1993 by Harper

Collins College Publishers. Reprinted by permission of Addison-Wesley Educational Publishers.
6-32

Protecting Surface Water—Protecting Surface Water

Storm Water Management Model (SWMM). Simulates the movement of precipitation

and pollutants from the ground surface through pipe and channel networks, storage treatment units, and receiving waters.

BASINS: A Powerful Tool for Managing Watersheds. A multi-purpose environmental analysis system that integrates a geographical information system (GIS), national watershed data, and state-of-the-art environmental assessment and modeling tools into one

package.

Source Loading and Management Model (SLAMM). Explores relationships between

sources of urban runoff pollutants and runoff quality. It includes a wide variety of source

area and outfall control practices. SLAMM is strongly based on actual field observations,

with minimal reliance on theoretical processes that have not been adequately documented

or confirmed in the field. SLAMM is mostly used as a planning tool, to better understand

sources of urban runoff pollutants and their control. 

Simulation for Water Resources in Rural Basins (SWRRB). Simulates hydrologic,

sedimentation, and nutrient and pesticide transport in large, complex rural watersheds. It

can predict the effect of management decisions on water, sediment, and pesticide yield

with seasonable accuracy for ungauged rural basins throughout the United States.

Pollutant Routing Model (P-ROUTE). Estimates aqueous pollutant concentrations on

a stream reach by stream reach flow basis, using 7Q10 or mean flow.

Enhanced Stream Water Quality Model (QUAL2E). Simulates the major reactions of

nutrient cycles, algal production, benthic and carbonaceous demand, atmospheric reaeration and their effects on the dissolved oxygen balance. It is intended as a water quality

planning tool for developing total maximum daily loads (TMDLs) and can also be used in

conjunction with field sampling for identifying the magnitude and quality characteristics

of nonpoint sources.
Protecting Surface Water—Protecting Surface Water

6-33

You should conduct the following activities when designing or operating surface-water

protection measures or systems in conjunction with waste management units.

■ Comply with applicable National Pollutant Discharge Elimination System (NPDES),

state, and local permitting requirements.

■ Assess operating practices, identify potential pollutant sources, determine what constituents in the unit pose the greatest threats to surface water, and calculate stormwater runoff flows to determine the need for and type of storm-water controls.

■ Choose a design storm event (e.g., a 24-hour, 25-year event) and obtain precipitation intensity data for that event to determine the most appropriate storm-water control devices.

■ Select and implement baseline and activity-specific BMPs, such as good housekeeping practices and spill prevention and response plans as appropriate for your waste

management unit.

■ Select and establish site-specific BMPs, such as diversion dikes, collection and sedimentation basins, and infiltration trenches as appropriate for your waste management unit.

■ Develop a plan for inspecting and maintaining the chosen storm-water controls; if

possible, include these measures as part of the operating plan for the waste management unit.

Protecting Surface Water Activity List
6-34

Protecting Surface Water—Protecting Surface Water

Dingman, S. 1994. Physical Hydrology. Prentice Hall.

Florida Department of Environmental Regulation. Storm Water Management: A Guide for Floridians.

Novotny, V., and H. Olem. 1994. Water Quality: Prevention, Identification, and Management of Diffuse

Pollution. Van Nostrand Reinhold.

Pitt, R. 1988. Source Loading and Management Model: An Urban Nonpoint Source Water Quality Model

(SLAMM). University of Alabama at Birmingham.

McGhee, T. 1991. McGraw-Hill Series in Water Resources and Environmental Engineering. 6th Ed.

Urbonas, B., and P. Stahre. 1993. Storm Water: Best Management Practices and Detention for Water Quality,

Drainage, and CSO Management. PTR Prentice Hall.

U.S. EPA. 1999. Introduction to the National Pretreatment Program. EPA833-B-98-002.

U.S. EPA. 1998. Water Quality Criteria and Standards Plan–Priorities for the Future. EPA822-R-98-003.

U.S. EPA. 1995a. Process Design Manual: Land Application of Sewage Sludge and Domestic Septage. EPA625-

R-95-001.

U.S. EPA. 1995b. Process Design Manual: Surface Disposal of Sewage Sludge and Domestic Septage. EPA625-

R-95-002.

U.S. EPA. 1995c. NPDES Storm Water Multi-Sector General Permit Information Package.

U.S. EPA. 1995d. Storm Water Discharges Potentially Addressed by Phase II of the National Pollutant

Discharge Elimination System Storm Water Program. Report to Congress. EPA833-K-94-002.

U.S. EPA. 1994a. Introduction to Water Quality Standards. EPA823-B-95-004.

U.S. EPA. 1994b. Project Summary: Potential Groundwater Contamination from Intentional and NonIntentional Storm Water Infiltration. EPA600-SR-94-061.

U.S. EPA. 1994c. Storm Water Pollution Abatement Technologies. EPA 600-R-94-129.

Resources
Protecting Surface Water—Protecting Surface Water

6-35

U.S. EPA. 1993a. Overview of the Storm Water Program. EPA833-F-93-001.

U.S. EPA. 1993b. NPDES Storm Water Program: Question and Answer Document, Volume 2. EPA833-

F093-002B.

U.S. EPA. 1992a. An Approach to Improving Decision Making in Wetland Restoration and Creation.

EPA600-R-92-150.

U.S. EPA. 1992b. NPDES Storm Water Program: Question and Answer Document, Volume 1. EPA833-F93-002.

U.S. EPA. 1992c. NPDES Storm Water Sampling Guidance Document. EPA833-B-92-001.

U.S. EPA. 1992d. Storm Water General Permits Briefing. EPA833-E-93-001.

U.S. EPA. 1992e. Storm Water Management for Industrial Activities: Developing Pollution Prevention Plans

and Best Management Practices. EPA832-R-92-006.

U.S. EPA. 1992f. Storm Water Management for Industrial Activities: Developing Pollution Prevention Plans

and Best Management Practices. Summary Guidance. EPA833-R-92-002.

Viessman Jr., W., and M.J. Hammer. 1985. Water Supply and Pollution Control. 4th Ed.

Washington State Department of Ecology. 1993. Storm Water Pollution Prevention Planning for Industrial

Facilities: Guidance for Developing Pollution Prevention Plans and Best Management Practices. Water

Quality Report. WQ-R-93-015. September.

Resources (cont.)
Part IV

Protecting Ground-Water Quality

Chapter 7: Section A

Assessing Risk
Contents

I. Assessing Risk ............................................................................................................................................7A-3

A. General Overview of the Risk Assessment Process ................................................................................7A-3

1. Problem Formulation ........................................................................................................................7A-3

2. Exposure Assessment ........................................................................................................................7A-4

3. Toxicity Assessment ..........................................................................................................................7A-5

4. Risk Characterization ........................................................................................................................7A-5

B. Ground-Water Risk................................................................................................................................7A-6

1. Problem Formulation ........................................................................................................................7A-6

2. Exposure Assessment ........................................................................................................................7A-7

3. Toxicity Assessment ........................................................................................................................7A-11

4.Risk Characterization........................................................................................................................7A-12

II. The IWEM Ground-Water Risk Evaluation ..........................................................................................7A-14

A. The Industrial Waste Management Evaluation Model (IWEM) ............................................................7A-15

1. Leachate Concentrations..................................................................................................................7A-16

2. Models Associated with IWEM........................................................................................................7A-16

3. Important Concepts for Use of IWEM ............................................................................................7A-18

B. Tier 1 Evaluations................................................................................................................................7A-22

1. How Are the Tier 1 Lookup Tables Used? ......................................................................................7A-23

2. What Do the Results Mean and How Do I Interpret Them? ............................................................7A-25

C. Tier 2 Evaluations................................................................................................................................7A-27

1. How is a Tier 2 Analysis Performed? ..............................................................................................7A-27

2. What Do the Results Mean and How Do I Interpret Them? ............................................................7A-32

D. Strengths and Limitations ....................................................................................................................7A-34

1. Strengths ........................................................................................................................................7A-34

2. Limitations ......................................................................................................................................7A-34

E. Tier 3: A Comprehensive Site-Specific Evaluation ..............................................................................7A-35

1. How is a Tier 3 Evaluation Performed?............................................................................................7A-35

Assessing Risk Activity List ........................................................................................................................7A-40

Resources ....................................................................................................................................................7A-41

Tables:

Table 1. Earth’s Water Resources ................................................................................................................7A-1

Table 2. Examples of Attenuation Processes ............................................................................................7A-10

Table 3. List of Constituents in IWEM with Maximum Contaminant Levels (MCLs) ..............................7A-13
Contents

Table 4. Example of Tier 1 Summary Table for MCL-based LCTVs for Landfill - No Liner/In situ Soils ..7A-24

Table 5. Example of Tier 1 Summary Table for HBN-based LCTVs for Landfill - No Liner/In situ Soils 7A-25

Table 6. Example of Tier 1 Summary Table for MCL-based LCTVs for Landfill - Single Clay Liner ...... 7A-25

Table 7. Example of Tier 1 Summary Table for MCL-based LCTVs for Landfill - Composite Liner ........ 7A-25

Table 8. Input Parameters for Tier 2 ........................................................................................................7A-29

Table 9. A Sample Set of Site-Specific Data for Input to Tier 2 ................................................................7A-31

Table 10. Example of Tier 2 Detailed Summary Table - No Liner/In situ Soils ........................................7A-31

Table 11. Example of Tier 2 Detailed Summary Table - Single Clay Liner................................................7A-32

Table 12. Example Site-Specific Ground-water Fate and Transport Models..............................................7A-38

Table 13. ASTM Ground-Water Modeling Standards ..............................................................................7A-39

Figures:

Figure 1: Representation of Contaminant Plume Movement ......................................................................7A-5

Figure 2: Three Liner Scenarios Considered in the Tiered Modeling Approach for Industrial 

Waste Guidelines ......................................................................................................................7A-22

Figure 3: Using Tier 1 Lookup Tables......................................................................................................7A-27
Protecting Ground Water—Assessing Risk 

7A-1

1 Surface water, in the form of lakes and rivers, is the other major drinking water source. Speidel, D., L.

Ruedisili, and A. Agnew. 1988. Perspectives on Water: Uses and Abuses.

2 Excludes cooling water for steam-electric power plants. U.S. Geological Survey. 1998. Estimated Use of

Water in the United States in 1995.

Ground water is

the water found

in the soil and

rock that make

up the Earth’s

surface. Although it comprises only about 0.69 percent of the Earth’s water

resources, ground water is of

great importance. It represents about 25 percent of

fresh water resources, and

when the largely inaccessible

fresh water in ice caps and

glaciers is discounted,

ground water is the Earth’s

largest fresh water

resource—easily surpassing

lakes and rivers, as shown in Table 1.

Statistics about the use of ground water as a

drinking water source underscore the importance of this resource. Ground water is a

source of drinking water for more than half of

the people in the United States.1 In rural

areas, 97 percent of households rely on

ground water as their primary source of

drinking water.

In addition to its importance as a domestic

water supply, ground water is heavily used by

industry and agriculture. It provides approximately 37 percent of the irrigation water and 18

percent of the total water used by industry.2

Ground water also has other important environmental functions, such as providing recharge to

lakes, rivers, wetlands, and estuaries. 

Water beneath the ground surface occurs in

an upper unsaturated (vadose) zone and a

deeper saturated zone. The unsaturated zone

is the area above the water table where the

soil pores are not filled with water, although

some water might be present. The subsurface

area below the water table where the pores

and cracks are filled with water is called the

saturated zone. This chapter focuses on

Assessing Risk

This chapter will help you:

• Protect ground water by assessing risks associated with new waste

management units and tailoring management controls accordingly. 

• Understand the three-tiered evaluation discussed in this chapter

that can be used to determine whether a liner system is necessary,

and if so, which liner system is recommended, or whether land

application is appropriate. 

• Follow guidance on liner design and land application practices.

Resource Percent of Percent of 

Total Nonoceanic

Oceans 97.25 —

Ice caps and glaciers 2.05 74.65

Ground water and soil moisture 0.685 24.94

Lakes and rivers 0.0101 0.37

Atmosphere 0.001 0.036

Biosphere 0.00004 0.0015

Table 1.

Earth’s Water Resources

Adapted from Berner, E.K. and R. Berner. 1987. The Global

Water Cycle: Geochemistry and Environment
7A-2

Protecting Ground Water—Assessing Risk 

ground water in the saturated zone, where most

ground-water withdrawals

are made.

Because ground water is a

major source of water for

drinking, irrigation, and

process water, many different

parties are concerned about

ground-water contamination,

including the public; industry; and federal, state, and

local governments. Many

potential threats to the quality of ground water exist,

such as the leaching of fertilizers and pesticides, contamination from faulty or

overloaded septic fields, and

releases from industrial facilities, including waste management units. 

If a source of ground

water becomes contaminated, remedial action and

monitoring can be costly.

Remediation can require

years of effort, or in some

circumstances, might be

technically infeasible. For

these reasons, preventing

ground-water contamination

is important, or at least minimizing impacts to ground

water by implementing controls tailored to the risks

associated with the waste. 

This chapter addresses how ground-water

resources can be protected through the use of

a systematic approach of assessing potential

risk to ground water from a proposed waste

management unit (WMU). It discusses assessing risk and the three-tiered ground-water risk

assessment approach implemented in the

Industrial Waste Management Evaluation

Model (IWEM), which was developed as part

of this Guide. Additionally, the chapter discusses the use of this tool and how to apply

its results and recommendations. It is highly

recommended that you also consult with your

state regulatory agency, as appropriate. More

specific information on the issues described in

Ground Water in the Hydrologic Cycle

The hydrologic cycle involves the continuous movement of

water between the atmosphere, surface water, and the

ground. Ground water must be understood in relation to

both surface water and atmospheric moisture. Most additions (recharge) to ground water come from the atmosphere

in the form of precipitation, but surface water in streams,

rivers, and lakes will move into the ground-water system

wherever the hydraulic head of the water surface is higher

than the water table. Most water entering the ground as precipitation returns to the atmosphere by evapotranspiration.

Most water that reaches the saturated zone eventually

returns to the surface by flowing to points of discharge,

such as rivers, lakes, or springs. Soil, geology, and climate

will determine the amounts and rates of flow among the

atmospheric, surface, and ground-water systems.

Lake

Runoff

Groundwater flow

Evaporation

Precipitation

Infiltration

Percolation

Runoff

Unsaturated Well

Groundwater

Groundwater

Saturated

Water Table

Transpiration

Flow

Zone

Zone

to lakes and streams
this chapter is available in the companion

documents to the IWEM software: User’s

Guide for the Industrial Waste Management

Evaluation Model (U.S. EPA, 2002b), and

Industrial Waste Management Evaluation Model

(IWEM) Technical Background Document (U.S.

EPA, 2002a).

I. Assessing Risk

A. General Overview of the

Risk Assessment Process

Our ground-water resources are essential

for biotic life on the planet. They also act as a

medium for the transport of contaminants

and, therefore, constitute an exposure pathway of concern. Leachate from WMUs can be

a source of ground-water contamination.

Residents who live close to a WMU and who

use wells for water supply can be directly

exposed to waste constituents by drinking or

bathing in contaminated ground water.

Residents also can be exposed by inhaling

volatile organic compounds (VOCs) and

semi-volatile organic compounds (SVOCs)

that are released indoors while using ground

water for showering or via soil gas migration

from subsurface plumes. 

The purpose of this section is to provide

general information on the risk assessment

process and a specific description of how

each of the areas of risk assessment is applied

in performing ground-water risk analyses.

Greater detail on each of the steps in the

process as they relate to assessing groundwater risk is provided in later sections of this

chapter.

In any risk assessment, there are basic

steps that are necessary for gathering and

evaluating data. This Guide uses a four-part

process to estimate the likelihood of chemicals coming into contact with people now or

in the future, and the likelihood that such

contact will harm these people. This process

shows how great (or small) the risks might

be. It also points to who is at risk, what is

causing the risk, and how certain one can be

about the risks. A general overview of these

steps is presented below to help explain how

the process is used in performing the assessments associated with IWEM. The components of a risk assessment that are discussed

in this section are: problem formulation,

exposure assessment, toxicity assessment, and

risk characterization. Each of these steps is

described as it specifically applies to risk

resulting from the release of chemical constituents from WMUs to ground water. 

1. Problem Formulation

The first step in the risk assessment

process is problem formulation. The purpose

of this step is to clearly define the risk question to be answered and identify the objectives, scope, and boundaries of the

assessment. This phase can be viewed as

developing the overall risk assessment study

design for a specific problem. Activities that

might occur during this phase include: 

• Articulating a clear understanding of

the purpose and intended use of the

risk assessment.

• Identifying the constituents of concern.

• Identifying potential release scenarios.

• Identifying potential exposure pathways.

• Collecting and reviewing available

data.

• Identifying data gaps.

• Recommending data collection

efforts.

• Developing a conceptual model of

what is occurring at the site. 

Protecting Ground Water—Assessing Risk 

7A-3
7A-4

Protecting Ground Water—Assessing Risk 

Although this step can be formal or informal, it is critical to the development of a successful assessment that fully addresses the

problem at hand. In addition, the development of a conceptual model helps direct the

next phases of the assessment and provides a

clear understanding of the scope and design

of the assessment.

2. Exposure Assessment

The goals of an exposure assessment are

to: 1) characterize the source, 2) characterize

the physical setting of the area that contains

the WMU, 3) identify potential exposure

pathways, 4) understand the fate and transport of constituents of concern, and 5) calculate constituent doses.

Source characterization involves defining

certain key parameters for the WMU. The

accuracy of predicting risks improves as more

site-specific information is used in the characterization. In general, critical aspects of the

source (e.g., type of WMU, size, location,

potential for leachate generation, and expected constituent concentrations in leachate)

should be obtained. Knowledge of the overall

composition of the waste deposited in the

WMU and of any treatment processes occurring in the WMU is important to determine

the overall characteristics of the leachate that

will be generated. 

The second step in evaluating exposure is

to characterize the site with respect to its

physical characteristics, as well as those of

the human populations near the site.

Important site characteristics include climate,

meteorology, geologic setting, and hydrogeology. Consultation with appropriate technical

experts (e.g., hydrogeologists, modelers)

might be needed to characterize the site.

Characterizing the populations near the site

with respect to proximity to the site, activity

patterns, and the presence of sensitive subgroups might also be appropriate. This group

of data will be useful in determining the

potential for exposure to and intake of constituents.

The next step in this process includes

identifying exposure pathways through

ground water and estimating exposure concentrations at the well3

. In modeling the

movement of the constituents away from the

WMU, the Guide generally assumes that the

constituents behave as a plume (see Figure

1), and the plume’s movement is modeled to

produce estimated concentrations of constituents at points of interest. As shown in

Figure 1, the unsaturated zone receives

leachate from the WMU. In general, the flow

in the unsaturated zone tends to be gravitydriven, although other factors (e.g., soil

porosity, capillarity, moisture potential) can

also influence downward flow.

Transport through the unsaturated zone

delivers constituents to the saturated zone, or

aquifer. Once the contaminant arrives at the

water table, it will be transported downgradient toward wells by the predominant flow

field in the saturated zone. The flow field is

governed by a number of hydrogeologic and

climate-driven factors, including regional

hydraulic gradient, hydraulic conductivity of

the saturated zone, saturated zone thickness,

local recharge rate (which might already be

accounted for in the regional hydraulic gradient), and infiltration rate through the WMU. 

The next step in the process is to estimate

the exposure concentrations at a well. Many

processes can occur in the unsaturated zone

and in the saturated zone that can influence

the concentrations of constituents in leachate

in a downgradient well. These processes

include dilution and attenuation, partitioning

to solid, hydrolysis, and degradation.

Typically, these factors should be considered

when estimating the expected constituent

concentrations at a receptor.

3 In this discussion and in IWEM, the term “well” is used to represent an actual or hypothetical groundwater monitoring well or drinking water well, located downgradient from a WMU.
Protecting Ground Water—Assessing Risk 

7A-5

The final step in this process is estimating

the dose. The dose is determined based on

the concentration of a constituent in a medium and the intake rate of that medium for

the receptor. For example, the dose is dependent on the concentration of a constituent in

a well and the ingestion rate of ground water

from that well by the receptor. The intake

rate is dependent on many behavior patterns,

including ingestion rate, exposure duration,

and exposure frequency. In addition, a risk

assessor should consider the various routes of

exposure (e.g., ingestion, inhalation) to determine a dose.

After all of this information has been collected, the exposure pathways at the site can

be characterized by identifying the potentially

exposed populations, exposure media, exposure points, and relevant exposure routes and

then calculating potential doses. 

3. Toxicity Assessment

The purpose of a toxicity assessment is to

weigh available evidence regarding the potential for constituents to cause adverse effects in

exposed individuals. It is also meant to provide, where possible, an estimate of the relationship between the extent of exposure to a

constituent and the increased likelihood

and/or severity of adverse effects. The intent

is to establish a dose-response relationship

between a constituent concentration and the

incidence of an adverse effect. It is usually a

five-step process that includes: 1) gathering

toxicity information for the substances being

evaluated, 2) identifying the exposure periods

for which toxicity values are necessary, 3)

determining the toxicity values for noncarcinogenic effects, 4) determining the toxicity

values for carcinogenic effects, and 5) summarizing the toxicity information. The derivation and interpretation of toxicity values

requires toxicological expertise and should

not be undertaken by those without training

and experience. It is recommended that you

contact your state regulatory agency for more

specific guidance.

4. Risk Characterization

This step involves summarizing and integrating the toxicity and exposure assessments

Figure 1: Representation of Contaminant Plume Movement

Waste Management Unit

C

Unsaturated

Zone

Saturated

Zone Leachate Plume

DAF

Leachate

Well

Land Surface

Water Table
7A-6

Protecting Ground Water—Assessing Risk 

and developing qualitative and quantitative

expressions of risk. To characterize noncarcinogenic effects, comparisons are made

between projected intakes of substances and

toxicity values to predict the likelihood that

exposure would result in a non-cancer health

problem, such as neurological effects. To characterize potential carcinogenic effects, the

probability that an individual will develop

cancer over a lifetime of exposure is estimated

from projected intake and chemical-specific

dose-response information. The dose of a particular contaminant to which an individual

was exposed—determined during the exposure assessment phase—is combined with the

toxicity value to generate a risk estimate.

Major assumptions, scientific judgements,

and, to the extent possible, estimates of the

uncertainties embodied in the assessment are

also presented. Risk characterization is a key

step in the ultimate decision-making process. 

B. Ground-Water Risk

The previous section provided an overview

of risk assessment; this section provides more

detailed information on conducting a risk

assessment specific to ground water. In particular, this section characterizes the phases of a

risk assessment—problem formulation, exposure assessment, toxicity assessment, and risk

characterization—in the context of a groundwater risk assessment.

1. Problem Formulation

The intent of the problem formulation

phase is to define the risk question to be

answered. For ground-water risk assessments,

the question often relates to whether releases

of constituents to the ground water are protective of human health, surface water, or

ground-water resources. This section discusses characterizing the waste and developing a

conceptual model of a site.

a. Waste Characterization

A critical component in a ground-water

risk assessment is the characterization of the

leachate released from a WMU. Leachate is

the liquid formed when rain or other water

comes into contact with waste. The characteristics of the leachate are a function of the

composition of the waste and other factors

(e.g., volume of infiltration, exposure to differing redox conditions, management of the

WMU). Waste characterization includes both

identification of the potential constituents in

the leachate and understanding the physical

and chemical properties of the waste.

Identification of the potential constituents

in leachate requires a thorough understanding

of the waste that will be placed in a WMU.

Potential constituents include those used in

typical facility processes, as well as degradation products from these constituents. For

ground-water risk analyses, it is important to

not only identify the potential constituents of

concern in the leachate, but also the likely

concentration of these constituents in leachate.

To assist in the identification of constituents

present in leachate, EPA has developed several

leachate tests including the Toxicity

Characteristic Leaching Procedure (TCLP), the

Synthetic Precipitation Leaching Procedure

(SPLP), and the Multiple Extraction Procedure

(MEP). These and other tests that can be used

to characterize leachate are discussed more

fully in Chapter 2—Characterizing Waste and

are described in EPA’s SW-846 Test Methods for

Evaluating Solid Wastes (U.S. EPA, 1996 and as

updated).

In addition to identifying the constituents

present, waste characterization includes

understanding the physical, biological, and

chemical properties of the waste. The physical

and chemical properties of the waste stream

affect the likelihood and rate that constituents

will move through the WMU. For example,

the waste properties influence the partitioning
Protecting Ground Water—Assessing Risk 

7A-7

4 Generally, the model considers a high ratio of solids to leachate, and therefore, the user should consider

this before applying a 20 to 1 solids to leachate ratio.

of constituents among the aqueous, vapor,

and solid phases. Temperature, pH, pressure,

chemical composition,4 and the presence of

microorganisms within WMUs may have significant effects on the concentration of constituents available for release in the leachate.

Another waste characteristic that can influence leachate production is the presence of

organic wastes as free liquids, also called

non-aqueous phase liquids (NAPLs). The

presence of NAPLs may affect the mobility of

constituents based on saturation and viscosity. Finally, characteristics such as acidity and

alkalinity can influence leachate generation

by affecting the permeability of underlying

soil or clay.

b. Development of a Conceptual

Model

The development of a conceptual model is

important for defining what is needed for the

exposure assessment and the toxicity assessment. The conceptual model identifies the

major routes of exposure to be evaluated and

presents the current understanding of the

toxicity of the constituents of concern.

For the ground-water pathway, the conceptual model identifies those pathways on

which the risk assessor should focus.

Potential pathways of interest include ground

water used as drinking water, ground water

used for other domestic purposes that might

release volatile organics, ground-water releases to surface water, vapor intrusion from

ground-water gases to indoor air, and ground

water used as irrigation water. The conceptual model should address the likelihood of

various ground-water pathways under present

or future circumstances, provide insight to

the likelihood of contact with receptors

through the various pathways, and identify

areas requiring further information. 

The conceptual model should also address

the toxicity of the constituents of concern.

Information about constituent toxicity can be

collected from publicly available resources

such as the Integrated Risk Information

System (IRIS) <www.epa.gov/iris> or from

detailed, chemical-specific literature searches.

The conceptual model should attempt to

identify the toxicity data that are most relevant to likely routes of ground-water exposure and identify areas requiring additional

research. The conceptual model should provide a draft plan of action for the next phases

of the risk assessment.

2. Exposure Assessment

Exposure assessment is generally comprised of two components: characterization of

the exposure setting and identification of the

exposure pathways. Characterization of the

exposure setting includes describing the

source characteristics and the site characteristics. Identification of the exposure pathway

involves understanding the process by which

a constituent is released from a source, travels

to a receptor, and is taken up by the receptor.

This section discusses the concepts of characterizing the source, characterizing the site setting, understanding the general dynamics of

contaminant fate and transport (or movement

of harmful chemicals to a receptor), identifying exposure pathways, and calculating the

dose to (or uptake by) a receptor.

a. Source Characterization

The characteristics of a source greatly

influence the release of leachate to ground

water. Some factors to consider include the

type of WMU, the size of the unit, and the

design and management of the unit. The type

of WMU is important because each unit has

distinct characteristics that affect release.

Landfills, for example, tend to be permanent

in nature, which provides a long time period

for leachate generation. Waste piles, on the

other hand, are temporary in design and
allow the user to remove the source of contaminated leachate at a future date. Surface

impoundments, which are generally managed

with standing water, provide a constant

source of liquid for leachate generation and

potentially result in greater volumes of

leachate.

The size of the unit is important because

units with larger areas have the potential to

generate greater volumes of contaminated

leachate than units with smaller areas. Also,

units such as landfills that are designed with a

greater depth below the ground’s surface can

result in decreased travel time from the bottom of the unit to the water table, resulting in

less sorption of constituents. In some cases, a

unit might be hydraulically connected with

the water table resulting in no attenuation in

the unsaturated zone. 

The design of the unit is important because

it might include an engineered liner system

that can reduce the amount of infiltration

through the WMU, or a cover that can reduce

the amount of water entering the WMU.

Typical designs might include compacted clay

liners or geosynthetic liners. For surface

impoundments, sludge layers from compacted

sediments might also help reduce the amount

of leachate released. The compacted sediments can have a lower hydraulic conductivity than the natural soils resulting in slower

movement of leachate from the bottom of the

unit. Covers also affect the rate of leachate

generation by limiting the amount of liquid

that reaches the waste, thereby limiting the

amount of liquid available to form leachate.

Co-disposal of different wastes can result in

increased or decreased rates of leachate generation. Generally, WMUs with appropriate

design specifications can result in reduced

leachate generation. 

b. Site Characterization

Site characterization addresses the physical

characteristics of the site as well as the populations at or near the site. Important physical

characteristics include the climate, geology,

hydrology, and hydrogeology. These physical

characteristics help define the likelihood that

water might enter the unit and the likelihood

that leachate might travel from the bottom of

the unit to the ground water. For example,

areas of high rainfall are more likely to generate leachate than arid regions. The geology of

the site also can affect the rate of infiltration

through the unsaturated zone. For example,

areas with fractured bedrock can allow

leachate through more quickly than a packed

clay material with a low hydraulic conductivity. Hydrology should also be considered

because ground water typically discharges to

surface water. The presence of surface waters

can restrict flow to wells or might require

analysis of the impact of contaminated ground

water on receptors present in the surface

water. Finally, factors related to the hydrogeology, such as the depth to the water table, also

influence the rate at which leachate reaches

the water table.

The characterization of the site also includes

identifying and characterizing populations at

or near the site. When characterizing populations, it is important to identify the relative

location of the populations to the site. For

example, it is important to determine whether

receptors are downgradient from the unit and

the likely distance from the unit to wells. It is

also important to determine typical activity

patterns, such as whether ground water is

used for drinking water or agricultural purposes. The presence of potential receptors is critical for determining a complete exposure

pathway. People might not live there now, but

they might live there in 50 years, based on

future use assumptions. State or local agencies

have relevant information to help you identify

7A-8

Protecting Ground Water—Assessing Risk 
Protecting Ground Water—Assessing Risk 

7A-9

areas that are designated as potential sources

of underground drinking water.

c. Understanding Fate and Transport

In general, the flow in the unsaturated zone

tends to be gravity-driven. As shown in Figure

1, the unsaturated zone receives leachate infiltration from the WMU. Therefore, the vertical

flow component accounts for most of the fluid

flux between the base of the WMU and the

water table. Water-borne constituents are carried vertically downward toward the water

table by the advection process. Mixing and

spreading occur as a result of hydrodynamic

dispersion and diffusion. Transport processes

in the saturated zone include advection,

hydrodynamic dispersion, and sorption.

Advection is the process by which constituents are transported by the motion of the

flowing ground water. Hydrodynamic dispersion is the tendency for some constituents to

spread out from the path that they would be

expected to flow. Sorption is the process by

which leachate molecules adhere to the surface of individual clay, soil, or sediment particles. Attenuation of some chemicals in the

unsaturated zone is attributable to various

biochemical or physicochemical processes,

such as degradation and sorption.

The type of geological material below the

unit affects the rate of movement because of

differences in hydraulic and transport properties. One of the key parameters controlling

contaminant migration rates is hydraulic conductivity. The larger the hydraulic conductivity, the greater the potential migration rate due

to lower hydraulic resistance of the formation.

Hydraulic conductivity values of some hydrogeologic environments, such as bedded sedimentary rock aquifers, might not be as large

as those of other hydrogeologic environments,

such as sand and gravel or fractured limestone. As a general principle, more rapid

movement of waste constituents can be

expected through coarse-textured materials,

such as sand and gravel, than through finetextured materials, such as silt and clay. Other

key flow and transport parameters include

dispersivity (which determines how far a

plume will spread horizontally and vertically

as it moves away from the source) and porosity (which determines the amount of pore

space in the geologic materials in the unsaturated and saturated zone used for flow and

transport and can affect transport velocity).

As waste constituents migrate through the

unsaturated and saturated zones, they can

undergo a number of biochemical and

physicochemical processes that can lead to a

reduction in concentration of potential

ground-water contaminants. These processes

are collectively referred to as attenuation

processes. Attenuation processes can remove

or degrade waste constituents through filtration, sorption, precipitation, hydrolysis, biological degradation, bio-uptake, and redox

reactions. Some of these processes (e.g.,

hydrolysis, biological degradation) can actually result in the formation of different chemicals and greater toxicity. Attenuation

processes are dependent upon several factors,

including ground-water pH, ground-water

temperature, and the presence of other compounds in the subsurface environment. Table

2 provides additional information on attenuation processes.

d. Exposure Pathways

A complete exposure pathway usually consists of four elements: 1) a source and mechanism of chemical release, 2) a retention or

transport medium (in this case, ground

water), 3) a point of potential human contact

with the contaminated medium (often referred

to as the exposure point), and 4) an exposure

route (e.g., ingestion). Residents who live near
7A-10

Protecting Ground Water—Assessing Risk 

a site might use ground water for their water

supply, and thus, the exposure point would be

a well. Exposure routes typical of residential

use of contaminated ground water include

direct ingestion through drinking water, dermal contact while bathing, and inhalation of

VOCs during showering or from other household water uses (e.g., dishwashers).

Another potential pathway of concern is

exposure to ground-water constituents from

the intrusion of vapors of VOCs and SVOCs

through the basements and concrete slabs

beneath houses. This pathway is characterized by the vapors seeping into households

through the cracks and holes in basements

and concrete slabs. In some cases, concentrations of constituents can reach levels that present chronic health hazards. Factors that can

contribute to the potential for vapor intrusion

include the types of constituents present in

the ground water, the presence of pavement

or frozen surface soils (which result in higher

subsurface pressure gradients and greater

transport), and the presence of subsurface

Biological degradation: Decomposition of a substance into more elementary compounds by action

of microorganisms such as bacteria. Sullivan. 1993. Environmental Regulatory Glossary, 6th Ed.

Government Institutes.

Bio-uptake: The uptake and (at least temporary) storage of a chemical by an exposed organism. The

chemical can be retained in its original form and/or modified by enzymatic and non-enzymatic reactions in the body. Typically, the concentrations of the substance in the organism exceed the concentrations in the environment since the organism will store the substance and not excrete it. Sullivan. 1993.

Environmental Regulatory Glossary, 6th Ed. Government Institutes.

Filtration: Physical process whereby solid particles and large dissolved molecules suspended in a

fluid are entrapped or removed by the pore spaces of the soil and aquifer media. Boulding, R. 1995.

Soil, Vadose Zone, and Ground-Water Contamination: Assessment, Prevention, and Remediation.

Hydrolysis: A chemical process of decomposition in which the elements of water react with another

substance to yield one or more entirely new substances. This transformation process changes the chemical structure of the substance. Sullivan. 1993. Environmental Regulatory Glossary, 6th Ed. Government

Institutes.

Oxidation/Reduction (Redox) reactions: Involve a transfer of electrons and, therefore, a change in

the oxidation state of elements. The chemical properties for elements can change substantially with

changes in the oxidation state. U.S. EPA. 1991. Site Characterization for Subsurface Remediation.

Precipitation: Chemical or physical change whereby a contaminant moves from a dissolved form in

a solution to a solid or insoluble form. It reduces the mobility of constituents, such as metals. Unlike

sorption, precipitation is not generally reversible. Boulding, R. 1995. Soil, Vadose Zone, and GroundWater Contamination: Assessment, Prevention, and Remediation.

Sorption: The ability of a chemical to partition between the liquid and solid phase by determining

its affinity for adhering to other solids in the system such as soils or sediments. The amount of chemical that "sorbs" to solids is dependent upon the characteristics of the chemical, the characteristics of the

surrounding soils and sediments, and the quantity of the chemical. Sorption generally is reversible.

Sorption often includes both adsorption and ion exchange.

Table 2:

Examples of Attenuation Processes
gases such as methane that affect the rate of

transport of other constituents. Because of the

complexity of this pathway and the evolving

science regarding this pathway, IWEM focuses

on the risks and pathways associated with

residential exposures to contaminated ground

water. If exposure through this route is likely,

the user might consider Tier 3 modeling to

assess this pathway. EPA is planning to issue a

reference document regarding the vapor

intrusion pathway in the near future.

e. Dose Calculation

The final element of the exposure assessment is the dose calculation. The dose to a

receptor is a function of the concentration at

the exposure point (i.e, the well) and the

intake rate by the receptor. The concentration

at the exposure point is based on the release

from the source and the fate and transport of

the constituent. The intake rate is dependent

on the exposure route, the frequency of exposure, and the duration of exposure. 

EPA produced the Exposure Factors

Handbook (U.S. EPA, 1997a) as a reference for

providing a consistent set of exposure factors

to calculate the dose. This reference is available from EPA’s National Center for

Environmental Assessment Web site

<www.epa.gov/ncea>. The purpose of the

handbook is to summarize data on human

behaviors and physical characteristics (e.g.,

body weight) that affect exposure to environmental contaminants and recommend values

to use for these factors. The result of a dose

calculation is expressed as a contaminant concentration per unit body weight per unit time

that can then be used as the output of the

exposure assessment for the risk characterization phase of the analysis.

3. Toxicity Assessment

A toxicity assessment weighs available evidence regarding the potential for particular

contaminants to cause adverse effects in

exposed individuals, and where possible, provides an estimate of the increased likelihood

and severity of adverse effects as a result of

exposure to a contaminant. IWEM uses two

different toxicity measures—maximum contaminant levels (MCLs) and health-based numbers (HBNs). Each of these measures is based

on toxicity values reflecting a cancer or noncancer effect. Toxicity data are based on

human epidemiologic data, animal data, or

other supporting studies (e.g., laboratory

studies). In general, data can be used to characterize the potential adverse effect of a constituent as either carcinogenic or

non-carcinogenic. For the carcinogenic effect,

EPA generally assumes there is a non-threshold effect and estimates a risk per unit dose.

For the noncarcinogenic effect, EPA generally

assumes there is a threshold below which no

adverse effects occur. The toxicity values used

in IWEM include:

• Oral cancer slope factors (CSFo) for

oral exposure to carcinogenic contaminants.

• Reference doses (RfD) for oral exposure to contaminants that cause noncancer health effects.

• Inhalation cancer slope factors (CSFi)

derived from Unit Risk Factors

(URFs) for inhalation exposure to carcinogenic contaminants.

• Reference concentrations (RfC) for

inhalation exposure to contaminants

that cause noncancer health effects.

EPA defines the cancer slope factor (CSF)

as, “an upper bound, approximating a 95 percent confidence limit, on the increased cancer

risk from a lifetime exposure to an agent [contaminant].” Because the CSF is an upper

bound estimate of increased risk, EPA is reasonably confident that the “true risk” will not

exceed the risk estimate derived using the CSF

and that the “true risk” is likely to be less than

Protecting Ground Water—Assessing Risk 

7A-11
predicted. CSFs are expressed in units of proportion (of a population) affected per milligram/kilogram-day (mg/kg-day). For

noncancer health effects, the RfD and the RfC

are used as health benchmarks for ingestion

and inhalation exposures, respectively. RfDs

and RfCs are estimates of daily oral exposure

or of continuous inhalation exposure, respectively, that are likely to be without an appreciable risk of adverse effects in the general

population, including sensitive individuals,

over a lifetime. The methodology used to

develop RfDs and RfCs is expected to have an

uncertainty spanning an order of magnitude.

a. Maximum Contaminant Levels

(MCLs)

MCLs are maximum permissible contaminant concentrations allowed in public drinking water and are established under the Safe

Drinking Water Act. For each constituent to

be regulated, EPA first sets a Maximum

Contaminant Level Goal (MCLG) as a level

that protects against health risks. The MCL

for each contaminant is then set as close to

its MCLG as possible. In developing MCLs,

EPA considers not only the health effects of

the constituents, but also additional factors,

such as the cost of treatment, available analytical and treatment technologies. Table 3

lists the 57 constituents that have MCLs that

are incorporated in IWEM.

b. Health-based Numbers (HBNs). 

The parameters that describe a chemical’s

toxicity and a receptor’s exposure to the chemical are considered in calculation of the

HBN(s) of that chemical. HBNs are the maximum contaminant concentrations in ground

water that are not expected to cause adverse

noncancer health effects in the general population (including sensitive subgroups) or that

will not result in an additional incidence of

cancer in more than approximately one in one

million individuals exposed to the contaminant. Lower concentrations of the contaminant are not likely to cause adverse health

effects. Exceptions might occur, however, in

individuals exposed to multiple contaminants

that produce the same health effect. Similarly,

a higher incidence of cancer among sensitive

subgroups, highly exposed subpopulations, or

populations exposed to more than one cancercausing contaminant might be expected. As

noted previously, the exposure factors used to

calculate HBNs are described in the Exposure

Factors Handbook (U.S. EPA, 1997a).

4. Risk Characterization

Risk characterization is the integration of

the exposure assessment and the toxicity

assessment to generate qualitative and quantitative expressions of risk. For carcinogens,

the target risk level used in IWEM to calculate the HBNs is 1 x 10-6. A risk of 1 x 10-6

describes an increased chance of one in a

million of a person developing cancer over a

lifetime, due to chronic exposure to a specific

chemical. The target hazard quotient used to

calculate the HBNs for noncarcinogens is 1.

A hazard quotient of 1 indicates that the estimated dose is equal to the RfD (the level

below which no adverse effect is expected).

An HQ of 1, therefore, is frequently EPA’s

threshold of concern for noncancer effects.

These targets are used to calculate unique

HBNs for each constituent of concern and

each exposure route of concern (i.e., ingestion or inhalation). 

Usually, doses less than the RfD (HQ = 1)

are not likely to be associated with adverse

health effects and, therefore, are less likely to

be of regulatory concern. As the frequency or

magnitude of the exposures exceeding the

RfD increase (HQ > 1), the probability of

adverse effects in a human population

increases. However, it should not be categorically concluded that all doses below the RfD

7A-12

Protecting Ground Water—Assessing Risk 
Protecting Ground Water—Assessing Risk 

7A-13

For list of current MCLs, visit: <www.epa.gov/safewater/mcl.html>

* Listed as Total Trihalomethanes (TTHMs), constituents do not have individually listed MCLs

** Arsenic standard will be lowered to 0.01 mg/L by 2006. 

*** Value is drinking water “action level” as specified by 40 CFR 141.32(e) (13) and (14).

Organics with an MCL mg/l mg/l

Benzene 0.005 HCH (Lindane) gamma- 0.0002

Benzo[a]pyrene 0.0002 Heptachlor 0.0004

Bis(2-ethylhexyl)phthalate 0.006 Heptachlor epoxide 0.0002

Bromodichloromethane* 0.10 Hexachlorobenzene 0.001

Butyl-4,6-dinitrophenol,2-sec-(Dinoseb) 0.007 Hexachlorocyclopentadiene 0.05

Carbon tetrachloride 0.005 Methoxychlor 0.04

Chlordane 0.002 Methylene chloride (Dichloromethane) 0.005

Chlorobenzene 0.1 Pentachlorophenol 0.001

Chlorodibromomethane* 0.10 Polychlorinated biphenyls (PCBs) 0.0005

Chloroform* 0.10 Styrene 0.1

Dibromo-3-chloropropane 1,2-(DBCP) 0.0002 TCD Dioxin 2,3,7,8- 0.00000003

Dichlorobenzene 1,2- 0.6 Tetrachloroethylene 0.005

Dichlorobenzene 1,4- 0.075 Toluene 1

Dichloroethane 1,2- 0.005 Toxaphene (chlorinated camphenes) 0.003

Dichloroethylene cis-1,2- 0.07 Tribromomethane (Bromoform)* 0.10

Dichloroethylene trans-1,2- 0.1 Trichlorobenzene 1,2,4- 0.07

Dichloroethylene 1,1-(Vinylidene chloride) 0.007 Trichloroethane 1,1,1- 0.2

Dichlorophenoxyacetic acid 2,4- (2,4-D) 0.07 Trichloroethane 1,1,2- 0.005

Dichloropropane 1,2- 0.005 Trichloroethylene (1,1,2- Trichloroethylene) 0.005

Endrin 0.002 2,4,5-TP (Silvex) 0.05

Ethylbenzene 0.7 Vinyl chloride 0.002

Ethylene dibromide (1,2- Dibromoethane) 0.00005 Xylenes 10

Inorganics with an MCL

Antimony 0.006 Copper*** 1.3

Arsenic** 0.05 Fluoride 4.0

Barium 2.0 Lead*** 0.015

Beryllium 0.004 Mercury (inorganic) 0.002

Cadmium 0.005 Selenium 0.05

Chromium 0.1 Thallium 0.002

(total used for Cr III and Cr VI)

Table 3. 

List of Constituents in IWEM with Maximum Contaminant Levels (MCLs)

(States can have more stringent standards than federal MCLs.)
7A-14

Protecting Ground Water—Assessing Risk 

are “acceptable’’ (or will be risk-free) and that

all doses in excess of the RfD are “unacceptable’’ (or will result in adverse effects). For

IWEM, the output from the risk characterization helps determine with 90 percent probability (i.e., with a confidence that for 90

percent of the realizations) whether or not a

design system is protective (i.e., has a cancer

risk of < 1 x 10-6, non-cancer hazard quotient

of < 1.0). IWEM does not address the cumulative risk due to simultaneous exposure to

multiple constituents. The results of the risk

assessment might encourage the user to conduct a more site-specific analysis, or consider

opportunities for waste minimization or pollution prevention.

II. The IWEM

Ground-Water

Risk Evaluation

This section takes the principles of risk

assessment described in Part I and applies

them to evaluating industrial waste management unit liner designs. This is accomplished

using IWEM and a three-tiered ground-water

modeling approach to make recommendations regarding the liner design systems that

should be considered for a potential unit, if a

liner design system is considered necessary.

The tiered approach was chosen to provide

facility managers, the public, and state regulators flexibility in assessing the appropriateness of particular WMU designs as the user

moves from a national assessment to an

assessment using site-specific parameters. 

The three tiers allow for three possible

approaches. The first approach is a quick

screening tool, a set of lookup tables, which

provides conservative national criteria. While

this approach, labeled Tier 1, does not take

into account site- (or even state-) specific conditions, it does provide a rapid and easy

screening. If the use of Tier 1 provides an

agreeable assessment, the conservative nature

of the model can be relied upon, and the

additional resources required for further

analysis can be avoided. Of course, where

there is concern with the results from Tier 1,

a more precise assessment of risk at the

planned unit location should be conducted.

The second approach is to try and accommodate many of the most important site-specific

factors in a simplified form, useable by industry, state, and environmental representatives.

This model, labeled Tier 2, is available as part

of this Guide, and is a major new step in

moving EPA guidance away from national,

“one size fits all” approaches. Third, a sitespecific risk analysis can be conducted. This

approach should provide the most precise

assessment of the risks posed by the planned

unit. Such an analysis, labeled Tier 3, should

be conducted by experts in ground-water

modeling, and can require significant

resources. This Guide identifies the benefits

and sources for selecting site-specific models,

but does not provide such models as part of

this Guide. In many cases, corporations will

go directly to conducting the more exacting

Tier 3 analysis, which EPA believes is acceptable under the Guide. There is, however, still

a need for the Tier 2 tool. State and environmental representatives might have limited

resources to conduct or examine a Tier 3

assessment; Tier 2 can provide a point of

comparison with the results of the Tier 3

analysis, narrow the technical discussion to

those factors which are different in the models, and form a basis for a more informed dialogue on the reasonableness of the differences.

IWEM is designed to address Tier 1 and

Tier 2 evaluations. Both tiers of the tool consider all portions of the risk assessment

process (i.e., problem formulation, exposure

assessment, toxicity assessment, and risk

characterization) to generate results that vary

from a national-level screening evaluation to
a site-specific assessment. The Tier 3 evaluation is a complex, site-specific hydrogeologic

investigation that would be performed with

other models such as those listed at the end

of this chapter. Those models could be used

to evaluate hydrogeological complexities that

are not addressed by IWEM. Brief outlines of

the three tiers follow.

A Tier 1 evaluation involves comparing the

expected leachate concentrations of wastes

being assessed against a set of pre-calculated

maximum recommended leachate concentrations (or Leachate Concentration Threshold

Values—LCTVs). The Tier 1 LCTVs are

nationwide, ground-water fate and transport

modeling results from EPA’s Composite Model

for Leachate Migration with Transformation

Products (EPACMTP). EPACMTP simulates

the fate and transport of leachate infiltrating

from the bottom of a WMU and predicts concentrations of those contaminants in a well. In

making these predictions, the model quantitatively accounts for many complex processes

that dilute and attenuate the concentrations of

waste constituents as they move through the

subsurface to the well. The results that are

generated show whether a liner system is considered necessary, and if so which liner systems will be protective for the constituents of

concern. Tier 1 results are designed to be protective with 90 percent certainty at a 1x10-6

risk level for carcinogens or a noncancer hazard quotient of < 1.0.

The Tier 2 evaluation incorporates a limited number of site-specific parameters to help

provide recommendations about which liner

system (if any is considered necessary) is protective for constituents of concern in settings

that are more reflective of your site. IWEM is

designed to facilitate site-specific simulations

without requiring the user to have any previous ground-water modeling experience. As

with any ground-water risk evaluation, however, the user is advised to discuss the results

of the Tier 2 evaluation with the appropriate

state regulatory agency before selecting a liner

design for a new WMU.

If the Tier 1 and Tier 2 modeling do not

adequately simulate conditions at a proposed

site because the hydrogeology of the site is

complex, or because the user believes Tier 2

does not adequately address a particular sitespecific parameter, the user is advised to consider a more in-depth, site-specific risk

assessment. This Tier 3 assessment involves a

more detailed, site-specific ground-water fate

and transport analysis. The user should consult with state officials and appropriate trade

associations to solicit recommendations for

approaches for the analysis.

The remainder of this section discusses in

greater detail how to use IWEM to perform a

Tier 1 or Tier 2 evaluation. In addition, this

section presents information concerning the

use of Tier 3 models. 

A. The Industrial Waste

Management Evaluation

Model (IWEM)

The IWEM is the ground-water modeling

component of the Guide for Industrial Waste

Management, used for recommending appropriate liner system designs, where they are

considered necessary, for the management of

RCRA Subtitle D industrial waste. IWEM

compares the expected leachate concentration

(entered by the user) for each waste constituent with a protective level calculated by a

ground-water fate and transport model to

determine whether a liner system is needed.

When IWEM determines a liner system is

necessary, it then evaluates two standard liner

types (i.e., single clay-liner and composite

liner). This section discusses components of

the tool and important concepts whose understanding is necessary for its effective use. The

user can refer to the User’s Guide for the

Protecting Ground Water—Assessing Risk 

7A-15
Industrial Waste Management Evaluation Model

(U.S. EPA, 2002b) for information necessary

to perform Tier 1 and Tier 2 analyses, and the

Industrial Waste Management Evaluation Model

Technical Background Document (U.S. EPA,

2002a), for more information on the use and

development of IWEM. 

1. Leachate Concentrations

The first step in determining a protective

waste management unit design is to identify

the expected constituents in the waste and

expected leachate concentrations from the

waste. In order to assess ground-water risks

using either the Tier 1 or Tier 2 evaluations

provided in IWEM, the expected leachate

concentration for each individual constituent

of interest must be entered into the model.

See Chapter 2—Characterizing Wastes, for a

detailed discussion of the various approaches

available to use in evaluating expected

leachate concentrations.

2. Models Associated with IWEM

One of the highlights of IWEM is its ability to simulate the fate and transport of waste

constituents at a WMU with a small number

of site-specific inputs. To accomplish this

task, IWEM incorporates the outputs of three

other models, specifically EPACMTP, MINTEQA2, and HELP. This section discusses these

three models.

a. EPACMTP

EPA’s Composite Model for Leachate

Migration with Transformation Products

(EPACMTP) is the backbone of IWEM.

EPACMTP is designed to simulate subsurface

fate and transport of contaminants leaching

from the bottom of a WMU and predict concentrations of those contaminants in a downgradient well. In making these predictions,

the model accounts for many complex

processes that occur as waste constituents

and their transformation products move to

and through ground water. As leachate carrying waste constituents migrates through the

unsaturated zone to the water table, attenuation processes, such as adsorption and degradation, reduce constituent concentrations.

Ground-water transport in the saturated zone

further reduces leachate concentrations

through dilution and attenuation. The concentration of constituents arriving at a well,

therefore, is lower than that in the leachate

released from a WMU. 

In the unsaturated zone, the model simulates one-dimensional vertical migration with

steady infiltration of constituents from the

WMU. In the saturated zone, EPACMTP simulates three-dimensional plume-movement

(i.e., horizontal as well as transverse and vertical spreading of a contaminant plume). The

model considers not only the subsurface fate

and transport of constituents, but also the

formation and the fate and transport of transformation (daughter and granddaughter)

products. The model also can simulate the

fate and transport of metals, taking into

account geochemical influences on the

mobility of metals. 

b. MINTEQA2

In the subsurface, metal contaminants can

undergo reactions with other substances in

the ground water and with the solid aquifer

or soil matrix material. Reactions in which

the metal is bound to the solid matrix are

referred to as sorption reactions, and the

metal bound to the solid is said to be sorbed.

During contaminant transport, sorption to

the solid matrix results in retardation (slower

movement) of the contaminant front.

Transport models such as EPACMTP incorporate a retardation factor to account for sorption processes.

7A-16

Protecting Ground Water—Assessing Risk 
The actual geochemical processes that control the sorption of metals can be quite complex, and are influenced by factors such as

pH, the type and concentration of the metal

in the leachate plume, the presence and concentrations of other constituents in the

leachate plume, and other factors. The

EPACMTP model is not capable of simulating

all these processes in detail. Another model,

MINTEQA25

, is used to determine a sorption

coefficient for each of the metals species. For

IWEM, distributions of variables (e.g., leachable organic matter, pH) were used to generate a distribution of isotherms for each metal

species. EPACMTP, in turn, samples from

these calculated sorption coefficients and uses

the selected isotherm as a modeling input to

account for the effects of nationwide or

aquifer-specific ground-water and leachate

geochemistry on the sorption and mobility of

metals constituents.

c. HELP

The Hydrologic Evaluation of Landfill

Performance (HELP) model is a quasi-twodimensional hydrologic model for computing

water balances of landfills, cover systems, and

other solid waste management facilities. The

primary purpose of the model is to assist in

the comparison of design alternatives. HELP

uses weather, soil, and design data to compute a water balance for landfill systems

accounting for the effects of surface storage;

snowmelt; runoff; infiltration; evapotranspiration; vegetative growth; soil moisture storage;

lateral subsurface drainage; leachate recirculation; unsaturated vertical drainage; and leakage through soil, geomembrane, or composite

liners. The HELP model can simulate landfill

systems consisting of various combinations of

vegetation, cover soils, waste cells, lateral

drain layers, low permeability barrier soils,

and synthetic geomembrane liners. For further information on the HELP model, visit:

<wes.army.mil/el/elmodels/helpinfo.html>.

For the application of HELP to IWEM, an

existing database of infiltration and recharge

rates was used for 97 climate stations in the

lower 48 contiguous states. Five climate stations (located in Alaska, Hawaii, and Puerto

Rico) were added to ensure coverage

throughout all of the United States. These climatic data were then used along with data on

the soil type and WMU design characteristics,

to calculate a water balance for each applicable liner design as a function of the amount

of precipitation that reaches the surface of the

unit, minus the amount of runoff and evapotranspiration. The HELP model then computed the net amount of water that infiltrates

through the surface of the unit (accounting

for recharge), the waste, and the unit’s bottom

layer (for unsaturated soil and clay liner scenarios only), based on the initial moisture

content and the hydraulic conductivity of

each layer. 

Although data were collected for all 102

sites, these data were only used for the

unlined landfills, waste piles, and land application units. For the clay liner scenarios

(landfills and waste piles only), EPA grouped

sites and ran the HELP model only for a subset of the facilities that were representative of

the ranges of precipitation, evaporation, and

soil type. The grouping is discussed further in

the IWEM Technical Background Document

(U.S. EPA, 2002a).

In addition to climate factors and the particular unit design, the infiltration rates calculated by HELP are affected by the landfill

cover design, the permeability of the waste

material in waste piles, and the soil type of

the land application unit. For every climate

station and WMU design, multiple HELP

infiltration rates are calculated. In Tier 1, for

a selected WMU type and design, the

EPACMTP Monte Carlo modeling process

was used to randomly select from among the

HELP-derived infiltration and recharge data.

Protecting Ground Water—Assessing Risk 

7A-17

5 MINTEQA2 is a geochemical equilibrium speciation model for computing equilibria among the dissolved, absorbed, solid, and gas phases in dilute aqueous solution.
This process captured both the nationwide

variation in climate conditions and variations

in soil type. In Tier 2, the WMU location is a

required user input, and the climate factors

used in HELP are fixed. However, in Tier 2,

the Monte Carlo process is still used to

account for local variability in the soil type,

landfill cover design, and permeability of

waste placed in waste piles.

3. Important Concepts for Use

of IWEM

Several important concepts are critical to

understanding how IWEM functions. These

concepts include 90th percentile exposure

concentration, dilution and attenuations factors (DAFs), reference ground-water concentrations (RGCs), leachate concentration

threshold values (LCTVs), and units designs. 

a. 90th Percentile Exposure

Concentration

The 90th percentile exposure concentration was chosen to represent the estimated

constituent concentration at a well for a

given leachate concentration. The 90th percentile exposure concentration was selected

because this concentration is protective for

90 percent of the model simulations conducted for a Tier 1 or Tier 2 analysis. In Tier

1, the 90th percentile concentration is used

to calculate a DAF, which is then used to generate a leachate concentration threshold value

(LCTV). In Tier 2, the 90th percentile concentration is directly compared with a reference ground-water concentration to

determine whether a liner system is necessary, and if so whether the particular liner

design is protective for a site.

The 90th percentile exposure concentration is determined by running EPACMTP in a

Monte Carlo mode for 10,000 realizations.

For each realization, EPACMTP calculates a

maximum average concentration at a well,

depending on the exposure duration of the

reference ground-water concentration (RGC)

of interest. For example, IWEM assumes a

30-year exposure duration for carcinogens,

and therefore, the maximum average concentration is the highest 30-year average across

the modeling horizon. After calculating the

maximum average concentrations across the

10,000 realizations, the concentrations are

arrayed from lowest to highest and the 90th

percentile of this distribution is selected as

the constituent concentration for IWEM.

Once the 90th percentile exposure concentration is determined, it is used in one of

two ways. For both the Tier 1 analysis and

the Tier 2 analysis, the 90th percentile exposure concentration is compared with the

expected waste leachate concentration to

generate a DAF. This calculation is discussed

further in the following section. For Tier 2,

the 90th percentile exposure concentration is

the concentration of interest for the analysis.

The 90th percentile exposure concentration

can be directly compared with the reference

ground-water concentration to assist in waste

management decision-making.

b. Dilution and Attenuation Factors 

DAFs represent the expected reduction in

waste constituent concentration resulting

from fate and transport in the subsurface. A

DAF is defined as the ratio of the constituent

concentration in the waste leachate to the

concentration at the well, or:

CL

DAF = ———

CW

where: DAF is the dilution and attenuation factor;

CL is the leachate concentration

(mg/L); and

CW is the ground-water well concentration (mg/L).

7A-18

Protecting Ground Water—Assessing Risk 
The magnitude of a DAF reflects the combined effect of all dilution and attenuation

processes that occur in the unsaturated and

saturated zones. The lowest possible value of

a DAF is one. A DAF of 1 means that there is

no dilution or attenuation at all; the concentration at a well is the same as that in the

waste leachate. High DAF values, on the

other hand, correspond to a high degree of

dilution and attenuation. This means that the

expected concentration at the well will be

much lower than the concentration in the

leachate. For any specific site, the DAF

depends on the interaction of waste constituent characteristics (e.g., whether or not

the constituent degrades or sorbs), site-specific factors (e.g., depth to ground water, hydrogeology), and physical and chemical

processes in the subsurface environment. In

addition, the DAF calculation does not take

into account when the exposure occurs, as

long as it is within a 10,000-year time-frame

following the initial release of leachate. Thus,

if two constituents have different mobility, the

first might reach the well in 10 years, while

the second constituent might not reach the

well for several hundred years. EPACMTP,

however, can calculate the same or very similar DAF values for both constituents. 

For the Tier 1 analysis in IWEM, DAFs are

based on the 90th percentile exposure concentration. EPACMTP was implemented by

randomly selecting one of the settings from

the WMU database and assigning a unit

leachate concentration to each site until

10,000 runs had been conducted for a WMU.

The resulting 10,000 maximum well concentrations based on the averaging period associated with the exposure duration of interest

(i.e., 1-year, 7-years, 30-years) were then

arrayed from lowest to highest. The 90th percentile concentration of this distribution is

then used as the concentration in the groundwater well (Cw) for calculating the DAF. The

DAF is similarly calculated for the Tier 2, but

because the site-specific leachate concentration is used in the EPACMTP model runs, the

90th percentile exposure concentration can

be compared directly to the RGC.

c. Reference Ground-Water

Concentration (RGC)

As used in this Guide and by IWEM, a reference ground-water concentration (RGC) is

defined as a constituent concentration threshold in a well that is protective of human

health. RGCs have been developed based on

maximum contaminant levels (MCLs) and

health-based-numbers (HBN). Each constituent can have up to five RGCs: 1) based

on an MCL, 2) based on carcinogenic effects

from ingestion, 3) based on carcinogenic

effects from inhalation while showering, 4)

based on non-carcinogenic effects from ingestion, and 5) based on non-carcinogenic

effects from inhalation while showering. 

The IWEM’s database includes 226 constituents with at least one RGC. Of the 226

constituents, 57 have MCLs (see Table 3),

212 have ground-water ingestion HBNs, 139

have inhalation HBNs, and 57 have both an

MCL and HBN. The HBNs were developed

using standard EPA exposure assumptions for

residential receptors. For carcinogens, IWEM

used a target risk level equal to the probability that there might be one increased cancer

case per one million exposed people (commonly referred to as a 1x10-6 cancer risk).

The target hazard quotient used to calculate

the HBNs for noncarcinogens was 1 (unitless). A hazard quotient of 1 indicates that

the estimated dose is equal to the oral reference dose (RfD) or inhalation reference concentration (RfC). These targets were used to

calculate unique HBNs for each constituent of

concern and each exposure route of concern

(ingestion or inhalation). For further information on the derivation of the IWEM RGCs,

see the Industrial Waste Management

Evaluation Model Technical Background

Protecting Ground Water—Assessing Risk 

7A-19
Document (U.S. EPA, 2002a). Users also can

add new constituents and RGCs can vary

depending on the protective goal. For example, states can impose more stringent drinking water standards than federal MCLs.6 To

keep the software developed for this Guide

up-to-date, and to accommodate concerns at

levels different from the current RGCs, the

RGC values in the IWEM software tool can

be modified by the user of the software.

d. Leachate Concentration Threshold

Values (LCTVs)

The purpose of the Tier 1 analysis in

IWEM is to determine whether a liner system

is needed, and if so, to recommend liner system designs or determine the appropriateness

of land application with minimal site-specific

data. These recommendations are based on

LCTVs that were calculated to be protective

for each waste constituent in a unit. These

LCTVs are the maximum leachate concentrations for which water in a well is not likely to

exceed the corresponding RGC. The LCTV

for each constituent accounts for dilution and

attenuation in the unsaturated and saturated

zones prior to reaching a well. An LCTV has

been generated for a no liner/in situ soils scenario and for two standard liner types (i.e.,

single clay liner and composite liner) and

each RGC developed for a constituent.

The LCTV for a specific constituent is the

product of the RGC and the DAF:

LCTV = DAF * MCL

or LCTV = DAF * HBN

Where: LCTV is the leachate concentration threshold value

DAF is the dilution and attenuation factor

MCL is the maximum concentration level

HBN is the health-based number

The evaluation of whether a liner system is

needed and subsequent liner system design

recommendations is determined by comparing the expected waste constituent leachate

concentrations to the corresponding calculated LCTVs. LCTVs are calculated for all unit

types (i.e., landfills, waste piles, surface

impoundments, land application units) by

type of design (i.e., no liner/in situ soils, single liner, or composite liner).7 The Tier 1

evaluation is generally the most protective

and calculates LCTVs using data collected on

WMUs throughout the United States.8 LCTVs

used in Tier 1 are designed to be protective

to a level of 1x10-6 for carcinogens or a noncancer hazard quotient of < 1.0 with a 90

percent certainty considering the range of

variability associated with the waste sites

across the United States. LCTVs from the Tier

1 analysis are generally applicable to sites

across the country; users can determine

whether a specific liner design for a WMU is

protective by comparing expected leachate

concentrations for constituents in their waste

with the LCTVs for each liner design.

The Tier 2 analysis differs from the Tier 1

analysis in that IWEM calculates a site-specific DAF in Tier 2. This allows the model to

calculate a site-specific 90th percentile exposure concentration that can be compared

with an RGC to determine if a liner system is

needed and to recommend the appropriate

liner system if necessary. The additional calculation of an LCTV is not necessary. IWEM

continues to perform the calculation, however, to help users determine whether waste

minimization might be appropriate to meet a

specific design. For example, a facility might

7A-20

6 For example, a state can make secondary MCLs mandatory, which are not federally enforceable standards, or a state might use different exposure assumptions, which can result in a different HBN. In

addition, states can choose to use a different risk target than is used in this Guidance.

7 LCTVs are influenced by liner designs because of different infiltration rates.

8 For additional information on the nationwide data used in the modeling, see the IWEM Technical

Background Document (U.S. EPA, 2002a).

Protecting Ground Water—Assessing Risk 
find it more cost effective to reduce the concentration of constituents in its waste and

design a clay-lined landfill than to dispose of

the current waste in a composite landfill. The

LCTV calculated for the Tier 2 analysis is

based on the expected leachate concentration

for a specific site and site-specific data for

several sensitive parameters. Because the Tier

2 analysis includes site-specific considerations, LCTVs from this analysis are not

applicable to other sites. 

e. Determination of Liner Designs

The primary method of controlling the

release of waste constituents to the subsurface

is to install a low permeability liner at the

base of a WMU. A liner generally consists of a

layer of clay or other material with a low

hydraulic conductivity that is used to prevent

or mitigate the flow of liquids from a WMU.

The type of liner that is appropriate for a specific WMU, however, is highly dependent

upon a number of location-specific characteristics, such as climate and hydrogeology.

These characteristics are critical in determining the amount of liquid that migrates into

the subsurface from a WMU and in predicting

the release of contaminants to ground water. 

The IWEM software is intended to assist

the user in determining if a new industrial

waste management unit can rely on a no

liner/in situ soils design, or whether one of

the two recommended liners designs, single

clay liner or composite liner, should be used.

The no liner/in situ soils design (Figure 2a)

represents a WMU that relies upon locationspecific conditions, such as low permeability

native soils beneath the unit or low annual

precipitation rates to mitigate the release of

contaminants to groundwater. The single clay

liner (Figure 2b) design represents a 3-foot

thick clay liner with a low hydraulic conductivity (1x10-7 cm/sec) beneath a WMU. A

composite liner design (Figure 2c) consists of

a flexible membrane liner in contact with a

clay liner. In Tier 2, users also can evaluate

other liner designs by providing a site-specific

infiltration rate based on the liner design. For

land applications units, only the no liner/in

situ soils scenario is evaluated because liners

are not typically used at this type of facility.

To determine an appropriate design in Tier

1, IWEM compares expected leachate concentrations for all of the constituents in the

leachate to constituent-specific LCTVs and

then reports the minimum design system that

is protective for all constituents. If the expected leachate concentrations of all waste constituents are lower than their respective no

liner/in situ soils LCTVs, the proposed WMU

does not need a liner to contain the waste.

On the other hand, if the Tier 1 screening

evaluation indicates a liner is recommended,

a user can verify this recommendation with a

follow-up Tier 2 (or possibly Tier 3) analysis

for at least those constituents whose expected

leachate concentrations exceed the Tier 1

LCTV values. 

If the user proceeds to a Tier 2 analysis,

IWEM will evaluate the three standard

designs or it can evaluate a user-supplied

liner design. The user can supply a liner

design by providing a site-specific infiltration

rate that reflects the expected infiltration rate

through the user’s liner system. In the Tier 2

analysis, IWEM conducts a location-adjusted

Monte Carlo analysis based on user inputs to

generate a 90th percentile exposure concentration for the site. The 90th percentile exposure concentration is then compared with the

RGC to determine whether a liner is considered necessary, and where appropriate, recommend the design that is protective for each

constituent expected in the leachate. If the

Tier 2 analysis indicates that the no liner/in

situ soils scenario or the user-defined liner is

not protective, the user can proceed to a full

site-specific Tier 3 analysis.

Protecting Ground Water—Assessing Risk 

7A-21
7A-22

Protecting Ground Water—Assessing Risk 

B. Tier 1 Evaluations

In a Tier 1 evaluation, IWEM compares

the expected leachate concentration for each

constituent with the LCTVs calculated for

these constituents and determines a minimum recommended design that is protective

for all waste constituents. The required

inputs are: the type of WMU the user wishes

to evaluate, the constituents of concern, and

the expected leachate concentrations of constituents of concern. The results for each

constituent have been compiled for each unit

type and design and are available in the

IWEM Technical Background Document (U.S.

EPA, 2002a) and in the model on the CDROM version of this Guide.

The tabulated results for Tier 1 of IWEM

have been generated by running the

EPACMTP for a wide range of conditions that

reflect the varying site conditions that can be

expected to occur at waste sites across the

United States. The process, which was used

to simulate varying site conditions, is known

as a Monte Carlo analysis. A Monte Carlo

analysis determines the statistical probability

or certainty that the release of leachate might

result in a ground-water concentration

exceeding regulatory or risk-based standards. 

For the Tier 1 analysis, 10,000 realizations

of EPACMTP were run for each constituent,

WMU, and design combination to generate

distributions of maximum average exposure

concentrations for each constituent by WMU

and design. These distributions reflect the variability among industrial waste management

units across the United States. The 90th percentile concentration from this distribution was

then used to calculate a DAF for each constituent by WMU and design. Each of these

DAFs was then combined with constituentspecific RGCs to generate the LCTVs presented

Figure 2. Three Liner Scenarios Considered in the Tiered Modeling Approach for Industrial

Waste Guidelines

  yyy yyyWaste

Native Soil

Waste

Clay Liner

Waste

Clay Liner

Flexible

Membrane

Liner

a) No Liner/In Situ Soils Scenario b) Single Liner Scenario c) Composite Liner Scenario

About Monte Carlo Analysis

Monte Carlo analysis is a computerbased method of analysis developed in

the 1940s that uses statistical sampling

techniques in obtaining a probabilistic

approximation to the solution of a mathematical equation or model. The name

refers to the city on the French Riviera,

which is known for its gambling and

other games of chance. Monte Carlo

analysis is increasingly used in risk

assessments because it allows the risk

manager to make decisions based on a

statistical level of protection that reflects

the variability and/or uncertainty in risk

parameters or processes, rather than

making decisions based on a single point

estimate of risk. For further information

on Monte Carlo analysis in risk assessment, see EPA’s Guiding Principles for

Monte Carlo Analysis. (U.S. EPA, 1997b).
in the IWEM software and in the tables included in the technical background document. 

The advantages of a Tier 1 screening evaluation are that it is fast, and it does not require

site-specific information. The disadvantage of

the Tier 1 screening evaluation is that the

analysis does not use site-specific information

and might result in a design recommendation

that is more stringent than is needed for a

particular site. For instance, site-specific conditions, such as low precipitation and a deep

unsaturated zone, might warrant a less stringent design. Before implementing a Tier 1

recommendation, it is recommended that you

also perform a Tier 2 assessment for at least

those waste constituents for which Tier 1

indicates that a no liner design is not protective. The following sections provide additional information on how to use the Tier 1

lookup tables.

1. How Are the Tier 1 Lookup

Tables Used?

The Tier 1 tables provide an easy-to-use

tool to assist waste management decisionmaking. Important benefits of the Tier 1

approach are that it requires minimum data

from the user and provides immediate guidance on protective design scenarios. There are

only three data requirements for the Tier 1

analysis: WMU type, constituents expected in

the waste leachate, and the expected leachate

concentration for each constituent in the

waste. The Tier 1 tables are able to provide

immediate guidance because EPACMTP simulations for each constituent, WMU, and

design combinations were run previously for

a national-scale assessment to generate appropriate LCTVs for each combination. Because

the simulations represent a national-scale

assessment, the LCTVs in the Tier 1 tables

represent levels in leachate that are protective

at most sites.

As noted previously in this chapter, one of

the first steps in a ground-water risk assessment is to characterize the waste going into a

unit. Characterization of the waste includes

identifying the constituents expected in the

leachate and estimating leachate concentrations for each of these constituents.

Identification of constituents expected in

leachate can be based on process knowledge

or chemical analysis of the waste. Leachate

concentrations can be estimated using

process knowledge or an analytical leaching

test appropriate to the circumstances, such as

the Toxicity Characteristic Leaching

Procedure (TCLP). For more information on

identifying waste constituents, estimating

waste constituent leachate concentrations,

and selecting appropriate leaching tests, refer

to Chapter 2 — Characterizing Waste.

The following example illustrates the Tier

1 process for evaluating a proposed design

for an industrial landfill. The example

assumes the expected leachate concentration

for toluene is 1.6 mg/L and styrene is 1.0

Protecting Ground Water—Assessing Risk 

7A-23

Information Needed to

Use Tier 1 Lookup Tables

Waste management Landfill, surface

unit types: impoundment,

waste pile, or land

application unit.

Constituents Constituent names

expected and/or CAS numbers.

in the leachate:

Leachate Expected leachate

concentrations: concentration of

each constituent or

concentration in

surface impoundments or waste to be

applied.
mg/L. Both toluene and styrene have three

LCTVs: one based on an MCL, one based on

non-cancer ingestion, and one based on noncancer inhalation. Tables 4 and 5 provide

detailed summary information for the no

liner/in situ soils scenario for MCL-based

LCTVs and the HBN-based LCTVs, respectively, that is similar to the information that

can be found in the actual look-up tables. 

For the Tier 1 MCL-based analysis presented in Table 4, the results provide the

following information: constituent CAS

number, constituent name, constituent-specific MCL, user-provided leachate concentration, constituent-specific DAF, the

constituent-specific LCTV, and whether the

specified design is protective at the target

risk level. To provide a recommendation as

to whether a specific design is protective or

not, IWEM compares the LCTV with the

leachate concentration to determine

whether the design is protective. In the

example presented in Table 4, the no

liner/in situ soils scenario is not protective

for styrene because the leachate concentration provided by the user (1.0 mg/L) is

greater than the Tier 1 LCTV (0.22 mg/L).

For toluene, the no liner/in situ soils scenario is protective because the leachate concentration (1.6 mg/L) is less than the Tier 1

LCTV (2.2 mg/L).

For the health-based number (HBN)-based

results presented in Table 5, the detailed

results present similar information to that

presented for the MCL-based results. The differences are that the HBN-results present the

constituent-specific HBN rather than the

MCL and include an additional column that

identifies the pathway and effect that support

the development of the LCTV. For the controlling pathway and effect column, IWEM

would indicate whether the most protective

pathway is ingestion of drinking water (indicated by ingestion) or inhalation during

showering (indicated by inhalation) and

whether the adverse effect is a cancer or noncancer effect. In this example, both styrene

and toluene have two HBN-based LCTVS:

one for ingestion non-cancer and one for

inhalation non-cancer. Only the results for

the controlling HBN exposure pathway and

effect are shown. In Table 5, only the results

for the inhalation-during-showering pathway

for non-cancer effects are shown because this

is the most protective pathway (that is, the

LCTV for the inhalation-during-showing

pathway is lower than the LCTV for ingestion

of drinking water) for both of these constituents. As shown in Table 5, comparison of

the leachate concentration of styrene (1.0

mg/L) and toluene (1.6 mg/L) to their respective LCTVs (8.0 mg/L and 2.9 mg/L) indicates that the no liner/in situ soils design is

protective for the Tier 1 HBN-based LCTVs. 

Based on the results for the no liner/in situ

soils scenario, the user could proceed to the

comparison of the expected leachate concentration for styrene with the MCL-based LCTV

for a single clay liner to determine whether

the single clay liner design is protective. The

7A-24

Protecting Ground Water—Assessing Risk 

CAS # Constituent MCL (mg/L) Leachate Concentration (mg/L) DAF LCTV (mg/L) Protective? 

100-42-5 Styrene 0.1 1.0 2.2 0.22 No

108-88-3 Toluene 1.0 1.6 2.2 2.2 Yes

Table 4: 

Example of Tier 1 Summary Table for MCL-based LCTVs for Landfills - No Liner/In situ Soils
user also can proceed to a Tier 2 or Tier 3

analysis to determine whether a more sitespecific approach might indicate that the no

liner/in situ soils design is protective for the

site. Table 6 presents the Tier 1 results for the

single clay liner. As shown, the single clay

liner would not be protective for the MCLbased analysis because the expected leachate

concentration for styrene (1.0 mg/L) exceeds

the LCTV for styrene (0.61 mg/L). Based on

these results, the user could continue on to

evaluate whether a composite liner is protective for styrene.

Table 7 presents the results of the Tier 1

MCL-based analysis for a composite liner.9 A

comparison of the leachate concentration for

styrene (1.0 mg/L) to the MCL-based LCTV

(1000 mg/L) indicates that the composite

liner is the recommended liner based on a

Tier 1 analysis that will be protective for both

styrene and toluene. 

2. What Do the Results Mean

and How Do I Interpret Them?

For the Tier 1 analysis, IWEM evaluates

the no liner/in situ soils, single clay liner, and

Protecting Ground Water—Assessing Risk 

7A-25

9 Table 7 also indicates the effect of the 1000 mg/L cap on the results. The LCTV results from multiplying the RGC with the DAF. In this example, the MCL for styrene (0.1 mg/L) multiplied by the unitless

DAF (5.4 x 104

) would result in an LCTV of 5,400 mg/L, but because LCTVs are capped, the LCTV for

styrene in a composite liner is capped at 1,000 mg/L. See Chapter 6 of the Industrial Waste Management

Evaluation Model Technical Background Document (U.S. EPA, 2002a) for further information.

CAS # Constituent HBN (mg/L) Leachate DAF LCTV (mg/L) Protective? Controlling 

Concentration Pathway &

(mg/L) Effect

100-42-5 Styrene 3.6 1.0 2.2 8.0 Yes Inhalation 

Non-cancer

108-88-3 Toluene 1.3 1.6 2.2 2.9 Yes Inhalation 

Non-cancer

Table 5:

Example of Tier 1 Summary Table for HBN-based LCTVs for Landfills - No Liner/In situ Soils

CAS # Constituent MCL (mg/L) Leachate Concentration (mg/L) DAF LCTV (mg/L) Protective? 

100-42-5 Styrene 0.1 1.0 5.4x104 1000 Yes

108-88-3 Toluene 1.0 1.6 2.9x104 1000 Yes

Table 7:

Example of Tier 1 Summary Table for MCL-based LCTVs for Landfills - Composite Liner

CAS # Constituent MCL (mg/L) Leachate Concentration (mg/L) DAF LCTV (mg/L) Protective? 

100-42-5 Styrene 0.1 1.0 6.1 0.61 No

108-88-3 Toluene 1.0 1.6 6.1 6.1 Yes

Table 6:

Example of Tier 1 Summary Table for MCL-based LCTVs for Landfills - Single Clay Liner
composite liner design scenarios, in that

order. Generally, if the expected leachate concentrations for all constituents are lower than

the no liner LCTVs, the proposed unit does

not need a liner to contain this waste. If any

expected constituent concentration is higher

than the no liner/in situ soils LCTV, a single

compacted clay liner or composite liner

would be recommended for containment of

the waste using the Tier 1 analysis. If any

expected concentration is higher than the

single clay liner LCTV, the recommendation

is at least a composite liner. If any expected

concentration is higher than the composite

liner LCTV, pollution prevention, treatment,

or additional controls should be considered,

or a Tier 2 or Tier 3 analysis can be conducted to consider site-specific factors before

making a final judgment. For waste streams

with multiple constituents, the most protective design that is recommended for any one

constituent is the overall recommendation. In

the example illustrated in Tables 4, 5, 6, and

7, the recommended design is a composite

liner because the expected leachate concentration for styrene exceeds the no liner/in situ

soils and clay liner LCTVs in the MCL-based

analysis, but is lower than the composite

liner LCTV. For the HBN-based analysis, a no

liner/in situ soils design would provide adequate protection for the site because, as

shown in Table 5, the leachate concentrations

for styrene and toluene are lower than their

respective HBN-based LCTVs.

The interpretation for land application is

similar to the interpretation for landfills.

However, only the no liner/in situ soils scenario is evaluated for land application

because these types of units generally do not

use liner systems. Thus, if all the waste

leachate concentrations are below the no

liner/in situ soils MCL-based and HBN-based

LCTVs in the Tier 1 lookup tables, landapplying waste might be appropriate for the

site. If the waste has one or more constituents whose concentrations exceed a land

application threshold, the recommendation is

that land application might not be appropriate. The model does not consider the other

design scenarios.

After conducting the Tier 1 evaluation,

users should consider the following steps:

• Perform additional evaluations.

The Tier 1 evaluation provides a conservative screening assessment whose

values are calculated to be protective

over a range of conditions and situations. Although a user could elect to

install a liner based on the Tier 1

results, it is appropriate that a user

consider Tier 2 or Tier 3 evaluations

to confirm these recommendations.

• Consider pollution prevention,

recycling, or treatment. If you do

not want to conduct a Tier 2 or Tier

3 analysis, and the waste has one or

more “problem” constituents that call

for a more stringent and costly design

system (or which make land application inappropriate), you could consider pollution prevention, recycling,

and treatment options for those constituents. Options that previously

might have appeared economically

infeasible, might be worthwhile if

they can reduce the problem constituent concentration to a level that

results in a different design recommendation or would make land

application appropriate. Then, after

implementing these measures, repeat

the Tier 1 evaluation. Based on the

results presented in Table 6, pollution

prevention, recycling, or treatment

measures could be used to reduce the

expected leachate concentration for

styrene below 0.61 mg/L so that a

single liner is recommended for the

unit. Consult Chapter 3—Integrating

7A-26

Protecting Ground Water—Assessing Risk 
Pollution Prevention, for ideas and

tools.

• Implement recommendations. You

can design the unit based on the

design recommendations of the Tier

1 lookup tables without performing

further analysis or considering pollution prevention or recycling activities.

In the case of land application, a land

application system might be developed (after evaluating other factors) if

the lookup tables found no liner necessary for all constituents. In either

case, it is recommended that you

consult the appropriate agency to ensure

compliance with

state regulations.

Figure 3 illustrates the

basic steps using the Tier 1

lookup tables to determine

an appropriate design for a

proposed waste management unit or whether land

application is appropriate.

C. Tier 2

Evaluations

The Tier 2 evaluation is

designed to provide a

more accurate evaluation

than Tier 1 by allowing

the user to provide sitespecific data. In many

cases, a Tier 2 evaluation

might suggest a less stringent and less costly design

than a Tier 1 evaluation

would recommend. This

section describes the

inputs for the analysis and

the process for determining a protective recommendation.

1. How is a Tier 2 Analysis

Performed?

Under Tier 2, the user can provide sitespecific information to refine the design recommendations. The Tier 2 analysis leads the

user through a series of data entry screens

and then runs EPACMTP to generate a design

recommendation based on the site-specific

information provided by the user. The user

can provide data related to the WMU, the

subsurface environment, infiltration rates,

physicochemical properties, and toxicity. The

user can evaluate the three designs discussed

above or provide data reflecting a site-specific

Protecting Ground Water—Assessing Risk 

7A-27

Consider implementing liner and/or land

application recommendation, or obtaining additional data for

a Tier 2 or Tier 3

analysis.

Consider a Tier 2 evaluation or

performing a comprehensive Tier

3 site-specific ground-water fate

and transport analysis.

Identify proposed WMU type.

Will pollution prevention, recycling, or treatment be implemented to

reduce concentrations of

problem constituents?

Do you have 

site-specific 

data?

YES

NO

YES

Estimate waste leachate concentration for

all potential constituents expected to be

present in the waste.

Compare expected leachate concentrations

to calculated LCTVs for all potential 

constituents.

Figure 3. Using Tier 1 Lookup Tables

NO
liner design. As a result, a Tier 2 analysis

provides a protective design recommendation

intended only for use at the user’s site, and is

not intended to be applied to other sites.

This section discusses the inputs that a user

can provide and the results from the analysis.

a. Tier 2 Inputs

In addition to the inputs required for the

Tier 1 analysis, a Tier 2 analysis allows users

to provide additional inputs that account for

attributes that are specific to the user’s site.

The Tier 2 inputs that are common to the

Tier 1 evaluation are: 

• WMU type—waste pile, surface

impoundment, or land application

unit.

• Chemical constituents of concern

present in the WMU.

• Leachate concentration (in mg/L) of

each constituent.

If the user has already performed a Tier 1

analysis and continues to a Tier 2 analysis,

the Tier 1 inputs are carried forward to the

Tier 2 analysis. In the Tier 2 analysis, however, the user can change these data without

changing the Tier 1 data.

In addition to the Tier 1 inputs, the user

also provides values for additional parameters

including WMU area, WMU depth for landfills, ponding depth for surface impoundments, and the climate center in the IWEM

database that is nearest to the site. These

parameters can have a significant influence

on the LCTVs generated by the model and

also are relatively easy to determine. The user

also has the option to provide values for several more parameters. Table 8 presents the

list of “required” and “optional” parameters.

Because site-specific data for all of the

EPACMTP parameters might not be available,

the model contains default values for the

“optional” parameters that are used unless

the user provides site-specific data. The

default values are derived from a number of

sources, including a survey of industrial

waste management units, a hydrogeologic

database, water-balance modeling, and values

reported in the scientific literature. The selection of default values is explained in the

IWEM Technical Background Document (U.S.

EPA, 2002a). If site-specific data are available, they should be used to derive the most

appropriate design scenario for a particular

site.10

In addition to the above parameters, users

can also enter certain constituent specific

properties, as follows:

• Organic carbon distribution coefficient (KOC). A function of the nature

of a sorbent (the soil and its organic

carbon content) and the properties of

a chemical (the leachate constituent).

It is equal to the ratio of the solid

and dissolved phase concentrations,

measured in milliliters per gram

(mL/g). The higher the value of the

distribution coefficient, the higher

the adsorbed-phase concentration,

meaning the constituent would be

less mobile. For metals, IWEM provides an option to enter a site-specific soil-water partition coefficient (Kd),

which overrides the MINTEQA2

default sorption isotherms.

• Degradation coefficient. The rate at

which constituents degrade or decay

within an aquifer due to biochemical

processes, such as hydrolysis or

biodegradation (measured in units of

1/year). The default decay rate in

IWEM represents degradation from

chemical hydrolysis only, since

biodegradation rates are strongly

influenced by site-specific factors. In

Tier 2, a user can enter an overall

7A-28

10 A Tier 2 evaluation is not always less conservative than a Tier 1. For example, if a site has a very large

area, a very shallow water table, and/or the aquifer thickness is well below the national average, then

the Tier 2 evaluation results can be more stringent than the Tier 1 analysis results.

Protecting Ground Water—Assessing Risk 
Parameter Description Use in Model Units Applicable Required or 

WMU Optional

WMU area Area covered by the WMU To determine the area for Square meters (m2) All Required

infiltration of leachate

WMU location Geographic location of WMU in terms of To determine local climatic Unitless All Required

the nearest of 102 climate stations conditions that affect infiltration 

and aquifer recharge

Total waste Depth of the unit for landfills (average For landfills, used to determine Meters (m) LF Required for 

management unit thickness of waste in the landfill, not the landfill depletion rate. For SI landfills and 

depth counting the thickness of a liner below the surface impoundments, used surface 

waste or the thickness of a final cover on as the hydraulic head to derive impoundments

top of the waste) and surface leakage

impoundments (depth of the free-standing 

liquid in the impoundment, not counting 

the thickness of any accumulated sediment 

layer at the base of the impoundment)

Depth of waste Depth of the base of the unit below the Used together with depth of the Meters (m) LF Optional

management unit ground surface water table to determine SI 

below ground distance leachate has to travel WP

surface through unsaturated zone to 

reach ground water

Surface Thickness of sediment at the base of Limits infiltration from unit. Meters (m) SI Optional

Impoundment surface impoundment (discounting 

sediment layer thickness of engineered liner, if present)

thickness

WMU operational Period of time WMU is in operation. IWEM assumes leachate Years WP Optional

life generation occurs over the same SI 

period of time. LAU

WMU infiltration Rate at which leachate flows from the Affected by area’s rainfall Meters per year All Optional

rate bottom of a WMU (including any liner) intensity and design (m/yr)

into unsaturated zone performance. Users either input 

infiltration rates directly or 

allow IWEM to estimate values 

based on the unit’s geographic 

location,11 liner design, cover 

design and WMU type.

Soil type Predominant soil type in the vicinity of Uses site-specific soil data to sandy loam All Optional

the WMU model leachate migration silt loam 

through unsaturated zone and silty clay loam

determine regional recharge rate

Distance to a well The distance from a WMU to a To determine the horizontal Meters (m) All Optional

downgradient well. distance over which dilution 

and attenuation occur.

Hydrogeological Information on the hydrogeological setting Determines certain aquifer Varies All Optional

setting of the WMU characteristics (depth to water 

table, saturated zone thickness, 

saturated zone hydraulic 

conductivity, ground-water 

hydraulic gradient) when 

complete information not 

available

Table 8.

Input Parameters for Tier 2

Protecting Ground Water—Assessing Risk 

7A-29

11 For surface impoundments IWEM can use either the unit’s geographic location or impoundment characteristics

(such as ponding depth, and thickness of sediment layer) to estimate the infiltration rates.
degradation rate which overrides the

IWEM default. A user can choose to

include degradation due to hydrolysis and biodegradation in the overall

degradation rate.

b. Tier 2 Results

After providing site-specific inputs, the

user generates design recommendations for

each constituent by launching EPACMTP

from within IWEM. EPACMTP will then simulate the site and determine the 90th percentile exposure concentration for each

design scenario. IWEM determines the minimum recommended design at a 90th percentile exposure concentration by performing

10,000 Monte Carlo simulations of

EPACMTP for each waste constituent and

design. Upon completion of the modeling

analyses, IWEM will display the minimum

design recommendation and the calculated,

location-specific LCTVs based on the 90th

percentile exposure concentration. 

The overall result of a Tier 2 analysis is a

design recommendation similar to the Tier 1

analysis. However, the basis for the recommendation differs slightly. To illustrate the

similarities and differences between the

results from the two tiers, the remainder of

this section continues the example Tier 1

evaluation through a Tier 2 evaluation. In the

Tier 1 example, the disposal of toluene and

styrene in a proposed landfill is evaluated.

The expected leachate concentration for

toluene is 1.6 mg/L and the expected

leachate concentration for styrene is 1.0

mg/L. In Tier 2, after inputting the site-specific data summarized in Table 9 and using

default data for the remaining parameters,

the user can then launch the EPACMTP

model simulations.

After completing the EPACMTP model

simulations, IWEM produces the results on

screen. Table 10 presents the detailed results

of a Tier 2 analysis for the no liner/in situ

soils scenario. The data presented in this

table are similar to the data presented in the

Tier 1 results, but the Tier 2 analysis expands

7A-30

Protecting Ground Water—Assessing Risk 

Parameter Description Use in Model Units Applicable Required or 

WMU Optional

Depth to the water The depth of the zone between the land Used to predict travel time. Meters (m) All Optional

table surface and the water table

Saturated zone Thickness of the saturated zone of the Delineates the depth over Meters (m) All Optional

thickness aquifer which leachates can mix with 

ground waters.

Saturated zone Hydraulic conductivity of the saturated With hydraulic gradient, used Meters per year All Optional

hydraulic zone, or the permeability of the saturated to calculate ground-water flow (m/yr)

conductivity zone in the horizontal direction. rates.

Ground-water Regional horizontal ground-water gradient With hydraulic conductivity, Meters per meter All Optional

hydraulic gradient used to calculate the ground- (m/m)

water flow rate.

Distance to nearest The distance from the unit to the nearest Affects the calculation of Meters (m) SI Optional

surface water body water body ground-water mounding at a site.

Table 8.

Input Parameters for Tier 2 (con’t)
the information provided to

the user. It includes additional

information regarding the toxicity standard, the reference

ground-water concentration

(RGC), and the 90th percentile exposure concentration. The toxicity standard is

included because the user can

select specific standards, provide a user-defined standard,

or compare to all standards. In

this example, all standards

were selected; the user can

identify the result for each

standard from a single table.

The LCTV continues to represent the maximum leachate

Protecting Ground Water—Assessing Risk 

7A-31

Parameters Site-Specific Data

Infiltration rate* Local climate: Madison, WI

Soil type: fine-grained soil

Waste management unit area 15,000 m2

Waste management unit depth 2 m

Depth to the water table 10 m

Aquifer thickness 25 m

Toxicity standards Compare to all

Distance to a well 150 m

Table 9. 

A Sample Set of Site-Specific Data for Input to Tier 2

* The Tier 2 model uses an infiltration rate for the liner scenarios

based on local climate and soil data.

CAS # Constituent Leachate DAF LCTV Toxicity Ref. 90th Percentile Protective?

Concentration (mg/L) Standard Ground- Exposure

(mg/L) water Concentration

Conc. (mg/L) (mg/L)

100-42-5 Styrene 1.0 8.3 0.83 MCL 0.1 0.1201 No

100-42-5 Styrene 1.0 8.3 29.88 HBN - 3.6 0.1201 Yes

Ingestion 

NonCancer

100-42-5 Styrene 1.0 8.3 40.67 HBN - 4.9 0.1201 Yes

Inhalation 

Noncancer

108-88-3 Toluene 1.6 8.3 8.3 MCL 1 0.1922 Yes

108-88-3 Toluene 1.6 8.4 10.92 HBN - 1.3 0.1894 Yes

Ingestion

Noncancer

108-88-3 Toluene 1.6 8.4 41.16 HBN - 4.9 0.1894 Yes

Inhalation

Noncancer 

Table 10: 

Example of Tier 2 Detailed Summary Table - No Liner/In situ Soils
concentration for a design scenario that is

still protective for a reference ground-water

concentration, but the LCTV is not the basis

for the design recommendation.

The RGC and 90th percentile exposure

concentration are provided because they are

the point of comparison for the Tier 2 analysis. (The LCTV, however, continues to provide

information about a threshold that might be

useful for pollution prevention or waste minimization efforts.) As shown in Table 10, the

no liner/in situ soils scenario is protective for

toluene because all of the 90th percentile

exposure concentrations are less than the

three RGCs for toluene, while the no liner/in

situ soils scenario is not protective for styrene

for the MCL comparison. For that standard,

the 90th percentile exposure concentration

(0.1201 mg/L) exceeds the RGC (0.1 mg/L).

In this case, IWEM would launch EPACMTP

to evaluate a clay liner to determine whether

that liner design would be protective.

Table 11 provides the single clay liner

results for a Tier 2 analysis. As shown in the

table, the single clay liner is protective

because the 90th percentile exposure concentration (0.0723 mg/L) is less than the reference ground-water concentration (0.1 mg/L).

In addition, under the “Protective?” column,

IWEM refers the user to the appropriate liner

result if a less stringent design is recommended. In Table 11, the user is referred to

the no liner/in situ soils results for the HBNbased ingestion and inhalation results

because, as shown in Table 10, the no

liner/in situ soils scenario is protective. If a

Tier 2 analysis determines that a single clay

liner is protective for all constituents, then

IWEM would not continue to an evaluation

of a composite liner. For this example of

styrene and toluene disposed of in a landfill,

the recommended minimum design is a single clay liner, because the 90th percentile

exposure concentration (0.0723) is less than

the MCL-based RGC (0.1).

2. What Do the Results Mean

and How Do I Interpret Them?

The Tier 2 analysis provides LCTVs and

recommendations for a minimum protective

design. In the Tier 1 analysis, that recommendation is based on a comparison of expected

leachate concentrations to LCTVs to determine

whether a design scenario is protective. In the

7A-32

Protecting Ground Water—Assessing Risk 

CAS # Constituent Leachate DAF LCTV Toxicity Ref. 90th Percentile Protective?

Concentration (mg/L) Standard Ground- Exposure

(mg/L) water Concentration

Conc. (mg/L) (mg/L)

100-42-5 Styrene 1.0 14 1.4 MCL 0.1 0.0723 Yes

100-42-5 Styrene 1.0 14 50.4 HBN - 3.6 0.0722 See No liner 

Ingestion Results

NonCancer

100-42-5 Styrene 1.0 14 68.6 HBN - 4.9 0.0722 See No liner 

Inhalation Results

Noncancer

Table 11: 

Example of Tier 2 Detailed Summary Table - Single Clay Liner
Tier 2 analysis, LCTVs can be used to help

waste managers determine whether waste minimization techniques might lower leachate

concentrations and enable them to use less

costly unit designs, but IWEM does not need

to calculate an LCTV to make a design recommendation. If the 90th percentile groundwater concentration does not exceed the

specified RGC, then the evaluated design scenario is protective for that constituent. If the

90th percentile ground-water concentrations

for all constituents under the no liner/in situ

soils scenario are below their respective RGCs ,

then IWEM will recommend that no liner/in

situ soils is needed to protect the ground

water. If the 90th percentile ground-water concentration of any constituent exceeds its RGC,

then a single clay liner is recommended (or, in

the case of land application units, land application is not recommended). Similarly, if the

90th percentile ground-water concentration of

any constituent under the single clay liner scenario exceeds its RGC, then a composite liner

is recommended. As previously noted, however, you may decide to conduct a Tier 3 sitespecific analysis to determine which design

scenario is most appropriate. See the ensuing

section on Tier 3 analyses for further information. For waste streams with multiple constituents, the most protective liner design that

is recommended for any one constituent is the

overall recommendation. As in the Tier 1 evaluation, pollution prevention, recycling, and

treatment practices could be considered when

the protective standard of a composite liner is

exceeded if you decide not to undertake a Tier

3 assessment to reflect site-specific conditions.

If the Tier 2 analysis found land application to be appropriate for the constituents of

concern, then a new land application system

may be considered (after evaluating other factors). Alternatively, if the waste has one or

more “problem” constituents that make land

application inappropriate, the user might

consider pollution prevention, recycling, and

treatment options for those constituents. If,

after conducting the Tier 2 evaluation, the

user is not satisfied with the resulting recommendations, or if site-specific conditions

seem likely to suggest a different conclusion

regarding the appropriateness of land application of a waste, then the user can conduct a

more in-depth, site-specific, ground-water

risk analysis (Tier 3).

In addition to the Tier 2 evaluation, other

fate and transport models have been developed that incorporate location-specific considerations, such as the American Petroleum

Institute’s (API’s) Graphical Approach for

Determining Site-Specific Dilution-Attenuation

Factors.12 API developed its approach to calculate facility-specific DAFs quickly using

graphs rather than computer models. Graphs

visually indicate the sensitivity to various

parameters. This approach can be used for

impacted soils located above or within an

aquifer. This approach accounts for attenuation with distance and time due to

advective/dispersive processes. API’s approach

has a preliminary level of analysis that uses a

small data set containing only measures of the

constituent plume’s geometry. The user can

read other necessary factors off graphs provided as part of the approach. This approach also

has a second level of analysis in which the

user can expand the data set to include sitespecific measures, such as duration of constituent leaching, biodegradation of

constituents, or site-specific dispersivity values. At either level of analysis, the calculation

results in a DAF. This approach is not appropriate for all situations; for example, it should

not be used to estimate constituent concentrations in active ground-water supply wells or

to model very complex hydrogeologic settings, such as fractured rock. It is recommended that you consult with the appropriate

state agency to discuss the applicability of the

API approach or any other location-adjusted

model prior to use.

Protecting Ground Water—Assessing Risk 

7A-33

12 A copy of API’s user manual, The Technical Background Document and User Manual (API Publication 4659),

can be obtained from the American Petroleum Institute, 1220 L Street, NW, Washington, DC 20005,

202 682-8375.
D. Strengths and

Limitations

Listed below are some of IWEM’s strengths

and limitations that the user should be aware of:

1. Strengths

• The tool is relatively easy to use and

requires a minimal amount of data

and modeling expertise.

• The tool can perform rapid Tier 1

screening evaluations. Tier 2 evaluations allow for many site-specific

adjustments.

• The tool is designed to be flexible

with respect to the availability of sitespecific data for a Tier 2 evaluation.

The user needs to provide only a

small number of inputs, but if more

data are available, the tool can

accommodate their input.

• Users can enter their own infiltration

rates to evaluate additional design

scenarios and still use IWEM to conduct a risk evaluation.

• The user can modify RGC values,

when appropriate, and in consultation with other stakeholders.

• The user can modify properties of

the 226 constituents (e.g., adding

biodegradation), and can add additional constituents for evaluation.

• The tool provides recommendations

for protective design systems. It can

also be used to evaluate whether

waste leachate reduction measures

would be appropriate.

2. Limitations

• IWEM considers only exposures

from contact with contaminated

ground water via ingestion of drinking water and inhalation while showering. IWEM does not consider

vapor intrusion into buildings. It also

does not address potential risks

through environmental pathways

other than ground water, such as

volatile emissions from a WMU, surface runoff and erosion, and indirect

exposures through the food chain

pathway. Other chapters in this

Guide, however, address ways to

assess or control potential risks via

such other pathways.

• The use of a waste concentration to

leachate concentration ratio of

10,000 in IWEM Tier 2 may overestimate the amount of contaminant

mass in the WMU, allowing the

modeling results to approach nondepleting source steady-state values

for WMUs without engineered liners.

This may result in an underestimation of the Tier 2 LCTVs.

• IWEM considers only human health

risks. Exposure and risk to ecological

receptors are not included.

• The conceptual flow model used in

EPACMTP in conjunction with

IWEM Tier 2 data input constraints

might produce ground-water velocities that might be greater than can be

assumed based on the site-specific

hydraulic conductivity and hydraulic

gradient values. The maximum values that the velocities can reach are

limited by a model constraint that

appropriately prevents the modeled

water level from rising above the

ground surface. Despite this constraint, modeled velocities might be

greater than expected velocities based

on site-specific hydraulic conductivity and hydraulic gradient.

7A-34

Protecting Ground Water—Assessing Risk 
• The risk evaluation in IWEM is based

on the ground-water concentration of

individual waste constituents. IWEM

does not address the cumulative risk

due to simultaneous exposure to multiple constituents (although it does

use a carcinogenic risk level at the

conservative end of EPA’s risk range).

• IWEM is not designed for sites with

complex hydrogeology, such as fractured (karst) aquifers.

• The tool is inappropriate for sites

where non-aqueous phase liquid

(NAPL) contaminants are present.

• IWEM does not account for all possible fate and transport processes. For

example, colloid transport might be

important at some sites but is not

considered in IWEM. While the user

can enter a constituent-specific

degradation rate constant to account

for biodegradation, IWEM simulates

biodegradation in a relatively simple

way by assuming the rate is the same

in both the unsaturated and the saturated zones.

E. Tier 3: A Comprehensive

Site-Specific Evaluation

If the Tier 1 and Tier 2 evaluations do not

adequately simulate conditions at a proposed

site, or if you decide that sufficient data are

available to skip a Tier 1 or Tier 2 analysis, a

site-specific risk assessment could be considered.13 In situations involving a complex

hydrogeologic setting or other site-specific

factors that are not accounted for in IWEM, a

detailed site-specific ground-water fate and

transport analysis might be appropriate for

determining risk to ground water and evaluating alternative designs or application rates.

It is recommended that you consult with the

appropriate state agency and use a qualified

professional experienced in ground-water

modeling. State officials and appropriate

trade associations might be able to suggest a

good consultant to perform the analysis.

1. How is a Tier 3 Evaluation

Performed?

A Tier 3 evaluation will generally involve a

more detailed site-specific analysis than Tier

2. Sites for which a Tier 3 evaluation might

be performed typically involve complex and

heterogeneous hydrogeology. Selection and

application of appropriate ground-water

models require a thorough understanding of

the waste and the physical, chemical, and

hydrogeologic characteristics of the site. 

A Tier 3 evaluation should involve the following steps:

• Developing a conceptual hydrogeological model of the site.

• Selecting a flow and transport simulation model.

• Applying the model to the site.

Protecting Ground Water—Assessing Risk 

7A-35

13 For example, if ground-water flow is subject to seasonal variations, use of the Tier 2 evaluation tool

might not be appropriate because the model is based on steady-state flow conditions.

Why is it important to use

a qualified professional?

• Fate and transport modeling can be

very complex; appropriate training

and experience are required to correctly use and interpret models.

• Incorrect fate and transport modeling

can result in a liner system that is not

sufficiently protective or an inappropriate land application rate.

• To avoid incorrect analyses, check to

see if the professional has sufficient

training and experience at analyzing

ground-water flow and contaminant

fate and transport.
As with all modeling, you should consult

with the state before investing significant

resources in a site-specific analysis. The state

might have a list of preferred models and

might be able to help plan the fate and transport analysis.

a. Developing a Conceptual

Hydrogeological Model

The first step in the site-specific Tier 3

evaluation is to develop a conceptual hydrogeological model of the site. The conceptual

model should describe the key features and

characteristics to be captured in the fate and

transport modeling. A complete conceptual

hydrogeological model is important to ensure

that the fate and transport model can simulate the important features of the site. The

conceptual hydrogeological model should

address questions such as:

• Does a confined aquifer, an unconfined aquifer, or both need to be simulated?

• Does the ground water flow through

porous media, fractures, or a combination of both?

• Is there single, or are there multiple,

hydrogeologic layers to be simulated?

• Is the hydrogeology constant or variable in layer thickness? 

• Are there other hydraulic sources or

sinks (e.g., extraction or injection

wells, lakes, streams, ponds)?

• What is the location of natural noflow boundaries and/or constant

head boundaries?

• How significant is temporal (seasonal) variation in ground-water flow

conditions? Does it require a transient flow model?

• What other contaminant sources are

present?

• What fate processes are likely to be

significant (e.g. sorption and

biodegradation)?

• Are plume concentrations high

enough to make density effects significant?

b. Selecting a Fate and Transport

Simulation Model

Numerous computer models exist to simulate ground-water fate and transport.

Relatively simple models are often based on

analytical solutions of the mathematical

equations governing ground-water flow and

solute transport equations. However, such

models generally cannot simulate the complexities of real world sites, and for a rigorous Tier 3 evaluation, numerical models

based on finite-difference or finite-element

techniques are recommended. The primary

criteria for selecting a particular model

should be that it is consistent with the characteristics of the site, as described in the conceptual site hydrogeological model, and that

it is able to simulate the significant processes

that control contaminant fate and transport.

In addition to evaluating whether a model

will adequately address site characteristics,

the following questions should be answered

to ensure that the model will provide accurate, verifiable results:

• What is the source of the model?

How easy is it to obtain and is the

model well documented? 

• Are documentation and user’s manuals available for the model? If yes, are

they clearly written and do they provide sufficient technical background

on the mathematical formulation and

solution techniques?

7A-36

Protecting Ground Water—Assessing Risk 
• Has the model been verified against

analytical solutions and other models? If yes, are the test cases available

so that a professional consultant can

test the model on his/her computer

system? 

• Has the model been validated using

field data?

Table 12 provides a brief description of a

number of commonly used ground-water fate

and transport models.

c. Applying the Model to the Site

For proper application of a ground-water

flow and transport model, expertise in hydrogeology and the principles of flow and transport, as well as experience in using models

and interpreting model results are essential.

The American Society for Testing and Materials

(ASTM) has developed guidance that might be

useful for conducting modeling. A listing of

guidance material can be found in Table 13. 

The first step in applying the model to a

site is to calibrate it. Model calibration is the

process of matching model predictions to

observed data by adjusting the values of

input parameters. In the case of ground-water

modeling, the calibration is usually done by

matching predicted and observed hydraulic

head values. Calibration is important even for

well-characterized sites, because the values of

measured or estimated model parameters are

always subject to uncertainty. Calibrating the

flow model is usually achieved by adjusting

the value(s) of hydraulic conductivity and

recharge rates. In addition, if plume monitoring data or tracer test data are available,

transport parameters such as dispersivity, and

sorption and degradation parameters can also

be calibrated. A properly calibrated model is

a powerful tool for predicting contaminant

fate and transport. Conversely, if no calibration is performed due to lack of suitable site

data, any Tier 3 model predictions will

remain subject to considerable uncertainty. 

At a minimum, a site-specific analysis

should provide estimated leachate concentrations at specified downgradient points for a

proposed design. For landfills, surface

impoundments and waste piles, you should

compare these concentrations to appropriate

MCLs, health-based standards, or state standards. For land application units, if a waste

leachate concentration is below the values

specified by the state, land application might

be appropriate. Conversely, if a leachate concentration is above state-specified values,

land application might not be protective of

the ground water. 

Protecting Ground Water—Assessing Risk 

7A-37

What are some useful resources for

selecting a ground-water fate and

transport model?

The following resources can help

select appropriate modeling software:

• Ground Water Modeling Compendium,

Second Edition (U.S. EPA, 1994c)

• Assessment Framework for GroundWater Modeling Applications (U.S. EPA,

1994b)

• Technical Guide to Ground-water Model

Selection at Sites Contaminated with

Radioactive Substances (U.S. EPA,

1994a)

• EPA’s Center for Subsurface Modeling

Support (CSMoS—RSKERL; Ada,

Oklahoma)

• Anderson, Mary P. and William W.

Woessner. Applied Groundwater

Modeling: Simulation of Flow and

Advective Transport (Academic Press,

1992)

• EPA regional offices
7A-38

Protecting Ground Water—Assessing Risk 

Model Name Description

MODFLOW MODFLOW is a 3-D, ground-water flow model for steady state and transient simulation of

saturated flow problems in confined and unconfined aquifers. It calculates flow rates and

water balances. The model includes flow towards wells, through riverbeds, and into drains.

MODFLOW is the industry standard for ground-water modeling that was developed and

still maintained by the United States Geological Survey (USGS). MODFLOW-2000 is the

current version. MODFLOW is a public domain model; numerous pre- and post-processing

software packages are available commercially. MODFLOW can simulate ground-water flow

only. In order to simulate contaminant transport, MODFLOW must be used in conjunction

with a compatible solute transport model (MT3DMS, see below).

MODFLOW and other USGS models can be obtained from the USGS Web site at

<water.usgs.gov/nrp/gwsoftware/modflow.html>.

MT3DMS Modular 3-D Transport model (MT3D) is commonly used in contaminant transport modeling and remediation assessment studies. Originally developed for EPA, the current version is

known as MT3DMS. MT3DMS has a comprehensive set of options and capabilities for simulating advection, dispersion/diffusion, and chemical reactions of contaminants in groundwater flow systems under general hydrogeologic conditions. MT3DMS retains the same

modular structure of the original MT3D code, similar to that implemented in MODFLOW.

The modular structure of the transport model makes it possible to simulate advection, dispersion/diffusion, source/sink mixing, and chemical reactions separately without reserving

computer memory space for unused options. New packages involving other transport

processes and reactions can be added to the model readily without having to modify the

existing code.

NOTE: The original version of this model known as MT3D, released in 1991, was based on

a mathematical formulation which could result in mass-balance errors. This version should

be avoided.

MT3DMS is maintained at the University of Alabama, and can be obtained at:

<hydro.geo.ua.edu/mt3d>. MT3DMS is also included, along with MODFLOW, in several

commercial ground-water modeling software packages.

BIOPLUME-III BIOPLUME-III is a 2-D, finite difference model for simulating the natural attenuation of

organic contaminants in ground water due to the processes of advection, dispersion, sorption, and biodegradation. Biotransformation processes are potentially important in the

restoration of aquifers contaminated with organic pollutants. As a result, these processes

require valuation in remedial action planning studies associated with hydrocarbon contaminants. The model is based on the USGS solute transport code MOC. It solves the solute

transport equation six times to determine the fate and transport of the hydrocarbons, the

electron acceptors (O2, NO3-, Fe3+, SO4

2-, and CO2), and the reaction byproducts (Fe2+). A

number of aerobic and anaerobic electron acceptors (e.g., oxygen, nitrate, sulfate, iron (III),

and carbon dioxide) have been considered in this model to simulate the biodegradation of

organic contaminants. Three different kinetic expressions can be used to simulate the aerobic and anaerobic biodegradation reactions.

BIOPLUME-III and other EPA supported ground-water modeling software can be obtained

via the EPA Center for Subsurface Modeling Support at the RS Kerr Environmental Research

Lab in Ada, Oklahoma: <www.epa.gov/ada/csmos/models.html>. 

Table 12. 

Example Site-Specific Ground-Water Fate and Transport Models
A well-executed site-specific analysis can be

a useful instrument to anticipate and avoid

potential risks. A poorly executed site-specific

analysis, however, could over- or underemphasize risks, possibly leading to adverse

human health and environmental effects, or

costly cleanup liability, or it could overemphasize risks, possibly leading to the unnecessary

expenditure of limited resources. If possible,

the model and the results of the final analyses,

including input and output parameters and

key assumptions, should be shared with

stakeholders. Chapter 1—Understanding Risk

and Building Partnerships provides a more

detailed description of activities to keep the

public informed and involved.

Protecting Ground Water—Assessing Risk 

7A-39

The American Society for Testing and Materials (ASTM), Section D-18.21.10 concerns

subsurface fluid-flow (ground-water) modeling. The ASTM ground-water modeling section

is one of several task groups funded under a cooperative agreement between USGS and EPA

to develop consensus standards for the environmental industry and keep the modeling

community informed as to the progress being made in development of modeling standards.

The standards being developed by D-18.21.10 are “guides” in ASTM terminology, which

means that the content is analogous to that of EPA guidance documents. The ASTM modeling guides are intended to document the state-of-the-science related to various topics in

subsurface modeling.

The following standards have been developed by D-18.21.10 and passed by ASTM.

They can be purchased from ASTM by calling 610 832-9585. To order or browse for publications, visit ASTM’s Web site <www.astm.org> .

D-5447 Guide for Application of a Ground-Water Flow Model to a Site-Specific Problem

D-5490 Guide for Comparing Ground-Water Flow Model Simulations to Site-Specific

Information

D-5609 Guide for Defining Boundary Conditions in Ground-Water Flow Modeling

D-5610 Guide for Defining Initial Conditions in Ground-Water Flow Modeling

D-5611 Guide for Conducting a Sensitivity Analysis for a Ground-Water Flow Model

Application

D-5718 Guide for Documenting a Ground-Water Flow Model Application

D-5719 Guide to Simulation of Subsurface Air Flow Using Ground-Water Flow

Modeling Codes

D-5880 Guide for Subsurface Flow and Transport Modeling

D-5981 Guide for Calibrating a Ground-Water Flow Model Application

A compilation of most of the current modeling and aquifer testing standards also can be

purchased. The title of the publication is ASTM Standards on Analysis of Hydrologic

Parameters and Ground Water Modeling, publication number 03-418096-38.

For more information by e-mail, contact service@astm.org.

Table 13. ASTM Ground-Water Modeling Standards
Protecting Ground Water—Assessing Risk 

■ Review the risk characterization tools recommended by this chapter.

■ Characterize the waste in accordance with the recommendations of Chapter 2 — Characterizing

Waste.

■ Obtain expected leachate concentrations for all relevant waste constituents.

■ If a Tier 1 evaluation is conducted, understand and use the Tier 1 Evaluation to obtain recommendations for the design of your waste management unit (as noted previously, you can skip the Tier 1

analysis and proceed directly to a Tier 2 or Tier 3 analysis).

■ If a design system or other measures are recommended in a Tier 1 analysis, perform a Tier 2 analysis if you believe the recommendations are overly protective. Also, if data are available, you can

conduct a Tier 2 or Tier 3 analysis without conducting a Tier 1 evaluation.

■ If your site characteristics or your waste management needs are particularly complex, or do not

adequately simulate conditions reflected in a Tier 1 or Tier 2 analysis, consult with your state and a

qualified professional and consider a more detailed, site-specific Tier 3 analysis.

Assessing Risk Activity List

7A-40
7A-41

ASTM. 1996. ASTM Standards on Analysis of Hydrologic Parameters and Ground Water Modeling,

Publication Number 03-418096-38.

ASTM. 1993. D-5447 Guide for Application of a Ground-Water Flow Model to a Site-Specific

Problem.

ASTM. 1993. D-5490 Guide for Comparing Ground-Water Flow Model Simulations to Site-specific

Information.

ASTM. 1994. D-5609 Guide for Defining Boundary Conditions in Ground-Water Flow Modeling.

ASTM. 1994. D-5610 Guide for Defining Initial Conditions in Ground-Water Flow Modeling.

ASTM. 1994. D-5611 Guide for Conducting a Sensitivity Analysis for a Ground-Water Flow Model

Application.

ASTM. 1994. D-5718 Guide for Documenting a Ground-Water Flow Model Application.

ASTM. 1994. D-5719 Guide to Simulation of Subsurface Air Flow Using Ground-Water Flow

Modeling Codes.

ASTM. 1995. D-5880 Guide for Subsurface Flow and Transport Modeling.

ASTM. 1996. D-5981 Guide for Calibrating a Ground-Water Flow Model Application.

Bagchi, A. 1994. Design, Construction, and Monitoring of Landfills.

Berner, E. K. and R. Berner. 1987. The Global Water Cycle: Geochemistry and Environment.

Boulding, R. 1995. Soil, Vadose Zone, and Ground-Water Contamination: Assessment, Prevention,

and Remediation.

Lee, C. 1992. Environmental Engineering Dictionary, 2d. Ed.

Sharma, H., and S. Lewis. 1994. Waste Containment Systems, Waste Stabilization, and Landfills.

Speidel, D., L. Ruedisili, and A. Agnew. 1988. Perspectives on Water: Uses and Abuses.

Resources

Protecting Ground Water—Assessing Risk 
Resources (cont.)

Protecting Ground Water—Assessing Risk 

U.S. EPA. 2002a. Industrial Waste Management Evaluation Model (IWEM) Technical

Background Document. EPA530-R-02-012.

U.S. EPA. 2002b. The User’s Guide for the Industrial Waste Management Evaluation Model.

EPA530-R- 02-013.

U.S. EPA. 2002c. EPACMTP Data/Parameters Background Document.

U.S. EPA. 2002d. EPACMTP Technical Background Document.

U.S. EPA. 1997a. Exposure Factors Handbook. EPA600-P-95-002F.

U.S. EPA. 1997b. Guiding Principles for Monte Carlo Analyses. EPA630-R-97-001.

U.S. EPA. 1994a. A Technical Guide to Ground-Water Model Selection at Sites Contaminated

with Radioactive Substance. EPA 4-2-R-94-012.

U.S. EPA. 1994b. Assessment Framework for Ground-Water Modeling Applications. EPA500-B94-003.

U.S. EPA. 1994c. Ground-Water Modeling Compendium, Second Edition. EPA500-B-94-003.

U.S. EPA. 1991. Seminar Publication: Site Characterization for Subsurface Remediation.

EPA625-4-91-026.

U.S. EPA. 1989. Exposure Assessment Methods Handbook.

U.S. EPA. 1988. Selection Criteria For Mathematical Models Used In Exposure Assessments:

Ground-water Models. EPA600-8-88-075.

U.S. EPA. 1988. Superfund Exposure Assessment Manual.

7A-42
Part IV

Protecting Ground Water

Chapter 7: Section B

Designing and Installing Liners

Technical Considerations for New Surface

Impoundments, Landfills, and Waste Piles
Contents

I. In-Situ Soil Liners ..................................................................................................................................7B-1

II. Single Liners ..........................................................................................................................................7B-2

A. Compacted Clay Liners ........................................................................................................................7B-2

B. Geomembranes or Flexible Membrane Liners ....................................................................................7B-10

C. Geosynthetic Clay Liners ....................................................................................................................7B-17

III. Composite Liners..................................................................................................................................7B-22

IV. Double Liners (Primary and Secondary Lined Systems) ........................................................................7B-23

V. Leachate Collection and Leak Detection Systems ..................................................................................7B-24

A. Leachate Collection System..................................................................................................................7B-24

B. Leak Detection System ........................................................................................................................7B-28

C. Leachate Treatment System ..................................................................................................................7B-29

VI. Construction Quality Assurance and Quality Control ..........................................................................7B-29

A. Compacted Clay Liner Quality Assurance and Quality Control ..........................................................7B-32

B. Geomembrane Liner Quality Assurance and Quality Control ..............................................................7B-32

C. Geosynthetic Clay Liner Quality Assurance and Quality Control ........................................................7B-33

D. Leachate Collection System Quality Assurance and Quality Control....................................................7B-34

Designing and Installing Liners Activity List................................................................................................7B-36

Resources ....................................................................................................................................................7B-37

Appendix ....................................................................................................................................................7B-43

Figures:

Figure 1. Water Content for Achieving a Specific Density ..........................................................................7B-6

Figure 2: Two Types of Footed Rollers........................................................................................................7B-8

Figure 3: Four Variations of GCL Bonding Methods ................................................................................7B-19

Figure 4: Typical Leachate Collection System ..........................................................................................7B-25

Figure 5: Typical Geonet Configuration....................................................................................................7B-27
Protecting Ground Water—Designing and Installing Liners

7B-1

Once risk has been characterized

and the most appropriate

design system is chosen, the

next step is unit design. The

Industrial Waste Management

Evaluation Model (IWEM), discussed in

Chapter 7, Section A—Assessing Risk can be

used to determine appropriate design system

recommendations. A critical part of this

design for new landfills, waste piles, and surface impoundments is the liner system. The

liner system recommendations in the Guide

do not apply to land application units, since

such operations generally do not include a

liner system as part of their design. (For

design of land application units, refer to

Chapter 7, Section C—Designing a Land

Application Program.) You should work with

your state agency to ensure consideration of

any applicable design system requirements,

recommendations, or standard practices the

state might have. In this chapter, sections I

though IV discuss four design options—no

liner/in-situ soils, single liner, composite liner,

and double liner. Section V covers leachate

collection and leak detection systems, and

section VI discusses construction quality

assurance and quality control.

I. In-Situ Soil

Liners

For the purpose of the Guide, in-situ soil

refers to simple, excavated areas or impoundments, without any additional engineering

controls. The ability of natural soils to hinder

transport and reduce the concentration of

constituent levels through dilution and attenuation can provide sufficient protection when

the initial constituent levels in the waste

stream are very low, when the wastes are

inert, or when the hydrogeologic setting

affords sufficient protection.

What are the recommendations

for in-situ soils?

The soil below and adjacent to a waste

management unit should be suitable for construction. It should provide a firm foundation

for the waste. Due to the low risk associated

with wastes being managed in these units, a

liner might not be necessary; however, it is

still helpful to review the recommended location considerations and operating practices for

the unit.

Designing and Installing Liners—Technical

Considerations for New Surface

Impoundments, Landfills, and Waste Piles

This chapter will help you:

• Employ liner systems where needed to protect ground water from

contamination. 

• Select from clay liners, synthetic liners, composite liners, leachate

collection systems, and leak detection systems as appropriate. 

• Consider technical issues carefully to ensure that the liner system

will function as designed.
7B-2

Protecting Ground Water—Designing and Installing Liners 

1 Many industry and trade periodicals, such as Waste Age, MSW Management, Solid Waste Technologies,

and World Wastes, have articles on liner types and their corresponding costs, as well as advertisements

and lists of vendors.

What technical issues should be

considered with the use of in-situ

soils?

In units using in-situ natural soils, construction and design of an engineered liner

will not be necessary; however, there are still

technical concerns to consider. These include

the following:

• The stability of foundation soils.

• The compatibility of the waste with

native soils.

• The location where the unit will be

sited.

• The potential to recompact existing

soils.

Potential instability can occur in the foundation soil, if its load-bearing capacity and

resistance to movement or consolidation are

insufficient to support the waste. The groundwater table or a weak soil layer also can influence the stability of the unit. You should take

measures, such as designing maximum slopes,

to avoid slope failure during construction and

operation of the waste management unit. Most

soil slopes are stable at a 3:1 horizontal to vertical inclination. There are common sense

operating practices to ensure that any wastes

to be managed on in-situ soils will not inappropriately interact with the soils. When using

in-situ soils, refer to Chapter 4—Considering

the Site. Selecting an appropriate location will

be of increased importance, since the added

barrier of an engineered liner will not be present. Because in-situ soil can have non-homogeneous material, root holes, and cracks, its

performance can be improved by scarifying

and compacting the top portion of the in-situ

natural soils.

II. Single Liners

If the risk evaluation recommended the use

of a single liner, the next step is to determine

the type of single liner system most appropriate for the site. The discussion below addresses three types of single liner systems:

compacted clay liners, geomembrane liners,

and geosynthetic clay liners. Determining

which material, or combination of materials, is

important for protecting human health and

the environment.1

A. Compacted Clay Liners 

A compacted clay liner can serve as a single

liner or as part of a composite or double liner

system. Compacted clay liners are composed

of natural mineral materials (natural soils),

bentonite-soil blends, and other materials

placed and compacted in layers called lifts. If

natural soils at the site contain a significant

quantity of clay, then liner materials can be

excavated from onsite locations known as borrow pits. Alternatively, if onsite soils do not

contain sufficient clay, clay materials can be

hauled from offsite sources, often referred to

as commercial pits.

Compacted clay liners can be designed to

work effectively as hydraulic barriers. To

ensure that compacted clay liners are well

constructed and perform as they are designed,

it is important to implement effective quality

control methods emphasizing soil investigations and construction practices. Three objectives of quality assurance and quality control

for compacted soil liners are to ensure that 1)

selected liner materials are suitable, 2) liner

materials are properly placed and compacted,

and 3) the completed liner is properly protected before, during, and after construction.

Quality assurance and quality control are discussed in greater detail in section VI.
What are the thickness and

hydraulic conductivity recommendations for compacted clay liners?

Compacted clay liners should be at least 2

feet thick and have a maximum hydraulic

conductivity of 1 x 10-7 cm/sec (4 x 10-8

in/sec). Hydraulic conductivity refers to the

degree of ease with which a fluid can flow

through a material. A low hydraulic conductivity will help minimize leachate migration

out of a unit. Designing a compacted clay

liner with a thickness ranging from 2 to 5 feet

will help ensure that the liner meets desired

hydraulic conductivity standards and will

also minimize leachate migration as a result

of any cracks or imperfections present in the

liner. Thicker compacted clay liners provide

additional time to minimize leachate migration prior to the clay becoming saturated.

What issues should be considered

in the design of a compacted clay

liner?

The first step in designing a compacted

clay liner is selecting the clay material. The

quality and properties of the material will

influence the performance of the liner. The

most common type of compacted soil is one

that is constructed from naturally occurring

soils that contain a significant quantity of

clay. Such soils are usually classified as CL,

CH, or SC in the Unified Soil Classification

System (USCS). Some of the factors to consider in choosing a soil include soil properties, interaction with wastes, and test results

for potentially available materials.

Soil Properties

Minimizing hydraulic conductivity is the

primary goal in constructing a soil liner.

Factors to consider are water content, plasticity

characteristics, percent fines, and percent gravel, as these properties affect the soil’s ability to

achieve a specified hydraulic conductivity.

Hydraulic conductivity. It is important to

select compacted clay liner materials so that

remolding and compacting of the materials

will produce a low hydraulic conductivity.

Factors influencing the hydraulic conductivity at a particular site include: the degree of

compaction, compaction method, type of clay

material used, soil moisture content, and

density of the soil during liner construction.

The hydraulic conductivity of a soil also

depends on the viscosity and density of the

fluid flowing through it. Consider measuring

hydraulic conductivity using methods such as

American Society of Testing and Materials

(ASTM) D-5084.2

Water content. Water content refers to the

amount of liquid, or free water, contained in a

given amount of material. Measuring water

content can help determine whether a clay

material needs preprocessing, such as moisture

adjustment or soil amendments, to yield a

specified density or hydraulic conductivity.

Compaction curves can be used to depict

moisture and density relationships, using

either ASTM D-698 or ASTM D-1557, the

standard or modified Proctor test methods,

depending on the compaction equipment used

and the degree of firmness in the foundation

materials.3 The critical relationship between

clay soil moisture content and density is

explained thoroughly in Chapter 2 of EPA’s

1993 technical guidance document Quality

Protecting Ground Water—Designing and Installing Liners

7B-3

2 ASTM D-5084, Standard Test Method for Measurement of Hydraulic Conductivity of Saturated Porous

Materials Using a Flexible Wall Permeameter.

3 ASTM D-698, Test Method for Laboratory Compaction Characteristics of Soil Using Standard Effort

(12,400 ft-lbf/ft3 (600 kN-m/m3)).

ASTM D-1557, Test Method for Laboratory Compaction Characteristics of Soil Using Modified Effort

(56,000 ft-lbf/ft3 (2,700 kN-m/m3

)).
7B-4

Protecting Ground Water—Designing and Installing Liners 

Assurance and Quality Control for Waste

Containment Facilities (U.S. EPA, 1993c).

Plasticity characteristics. Plasticity characteristics describe a material’s ability to

behave as a plastic or moldable material.

Soils containing clay are generally categorized

as plastic. Soils that do not contain clay are

non-plastic and typically considered unsuitable materials for compacted clay liners,

unless soil amendments such as bentonite

clay are introduced. 

Plasticity characteristics are quantified by

three parameters: liquid limit, plastic limit,

and plasticity index. The liquid limit is

defined as the minimum moisture content (in

percent of oven-dried weight) at which a soilwater mixture can flow. The plastic limit is

the minimum moisture content at which a

soil can be molded. The plasticity index is

defined as the liquid limit minus the plastic

limit and defines the range of moisture content over which a soil exhibits plastic behavior. When soils with high plastic limits are

too dry during placement, they tend to form

clods, or hardened clumps, that are difficult

to break down during compaction. As a

result, preferential pathways can form around

these clumps allowing leachate to flow

through the material at a higher rate. Soil

plasticity indices typically range from 10 percent to 30 percent. Soils with a plasticity

index greater than 30 percent are cohesive,

sticky, and difficult to work with in the field.

Common testing methods for plasticity characteristics include the methods specified in

ASTM D-4318, also known as Atterberg limits tests.4

Percent fines and percent gravel. Typical

soil liner materials contain at least 30 percent

fines and can contain up to 50 percent gravel,

by weight. Common testing methods for percent fines and percent gravel are specified in

ASTM D-422, also referred to as grain size

distribution tests.5 Fines refer to silt and claysized particles. Soils with less than 30 percent

fines can be worked to obtain hydraulic conductivities below 1 x 10-7 cm/sec (4 x 10-8

in./sec), but use of these soils requires more

careful construction practices.

Gravel is defined as particles unable to

pass through the openings of a Number 4

sieve, which has an opening size equal to

4.76 mm (0.2 in.). Although gravel itself has

a high hydraulic conductivity, relatively large

amounts of gravel, up to 50 percent by

weight, can be uniformly mixed with clay

materials without significantly increasing the

hydraulic conductivity of the material. Clay

materials fill voids created between gravel

particles, thereby creating a gravel-clay mixture with a low hydraulic conductivity. As

long as the percent gravel in a compacted

clay mixture remains below 50 percent, creating a uniform mixture of clay and gravel,

where clay can fill in gaps, is more critical

than the actual gravel content of the mixture. 

You should pay close attention to the percent gravel in cases where a compacted clay

liner functions as a bottom layer to a geosynthetic, as gravel can cause puncturing in

geosynthetic materials. Controlling the maximum particle size and angularity of the gravel should help prevent puncturing, as well as

prevent gravel from creating preferential flow

paths. Similar to gravel, soil particles or rock

fragments also can create preferential flow

paths. To help prevent the development of

preferential pathways and an increased

hydraulic conductivity, it is best to use soil

liner materials where the soil particles and

rock fragments are typically small (e.g., 3/4

inch in diameter).

Interactions With Waste

Waste placed in a unit can interact with

compacted clay liner materials, thereby influencing soil properties such as hydraulic con4 ASTM D-4318, Standard Test Method for Liquid Limit, Plastic Limit, and Plasticity Index of Soils.

5 ASTM D-422, Standard Test Method for Particle-Size Analysis of Soils.
Protecting Ground Water—Designing and Installing Liners

7B-5

6 SW-846, Test Methods for Evaluating Solid Waste: Physical/Chemical Methods.

ductivity and permeability. Two ways that

waste materials can influence the hydraulic

conductivity of the liner materials are

through dissolution of soil minerals and

changes in clay structure. Soil minerals can

be dissolved, or reduced to liquid form, as a

result of interaction with acids and bases. For

example, aluminum and iron in the soil can

be dissolved by acids, and silica can be dissolved by bases. While some plugging of soil

pores by dissolved minerals can lower

hydraulic conductivity in the short term, the

creation of piping and channels over time can

lead to an increased hydraulic conductivity in

the long term. The interaction of waste and

clay materials can also cause the creation of

positive ions, or cations. The presence of

cations such as sodium, potassium, calcium,

and magnesium can change the clay structure, thereby influencing the hydraulic conductivity of the liner. Depending on the

cation type and the clay mineral, an increased

presence of such cations can cause the clay

minerals to form clusters and increase the

permeability of the clay. Therefore, before

selecting a compacted clay liner material, it is

important to develop a good understanding

of the composition of the waste that will be

placed in the waste management unit. EPA’s

Method 9100, in publication SW-846, measures the hydraulic conductivity of soil samples before and after exposure to permeants.6

Locating and Testing Material

Although the selection process for compacted clay liner construction materials can

vary from project to project, some common

material selection steps include locating and

testing materials at a potential borrow or

commercial pit before construction, and

observing and testing material performance

throughout construction. First, investigate a

potential borrow or commercial pit to determine the volume of materials available. The

next step is to test a representative sample of

soil to determine material properties such as

plasticity characteristics, percent gravel, and

percent fines. To confirm the suitability of the

materials once construction begins, you

should consider requesting that representative samples from the materials in the borrow

or commercial pit be tested periodically after

work has started. 

Material selection steps will vary, depending on the origin of the materials for the project. For example, if a commercial pit provides

the materials, locating an appropriate onsite

borrow pit is not necessary. In addition to the

tests performed on the material, it is recommended that a qualified inspector make visual

observations throughout the construction

process to ensure that harmful materials, such

as stones or other large matter, are not present

in the liner material.

What issues should be considered

in the construction of a liner and

the operation of a unit?

You should develop test pads to demonstrate construction techniques and material

performance on a small scale. During unit construction and operation, some additional factors influencing the performance of the liner

include: preprocessing, subgrade preparation,

method of compaction, and protection against

desiccation and cracking. Each of these steps,

from preprocessing through protection against

desiccation and cracking, should be repeated

for each lift or layer of soil.

Test Pads

Preparing a test pad for the compacted

clay liner helps verify that the materials and

methods proposed will yield a liner that

meets the desired hydraulic conductivity. A

test pad also provides an opportunity to
7B-6

Protecting Ground Water—Designing and Installing Liners 

demonstrate the performance of alternative

materials or methods of construction. A test

pad should be constructed with the soil liner

materials proposed for a particular project,

using the same preprocessing procedures,

compaction equipment, and construction

practices proposed for the actual liner. A

complete discussion of test pads (covering

dimensions, materials, and construction) can

be found in Chapter 2 of EPA’s 1993 technical guidance document Quality Assurance and

Quality Control for Waste Containment Facilities

(U.S. EPA, 1993c). A discussion of commonly

used methods to measure in-situ hydraulic

conductivity is also contained in that chapter.

Preprocessing

Although some liner

materials can be ready

for use in construction

immediately after they

are excavated, many

materials will require

some degree of preprocessing. Preprocessing

methods include: water

content adjustment,

removal of oversized

particles, pulverization

of any clumps, homogenization of the soils, and

introduction of additives, such as bentonite.

Water content

adjustment. For natural

soils, the degree of saturation of the soil liner at

the time of compaction,

known as molding water

content, influences the

engineering properties of

the compacted material.

Soils compacted at water

contents less than optimum tend to have a relatively high hydraulic

conductivity. Soils compacted at water contents greater than optimum tend to have low

hydraulic conductivity and low strength. 

Proper soil water content revolves around

achieving a minimum dry density, which is

expressed as a percentage of the soil’s maximum dry density. The minimum dry density

typically falls in the range of 90 to 95 percent

of the soil’s maximum dry density value. From

the minimum dry density range, the required

water content range can be calculated, as

shown in Figure 1. In this example the soil

has a maximum dry density of 115 lb/cu ft.

Based upon a required minimum dry density

value of 90 percent of maximum dry density,

Figure 1. 

Water Content for Achieving a Specific Density

Source: U.S. EPA, 1988.
Protecting Ground Water—Designing and Installing Liners

7B-7

which is equal to 103.5 lb/cu ft, the required

water content ranges from 10 to 28 percent.

It is less problematic to compact clay soil

at the lower end of the required water content range because it is easier to add water to

the clay soil than to remove it. Thus, if precipitation occurs during construction of a site

which is being placed at the lower end of the

required water content range, the additional

water might not result in a soil water content

greater than the required range. Conversely, if

the site is being placed at the upper end of

the range, for example at 25 percent, any

additional moisture will be excessive, resulting in water content over 28 percent and

making the 90 percent maximum dry density

unattainable. Under such conditions construction should halt while the soil is aerated

and excess moisture is allowed to evaporate.

Removal of oversized particles.

Preprocessing clay materials, to remove cobbles or large stones that exceed the maximum

allowable particle size, can improve the soil’s

compactibility and protect any adjacent

geomembrane from puncture. Particle size

should be small (e.g., 3/4 inch in diameter)

for compaction purposes. If a geomembrane

will be placed over the compacted clay, only

the upper lift of clay needs to address concerns regarding puncture resistance.

Observation by quality assurance and quality

control personnel is the most effective

method to identify areas where oversized particles need to be removed. Cobbles and

stones are not the only materials that can

interfere with compactive efforts. Chunks of

dry, hard clay, also known as clods, often

need to be broken into smaller pieces to be

properly hydrated, remolded, and compacted. In wet clay, clods are less of a concern

since wet clods can often be remolded with a

reasonable compactive effort.

Soil amendments. If the soils at a unit do

not have a sufficient percentage of clay, a common practice is to blend bentonite with them

to reduce the hydraulic conductivity. Bentonite

is a clay mineral that expands when it comes

into contact with water. Relatively small

amounts of bentonite, on the order of 5 to 10

percent, can be added to sand or other noncohesive soils to increase the cohesion of the

material and reduce hydraulic conductivity. 

Sodium bentonite is a common additive

used to amend soils. However, this additive is

vulnerable to degradation as a result of contact with certain chemicals and waste

leachates. Calcium bentonite, a more permeable material than sodium bentonite, is another common additive used to amend soils.

Approximately twice as much calcium bentonite is needed to achieve a hydraulic conductivity comparable to that of sodium

bentonite. Amended soil mixtures generally

require mixing in a pug mill, cement mixer, or

other mixing equipment that allows water to

be added during the mixing process.

Throughout the mixing and placement

processes, water content, bentonite content,

and particle distribution should be controlled.

Other materials that can be used as soil additives include lime cement and other clay minerals, such as atapulgite. It can be difficult to

mix additives thoroughly with cohesive soils,

or clays; the resultant mixture might not

achieve the desired level of hydraulic conductivity throughout the entire liner. 

Subgrade Preparation

It is important to ensure that the subgrade

on which a compacted clay liner will be constructed is properly prepared. When a compacted clay liner is the lowest component of a

liner system, the subgrade consists of native

soil or rock. Subgrade preparation for these

systems involves compacting the native soil

to remove any soft spots and adding water to

or removing water from the native soil to

obtain a specified firmness. Alternatively, in
7B-8

Protecting Ground Water—Designing and Installing Liners 

some cases, the compacted clay liner can be

placed on top of a geosynthetic material, such

as a geotextile. In such cases, subgrade preparation involves ensuring the smoothness of

the geosynthetic on which the clay liner will

be placed and the conformity of the geosynthetic material to the underlying material.

Compaction

The main purpose of compaction is to

densify the clay materials by breaking and

remolding clods of material into a uniform

mass. Since amended soils usually do not

develop clumps, the primary objective of

compaction for such materials is to increase

the material’s density. Proper compaction of

liner materials is essential to ensure that a

compacted clay liner meets specified

hydraulic conductivity standards. Factors

influencing the effectiveness of compaction

efforts include: the type of equipment selected, the number of passes made over the

materials by such equipment, the lift thickness, and the bonding between the lifts.

Molding water content, described earlier

under preprocessing, is another factor influencing the effectiveness of compaction. 

Type of equipment. Factors to consider

when selecting compaction equipment

include: the type and weight of the compactor, the characteristics of any feet on the

drum, and the weight of the roller per unit

length of drummed surface. Heavy compactors, weighing more than 50,000 pounds,

with feet long enough to penetrate a loose lift

of soil, are often the best types of compactor

for clay liners. For bentonite-soil mixtures, a

footed roller might not be appropriate. For

these mixtures, where densification of the

material is more important than kneading or

remolding it to meet low hydraulic conductivity specifications, a smooth-drum roller or

a rubber- tired roller might produce better

results. Figure 2 depicts two types of footed

rollers, a fully penetrating footed roller and a

partially-penetrating footed roller.

Source: U.S. EPA, 1993c.

Figure 2 Two Types of Footed Rollers
Protecting Ground Water—Designing and Installing Liners

7B-9

For placement of liners on side slopes,

consider the angle and length of the slope.

Placing continuous lifts on a gradually

inclined slope will provide better continuity

between the bottom and sidewalls of the

liner. Since continuous lifts might be impossible to construct on steeper slopes due to the

difficulties of operating heavy compaction

equipment on these slopes, materials might

need to be placed and compacted in horizontal lifts. When sidewalls are compacted horizontally, it is important to avoid creating

seepage planes, by securely connecting the

edges of the horizontal lift with the bottom of

the liner. Because the lift needs to be wide

enough to accommodate compaction equipment, the thickness of the horizontal lift is

often greater than the thickness specified in

the design. In such cases, you should consider trimming soil material from the constructed side slopes and sealing the trimmed

surface using a sealed drum roller.

It is common for contractors to use several

different types of compaction equipment during liner construction. Initial lifts might need

the use of a footed roller to fully penetrate a

loose lift. Final lifts also might need the use

of a footed roller for compaction, however,

they might be formed better by using a

smooth roller after the lift has been compacted to smooth the surface of the lift in preparation for placement of an overlying

geomembrane.

Number of passes. The number of passes

made by a compactor over clay materials can

influence the overall hydraulic conductivity

of the liner. The minimum number of passes

that is reasonable depends on a variety of

site-specific factors and cannot be generalized. In some cases, where a minimum coverage is specified, it might be possible to

calculate the minimum number of passes to

meet such a specification. At least 5 to 15

passes with a compactor over a given point

are usually necessary to remold and compact

clay liner materials thoroughly.

An equipment pass can be defined as one

pass of the compaction equipment or as one

pass of a drum over a given area of soil. It is

important to clearly define what is meant by

a pass in any quality assurance or quality

control plans. It does not matter which definition is agreed upon, as long as the definition

is used consistently throughout the project.

Lift thickness. You should determine the

appropriate thickness (as measured before

compaction) of each of the several lifts that

will make up the clay liner. The initial thickness of a loose lift will affect the compactive

effort needed to reach the lower portions of

the lift. Thinner lifts allow compactive efforts

to reach the bottom of a lift and provide

greater assurance that compaction will be sufficient to allow homogenous bonding

between subsequent lifts. Loose lift thicknesses typically range between 13 and 25 cm (5

and 10 in.). Factors influencing lift thickness

are: soil characteristics, compaction equipment, firmness of the foundation materials,

and the anticipated compaction necessary to

meet hydraulic conductivity requirements. 

Bonding between lifts. Since it is

inevitable that some zones of higher and

lower hydraulic conductivity, also known as

preferential pathways, will be present within

each lift, lifts should be joined or bonded in a

way that minimizes extending these zones or

pathways between lifts. If good bonding is

achieved, the preferential pathways will be

truncated by the bonded zone between the

lifts. At least two recommended methods

exist for preparing proper bonds. The first

method involves kneading, or blending the

new lift with the previously compacted lift

using a footed roller. Using a roller with feet

long enough to fully penetrate through the

top lift and knead the previous lift improves

the quality of the bond. A second method
7B-10

Protecting Ground Water—Designing and Installing Liners 

involves using a disc harrow or similar equipment to scarify, or roughen, and wet the top

inch of the recently placed lift, prior to placing the next lift. 

Protection Against Desiccation and

Cracking

You should consider how to protect compacted clay liners against desiccation and

freezing during and after construction.

Protection against desiccation is important,

because clay soil shrinks as it dries. Depending on the extent of shrinkage, it can crack.

Deep cracks, extending through more than

one lift, can cause problems. You should

measure water content to determine whether

desiccation is occurring. 

There are several ways to protect compacted clay liners from desiccation. One preventive measure is to smooth roll the surface with

a steel drummed roller to produce a thin,

dense skin of soil; this layer can help minimize the movement of water into or out of the

compacted material. Another option is to wet

the clay periodically in a uniform manner;

however, it is important to make sure to avoid

creating areas of excessive wetness. A third

measure involves covering compacted clay

liner materials with a sheet of white or clear

plastic or tarp to help prevent against desiccation and cracking. The cover should be

weighted down with sandbags or other material to minimize exposure of the underlying

materials to air. Using a light-colored plastic

will help prevent overheating, which can dry

out the clay materials. If the clay liner is not

being covered with a geosynthetic, another

method to prevent desiccation involves covering the clay with a layer of protective cover

soil or intentionally overbuilding the clay liner

and shaving it down to liner grade.

Protection against freezing is another

important consideration, because freezing can

increase the hydraulic conductivity of a liner.

It is important to avoid construction during

freezing weather. If freezing does occur and

the damage affects only a shallow depth, the

liner can be repaired by rerolling the surface.

If deeper freezing occurs, the repairs might

be more complicated. For a general guide to

frost depths, see Figure 1 of Chapter 11—

Performing Closure and Post-Closure Care.

B. Geomembranes or

Flexible Membrane Liners 

Geomembranes or flexible membrane liners are used to contain or prevent waste constituents and leachate from escaping a waste

management unit. Geomembranes are made

by combining one or more plastic polymers

with ingredients such as carbon black, pigments, fillers, plasticizers, processing aids,

crosslinking chemicals, anti-degradants, and

biocides. A wide range of plastic resins are

used for geomembranes, including high density polyethylene (HDPE), linear low density

polyethylene (LLDPE), low density linear

polyethlene (LDLPE), very low density polyethlene (VLDPE), polyvinyl chloride (PVC),

flexible polypropylene (fPP), chlorosulfonated

polyethylene (CSPE or Hypalon), and ethylene propylene diene termonomer (EPDM).

Most manufacturers produce geomembranes

through extrusion or calendering. In the

extrusion process, a molten polymer is

stretched into a nonreinforced sheet; extruded geomembranes are usually made of HDPE

and LLDPE. During the calendering process,

a heated polymeric compound is passed

through a series of rollers. In this process, a

geomembrane can be reinforced with a

woven fabric or fibers. Calendered geomembranes are usually made of PVC and CSPE.
What are the thickness recommendations for geomembrane liners?

Geomembranes range in thicknesses from 20

to 120 mil (1 mil = 0.001 in.). A good design

should include a minimum thickness of 30 mil,

except for HDPE liners, which should have a

minimum thickness of 60 mil. These recommended minimum thicknesses ensure that the

liner material will withstand the stress of construction and the weight load of the waste, and

allow adequate seaming to bind separate

geomembrane panels. Reducing the potential

for tearing or puncture, through proper construction and quality control, is essential for a

geomembrane to perform effectively. 

What issues should be considered

in the design of a geomembrane

liner?

Several factors to address in the design

include: determining appropriate material

properties and testing to ensure these properties are met, understanding how the liner will

interact with the intended waste stream,

accounting for all stresses imposed by the

design, and ensuring adequate friction.

Material Properties and Selection 

When designing a geomembrane liner, you

should examine several properties of the

geomembrane material in addition to thickness, including: tensile behavior, tear resistance, puncture resistance, susceptibility to

environmental stress cracks, ultraviolet resistance, and carbon black content. 

Tensile behavior. Tensile behavior refers to

the tensile strength of a material and its ability

to elongate under strain. Tensile strength is the

ability of a material to resist pulling stresses

without tearing. The tensile properties of a

geomembrane must be sufficient to satisfy the

stresses anticipated during its service life.

These stresses include the self-weight of the

geomembrane and any down drag caused by

waste settlement on side slope liners. 

Puncture and tear resistance.

Geomembrane liners can be subject to tearing

during installation due to high winds or handling. Puncture resistance is also important to

consider since geomembranes are often

placed above or below materials that might

have jagged or angular edges. For example,

geomembranes might be installed above a

granular drainage system that includes gravel.

Susceptibility to environmental stress

cracks. Environmental factors can cause

cracks or failures before a liner is stressed to

its manufactured strength. These imperfections, referred to as environmental stress

cracks, often occur in areas where a liner has

been scratched or stressed by fatigue. These

cracks can also result in areas where excess

surface wetting agents have been applied. In

surface impoundments, where the geomembrane liner has greater exposure to the atmosphere and temperature changes, such

exposure can increase the potential for environmental stress cracking.

Ultraviolet resistance. Ultraviolet resistance is another factor to consider in the

design of geomembrane liners, especially in

cases where the liner might be exposed to

ultraviolet radiation for prolonged periods of

time. In such cases, which often occur in surface impoundments, ultraviolet radiation can

cause degradation and cracking in the

geomembrane. Adding carbon black or other

additives during the manufacturing process

can increase a geomembrane’s ultraviolet

resistance. Backfilling over the exposed

geomembrane also works to prevent degradation due to ultraviolet radiation.

Interactions With Waste

Since the main purpose of a geomembrane

is to provide a barrier and prevent contamiProtecting Ground Water—Designing and Installing Liners

7B-11
nants from penetrating through the geomembrane, chemical resistance is a critical consideration. Testing for chemical resistance might

be warranted depending on the type, volumes, and characteristics of waste managed

at a particular unit and the type of geomembrane to be used. An established method for

testing the chemical resistance of geomembranes, EPA Method 9090, can be found in

SW-846. ASTM has also adopted standards

for testing the chemical compatibility of various geosynthetics, including geomembranes,

with leachates from waste management units.

ASTM D-5747 provides a standard for testing

the chemical compatibility of

geomembranes.7

Stresses Imposed by Liner Design

A liner design should take into account the

stresses imposed on the liner by the design

configuration. These stresses include: the differential settlement in foundation soil, strain

requirements at the anchor trench, strain

requirements over long, steep side slopes,

stresses resulting from compaction, and seismic stresses. Often an anchor trench designed

to secure the geomembrane during construction is prepared along the perimeter of a unit

cell. This action can help prevent the

geomembrane from slipping down the interior side slopes. Trench designs should include

a depth of burial sufficient to hold the specified length of liner. If forces larger than the

tensile strength of the liner are inadvertently

developed, then the liner could tear. For this

reason, the geomembrane liner should be

allowed to slip or give in the trench after construction to prevent such tearing. To help

reduce unnecessary stresses in the liner design, it is advisable to avoid using horizontal

seams. For more information on design stresses, consult Geosynthetic Guidance for

Hazardous Waste Landfill Cells and Surface

Impoundments (U.S. EPA, 1987).

Designing for Adequate Friction

Adequate friction between the geomembrane liner and the soil subgrade, as well as

between any geosynthetic components, is

necessary to prevent extensive slippage or

sloughing on the slopes of a unit. Design

equations for such components should evaluate: 1) the ability of a liner to support its own

weight on side slopes, 2) the ability of a liner

to withstand down-dragging during and after

waste placement, 3) the best anchorage configuration for the liner, 4) the stability of soil

cover on top of a liner, and 5) the stability of

other geosynthetic components, such as geotextiles or geonets, on top of a liner. An evaluation of these issues can affect the choice of

geomembrane material, polymer type, fabric

reinforcement, thickness, and texture necessary to achieve the design requirements.

Interface strengths can be significantly

improved by using textured geomembranes.

What issues should be considered in the construction of a

geomembrane liner?

When preparing to construct a geomembrane liner, you should plan appropriate

shipment and handling procedures, perform

testing prior to construction, prepare the

subgrade, consider temperature effects, and

account for wind effects. In addition, you

should select a seaming process, determine a

material for and method of backfilling, and

plan for testing during construction.

Shipment, Handling, and Site Storage 

You should follow quality assurance and

quality control procedures to ensure proper

handling of geomembranes. Different types of

geomembrane liners require different types of

packaging for shipment and storage.

Typically a geomembrane manufacturer will

provide specific instructions outlining the

7B-12

7 ASTM D-5747, Practice for Tests to Evaluate the Chemical Resistance of Geomembranes to Liquids.

Protecting Ground Water—Designing and Installing Liners 
handling, storage, and construction specifications for a product. In general, HDPE and

LLDPE geomembrane liners are packaged in a

roll form, while PVC and CSPE-R liners

(CSPE-R refers to a CSPE geomembrane liner

reinforced with a fabric layer) are packaged in

panels, accordion-folded in two directions,

and placed onto pallets. Whether the liner is

shipped in rolls or panels, you should provide for proper storage. The rolls and panels

should be packaged so that fork lifts or other

equipment can safely transport them. For

rolls, this involves preparing the roll to have a

sufficient inside diameter so that a fork lift

with a long rod, known as a stinger, can be

used for lifting and moving. For accordion

panels, proper packaging involves using a

structurally-sound pallet, wrapping panels in

treated cardboard or plastic wrapping to protect against ultraviolet exposure, and using

banding straps with appropriate cushioning.

Once the liners have been transported to the

site, the rolls or panels can be stored until the

subgrade or subbase (either natural soils or

another geosynthetic) is prepared.

Subgrade Preparation 

Before a geomembrane liner is installed,

you should prepare the subgrade or subbase.

The subgrade material should meet specified

grading, moisture content, and density

requirements. In the case of a soil subgrade,

it is important to prevent construction equipment used to place the liner from deforming

the underlying materials. If the underlying

materials are geosynthetics, such as geonets

or geotextiles, you should remove all folds

and wrinkles before the liner is placed. For

further information on geomembrane placement, see Chapter 3 of EPA’s Technical

Guidance Document: Quality Assurance and

Quality Control for Waste Containment Facilities

(U.S. EPA, 1993c).

Testing Prior to Construction 

Before any construction begins, is it recommended that you test both the geomembrane

materials from the manufacturer and the

installation procedures. Acceptance and conformance testing is used to evaluate the performance of the manufactured geomembranes.

Constructing test strips can help evaluate how

well the intended construction process and

quality control procedures will work.

Acceptance and conformance testing.

You should perform acceptance and conformance testing on the geomembrane liner

received from the manufacturer to determine

whether the materials meet the specifications

requested. While the specific ASTM test

methods vary depending on geomembrane

type, recommended acceptance and conformance testing for geomembranes includes

evaluations of thickness, tensile strength and

elongation, and puncture and tear resistance

testing, as appropriate. For most geomembrane liner types, the recommended ASTM

method for testing thickness is ASTM D5199.8 For measuring the thickness of textured geomembranes, you should use ASTM

D-5994.9 For tensile strength and elongation,

ASTM D-638 is recommended for the HDPE

and LLDPE sheets, while ASTM D-882 and

ASTM D-751 are recommended for PVC and

CSPE geomembranes, respectively.10 Puncture

resistance testing is typically recommended

for HDPE and LLDPE geomembranes using

ASTM D-4833.11 To evaluate tear resistance

for HDPE, LLDPE, and PVC geomembrane

Protecting Ground Water—Designing and Installing Liners

7B-13

8 ASTM D-5199, Standard Test Method for Measuring Nominal Thickness of Geotextiles and

Geomembranes.

9 ASTM D-5994, Measuring Core Thickness of Textured Geomembranes.

10 ASTM D-638, Standard Test Method for Tensile Properties of Plastics.

ASTM D-882, Standard Test Methods for Tensile Properties of Thin Plastic Sheeting.

ASTM D-751, Standard Test Methods for Coated Fabrics.

11 ASTM D-4833, Standard Test Method for Index Puncture Resistance of Geotextiles, Geomembranes,

and Related Products.
liners, the recommended testing method is

ASTM D-1004, Die C.12 For CSPE-R

geomembranes, ply adhesion is more of a

concern than tear or puncture resistance and

can be evaluated using ASTM D-413,

Machine Method, Type A.13

Test strips. In preparation for liner placement and field seaming, you should develop

test strips and trial seams as part of the construction process. Construction of such samples should be performed in a manner that

reproduces all aspects of field production.

Providing an opportunity to test seaming

methods and workmanship helps ensure that

the quality of the seams remains constant

and meets specifications throughout the

entire seaming process. 

Temperature Effects 

Liner material properties can be altered by

extreme temperatures. High temperatures can

cause geomembrane liner surfaces to stick

together, a process commonly referred to as

blocking. On the other hand, low temperature can cause the liner to crack when

unrolled or unfolded. Recommended maximum and minimum allowable sheet temperatures for unrolling or unfolding geomembrane

liners are 50°C (122°F) and 0°C (32°F),

respectively. In addition to sticking and cracking, extreme temperatures can cause geomembranes to contract or expand. Polyethylene

geomembranes expand when heated and contract when cooled. Other geomembranes can

contract slightly when heated. Those responsible for placing the liner should take temperature effects into account as they place, seam,

and backfill in the field. 

Wind Effects

It is recommended that you take measures

to protect geomembrane liners from wind

damage. Windy conditions can increase the

potential for tearing as a result of uplift. If

wind uplift is a potential problem, panels can

be weighted down with sand bags.

Seaming Processes

Once panels or rolls have been placed,

another critical step involves field-seaming

the separate panels or rolls together. The

selected seaming process, such as thermal or

chemical seaming, will depend on the chemical composition of the liner. To ensure the

integrity of the seam, you should use the

seaming method recommended by the manufacturer. Thermal seaming uses heat to bond

together the geomembrane panels. Examples

of thermal seaming processes include extrusion welding and thermal fusion (or melt

bonding). Chemical seaming involves the use

of solvents, cement, or an adhesive. Chemical

seaming processes include chemical fusion

and adhesive seaming. For more information

on seaming methods, Technical Guidance

Document: Inspection Techniques for the

Fabrication of Geomembrane Field Seams (U.S.

EPA, 1991c), contains a full chapter on each

of the traditional seaming methods and additional discussion of emerging techniques,

such as ultrasonic, electrical conduction, and

magnetic energy source methods.

Consistent quality in fabricating field

seams is paramount to liner performance.

Conditions that could affect seaming should

be monitored and controlled during installation. Factors influencing seam construction

and performance include: ambient temperature, relative humidity, wind uplift, changes

in geomembrane temperature, subsurface

water content, type of supporting surface

used, skill of the seaming crew, quality and

consistency of chemical or welding materials,

preparation of liner surfaces to be joined,

moisture at the seam interface, and cleanliness of the seam interface. 

7B-14

12 ASTM D-1004, Standard Test Method for Initial Tear Resistance of Plastic Film and Sheeting.

13 ASTM D-413, Standard Test Methods for Rubber Property-Adhesion to Flexible Substrate.

Protecting Ground Water—Designing and Installing Liners 
To help control some of these factors, no

more than the amount of sheeting that can be

used during a shift or a work day should be

deployed at one time. To prevent erosion of

the underlying soil surface or washout of the

geomembrane, proper storm water control

measures should be employed. Ambient temperature can become a concern, if the

geomembrane liner has a high percentage of

carbon black. Although the carbon black will

help to prevent damage resulting from ultraviolet radiation, because its dark color

absorbs heat, it can increase the ambient temperature of the geomembrane, making installation more complicated. To avoid surface

moisture or high subsurface water content,

geomembranes should not be deployed when

the subgrade is wet.

Regardless of how well a geomembrane

liner is designed, its ability to meet performance standards depends on proper quality

assurance and quality control during installation. Geomembrane sheets and seams are

subject to tearing and puncture during installation; punctures or tears can result from contact with jagged edges or underlying materials

or by applying stresses greater than the

geomembrane sheet can handle. Proper quality assurance and quality control can help

minimize the occurrence of pinhole or seam

leaks. For example, properly preparing the

underlying layer and ensuring that the gravel

is of an acceptable size reduces the potential

for punctures. 

Protection and Backfilling

Geomembrane liners that can be damaged

by exposure to weather or work activities

should be covered with a layer of soil or a

geosynthetic as soon as possible after quality

assurance activities associated with geomembrane testing are completed. If the backfill

layer is a soil material, it will typically be a

drainage material like sand or gravel. If the

cover layer is a geosynthetic, it will typically

be a geonet or geocomposite drain placed

directly over the geomembrane. Careful

placement of backfill materials is critical to

avoid puncturing or tearing the geomembrane material.

For soil covers, three considerations determine the amount of slack to be placed in the

underlying geomembrane. These considerations include selecting the appropriate type of

soil, using the proper type of equipment, and

establishing a placement procedure for the

soil. When selecting a soil for backfilling,

characteristics to consider include particle

size, hardness, and angularity, as each of these

can affect the potential for tearing or puncturing the liner. To prevent wrinkling, soil covers

should be placed over the geomembrane in

such a way that construction vehicles do not

drive directly on the liner. Care should be

taken not to push heavy loads of soil over the

geomembrane in a continuous manner.

Forward pushing can cause localized wrinkles

to develop and overturn in the direction of

movement. Overturned wrinkles create sharp

creases and localized stress in the liner and

can lead to premature failure. A recommended method for placing soil involves continually placing small amounts of soil or drainage

material and working outward over the toe of

the previously placed material. 

Another recommended method involves

placing soil over the liner with a large backhoe and spreading it with a bulldozer or similar equipment. If a predetermined amount of

slack is to be placed in the geomembrane, the

temperature of the liner becomes an important factor, as it will effect the ability of the

liner to contract and expand. Although the

recommended methods for covering

geomembrane liners with soil can take more

time than backfilling with larger amounts of

soil, these methods are designed to prevent

damage caused by covering the liner with too

Protecting Ground Water—Designing and Installing Liners

7B-15
much soil too quickly. In the long run, preventing premature liner failure can be faster

and more cost-effective than having to repair

a damaged liner. 

The types of geosynthetics that are often

used as protective covering include geotextiles and geonets. Geogrids and drainage geocomposites can be used for cover soil

reinforcement on slopes. The appendix at the

end of this chapter provides additional information on geosynthetic materials. For

geosynthetic protective covers, as with soil

backfilling, to prevent tearing or puncturing,

most construction vehicles should not be

permitted to move directly on the geomembrane. Some possible exceptions include

small, 4-wheel, all terrain vehicles or other

types of low ground pressure equipment.

Even with these types of vehicles, drivers

should take extreme care to avoid movements, such as sudden starts, stops, and

turns, which can damage the geomembrane.

Seaming-related equipment should be

allowed on the geomembrane liner, as long as

it does not damage the liner. Geosynthetic

materials are placed directly on the liner and

are not bonded to it.

Testing During Construction

Testing during construction enables assessment of the integrity of the seams connecting

the geomembrane panels. Tests performed on

the geomembrane seams are categorized as

either destructive or nondestructive.

Destructive testing. Destructive testing

refers to removing a sample from the liner

seam or sheet and performing tests on the

sample. For liner seams, destructive testing

includes shear testing and peel testing; for

liner sheets, it involves tensile testing. While

quality control procedures often require

destructive testing prior to construction, in

order to ensure that the installed seams and

sheets meet performance standards, destructive testing should be performed during construction also. For increased quality assurance, it is recommended that peel and shear

tests on samples from the installed geomembrane be performed by an independent laboratory. Testing methods for shear testing, peel

testing, and tensile testing vary for different

geomembrane liner types.

Determining the number of samples to

take is a difficult step. Taking too few samples results in a poor statistical representation

of the geomembrane quality. On the other

hand, taking too many samples requires

additional costs and increases the potential

for defects. Defects can result from the repair

patches used to cover the areas from which

samples were taken. 

A common sampling strategy is “fixed

increment sampling” where samples are

taken at a fixed increment along the length of

the geomembrane. Increments range from 80

to 300 m (250 to 1,000 ft). The type of

welding, such as extrusion or fusion welding,

used to connect the seams and the type of

geomembrane liner can also help determine

the appropriate sampling interval. For example, extrusion seams on HDPE require grinding prior to welding and if extensive grinding

occurs, the strength of the HDPE might

decrease. In such cases, sampling at closer

intervals, such as 90 to 120 m (300 to 400

ft), might provide a more accurate description of material properties. If the seam is a

dual hot edge seam, both the inner and outer

seams might need to be sampled and tested. 

If test results for the seam or sheet samples

do not meet the acceptance criteria for the

destructive tests, you should continue testing

the area surrounding the rejected sample to

determine the limits of the low quality seam.

Once the area of low quality has been identified, then corrective measures, such as seaming

a cap over the length of the seam or reseaming

the affected area, might be necessary.

7B-16

Protecting Ground Water—Designing and Installing Liners 
Nondestructive testing. Unlike destructive tests, which examine samples taken from

the geomembrane liner in the containment

area, nondestructive tests are designed to

evaluate the integrity of larger portions of

geomembrane seams without removing pieces

of the geomembrane for testing. Common

nondestructive testing methods include: the

probe test, air lance, vacuum box, ultrasonic

methods (pulse echo, shadow, and impedance

planes), electrical spark test, pressurized dual

seam, and electrical resistivity. You should

select the test method most appropriate for

the material and seaming method. If sections

of a seam fail to meet the acceptable criteria

of the appropriate nondestructive test, then

those sections need to be delineated and

patched, reseamed, or retested. If repairing

such sections results in large patches or areas

of reseaming, then destructive test methods

are recommended to verify the integrity of

such pieces. 

C. Geosynthetic Clay Liners

If a risk evaluation recommended the use

of a single liner, another option to consider is

a geosynthetic clay liner (GCL). GCLs are factory-manufactured, hydraulic barriers typically consisting of bentonite clay (or other very

low permeability materials), supported by

geotextiles or geomembranes held together by

needling, stitching, or chemical adhesives.

GCLs can be used to augment or replace

compacted clay liners or geomembranes, or

they can be used in a composite manner to

augment the more traditional compacted clay

or geomembrane materials. GCLs are typically used in areas where clay is not readily

available or where conserving air space is an

important factor. As GCLs do not have the

level of long-term field performance data that

geomembranes or compacted clay liners do,

states might request a demonstration that

performance of the GCL design will be comparable to that of compacted clay or

geomembrane liners.

What are the mass per unit area

and hydraulic conductivity recommendations for geosynthetic clay

liners?

Geosynthetic clay liners are often designed

to perform the same function as compacted

clay and geomembrane liner components. For

geosynthetic clay liners, you should design

for a minimum of 3.7 kg/m2 (0.75 lb/ft2

) dry

weight (oven dried at 105°C) of bentonite

clay with a hydrated hydraulic conductivity

of no more than 5 x 10-9 cm/sec (2 x 10-9

in/sec). It is important to follow manufacturer

specifications for proper GCL installation.

What issues should be considered in the design of a geosynthetic clay liner?

Factors to consider in GCL design are the

specific material properties needed for the

liner and the chemical interaction or compatibility of the waste with the GCL. When considering material properties, it is important to

keep in mind that bentonite has a low shear

strength when it is hydrated. Manufacturers

have developed products designed to increase

shear strength. 

Materials Selection and Properties

For an effective GCL design, material

properties should be clearly defined in the

specifications used during both manufacture

and construction. The properties that should

be specified include: type of bonds, thickness, moisture content, mass per unit area,

shear strength, and tensile strength. Each of

these properties is described below.

Protecting Ground Water—Designing and Installing Liners

7B-17
Type of bonds. Geosynthetic clay liners

are available with a variety of bonding

designs, which include a combination of clay,

adhesives, and geomembranes or geotextiles.

The type of adhesives, geotextiles, and

geomembranes used as components of GCLs

varies widely. One type of available GCL

design uses a bentonite clay mixed with an

adhesive bound on each side by geotextiles.

A variation on this design involves stitching

the upper and lower geotextiles together

through the clay layer. Alternatively, another

option is to use a GCL where geotextiles on

each side of adhesive or nonadhesive bentonite clay are connected by needle punching. A fourth variation uses a clay mixed with

an adhesive bound to a geomembrane on one

side; the geomembrane can be either the

lower or the upper surface. Figure 3 displays

cross section sketches of the four variations

of GCL bonds. While these options describe

GCLs available at the time of this Guide,

emerging technologies in GCL designs

should also be reviewed and considered.

Thickness. The thickness of the various

available GCL products ranges from 4 to 6

mm (160 to 320 mil). Thickness measurements are product dependent. Some GCLs

can be quality controlled for thickness while

others cannot.

Moisture content. GCLs are delivered to

the job site at moisture contents ranging from

5 to 23 percent, referred to as the “dry” state.

GCLs are delivered dry to prevent premature

hydration, which can cause unwanted variations in the thickness of the clay component

as a result of uneven swelling.

Stability and shear strength. GCLs

should be manufactured and selected to meet

the shear strength requirements specified in

design plans. In this context, shear strength

is the ability of two layers to resist forces

moving them in opposite directions. Since

hydrated bentonite clay has low shear

strength, bentonite clay can be placed

between geotextiles and stitch bonded or

needle- punched to provide additional stability. For example, a GCL with geotextiles supported by stitch bonding has greater internal

resistance to shear in the clay layer than a

GCL without any stitching. Needle-punched

GCLs tend to provide greater resistance than

stitch-bonded GCLs and can also provide

increased friction resistance against an

adjoining layer, because they require the use

of nonwoven geotextiles. Increased friction is

an important consideration on side slopes.

Mass per unit area. Mass per unit area

refers to the bentonite content of a GCL. It is

important to distribute bentonite evenly

throughout the GCL in order to meet desired

hydraulic conductivity specifications. All

GCL products available in North America use

a sodium bentonite clay with a mass per unit

area ranging from 3.2 to 6.0 kg/m2 (0.66 to

1.2 lb/ft2

), as manufactured.

Interaction With Waste

During the selection process for a GCL

liner, you should evaluate the chemical compatibility of the liner materials with the types

of waste that are expected to be placed in the

unit. Certain chemicals, such as calcium, can

have an adverse effect on GCLs, resulting in a

loss of liner integrity. Specific information on

GCL compatibilities should be available from

the manufacturer.

What issues should be considered in the construction of a

geosynthetic clay liner?

Prior to and during construction, it is recommended that a qualified professional

should prepare construction specifications for

the GCL. In these specifications, procedures

for shipping and storing materials, as well as

performing acceptance testing on delivered

7B-18

Protecting Ground Water—Designing and Installing Liners 
Protecting Ground Water—Designing and Installing Liners

7B-19

Figure 3

Four Variations of GCL Bonding Methods

Source: U.S. EPA, 1993c.
materials, should be identified. The specifications should also address methods for subgrade preparation, joining panels, repairing

sections, and protective backfilling.

Shipment, Handling, and Site

Storage

GCLs are manufactured in widths of

approximately 2 to 5 m (7 to 17 ft) and

lengths of 30 to 60 m (100 to 200 ft).

Directly after manufacturing, GCLs are rolled

around a core and covered with a thin plastic

protective covering. This waterproof covering

serves to protect the material from premature

hydration. GCLs should be stored at the factory with these protective coverings. Typical

storage lengths range from a few days to 6

months. To ensure protection of the plastic

covering and the rolls themselves during

loading and unloading, it is recommended

that qualified professionals specify the equipment needed at the site to lift and deploy the

rolls properly.

To reduce the potential for accidental

damage or for GCLs to absorb moisture at

the site, you should try to arrange for “justin-time-delivery” for GCLs transported from

the factory to the field. Even with “just-intime-delivery,” it might be necessary to store

GCLs for short periods of time at the site.

Often the rolls can be delivered in trailers,

which can then serve as temporary storage.

To help protect the GCLs prior to deployment, you should use wooden pallets to keep

the rolls off the ground, placing heavy, waterproof tarps over the GCL rolls to protect

them from precipitation, and using sandbags

to help keep the tarps in place.

Manufacturer specifications should also

indicate how high rolls of GCLs can be

stacked horizontally during storage. Overstacking can cause compression of the core

around which the GCL is wrapped. A damaged core makes deployment more difficult

and can lead to other problems. For example,

rolls are sometimes handled by a fork lift

with a stinger attached. The stinger is a long

tapered rod that fits inside the core. If the

core is crushed, the stinger can damage the

liner during deployment.

Acceptance and Conformance

Testing

Acceptance and conformance testing is recommended either upon delivery of the GCL

rolls or at the manufacturer’s facility prior to

delivery. Conformance test samples are used

to ensure that the GCL meets the project

plans and specifications. GCLs should be

rewrapped and replaced in dry storage areas

immediately after test samples are removed.

Liner specifications should prescribe sampling

frequencies based on either total area or on

number of rolls. Since variability in GCLs can

exist between individual rolls, it is important

for acceptance and conformance testing to

account for this. Conformance testing can

include the following.

Mass per unit area test. The purpose of

evaluating mass per unit area is to ensure an

even distribution of bentonite throughout the

GCL panel. Although mass per unit area

varies from manufacturer to manufacturer, a

typical minimum value for oven dry weight

is 3.7 kg/m2 (0.75 lb/ft2

). Mass per unit area

should be tested using ASTM D-5993.14 This

test measures the mass of bentonite per unit

area of GCL. Sampling frequencies should be

determined using ASTM D- 4354.15

Free swell test. Free swell refers to the

ability of the clay to absorb liquid. Either

ASTM D-5890 or GRI-GCL1, a test method

developed by the Geosynthetic Research

Institute, can be used to evaluate the free

swell of the material.16

7B-20

14 ASTM D-5993, Standard Test Method for Measuring Mass per Unit Area of Geosynthetic Clay Liners.

15 ASTM D-4354, Standard Practice for Sampling of Geosynthetics for Testing.

16 ASTM D-5890, Test Method for Swell Index of Clay Mineral Components of Geosynthetic Clay Liners.

GRI-GCL1, Swell Measurement of the Clay Component of Geosynthetic Clay Liners.

Protecting Ground Water—Designing and Installing Liners 
Direct shear test. Shear strength of the

GCLs can be evaluated using ASTM D-5321.17

The sampling frequency for this performanceoriented test is often based on area, such as

one test per 10,000 m2 (100,000 ft2

).

Hydraulic conductivity test. Either ASTM

D-5084 (modified) or GRI-GCL2 will measure the ease with which liquids can move

through the GCL.18

Other tests. Testing of any geotextiles or

geomembranes should be made on the original rolls of the geotextiles or geomembranes

and before they are fabricated into the GCL

product. Once these materials have been

made part of the GCL product, their properties can change as a result of any needling,

stitching, or gluing. Additionally, any peel

tests performed on needle punched or stitch

bonded GCLs should use the modified ASTM

D-413 with a recommended sampling frequency of one test per 2,000 m2 (20,000 ft2

).19

Subgrade Preparation

Because the GCL layer is relatively thin,

the first foot of soil underlying the GCL

should have a hydraulic conductivity of 1 x

10-5 cm/sec or less. Proper subgrade preparation is essential to prevent damage to the

GCL layer as it is installed. This includes

clearing away any roots or large particles that

could potentially puncture the GCL and its

geotextile or geomembrane components. The

soil subgrade should be of the specified grading, moisture content, and density required

by the installer and approved by a construction quality assurance engineer for placement

of the GCL. Construction equipment deploying the rolls should not deform or rut the soil

subgrade excessively. To help ensure this, the

soil subgrade should be smooth rolled with a

smooth-wheel roller and maintained in a

smooth condition prior to deployment.

Joining Panels

GCLs are typically joined by overlapping

panels, without sewing or mechanically connecting pieces together. To ensure proper

joints, you should specify minimum and

maximum overlap distances. Typical overlap

distances range from 150 to 300 mm (6 to 12

in.). For some GCLs, such as needle punched

GCLs with nonwoven geotextiles, it might be

necessary to place bentonite on the area of

overlap. If this is necessary, you should take

steps to prevent fugitive bentonite particles

from coming into contact with the leachate

collection system, as they can cause physical

clogging.

Repair of Sections Damaged During

Liner Placement

During installation, GCLs might incur

some damage to either the clay component or

to any geotextiles or geomembranes. For

damage to geotextile or geomembrane components, repairs include patching using geotextile or geomembrane materials. If the clay

component is disturbed, a patch made from

the same GCL product should be used to perform any repairs. 

Protective Backfilling

As soon as possible after completion of

quality assurance and quality control activities, you should cover GCLs with either a soil

layer or a geosynthetic layer to prevent

hydration. The soil layer can be a compacted

clay liner or a layer of coarse drainage material. The geosynthetic layer is typically a

Protecting Ground Water—Designing and Installing Liners

7B-21

17 ASTM D-5321, Standard Test Method for Determining the Coefficient of Soil and Geosynthetic or

Geosynthetic and Geosynthetic Friction by the Direct Shear Method.

18 ASTM D-5084, Standard Test Method for Measurement of Hydraulic Conductivity of Saturated Porous

Materials Using a Flexible Wall Permeameter.

GRI-GCL2, Permeability of Geosynthetic Clay Liners (GCLs).

19 ASTM D-413, Standard Test Methods for Rubber Property-Adhesion to Flexible Substrate.
geomembrane; however, depending on sitespecific designs, it can be a geotextile. As

noted earlier, premature hydration before

covering can lead to uneven swelling, resulting in a GCL with varied thickness.

Therefore, a GCL should be covered with its

subsequent soil or geosynthetic layer before a

rainfall or snowfall occurs. Premature hydration is less of a concern for GCLs, where the

geosynthetic components are needle punched

or stitch bonded, because these types of connections can better limit clay expansion.

III. Composite

Liners

A composite liner consists of both a

geomembrane liner and natural soil. The

geomembrane forms the upper component

with the natural soil being the lower component. The ususal variations are:

• Geomembrane over compacted clay

liner (GM/CCL).

• Geomembrane over geosynthetic clay

liner (GM/GCL).

• Geomembrane over geosynthetic clay

liner over compacted clay liner

(GM/GCL/CCL).

A composite liner provides an effective

hydraulic barrier by combining the complementary properties of the two different liners

into one system. The geomembrane provides a

highly impermeable layer to maximize leachate

collection and removal. The natural soil liner

serves as a backup in the event of any leakage

from the geomembrane. With a composite

liner design, you should construct a leachate

collection and removal system above the

geomembrane. Information on design and construction of leachate collection and removal

systems is provided in Section V below.

What are the thickness and

hydraulic conductivity recommendations for composite liners?

Each component of the composite liner

should follow the recommendations for

geomembranes, geosynthetic clay liners, and

compacted clay liners described earlier.

Geomembrane liners should have a minimum thickness of 30 mil, except for HDPE

liners, which should have a minimum thickness of 60 mil. Similarly, compacted clay liners should be at least 2 feet thick and are

typically 2 to 5 feet thick. For compacted

clay liners and geosynthetic clay liners, you

should use materials with maximum

hydraulic conductivities of 1 x 10-7 cm/sec (4

x 10-8 in/sec) and 5 x 10-9 cm/sec (2 x 10-9

in/sec), respectively.

What issues should be considered in the design of a composite liner?

As a starting point, you should follow the

design considerations discussed previously for

single liners. In addition, to achieve the benefits of a combined liner system, you should

install the geomembrane to ensure good contact with the compacted clay layer. The uniformity of contact between the geomembrane

and the compacted clay layer helps control

the flow of leachate. Porous material, such as

drainage sand or a geonet, should not be

placed between the geomembrane and the

clay layer. Porous materials will create a layer

of higher hydraulic conductivity, which will

increase the amount of leakage below any

geomembrane imperfection.

You should consider the friction or shear

strength between a compacted clay layer and

a geomembrane. The friction or shear stress

at this surface is often low and can form a

weak plane on which sliding can occur.

7B-22

Protecting Ground Water—Designing and Installing Liners 
ASTM D-5321 provides a test method for

determining the friction coefficient of soil and

geomembranes.20 When using bentoniteamended soils, it is important to account for

how the percentage of bentonite added and

the degree of saturation affect interface friction. To provide for stable slopes, it is important to control both the bentonite and

moisture contents. A textured geomembrane

can increase the friction with the clay layer

and improve stability. 

What issues should be considered in the construction of a

composite liner?

To achieve good composite bonding, the

geomembrane and the compacted clay layer

should have good hydraulic contact. To

improve good contact, you should smoothroll the surface of the compacted clay layer

using a smooth, steel-drummed roller and

remove any stones. In addition, you should

place and backfill the geomembrane so as to

minimize wrinkles.

The placement of geomembranes onto a

compacted clay layer poses a challenge,

because workers cannot drive heavy

machines over the clay surface without

potentially damaging the compacted clay

component. Even inappropriate footwear can

leave imprints in the clay layer. It might be

possible to drive some types of low ground

pressure equipment or small, 4-wheel, all terrain vehicles over the clay surface, but drivers

should take extreme care to avoid movements, such as sudden starts, stops, and

turns, that could damage the surface. To

avoid damaging the clay layer, it is recommended that you unroll geomembranes by

lifting the rolls onto jacks at a cell side and

pulling down on the geomembrane manually.

Also, the entire roll with its core can be

unrolled onto the cell (with auxiliary support

using ropes on embankments). 

To minimize desiccation of the compacted

clay layer, you should place the geomembrane over the clay layer as soon as possible.

Additional cover materials should also be

placed over the geomembrane. Exposed

geomembranes absorb heat, and high temperatures can dry out and crack an underlying

compacted clay layer. Daily cyclic changes in

temperature can draw water from the clay

layer and cause this water to condense on the

underside of the geomembrane. This withdrawal of water can lead to desiccation cracking and potential interface stability concerns. 

IV. Double Liners

(Primary and

Secondary Lined

Systems)

In a double-lined waste management unit,

there are two distinct liners—one primary

(top) liner and one secondary (bottom) liner.

Each liner might consist of compacted clay, a

geomembrane, or a composite (consisting of a

geomembrane and a compacted clay layer or

GCL). Above the primary liner, it is recommended that you construct a leachate collection and removal system to collect and convey

liquids out of the waste management unit and

to control the depth of liquids above the primary liner. In addition, you should place a

leak detection, collection, and removal system

between the primary and secondary liner.

This leak detection system will provide leak

warning, as well as collect and remove any

liquid or leachate that has escaped the primary liner. See section V below for information

on the design of leachate collection and

removal systems and leak detection, collection, and removal systems.

Protecting Ground Water—Designing and Installing Liners

7B-23

20 ASTM D-5321, Standard Test Method for Determining the Coefficient of Soil and Geosynthetic or

Geosynthetic and Geosynthetic Friction by the Direct Shear Method.
What are the thickness and

hydraulic conductivity recommendations for double liners?

Each component of the double liner

should follow the recommendations for

geomembranes, compacted clay liners, or

composite liners described earlier.

Geomembrane liners should have a minimum

thickness of 30 mil, except for HDPE liners,

which should have a minimum thickness of

60 mil. Similarly, compacted clay liners

should be at least 2 feet thick and are typically 2 to 5 feet thick. For compacted clay liners

and geosynthetic clay liners, use materials

with maximum hydraulic conductivities of 1

x 10-7 cm/sec (4 x 10-8 in/sec) and 5 x 10-9

cm/sec (2 x 10-9 in/sec), respectively.

What issues should be considered in the design and construction of a double liner?

Like composite liners, double liners are

composed of a combination of single liners.

When planning to design and construct a

double liner, you should consult the sections

on composite and single liners first. In addition, you should consult the sections on

leachate collection and removal systems and

leak detection systems.

V. Leachate

Collection and

Leak Detection

Systems

One of the most important functions of a

waste management unit is controlling

leachate and preventing contamination of the

underlying ground water. Both leachate collection and removal systems and leak detection systems serve this purpose. You should

consult with the state agency too determine if

such systems are required. The primary function of a leachate collection and removal system is to collect and convey leachate out of a

unit and to control the depth of leachate

above a liner. The primary function of a leak

detection system is to detect leachate that has

escaped the primary liner. A leak detection

system refers to drainage material located

below the primary liner and above a secondary liner (if there is one); it acts as a secondary leachate collection and removal

system. After the leachate has been removed

and collected, a leachate treatment system

might be incorporated to process the leachate

and remove harmful constituents.

The information in this section on leachate

collection and leak detection systems is

applicable if the unit is a landfill or a waste

pile. Surface impoundments, which manage

liquid wastes, usually will not have leachate

collection and removal systems unless they

will be closed in-place as landfills; they might

have leak detection systems to detect liquid

wastes that have escaped the primary liner.

Leachate collection or leak detection systems

generally are not used with land application.

A. Leachate Collection

System

A typical leachate collection system

includes a drainage layer, collection pipes, a

removal system, and a protective filter layer.

Leachate collection systems are designed to

collect leachate for treatment or alternate disposal and to reduce the buildup of leachate

above the liner system. Figure 4 shows a

cross section of a typical leachate collection

system showing access to pipes for cleaning.

7B-24

Protecting Ground Water—Designing and Installing Liners 
What are the recommendations

for leachate collection and

removal systems?

You should design a leachate collection and

removal system to maintain less than 30 cm

(12 in.) depth of leachate, or “head,” above

the liner if granular soil or a geosynthetic

material is used. The reason for maintaining

this level is to prevent excessive leachate from

building up above the liner, which could

jeopardize the liner’s performance. This

should be the underlying factor guiding the

design, construction, and operation of the

leachate collection and removal system.

You should design a leachate collection

and removal system capable of controlling the

estimated volume of leachate. To determine

potential leachate generation, you should use

water balance equations or models. The most

commonly used method to estimate leachate

generation is EPA’s Hydrogeologic Evaluation

of Landfill Performance (HELP) model.21 This

model uses weather, soil, and waste management unit design data to determine leachate

generation rates.

What issues should be considered in the design of a leachate

collection and removal system?

You should design a leachate collection

and removal system to include the following

elements: a low-permeability base, a highpermeability drainage layer, perforated

leachate collection pipes, a protective filter

layer, and a leachate removal system. During

Protecting Ground Water—Designing and Installing Liners

7B-25

21 Available on the CD-ROM version of the Guide, as well as from the U.S. Army Corps of Engineers Web

site <www.wes.army.mil/el/elmodels/index.html#landfill>

Source: U.S. EPA, 1995b

Figure 4

Typical Leachate Collection System
design, you should consider the stability of

the base, the transmissivity of the drainage

layers, and the strength of the collection

pipes. It is also prudent to consider methods

to minimize physical, biological, and chemical clogging within the system.

Low-Permeability Base

A leachate collection system is placed over

the unit’s liner system. The bottom liner

should have a minimum slope of 2 percent to

allow the leachate collection system to gravity

flow to a collection sump. This grade is necessary to provide proper leachate drainage

throughout the operation, closure, and postclosure of the unit. Estimates of foundation

soil settlement should include this 2 percent

grade as a post-settlement design.

High-Permeability Drainage Layer

A high-permeability drainage layer consists

of drainage materials placed directly over the

low-permeability base, at the same minimum

2 percent grade. The drainage materials can

be either granular soil or geosynthetic materials. For soil drainage materials, a maximum of

12 inches of materials with a hydraulic conductivity of at least 1 x 10-2 cm/sec (4 x 10-3

in/sec) is recommended. For this reason, sand

and gravel are the most common soil materials used. If the drainage layer is going to

incorporate sand or gravel, it should be

demonstrated that the layer will have sufficient bearing capacity to withstand the waste

load of the full unit. Additionally, if the waste

management unit is designed on grades of 15

percent or higher, it should be demonstrated

that the soil drainage materials will be stable

on the steepest slope in the design.

Geosynthetic drainage materials such as

geonets can be used in addition to, or in place

of, soil materials. Geonets promote rapid

transmission of liquids and are most effective

when used in conjunction with a filter layer

or geotextile to prevent clogging. Geonets

consist of integrally connected parallel sets of

plastic ribs overlying similar sets at various

angles. Geonets are often used on the side

walls of waste management units because of

their ease of installation. Figure 5 depicts a

typical geonet material configuration.

The most critical factor involved with using

geonets in a high-permeability drainage layer

is the material’s ability to transmit fluids

under load. The flow rate of a geonet can be

evaluated by ASTM D-4716.22 Several additional measures for determining the transmissivity of geonets are discussed in the Solid

Waste Disposal Facility Criteria: Technical

Manual (U.S. EPA, 1993b).

Perforated Leachate Collection Pipes

Whenever the leachate collection system is

a natural soil, a perforated piping system

should be located within it to rapidly transmit the leachate to a sump and removal system. Through the piping system, leachate

flows gravitationally to a low point where the

sump and removal system is located. The

design of perforated leachate collection pipes,

therefore, should consider necessary flow

rates, pipe sizing, and pipe structural

strength. After estimating the amount of

leachate using the HELP model or a similar

water balance model, it is possible to calculate the appropriate pipe diameter and spacing. For the leachate collection system

design, you should select piping material that

can withstand the anticipated weight of the

waste, construction and operating equipment

stresses, and foundation settling. Most

leachate collection pipes used in modern

waste management units are constructed of

HDPE. HDPE pipes provide great structural

strength, while allowing significant chemical

resistance to the many constituents found in

leachate. PVC pipes are also used in waste

7B-26

22 ASTM D-4716, Standard Test Method for Constant Head Hydraulic Transmissivity (In-Plane Flow) of

Geotextiles and Geotextile Related Products.

Protecting Ground Water—Designing and Installing Liners 
management units, but they are not as chemically resistant as HDPE pipes. 

Protective Filter Layer

To protect the drainage layer and perforated leachate collection piping from clogging,

you should place a filter layer over the highpermeability drainage layer. To prevent waste

material from moving into the drainage layer,

the filter layer should consist of a material

with smaller pore space than the drainage

layer materials or the perforation openings in

the collection pipes. Sand and geotextiles are

the two most common materials used for filtration. You should select sand that allows

adequate flow of liquids, prevents migration

of overlying solids or soils into the drainage

layer, and minimizes clogging during the service life. In designing the sand filter, you

should consider particle size and hydraulic

conductivity. The advantages of using sand

materials include common usage, traditional

design, and durability.

Any evaluation of geotextile materials

should address the same concerns but with a

few differences. To begin with, the average

pore size of the geotextile should be large

enough to allow the finer soil particles to pass

but small enough to

retain larger soil particles. The number of

openings in the geotextile should be large

enough that, even if

some of the openings

clog, the remaining

openings will be sufficient to pass the design

flow rate. In addition to

pore size, geotextile filter specifications should

include durability

requirements. The

advantages of geotextile

materials include vertical space savings and

easy placement. Chapter 5 of Technical

Guidance Document: Quality Assurance and

Quality Control for Waste Containment Facilities

(U.S. EPA, 1993c) offers guidance on protection of drainage layers.

Leachate Removal System

Leachate removal often involves housing a

sump within the leachate collection drainage

layer. A sump is a low point in the liner constructed to collect leachate. Modern waste

management unit sumps often consist of prefabricated polyethylene structures supported

on a steel plate above the liner. Especially

with geomembrane liners, the steel plate

serves to support the weight of the sump and

protect the liner from puncture. Gravel filled

earthen depressions can serve as the sump.

Reinforced concrete pipe and concrete flooring also can be used in place of the polyethylene structure but are considerably heavier.

To remove leachate that has collected in

the sump, you should use a submersible

pump. Ideally, the sump should be placed at

a depth of 1 to 1.5 m (3 to 5 ft) to allow

enough leachate collection to prevent the

pump from running dry. You should consider

Protecting Ground Water—Designing and Installing Liners

7B-27

Figure 5

Typical Geonet Configuration
installing a level control, backup pump, and

warning system to ensure proper sump operation. Also consider using a backup pump as

an alternate to the primary pump and to

assist it during high flow periods. A warning

system should be used to indicate pump malfunction.

Standpipes, vertical pipes extending

through the waste and cover system, offer

one method of removing leachate from a

sump without puncturing the liner.

Alternatively, you can remove leachate from a

sump using pipes that are designed to penetrate the liner. When installing pipe penetrations through the liner, you should proceed

with extreme caution to prevent any liner

damage that could result in uncontained

leachate. Both of these options rely on gravity

to direct leachate to a leachate collection

pond or to an external pumping station.

Minimizing Clogging

Leachate collection and removal systems

are susceptible to physical, biological, and

chemical clogging. Physical clogging can

occur through the migration of finer-grained

materials into coarser-grained materials, thus

reducing the hydraulic conductivity of the

coarser-grained material. Biological clogging

can occur through bacterial growth in the

system due to the organic and nutrient materials in leachate. Chemical clogging can be

caused by chemical precipitates, such as calcium carbonates, causing blockage or cementation of granular drainage material.

Proper selection of drainage and filter materials is essential to minimize clogging in the

high-permeability drainage layer. Soil and geotextile filters can be used to minimize physical

clogging of both granular drainage material

and leachate collection pipes. When placed

above granular drainage material, these filters

can also double as an operations layer to prevent sharp waste from damaging the liner or

leachate collection and removal systems. To

minimize chemical and biological clogging for

granular drainage material, the best procedure

is to keep the interstices of the granular

drainage material as open as possible.

The leachate collection pipes are also susceptible to similar clogging. To prevent this,

you should incorporate measures into the

design to allow for routine pipe cleaning,

using either mechanical or hydraulic methods. The cleaning components can include

pipes with a 15 cm (6 in) minimum diameter

to facilitate cleaning; access located at major

pipe intersections or bends to allow for

inspections and cleaning; and valves, ports,

or other appurtenances to introduce biocides

and cleaning solutions. Also, you should

check that the design does not include wrapping perforated leachate collection pipes

directly with geotextile filters. If the geotextile becomes clogged, it can block flow into

the pipe.

B. Leak Detection System

The leak detection system (LDS) is also

known as the secondary leachate collection

and removal system. It uses the same

drainage and collection components as the

primary leachate collection and removal system and identifies, collects, and removes any

leakage from the primary system. The LDS

should be located directly below the primary

liner and above the secondary liner.

What are the recommendations

for leak detection systems?

The LDS should be designed to assess the

adequacy of the primary liner against

leachate leakage; it should cover both the

bottom and side walls of a waste management unit. The LDS should be designed to

collect leakage through the primary layer and

transport it to a sump within 24 hours.

7B-28

Protecting Ground Water—Designing and Installing Liners 
The LDS should allow for monitoring and

collection of leachate escaping the primary

liner system. You should monitor the LDS on

a regular basis. If the volume of leachate

detected by the LDS appears to be increasing

or is significant, you should consider a closer

examination to determine possible remediation measures. A good rule of thumb is that if

the LDS indicates a seepage level greater than

20 gallons per acre per day, the system might

need closer monitoring or remediation.

C. Leachate Treatment

System

Once the leachate has been removed from

the unit and collected, you should consider

taking measures to characterize the leachate

in order to ensure proper management. There

are several methods of disposal for leachate,

and the treatment strategy will vary according

to the disposal method chosen. Leachate disposal options include discharging to or

pumping and hauling to a publicly owned

treatment works or to an onsite treatment

system; treating and discharging to the environment; land application; and natural or

mechanical evaporation.

When discharging to or pumping and

hauling leachate to a publicly owned treatment works, a typical treatment strategy

includes pretreatment. Pretreatment could

involve equalization, aeration, sedimentation,

pH adjustment, or metals removal.23 If the

plan for leachate disposal does not involve a

remote treatment facility, pretreatment alone

usually is not sufficient.

There are two categories of leachate treatment, biological and physical/chemical. The

most common method of biological treatment

is activated sludge. Activated sludge is a “suspended-growth process that uses aerobic

microorganisms to biodegrade organic contaminants in leachate.”24 Among physical/chemical

treatment techniques, the carbon absorption

process and reverse osmosis are the two most

common methods. Carbon absorption uses

carbon to remove dissolved organics from

leachate and is very expensive. Reverse osmosis involves feeding leachate into a tubular

chamber whose wall acts as a synthetic membrane, allowing water molecules to pass

through but not pollutant molecules, thereby

separating clean water from waste constituents.

What are the recommendations

for leachate treatment systems?

You should review all applicable federal

and state regulations and discharge standards

to determine which treatment system will

ensure long-term compliance and flexibility

for the unit. Site-specific factors will also play

a fundamental role in determining the proper

leachate treatment system. For some facilities,

onsite storage and treatment might not be an

option due to space constraints. For other

facilities, having a nearby, publicly owned

treatment works might make pretreatment

and discharge to the treatment works an

attractive alternative.

VI. Construction

Quality

Assurance and

Quality Control

Even the best unit design will not translate

into a structure that is protective of human

health and the environment, if the unit is not

properly constructed. Manufacturing quality

assurance and manufacturing quality control

(MQA and MQC) are also important issues

for the overall project; however, they are discussed only briefly here since they are primarily the responsibility of a manufacturer.

Nonetheless, it is best to select a manufacturProtecting Ground Water—Designing and Installing Liners

7B-29

23 Arts, Tom. “Alternative Approaches For Leachate Treatment.” World Wastes.

24 Ibid.
er who incorporates appropriate quality

assurance and quality control (QA and QC)

mechanisms as part of the manufacturing

process. The remainder of this section provides a general description of the components of a construction quality assurance and

construction quality control (CQA and CQC)

program for a project. CQA and CQC are

critical factors for waste management units.

They are not interchangeable, and the distinction between them should be kept in

mind when preparing plans. CQA is third

party verification of quality, while CQC consists of in-process measures taken by the contractor or installer to maintain quality. You

should establish clear protocols for identifying and addressing issues of concern

throughout every stage of construction.

What is manufacturing quality

assurance?

The desired characteristics of liner materials should be specified in the unit’s contract

with the manufacturer. The manufacturer

should be responsible for certifying that materials delivered conform to those specifications.

MQC implemented to ensure such conformance might take the form of process quality

control or computer-aided quality control. If

requested, the manufacturer should provide

information on the MQC measures used,

allow unit personnel or engineers to visit the

manufacturing facility, and provide liner samples for testing. It is good practice for the

manufacturer to have a dedicated individual

in charge of MQC who would work with unit

personnel in these areas.

What is construction quality

assurance?

CQA is a verification tool employed by the

facility manager or regulatory agency, consisting of a planned series of observations and

tests designed to ensure that the final product meets project specifications. CQA testing,

often referred to as acceptance inspection,

provides a measure of the final product quality and its conformance with project plans

and specifications. Performing acceptance

inspections routinely, as portions of the project become complete, allows early detection

and correction of deficiencies, before they

become large and costly.

On routine construction projects, CQA is

normally the concern of the facility manager

and is usually performed by an independent,

third-party testing firm. The independence of

the testing firm is important, particularly

when a facility manager has the capacity to

perform the CQA activities. Although the

7B-30

Protecting Ground Water—Designing and Installing Liners 

MQC, MQA, CQC, and CQA

Manufacturing quality control

(MQC) is measures taken by the manufacturer to ensure compliance with the

material and workmanship specifications

of the facility manager.

Manufacturer quality assurance

(MQA) is measures taken by facility personnel, or by an impartial party brought

in expressly for the purpose, to determine if the manufacturer is in compliance with the specifications of the facility

manager.

Construction quality control (CQC)

is measures taken by the installer or contractor to ensure compliance with the

installation specifications of the facility

manager.

Construction quality assurance

(CQA) is measures taken by facility personnel, or by an impartial party brought

in expressly for the purpose, to determine if the installer or contractor is in

compliance with the installation specifications of the facility manager.
facility’s in-house CQA personnel might be

registered professional engineers, a perception

of misrepresentation might arise if CQA is not

performed by an independent third party.

The independent party should designate a

CQA officer and fully disclose any activities

or relationships that the officer has with the

facility manager that might impact his or her

impartiality or objectivity. If such activities or

relationships exist, the CQA officer should

describe actions that have been or can be

taken to avoid, mitigate, or neutralize the

possibility they might affect the CQA officer’s

objectivity. State regulatory representatives

can help evaluate whether these mechanisms

are sufficient to ensure acceptable CQA.

What is construction quality 

control?

CQC is an ongoing process of measuring

and controlling the characteristics of the product in order to meet manufacturer’s or project

specifications. CQC inspections are typically

performed by the contractor to provide an inprocess measure of construction quality and

conformance with the project plans and specifications, thereby allowing the contractor to

correct the construction process if the quality

of the product is not meeting the specifications and plans. Since CQC is a production

tool employed by the manufacturer of materials and by the contractor installing the materials at the site, the Guide does not cover CQC

in detail. CQC is performed independently of

CQA. For example, while a geomembrane

liner installer will perform CQC testing of

field seams, the CQA program should require

independent testing of those same seams by a

third-party inspector.

How can implementation of CQA

and CQC plans be ensured?

When preparing to design and construct a

waste management unit, regardless of design,

you should develop CQA and CQC plans

customized to the project. To help the project

run smoothly, the CQA plan should be easy

to follow. You should organize the CQA plan

to reflect the sequence of construction and

write it in language that will be familiar to an

average field technician. For a more detailed

discussion of specific CQA and CQC activities recommended for each type of waste

management unit, you should consult

Technical Guidance Document: Quality

Assurance and Quality Control for Waste

Management Containment Facilities (U.S. EPA,

1993c). This document provides information

to develop comprehensive QA plans and to

carry out QC procedures at waste management units. 

CQA and CQC plans can be implemented

through a series of meetings and inspections,

which should be documented thoroughly.

Communication among all parties involved in

design and construction of a waste management unit is essential to ensuring a quality

product. You should define responsibility and

authority in written QA and QC plans and

ensure that each party involved understands

its role. Pre-construction meetings are one

way to help clarify roles and responsibilities.

During construction, meetings can continue

to be useful to help resolve misunderstandings

and to identify solutions to unanticipated

problems that might develop. Some examples

of typical meetings during the course of any

construction project include pre-bid meetings,

resolution meetings, pre-construction meetings, and progress meetings.

Protecting Ground Water—Designing and Installing Liners

7B-31
A. Compacted Clay Liner

Quality Assurance and

Quality Control

Although manufacturing quality control

and quality assurance are often the responsibility of the materials manufacturer, in the

case of soil components, manufacturing and

construction quality control testing can be

the responsibility of the facility manager. The

CQA and CQC plans should specify procedures for quality assurance and quality control during construction of the compacted

clay liners.

How can implementation of QA

and QC be ensured for a compacted clay liner?

QC testing is typically performed by the

contractor on materials used in construction

of the liner. This testing examines material

properties such as moisture content, soil density, Atterberg limits, grain size, and laboratory hydraulic conductivity. Additional testing

of soil moisture content, density, lift thickness, and hydraulic conductivity helps ensure

that the waste management unit has been

constructed in accordance with the plans and

technical specifications.

CQA testing for soil liners includes the

same tests described for QC testing in the

paragraph above. Generally, the tests are performed less frequently. CQA testing is performed by an individual or an entity

independent of the contractor. Activities of

the CQA officer are essential to document

quality of construction. The responsibilities

of the CQA officer and his or her staff might

include communicating with the contractor;

interpreting and clarifying project drawings

and specifications with the designer, facility

manager, and contractor; recommending

acceptance or rejection by the facility manager of work completed by the construction

contractor; and submitting blind samples,

such as duplicates and blanks, for analysis by

the contractor’s testing staff or independent

laboratories.

You should also consider constructing a

test pad prior to full-scale construction as a

CQA tool. As described earlier in the section

on compacted clay liners, pilot construction

or test fill of a small-scale test pad can be

used to verify that the soil, equipment, and

construction procedures can produce a liner

that performs according to the construction

drawings and specifications. 

Specific factors to examine or test during

construction of a test fill include: preparation

and compaction of foundation material to the

required bearing strength; methods of controlling uniformity of the soil material; compactive effort, such as type of equipment and

number of passes needed to achieve required

soil density and hydraulic conductivity; and

lift thickness and placement procedures

needed to achieve uniformity of density

throughout a lift and prevent boundary

effects between lifts or between placements in

the same lift. Test pads can also provide a

means to evaluate the ability of different

types of soil to meet hydraulic conductivity

requirements in the field. In addition to

allowing an opportunity to evaluate material

performance, test pads also allow evaluation

of the skill and competence of the construction team, including equipment operators

and QC specialists.

B. Geomembrane Liner

Quality Assurance and

Quality Control

As with the construction of soil liners,

installation of geomembrane liners should be

in conformance with a CQA and CQC plan.

The responsibilities of the CQA personnel for

the installation of the geomembrane are gen7B-32

Protecting Ground Water—Designing and Installing Liners 
erally the same as the responsibilities for the

construction of a compacted clay liner, with

the addition of certain activities including

observations of the liner storage area and liners in storage, and handling of the liner as the

panels are positioned in the cell.

Geomembrane CQA staff should also observe

seam preparation, seam overlap, and materials underlying the liner.

How can implementation of QA

and QC be ensured for a

geomembrane liner?

Prior to installation, you should work with

the geomembrane manufacturer to ensure the

labeling system for the geomembrane rolls is

clear and logical, allowing easy tracking of the

placement of the rolls within the unit. It is

important to examine the subgrade surface

with both the subgrade contractor and the liner

installer to ensure it conforms to specifications.

Once liner installation is underway, CQA

staff might be responsible for observations of

destructive testing conducted on scrap test

welds prior to seaming. Geomembrane CQA

staff might also be responsible for sending

destructive seam sampling to an independent

testing laboratory and reviewing the results for

conformance to specifications. Other observations for which the CQA staff are typically

responsible include observations of all seams

and panels for defects due to manufacturing

and handling, and placement and observations

of all pipe penetrations through a liner. 

Test methods, test parameters, and testing

frequencies should be specified in the CQA

plan to provide context for any data collected. It is prudent to allow for testing frequency to change, based on the performance of

the geomembrane installer. If test results indicate poor workmanship, you should increase

testing. If test results indicate high quality

installation work, you can consider reducing

testing frequencies. When varying testing frequency, you should establish well-defined

procedures for modifying testing frequency. It

is also important to evaluate testing methods,

understand the differences among testing

methods, and request those methods appropriate for the material and seaming method

be used. Nondestructive testing methods are

preferrable when possible to help reduce the

number of holes cut into the geomembrane.

Geomembrane CQA staff also should document the results of their observations and prepare reports indicating the types of sampling

conducted and sampling results, locations of

destructive samples, locations of patches,

locations of seams constructed, and any problems encountered. In some cases, they might

need to prepare drawings of the liner installation. Record drawing preparation is frequently

assigned to the contractor, to a representative

of the facility manager, or to the engineer. You

should request complete reports from any

CQA staff and the installers. To ensure complete CQA documentation, it is important to

maintain daily CQA reports and prepare

weekly summaries.

C. Geosynthetic Clay Liner

Quality Assurance and

Quality Control

Construction quality assurance for geosynthetic clay liners is still a developing area; the

GCL industry is continuing to establish standardized quality assurance and quality control procedures. The CQA recommendation

for GCLs can serve as a starting point. You

should check with the GCL manufacturer and

installer for more specific information.

Protecting Ground Water—Designing and Installing Liners

7B-33
How can implementation of QA

and QC be ensured for a geosynthetic clay liner?

It is recommended that you develop a

detailed CQA plan, including product specifications; shipping, handling, and storage

procedures; seaming methods; and placement

of overlying material. It is important to work

with the manufacturer to verify that the

product meets specifications. Upon receipt of

the GCL product, you should also verify that

it has arrived in good condition.

During construction, CQA staff should

ensure that seams are overlapped properly

and conform to specifications. CQA staff

should also check that panels, not deployed

within a short period of time, are stored

properly. In addition, as overlying material is

placed on the GCL, it is important to restrict

vehicle traffic directly on the GCL. You

should prohibit direct vehicle traffic, with the

exception of small, 4-wheel, all terrain vehicles. Even with the small all-terrain vehicles,

drivers should take extreme care to avoid

movements, such as sudden starts, stops, and

turns, which can damage the GCL. 

As part of the CQA documentation, it is

important to maintain records of weather

conditions, subgrade conditions, and GCL

panel locations. Also, you should document

any repairs that were necessary or other

problems identified and addressed.

D. Leachate Collection

System Quality

Assurance and Quality

Control

Leachate collection system CQC should be

performed by the contractor. Similar activities should be performed for CQA by an

independent party acting on behalf of the

facility manager. The purpose of leachate collection system CQA is to document that the

system is constructed in accordance with

design specifications. 

How can implementation of QA

and QC be ensured for a

leachate collection system?

Prior to construction, CQA staff should

inspect all materials to confirm that they meet

the construction plans and specifications.

These materials include: geonets; geotextiles;

pipes; granular material; mechanical, electrical, and monitoring equipment; concrete

forms and reinforcements; and prefabricated

structures such as sumps and manholes. The

leachate collection system foundation, either a

geomembrane or compacted clay liner, should

also be inspected, upon its completion, to

ensure that it has proper grading and is free

of debris and liquids.

During construction, CQA staff should

observe and document, as appropriate, the

placement and installation of pipes, filter layers, drainage layers, geonets and geotextiles,

sumps, and mechanical and electrical equipment. For pipes, observations might include

descriptions of pipe bedding material, quality

and thickness, as well as the total area covered by the bedding material. Observations

of pipe installations should focus on the location, configuration, and grading of the pipes,

as well as the quality of connections at joints. 

For granular filter layers, CQA activities

might include observing and documenting

material thickness and quality during placement. For granular drainage layers, CQA

might focus on the protection of underlying

liners, material thickness, proper overlap

with filter fabrics and geonets (if applicable),

and documentation of any weather conditions that might affect the overall performance of the drainage layer. For geonets and

7B-34

Protecting Ground Water—Designing and Installing Liners 
other geosynthetics, CQA observations

should focus on the area of coverage and layout pattern, as well as the overlap between

panels. For geonets, CQA staff might want to

make sure that the materials do not become

clogged by granular material that can be carried over, as a result of either wind or runoff

during construction.

Upon completion of construction, each

component should be inspected to identify

any damage that might have occurred during

its installation or during construction of

another component. For example, a leachate

collection pipe can be crushed during placement of a granular drainage layer. Any damage that does occur should be repaired, and

the repairs should be documented in the

CQA records.

Protecting Ground Water—Designing and Installing Liners

7B-35
7B-36

Protecting Ground Water—Designing and Installing Liners 

■ Review the recommended location considerations and operating practices for the unit.

■ Select appropriate liner type—single, composite, or double liner—or in-situ soils, based on risk

characterization.

■ Evaluate liner material properties and select appropriate clay, geosynthetic, or combination of materials; consider interactions of liner and soil material with waste.

■ Develop a construction quality assurance (CQA) plan defining staff roles and responsibilities and

specifying test methods, storage procedures, and construction protocols. 

■ Ensure a stable in-situ soil foundation, for nonengineered liners.

■ Prepare and inspect subgrade for engineered liners.

■ Work with manufacturer to ensure protective shipping, handling, and storage of all materials.

■ Construct a test pad for compacted clay liners.

■ Test compacted clay liner material before and during construction.

■ Preprocess clay material to ensure proper water content, remove oversized particles, and add soil

amendments, as applicable.

■ Use proper lift thickness and number of equipment passes to achieve adequate compaction.

■ Protect clay material from drying and cracking.

■ Develop test strips and trial seams to evaluate geomembrane seaming method.

■ Verify integrity of factory and field seams for geomembrane materials before and during construction.

■ Backfill with soil or geosynthetics to protect geomembranes and geosynthetic clay liners during

construction.

■ Place backfill materials carefully to avoid damaging the underlying materials.

■ Install geosynthetic clay liner with proper overlap.

■ Patch any damage that occurs during geomembrane or geosynthetic clay liner installation.

■ Design leachate collection and removal system to allow adequate flow and to minimize clogging;

include leachate treatment and leak detection systems, as appropriate.

■ Document all CQA activities, including meetings, inspections, and repairs.

Designing and Installing Liners Activity List
Protecting Ground Water—Designing and Installing Liners

7B-37

ASTM D-413. 1993. Standard Test Methods for Rubber Property-Adhesion to Flexible Substrate.

ASTM D-422. 1990. Standard Test Method for Particle-Size Analysis of Soils.

ASTM D-638. 1991. Standard Test Method for Tensile Properties of Plastics.

ASTM D-698. 1991. Test Method for Laboratory Compaction Characteristics of Soil Using Standard

Effort (12,400 ft-lbf/ft3 (600 kN-m/m3

)).

ASTM D-751. 1989. Standard Test Methods for Coated Fabrics.

ASTM D-882. 1991. Standard Test Methods for Tensile Properties of Thin Plastic Sheeting.

ASTM D-1004. 1990. Standard Test Method for Initial Tear Resistance of Plastic Film and Sheeting.

ASTM D-1557. 1991. Test Method for Laboratory Compaction Characteristics of Soil Using Modified

Effort (56,000 ft-lbf/ft3 (2,700 kN-m/m3

)).

ASTM D-4318. 1993. Standard Test Method for Liquid Limit, Plastic Limit, and Plasticity Index of

Soils.

ASTM D-4354. 1989. Standard Practice for Sampling of Geosynthetics for Testing.

ASTM D-4716. 1987. Standard Test Method for Constant Head Hydraulic Transmissivity (In-Plane

Flow) of Geotextiles and Geotextile Related Products.

ASTM D-5084. 1990. Standard Test Method for Measurement of Hydraulic Conductivity of Saturated

Porous Materials Using a Flexible Wall Permeameter.

ASTM D-5199. 1991. Standard Test Method for Measuring Nominal Thickness of Geotextiles and

Geomembranes.

ASTM D-5261. 1992. Standard Test Method for Measuring Mass per Unit Area of Geotextiles.

ASTM D-5321. 1992. Standard Test Method for Determining the Coefficient of Soil and Geosynthetic

or Geosynthetic and Geosynthetic Friction by the Direct Shear Method.

Resources
7B-38

Protecting Ground Water—Designing and Installing Liners 

Resources (cont.)

Bagchi, A. 1994. Design, Construction, and Monitoring of Landfills. 

Berg, R., and L. Well. 1996. A Position Paper on: The Use of Geosynthetic Barriers in Nonhazardous

Industrial Waste Containment.

Berger, E. K. and R. Berger. 1997. The Global Water Cycle.

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Boulding, J.R. 1995. Practical Handbook of Soil, Vadose Zone, and Ground Water Contamination:

Assessment, Prevention and Remediation. Lewis Publishers.

Brandt, R.C. and K.S. Martin. 1996. The Food Processing Residual Management Manual. September.

Daniel, D.E., and R.M. Koerner. 1991. Landfill Liners from Top to Bottom. Civil Engineering. December.

Daniel, D.E., and R.M. Koerner. 1993. Technical Guidance Document: Quality Assurance and Quality

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Daniel, D.E., and R.M. Koerner. 1995. Waste Containment Facilities: Guidance for Construction, Quality

Assurance and Quality Control of Liner and Cover Systems.

Evanylo, G.K. and W. L. Daniels. 1996. The Value and Suitability of Papermill Sludge and Sludge

Compost as a Soil Amendment and Soilless Media Substitute. Final Report. The Virginia Department of

Agriculture and Consumer Services, P.O. Box 1163, Room 402, Richmond, VA. April.

Federal Test Method Standard 101C. 1980. Puncture Resistance and Elongation Test (1/8 Inch Radius

Probe Method).

Fipps, G. 1995. Managing Irrigation Water Salinity in the Lower Rio Grande Valley. <hermes.ecn.purdue.edu/sgml/water_quality/texas/b1667.ascii>

Geosynthetic Research Institute. 1993. GRI-GCL1, Swell Measurement of the Clay Component of GCLs.

Geosynthetic Research Institute. 1993. GRI-GCL2, Permeability of Geosynthetic Clay Liners (GCLs).
Protecting Ground Water—Designing and Installing Liners

7B-39

Resources (cont.)

Idaho Department of Health and Welfare. 1988. Guidelines for Land Application of Municipal and

Industrial Wastewater. March.

Koerner, R.M. 1994. Designing with Geosynthetics, Third Edition.

McGrath, L., and P. Creamer. 1995. Geosynthetic Clay Liner Applications in Waste Disposal

Facilities.

McGrath, L., and P. Creamer. 1995. Geosynthetic Clay Liner Applications. Waste Age. May.

Michigan Department of Natural Resources, Waste Characterization Unit. 1991. Guidance for Land

Application of Wastewater Sludge in Michigan. March.

Michigan Department of Natural Resources, Waste Characterization Unit. 1991. Guide to Preparing

a Residuals Management Plan. March.

Minnesota Pollution Control Agency. 1993. Land Treatment of Landfill Leachate. February.

Northeast Regional Agricultural Engineering Cooperative Extension. 1996. Nutrient Management

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Northeast Regional Agricultural Engineering Cooperative Extension. 1996. Animal Agriculture and

the Environment: Nutrients, Pathogens, and Community Relations. NRAES-96. December.

Northeast Regional Agricultural Engineering Cooperative Extension. 1993. Utilization of Food

Processing Residuals. Selected Papers Representing University, Industry, and Regulatory

Applications. NRAES-69. March.

North Carolina Cooperative Extension Service. 1994. Soil facts: Careful Soil Sampling - The Key to

Reliable Soil Test Information. AG-439-30.

Oklahoma Department of Environmental Quality. Title 252. Oklahoma Administrative Code,

Chapter 647. Sludge and Land Application of Wastewater.

Sharma, H., and S. Lewis. 1994. Waste Containment Systems, Waste Stabilization, and Landfills:

Design and Evaluation.

Smith, M.E., S. Purdy, and M. Hlinko. 1996. Some Do’s and Don’ts of Construction Quality

Assurance. Geotechnical Fabrics Report. January/February.
7B-40

Protecting Ground Water—Designing and Installing Liners 

Resources (cont.)

Spellman, F. R. 1997. Wastewater Biosolids to Compost.

Texas Water Commission. 1983. Industrial Solid Waste Management Technical Guideline No. 5: Land

Application. December.

Tsinger, L. 1996. Chemical Compatibility Testing: The State of Practice. Geotechnical Fabrics Report.

October/November.

University of Nebraska Cooperative Extension Institute of Agriculture and Natural Resources. 1991.

Guidelines for Soil Sampling. G91-1000-A. February.

U.S. EPA. 2001. Technical Resource Document: Assessment and recommendations for Improving the

Performance of Waste Containment Systems. Draft.

U.S. EPA. 1996a. Issue Paper on Geosynthetic Clay Liners (GCLs). 

U.S. EPA. 1996b. Report of 1995 Workshop on Geosynthetic Clay Liners. EPA600-R-96-149. June.

U.S. EPA. 1995a. A Guide to the Biosolids Risk Assessments for the EPA Part 503 Rule. EPA832-B-93-

005. September.

U.S. EPA. 1995b. Decision Maker’s Guide to Solid Waste Management. Volume II. EPA530-R-95-023.

U.S. EPA. 1995c. Laboratory Methods for Soil and Foliar Analysis in Long-Term Environmental

Monitoring Programs. EPA600-R-95-077.

U.S. EPA. 1995d. Process Design Manual: Land Application of Sewage Sludge and Domestic Septage.

EPA625-R-95-001. September.

U.S. EPA. 1995e. Process Design Manual: Surface Disposal of Sewage Sludge and Domestic Septage.

EPA625-R-95-002. September.

U.S. EPA. 1994a. A Plain English Guide to the EPA Part 503 Biosolids Rule. EPA832-R-93-003.

September.

U.S. EPA. 1994b. Biosolids Recycling: Beneficial Technology for a Better Environment. EPA832-R-94-

009. June.

U.S. EPA. 1994c. Guide to Septage Treatment and Disposal. EPA625-R-94-002. September.
Protecting Ground Water—Designing and Installing Liners

7B-41

Resources (cont.)

U.S. EPA. 1994d. Land Application of Sewage Sludge: A Guide for Land Appliers on the Requirements

of the Federal Standards for the Use or Disposal of Sewage Sludge, 40 CFR Part 503. EPA831-B-93-

002b. December.

U.S. EPA. 1994e. Seminar Publication: Design, Operation, and Closure of Municipal Solid Waste

Landfills. EPA625-R-94-008.

U.S. EPA. 1993a. Domestic Septage Regulatory Guidance: A Guide to the EPA 503 Rule. EPA832-B-92-

005. September.

U.S. EPA. 1993b. Solid Waste Disposal Facility Criteria: Technical Manual. EPA530-R-93-017.

U.S. EPA. 1993c. Technical Guidance Document: Quality Assurance and Quality Control for Waste

Containment Facilities. EPA600-R-93-182.

U.S. EPA. 1992. Control of Pathogens and Vector Attraction in Sewage Sludge. EPA625-R-92-013.

December.

U.S. EPA. 1991a. Seminar Publication: Design and Construction of RCRA/CERCLA Final Covers.

EPA625-4-91-025.

U.S. EPA. 1991b. Seminar Publication: Site Characterization for Subsurface Remediation. EPA625-4-91-

026.

U.S. EPA. 1991c. Technical Guidance Document: Inspection Techniques for the Fabrication of

Geomembrane Field Seams. EPA530-SW-91-051.

U.S. EPA. 1990. State Sludge Management Program Guidance Manual. October.

U.S. EPA. 1989a. Seminar Publication: Requirements for Hazardous Waste Landfill Design,

Construction, and Closure. EPA625-4-89-022.

U.S. EPA. 1989b. Seminar Publication: Corrective Action: Technologies and Applications. EPA625-4-89-

020.

U.S. EPA. 1988. Lining of Waste Containment and Other Impoundment Facilities. EPA600-2-88-052.

U.S. EPA. 1987. Geosynthetic Guidance for Hazardous Waste Landfill Cells and Surface Impoundments.

EPA600-2-87-097.
7B-42

Protecting Ground Water—Designing and Installing Liners 

Resources (cont.)

U.S. EPA. 1986a. Project Summary: Avoiding Failure of Leachate Collection and Cap Drainage Systems.

EPA600-S2-86-058.

U.S. EPA. 1986b. Test Methods for Evaluating Solid Waste: Physical/Chemical Methods. EPASW-846.

U.S. EPA. 1983. Process Design Manual for Land Application of Municipal Sludge. EPA625-1-83-016.

October.

U.S. EPA, U.S. Army Corps of Engineers, U.S. Department of Interior, and U.S. Department of

Agriculture. 1981. Process Design Manual for Land Treatment of Municipal Wastewater. EPA625-1-81-

013. October.

U.S. EPA. 1979. Methods for Chemical Analysis of Water and Wastes. EPA600-4-79-020.

Viessman Jr., W. and M.J. Hammer. 1985. Water Supply and Pollution Control. 4th ed.

Washington State Department of Ecology. 1993. Guidelines for Preparation of Engineering Reports for

Industrial Wastewater Land Application Systems. Publication #93-36. May.

Webber, M.D. and S.S. Sing. 1995. Contamination of Agricultural Soils. In Action, D.F. and L.J.

Gregorich, eds. The Health of Our Soils.

Wisconsin Department of Natural Resources. 1996. Chapter NR 518: Landspreading of Solid Waste. April.
Protecting Ground Water—Designing and Installing Liners

7B-43

Geosynthetic Materials25

Geotextiles

Geotextiles form one of the two largest

group of geosynthetics. Their rise in growth

during the past fifteen years has been nothing

short of awesome. They are indeed textiles in

the traditional sense, but consist of synthetic

fibers rather than natural ones such as cotton,

wool, or silk. Thus biodegradation is not a

problem. These synthetic fibers are made into

a flexible, porous fabric by standard weaving

machinery or are matted together in a random, or nonwoven, manner. Some are also

knit. The major point is that they are porous

to water flow across their manufactured plane

and also within their plane, but to a widely

varying degree. There are at least 80 specific

application areas for geotextiles that have been

developed; however, the fabric always performs at least one of five discrete functions:

1. Separation

2. Reinforcement

3. Filtration

4. Drainage

5. Moisture barrier (when impregnated)

Geogrids

Geogrids represent a rapidly growing segment within the geosynthetics area. Rather

than being a woven, nonwoven or knit textile

(or even a textile-like) fabric, geogrids are

plastics formed into a very open, gridlike

configuration (i.e., they have large apertures).

Geogrids are either stretched in one or two

directions for improved physical properties or

made on weaving machinery by unique

methods. By themselves, there are at least 25

application areas, however, they function

almost exclusively as reinforcement materials.

Geonets

Geonets, called geospacers by some, constitute another specialized segment within the

geosynthetic area. They are usually formed by

a continuous extrusion of parallel sets of

polymeric ribs at acute angles to one another.

When the ribs are opened, relatively large

apertures are formed into a netlike configuration. Their design function is completely

within the drainage area where they have

been used to convey fluids of all types.

Geomembranes

Geomembranes represent the other largest

group of geosynthetics and in dollar volume

their sales are probably larger than that of

geotextiles. Their growth has been stimulated

by governmental regulations originally enacted in 1982. The materials themselves are

“impervious” thin sheets of rubber or plastic

material used primarily for linings and covers

of liquid- or solid-storage facilities. Thus the

primary function is always as a liquid or

vapor barrier. The range of applications, however, is very great, and at least 30 individual

applications in civil engineering have been

developed.

Geosynthetic Clay Liners

Geosynthetic clay liners (or GCLs) are the

newest subset within geosynthetic materials.

They are rolls of factory fabricated thin layers

of bentonite clay sandwiched between two

geotextiles or bonded to a geomembrane.

Structural integrity is maintained by needle

punching, stitching or physical bonding.

They are seeing use as a composite compo25 Created by Geosynthetic Research Institute. Accessed from the Internet on October 16, 2001 at

<www.drexel.edu/gri/gmat.html>.

Appendix
7B-44

Protecting Ground Water—Designing and Installing Liners 

nent beneath a geomembrane or by themselves as primary or secondary liners.

Geopipe (aka Buried Plastic Pipe)

Perhaps the original geosynthetic material

still available today is buried plastic pipe. This

“orphan” of the Civil Engineering curriculum

was included due to an awareness that plastic

pipe is being used in all aspects of geotechnical, transportation, and environmental engineering with little design and testing

awareness. This is felt to be due to a general

lack of formalized training. The critical nature

of leachate collection pipes coupled with high

compressive loads makes geopipe a bona-fide

member of the geosynthetics family. The function is clearly drainage.

Geocomposites

A geocomposite consists of a combination

of geotextile and geogrid; or geogrid and

geomembrane; or geotextile, geogrid, and

geomembrane; or any one of these three

materials with another material (e.g.,

deformed plastic sheets, steel cables, or steel

anchors). This exciting area brings out the

best creative efforts of the engineer, manufacturer, and contractor. The application areas

are numerous and growing steadily. The

major functions encompass the entire range

of functions listed for geosynthetics discussed

previously: separation, reinforcement, filtration, drainage, and liquid barrier.

“Geo-Others”

The general area of geosynthetics has

exhibited such innovation that many systems

defy categorization. For want of a better

phrase, geo-others, describes items such as

threaded soil masses, polymeric anchors, and

encapsulated soil cells. As with geocomposites their primary function is product-dependent and can be any of the five major

functions of geosynthetics.
Part IV

Protecting Ground Water

Chapter 7: Section C

Designing A Land Application Program
Contents

I. Identifying Waste Constituents for Land Application..............................................................................7C-2

II. Evaluating Waste Parameters ..................................................................................................................7C-4

A. Total Solids Content ..............................................................................................................................7C-4

B. pH ........................................................................................................................................................7C-5

C. Biodegradable Organic Matter ..............................................................................................................7C-6

D. Nutrients ..............................................................................................................................................7C-6

E. Metals....................................................................................................................................................7C-8

F. Carbon-to-Nitrogen Ratio......................................................................................................................7C-8

G. Soluble Salts ..........................................................................................................................................7C-9

H.Calcium Carbonate Equivalent ............................................................................................................7C-11

I. Pathogens ............................................................................................................................................7C-11

III. Measuring Soil Properties ....................................................................................................................7C-12

IV. Studying the Interaction of Plants and Microbes with Waste ................................................................7C-14

A. Greenhouse and Field Studies ............................................................................................................7C-15

B. Assessing Plant and Microbial Uptake Rates ........................................................................................7C-16

C. Effects of Waste on Plant and Microbe Growth....................................................................................7C-17

D. Grazing and Harvesting Restrictions....................................................................................................7C-18

V. Considering Direct Exposure, Ecosystem Impacts, & Bioaccumulation of Waste..................................7C-18

VI. Accounting for Climate ........................................................................................................................7C-19

VII. Calculating An Agronomic Application Rate ........................................................................................7C-19

VIII.Monitoring ..........................................................................................................................................7C-21

IX. Odor Controls ......................................................................................................................................7C-22

Designing a Land Application Program Activity List ..................................................................................7C-23

Resources....................................................................................................................................................7C-24

Tables:

Table 1: Summary of Important Waste Parameters ....................................................................................7C-4

Table 2: Salinity Tolerance of Selected Crops ..........................................................................................7C-10

Table 3: EC and SAR Levels Indicative of Saline, Sodic, and Saline-Sodic Soils ......................................7C-11

Figures:

Figure 1: A Recommended Framework for Evaluating Land Application ..................................................7C-3

Figure 2: The Nitrogen Cycle ....................................................................................................................7C-7
Protecting Ground Water—Designing A Land Application Program 

7C-1

L

and application can be a beneficial

and practical method for treating and

disposing of some wastes. Because

land application does not rely on liners to contain waste, however, there

are some associated risks. With proper planning

and design, a land application program can

meet waste management and land preservation

goals, and avoid negative impacts such as noxious odors, long-term damage to soil, and

releases of contaminants to ground water, surface water, or the air. This chapter describes and

recommends a framework for addressing a variety of waste parameters, in addition to the constituents outlined in Chapter 7, Section

A—Assessing Risk,1 and other factors such as

soil properties and plant and microbial nutrient

use2 that can affect the ability of the land to

safely assimilate directly applied waste.

Successful land application programs address

the interactions among all these factors. 

Some of the benefits of land application

include: 

• Biodegradation of waste. If a waste

stream contains sufficient organic

material, plants and microorganisms

can significantly biodegrade the

waste, assimilating its organic components into the soil. After allowing sufficient time for assimilation of the

waste, more waste can be applied to a

given site without significantly

increasing the total volume of waste at

the site. This is in contrast to landfills

and waste piles, in which waste accumulates continually and generally

does not biodegrade quickly enough

to reduce its volume significantly.

• Inclusion of liquids. Land application units can accept bulk, non-containerized liquid waste. The water

1 The constituents incorporated in IWEM, including the heavy metals and synthetic organic chemicals,

typically have little or no agricultural value and can threaten human health and the environment even

in small quantities. The term “waste parameters” as used in this section refers to some additional constituents such as nitrogen and biodegradable organic matter and other site-specific properties such as

pH, that can have considerable agricultural significance and that can significantly impact human health

and the environment. 

2 40 CFR Part 503 specifies requirements for land application of sludge from municipal sewage treatment

plants. The Part 503 regulations apply to sewage sludge (now generally referred to as “biosolids”) or

mixtures of sewage sludge and industrial process wastes, not to industrial wastes alone. Some of the

specifications in Part 503, for example those concerning pathogens, might be helpful in evaluating land

application of industrial wastes. For mixtures of sewage sludge and industrial waste, the ground-water

and air risk assessments and the framework laid out in the Guide can help address constituents that are

not covered under the Part 503 regulations.

Designing A Land Application Program

This chapter will help you:

• Assess the risks associated with waste constituents when considering application directly to the land as a soil amendment, or for

treatment, or disposal. 

• Account for the designated ground-water constituents identified in

Chapter 7, Section A—Assessing Risk, as well as other waste parameters such as soil properties and plant and microbial interactions. 

• Evaluate the capacity of the soil, vegetation, and microbial life to

safely assimilate the waste when developing an application rate.
7C-2

Protecting Ground Water—Designing A Land Application Program 

3 EPA has signed agreements with states, industries, and individual sites concerning land application. One

example is EPA’s Memorandum of Understanding (MOU) between the American Forest and Paper

Association (AFPA) and the U.S. EPA Regarding the Implementation of the Land Application Agreements

Among AF&PA Member Pulp and Paper Mills and the U.S. EPA, January 1994. For more information on

this MOU contact either AFPA’s Director of Industrial Waste Programs at 111 19th Street, N.W.,

Washington, D.C. 20036 or EPA’s Director of the Office of Pollution Prevention and Toxics.

content of some liquid wastes make

them desirable at land application

sites in arid climates. When managing

liquid waste, land application can

reduce the need for expensive dewatering processes.

• Improvement of soil. Applying waste

directly to land can improve soil quality if the waste contains appropriate

levels of biodegradable organic matter

and nutrients. Nutrients can improve

the chemical composition of the soil

to the extent that it can better support

vegetation, while biodegradable organic matter can improve its physical

properties and increase its water

retention capacity. This potential for

chemical and physical improvements

through land application have led to

its use in conditioning soil for agricultural use.

Figure 1 outlines a framework for evaluating land application. This framework incorporates both the ground-water risk assessment

methodology recommended in Chapter 7,

Section A–Assessing Risk, as well as the other

waste parameters and factors important to

land application. 

I. Identifying

Waste

Constituents for

Land Application

If a waste leachate contains any of the constituents covered in the IWEM ground-water

model, you should first check with a federal,

state, or other regulatory agency to see if the

waste constituents identified in the waste are

covered by any permits, MOUs, or other agreements concerning land application. The Guide

does not supersede or modify conditions established in regulatory or other binding mechanisms, such as MOUs or agreements.3

Some wastes might be designated by state

or local regulators as essentially equivalent to

a manufactured product or raw material. Such

designations usually are granted only when

use of the designated waste would not present

a greater environmental and health risk than

would use of the manufactured or raw material it replaces. Equivalence designations are

included in the category of “other agreements”

above. If there are no designated ground-water

constituents other than those on which the

designation is based, then the guidelines

described in this chapter can help you to

determine an appropriate application rate.

If the constituent(s) identified in the waste

is not currently covered under an agreement,

IWEM or another site-specific model can help

you determine whether land application of the

constituent(s) will be protective of ground

water. In some cases, pollution prevention or

treatment can lower constituents levels so that

a waste can be land applied. In other cases,

land application might not be feasible. In this

event, you should pursue other waste management options. If your modeling results indicate that the constituents can be land applied,

then the guidelines described in this chapter

can once again help you to determine an

appropriate application rate.

Your modeling efforts should consider both

the direct exposure and ecosystem pathways.

These pathways are extremely important in

land application since waste is placed on the

land and attenuated by the natural environment rather than contained by an engineered

structure. 
Protecting Ground Water—Designing A Land Application Program 

7C-3

Figure 1. A Recommended Framework for Evaluating Land Application

Evaluate application

rate. If waste stream

exceeds rate, consider

additional management

measures

Identify waste constituents

Evaluate waste 

parameters

Follow terms of

permit, MOU,

or agreement

Yes

No

Evaluate IWEM constituents identified in

the waste to determine whether land application is protective of ground water using

IWEM or other risk assessment tool

No

Constituents should not be land applied

and you should treat wastes and 

reassess land application potential or

identify other disposal options

Yes

Perform waste characterization

• Ground-water constituents

• Other waste parameters

Are all IWEM constituents identified in the waste

covered by permit, MOU, or other agreement?*

Measure soil 

parameters

Study interaction of 

plants and microbes

with waste 

Consider direct exposure, ecosystem

impacts, and bioaccumulation of waste 

Account for climate

Calculate agronomic

application rate

* All constituents should have been

assessed and shown not to be a risk, or are

addressed by constituents directly covered

by MOU, permit, or other agreement.
7C-4

Protecting Ground Water—Designing A Land Application Program 

II. Evaluating

Waste

Parameters

In addition to the ground-water constituents designated in Chapter 7, Section

A–Assessing Risk, you should evaluate the

waste’s total solids content, pH, biodegradable

matter, pathogens, nutrients, metals, carbon

to nitrogen ratio, soluble salts, and calcium

carbonate equivalent when considering land

application. These parameters provide the

basis for determining an initial waste application rate and are summarized in Table 1. After

the initial evaluation, you should sample and

characterize the waste on a regular basis and

after process changes that might affect waste

characteristics to help determine whether you

should change application practices or consider other waste management options.

A. Total Solids Content

Total solids content indicates the ratio of

solids to water in a waste. It includes both

suspended and dissolved solids, and is usually expressed as a percentage of the waste.

Waste Parameter Significance

Total solids content Indicates ratio of solids to water in waste and influences application

method.

pH Controls metals solubility (and therefore mobility of metals toward

ground water) and affects biological processes.

Biodegradable organic matter Influences soil’s water holding capacity, cation exchange, and other

physical and chemical properties, including odor.

Nutrients (nitrogen, phosphorus, Affect plant growth; nitrogen is a major determinant of application rate; 

and potassium) can contaminate ground water or cause phytotoxicity if applied in

excess.

Carbon to nitrogen ratio Influences availability of nitrogen to plants.

Soluble salts Can inhibit plant growth, reduce soil permeability, and contaminate

ground water.

Calcium carbonate equivalent Measures a waste’s ability to neutralize soil acidity.

Pathogens Can threaten public health by migrating to ground water or being carried by surface water, wind, or other vectors.

Ground-water constituents Can present public health risk through ground-water contamination, 

designated in Chapter 7, Section A– direct contact with waste-soil mix, transport by surface water, and 

Risk Assessment including metals accumulation in plants. Metals inhibit plant growth and can be 

and organic chemicals phytotoxic at elevated concentrations. Zinc, copper, and nickel are

micronutrients essential to plant growth, but can inhibit growth at high

levels.

Table 1

Summary of Important Waste Parameters
Protecting Ground Water—Designing A Land Application Program 

7C-5

Total solids content depends on the type of

waste, as well as whether the waste has been

treated prior to land application. If waste is

dried, composted, dewatered, thickened, or

conditioned prior to land application, water

content is decreased, thereby increasing the

total solids content (for some dry, fine, particulate wastes, such as cement kiln dust, conditioning might involve adding water).4

Understanding the total solids content will

help you develop appropriate storage and

handling procedures and establish an application rate. Total solids content also can affect

your choice of application method and equipment. Some methods, such as spray irrigation, might not work effectively if the solids

content is too high. If it is low, meaning liquid content is correspondingly high, waste

transportation costs could increase. If the

total solids content of the waste is expected

to vary, you can select equipment to accommodate materials with a range of solids content. For example, selecting spreaders that

will not clog if the waste is slightly drier than

usual will help operations run more efficiently and reduce equipment problems.

B. pH

A waste’s pH is a measure of its acidic or

alkaline quality. Most grasses and legumes, as

well as many shrubs and deciduous trees,

grow best in soils with a pH range from 5.5

to 7.5. If a waste is sufficiently acidic or alkaline5 to move soil pH out of that range, it can

hamper plant growth. Acidic waste promotes

leaching of metals, because most metals are

more soluble under acidic conditions than

neutral or alkaline conditions. Once in solution, the metals would be available for plant

uptake or could migrate to ground water.

Alkaline conditions inhibit movement of

most metals. Extreme alkalinity, where pH is

greater than 11, impairs growth of most soil

microorganisms and can increase the mobility

of zinc, cadmium, and lead.

Aqueous waste with a pH of 2 or less or a

pH of 12.5 or more meets the definition of

hazardous waste under federal regulations (40

CFR 261.22(a)). If the pH of a waste makes it

too acidic for land application, you can consider adjusting waste pH before application.

Lime is often used to raise pH, but other

materials are also available. The pH is also

important to consider when developing waste

handling and storage procedures.

4 Some states consider composted materials to no longer be wastes. Consult with the regulatory agency

for applicable definitions.

5 A pH of 7 is neutral. Materials with pH less than 7 are acidic, while those with pH greater than 7 are

alkaline.

Source: Ag-Chem Equipment Co., Inc.

Reprinted with permission

Source: Ag-Chem Equipment Co., Inc.

Reprinted with permission

Source: Ag-Chem Equipment Co., Inc.

Reprinted with permission
7C-6

Protecting Ground Water—Designing A Land Application Program 

C. Biodegradable Organic

Matter

Wastes containing a relatively high percentage of biodegradable organic matter have

greater potential as conditioners to improve

the physical properties of soil. The percentage

of biodegradable organic matter in soil is

important to soil fertility, as organic matter

can add nutrients; serve as an absorption and

retention site for nutrients; and provide chemical compounds, such as chelating agents, that

help change nutrients into more plant-available forms. The content of biodegradable

organic matter is typically expressed as a percentage of sample dry weight.

Biodegradable organic matter also influences soil characteristics. Soils with high

organic matter content often have a darker

color (ranging from brown to black), increased

cation exchange capacity—capacity to take up

and give off positively charged ions—and

greater water holding capacity. Biodegradable

organic matter also can help stabilize and

improve the soil structure, decrease the density

of the material, and improve aeration in the

soil. In addition, organic nutrients are less likely than inorganic nutrients to leach.

How can biodegradable organic

matter affect the waste application rate?

While organic materials provide a significant source of nutrients for plant growth,

decomposition rates can vary significantly

among materials. Food processing residues, for

example, generally decompose faster than

denser organic materials, such as wood chips.

It is important to account for the decomposition rate when determining the volume, rate

and frequency of waste application. Loading

the soil with too much decomposing organic

matter (such as by applying new waste before

a previous application of slowly decomposing

waste has broken down) can induce nitrogen

deficiency (see section D. below) or lead to

anaerobic conditions.

D. Nutrients

Nitrogen, phosphorus, and potassium are

often referred to as primary or macro-nutrients and plants use them in large amounts.

Plants use secondary nutrients, including sulfur, magnesium, and calcium, in intermediate

quantities. They use micronutrients, including iron, manganese, boron, chlorine, zinc,

copper, and molybdenum, in very small

quantities. Land application is often used to

increase the supply of these nutrients, especially the primary nutrients, in an effort to

improve plant growth.

Nutrient levels are key determinants of

application rates. Excessive soil nutrient levels, caused by high waste application rates,

can be phytotoxic or result in contamination

of ground water, soil, and surface water.

Nutrient loading is dependent on nutrient

levels in both the waste and the soil, making

characterization of the soil, as well as of the

waste, important.

Nitrogen. Nitrogen content is often the

primary factor determining whether a waste

is agriculturally suitable for land application,

and, if so, at what rate to apply it. Nitrogen

deficiency is detrimental to the most basic

plant processes, as nitrogen is an essential

element for photosynthesis. Sufficient nitrogen promotes healthy growth and imparts a

dark green color in vegetation. Lack of nitrogen can be identified by stunted plant growth

and pale green or yellowish colored vegetation. Extreme nitrogen deficiency can cause

plants to turn brown and die. On the other

extreme, excessive nitrogen levels can result

in nitrate leaching, which can contaminate

ground-water supplies.
Protecting Ground Water—Designing A Land Application Program 

7C-7

6 U.S. Department of Agriculture, Agricultural Research Service. Agricultural Phosphorus and

Eutrophication, 1999. Washington, DC.

Although nitrate poses the greatest threat

to ground water, nitrogen occurs in a variety

of forms including ammonium, nitrate,

nitrite, and organic nitrogen. These forms

taken together are measured as total nitrogen.

You should account for the ever-occurring

nitrogen transformations that take place in

the soil before and after waste is applied.

These transformations are commonly

described as the nitrogen cycle and are illustrated below in Figure 2.

Phosphorus. Phosphorus plays a role in

the metabolic processes and reproduction of

plants. When soil contains sufficient quantities of phosphorus, root growth and plant

maturation improve. Conversely, phosphorus-deficient soils can cause stunted plant

growth. Excessive phosphorus can lead to

inefficient use of other nutrients and, at

extreme levels, zinc deficiency. High phosphorus usage on crops and its associated

runoff into surface water bodies has increased

the biological productivity of surface waters

by accelerating eutrophication, which is the

natural aging of lakes or streams brought on

by nutrient enrichment.6 Eutrophication has

been identified as the main cause of impaired

surface water quality in the United States.

Potassium. Potassium is an essential

nutrient for protein synthesis and plays an

important role in plant hardiness and disease

tolerance. In its ionic form (K+

), potassium

helps to regulate the hydration of plants. It

also works in the ion transport system across

cell membranes and activates many plant

enzymes. Like other nutrients, symptoms of

deficiencies include yellowing, burnt or

dying leaves, as well as stunted plant growth.

Symptoms of potassium deficiency also, in

certain plants, can include

reduced disease resistance and

winter hardiness.

How can I take nutrient

levels into account?

You should develop a nutrient management plan that

accounts for the amount of

nitrogen, phosphorus, and

potassium being supplied by all

sources at a site. The U.S.

Department of Agriculture,

Natural Resources Conservation

Service has developed a conservation practice standard

“Nutrient Management” Code 590 that can

be used as the basis for your nutrient management plan. The purpose of this standard

is to budget and supply nutrients for plant

production, to properly utilize manure or

organic by-products as a plant nutrient

source, to minimize agricultural nonpoint

source pollution of surface and ground-water

resources, and to maintain or improve the

physical, chemical, and biological condition

of the soil. Updated versions of this standard

can be obtained from the Internet at

<www.nrcs.usda.gov/technical/ECS/

nutrient/documents.html>.

Nitrogen is generally the most limiting

nutrient in crop production systems and is

added to the soil environment in the greatest

Figure 2. The Nitrogen Cycle

Gaseous

Losses (N2, NOx)

Denitrification

Nitrates

(NO3)

Leaching

Nitrification

Plant

Consumption

Precipitation

Nitrites (NO2)

Clay

Minerals

Micelle

Fixation

Ammonium (NH4)

Nitrification

Mineralization

Organic Matter

(R-NH2)

Organic Residues
7C-8

7 Nutrient Management Software: Proceedings from the Nutrient Management Software Workshop. To

order, call NRAES at 607 255-7654 and request publication number NRAES-100.

Protecting Ground Water—Designing A Land Application Program 

amount of any of the plant nutrients. If, however, waste application rates are based solely

on nitrogen levels, resulting levels of other

nutrients such as phosphorus and potassium

can exceed crop needs or threaten ground

water or surface water bodies. You should

avoid excessive nutrient levels by monitoring

waste concentrations and soil buildup of

nutrients and reducing the application rate as

necessary, or by spacing applications to allow

plant uptake between applications. Your

local, state, or regional agricultural extension

service might have already developed materials on or identified software for nutrient

management planning. Consult with them

about the availability of such information.

Northeast Regional Agricultural Engineering

Services (NRAES) Cooperative Extension, for

example, has compiled information on nutrient management software programs.7

E. Metals

A number of metals are included in IWEM

for evaluating ground-water risk. Some metals,

such as zinc, copper, and manganese, are

essential soil micronutrients for plant growth.

These are often added to inorganic commercial

fertilizers. At excessive concentrations, however, some of these metals can be toxic to

humans, animals, and plants. High concentrations of copper, nickel, and zinc, for example,

can cause phytotoxicity or inhibit plant

growth. Also, the uptake and accumulation of

metals in plants depends on a variety of plant

and soil factors, including pH, biodegradable

organic matter content, and cation exchange

capacity. Therefore, it is important to evaluate

levels of these metals in waste, soil, and plants

from the standpoint of agricultural significance

as well as health and environmental risk.

How can I determine acceptable

metal concentrations?

The Tier I and II ground-water models can

help you identify acceptable metals concentrations for land application. Also it is important

to consult with your local, state, or regional

agriculture extension center on appropriate

nutrient concentrations for plant growth. If the

risk evaluation indicates that a waste is appropriate for land application, but subsequent soil

or plant tissue testing finds excessive levels of

metals, you can consider pretreating the waste

with a physical or chemical process, such as

chemical precipitation to remove some metals

before application. 

F. Carbon-to-Nitrogen Ratio

The carbon-to-nitrogen ratio refers to the

relative quantities of these two elements in a

waste or soil. Carbon is associated with

organic matter, and the carbon-to-nitrogen

ratio reflects the level of inorganic nitrogen

available. Plants cannot use organic nitrogen,

but they can absorb inorganic nitrogen such

as ammonium. For many wastes, the carbonto-nitrogen ratio is computed as the dry

weight content of organic carbon divided by

the total nitrogen content of waste.

Some wastes rich in organic materials (carbon) can actually induce nitrogen deficiencies. This occurs when wastes provide carbon

in quantities that microbes cannot process

without depleting available nitrogen. Soil

microbes use carbon to build cells and nitrogen to synthesize proteins. Any excess organic nitrogen is then converted to inorganic

nitrogen, which plants can use. The carbonto-nitrogen ratio tells whether excess organic

nitrogen will be available for this conversion.

When the carbon-to-nitrogen ratio is less

than 20 to 1—indicating a high nitrogen content—organic nitrogen is mineralized, or con-
Protecting Ground Water—Designing A Land Application Program 

7C-9

verted from organic nitrogen to inorganic

ammonium, and becomes available for plant

growth. For maximal plant growth, the literature recommends maintaining a ratio below

20 to 1. When the carbon-to-nitrogen ratio is

in the range of 20 to 1 to 30 to 1—a low

nitrogen content—soil micro-organisms use

much of the organic nitrogen to synthesize

proteins, leaving only small excess amounts

to be mineralized. This phenomenon, known

as immobilization, leaves little inorganic

nitrogen available for plant uptake. When the

carbon-to-nitrogen ratio is greater than 30 to

1, immobilization is the dominant process,

causing stunted plant growth. The period of

immobilization, also known as nitrogen or

nitrate depression, will vary in length

depending on the decay rate of the organic

matter in the waste. As a result, plant growth

within that range might not be stunted, but is

not likely to be maximized.

How can I manage changing 

carbon-to-nitrogen ratios?

The cycle of nitrogen conversions within

the soil is a complex, continually changing

process (see Figure 2). As a result, if applying

waste based only on assumed nitrogen mineralization rates, it is often difficult to ensure

that the soil contains sufficient inorganic

nitrogen for plants at appropriate times. If

you are concerned about reductions in crop

yield, you should monitor the soil’s carbonto-nitrogen ratio and, when it exceeds 20 to

1, reduce organic waste application and/or

supplement the naturally mineralized nitrogen with an inorganic nitrogen fertilizer, such

as ammonium nitrate. Methods to measure

soil carbon include EPA Method 9060 in Test

Methods for Evaluating Solid Waste,

Physical/Chemical Methods—SW-846. Nitrogen

content can be measured with simple laboratory titrations.

G. Soluble Salts

The term soluble salts refers to the inorganic

soil constituents (ions) that are dissolved in the

soil water. Major soluble salt ions include calcium (Ca2+), magnesium (Mg2+), sodium (Na+

),

potassium (K+

), chloride (Cl-), sulfate (SO4

2-),

bicarbonate (HCO3

-

), and nitrate (NO3

-

). Total

dissolved solids (TDS) refers to the total

amount of all minerals, organic matter, and

nutrients that are dissolved in water. The soluble salt content of a material can be determined

by analyzing the concentration of the individual constituent ions and summing them, but

this is a lengthy procedure. TDS of soil or

waste can reasonably be estimated by measuring the electrical conductivity (EC) of a mixture

of the material and water. EC can be measured

directly on liquid samples. TDS is found by

multiplying the electrical conductivity reading

in millimhos/cm (mmhos/cm) by 700 to give

TDS in parts per million (ppm) or mg/l.

Soluble salts are important for several reasons. First, saline soil, or soil with excessive

salt concentrations, can reduce plant growth

and seed germination. As salt concentration

in soil increases, osmotic pressure effects

make it increasingly difficult for plant roots to

extract water from the soil. Through a certain

range, this will result in reduced crop yield,

up to a maximum beyond which crops will

be unable to grow. The range and maximum

for a few representative crops are shown in

Table 2. For this reason, the salt content of

the waste, rather than its nitrogen content,

can be the primary determinant of its agricultural suitability for land application, especially on irrigated soils in arid regions.

The second reason soluble salts are important is that sodic soil, or soil with excessive

levels of sodium ions (Na+

) relative to divalent ions (Ca2+, Mg2+), can alter soil structure

and reduce soil permeability. The sodium

absorption rate (SAR) of a waste is an indicator of its sodicity. To calculate the SAR of a
7C-10

Protecting Ground Water—Designing A Land Application Program 

waste or soil, determine the Na+, Ca2+, and

Mg2+ concentrations in milliequivalents per

liter8 for use in the following equation:9

Soils characterized by both high salts

(excessive TDS as indicated by EC) and

excessive sodium ions (excessive Na+ as indicated by SAR) are called saline-sodic soils,

and can be expected to have the negative

characteristics of both saline soils and sodic

soils described above. Table 3 displays EC

and SAR levels indicative of saline, sodic, and

saline-sodic soils. 

The third reason soluble salts are important is that specific ions can induce plant toxicities or contaminate ground water. Sodium

and chloride ions, for example, can become

phytotoxic at high concentrations. To assess

sodic- or toxic-inducing characteristics, you

should conduct an analysis of specific ions in

addition to measuring EC.

What can I do if a waste is either

saline or sodic?

Saline waste. If a waste is saline, careful

attention to soil texture, plant selection, and

application rate and timing can help. Coarse

soils often have a lower clay content and are

less subject to sodium-induced soil structure

8 The term milliequivalents per liter (meq/l) expresses the concentration of a dissolved substance in

terms of its combining weight. Milliequivalents are calculated for elemental ions such as Na+, Ca2+, and

Mg2+ by multiplying the concentration in mg/l by the valence number (1 for Na+, 2 for Ca2+ or Mg2+)

and dividing by the atomic weight (22.99 for Na+, 40.08 for Ca2+, or 24.31 for Mg2+).

9 If the proper equipment to measure these concentrations is not available, consider sending soil and

waste samples to a soil testing laboratory, such as that of the local extension service (visit <www.reeusda.gov/statepartners/usa.htm> for contact information) or nearby university. Such a laboratory will be

able to perform the necessary tests and calculate the SAR.

Source: Borrelli, J. and D. Brosz. 1986. Effects of Soil Salinity on Crop Yields.

a A rule of thumb from the irrigation industry holds that soil salinity will be 11⁄2 times the salinity of applied

irrigation water. The effect that waste salinity will have on soil salinity, however, is not as easily predicted

and depends on the waste’s water content and other properties and on the application rate.

b Reductions are stated as a percentage of maximum expected yield.

Soil Salinity (mmhos/cm) a that will result in:

Crop 0% yield 50% yield 100% yield

reductionb reductionb reductionb

Alfalfa 2.0 8.8 16

Bermuda grass 6.9 14.7 23

Clover 1.5 10.3 19

Perennial rye 5.6 12.1 19

Tall fescue 3.9 13.3 32

Table 2: 

Salinity Tolerance of Selected Crops

SAR =

Na+

1⁄2(Ca2+ + Mg2+)
problems. While coarse soils help minimize

soil structural problems associated with salinity, they also have higher infiltration and permeability rates, which allow for more rapid

percolation or flushing of the root zone. This

can increase the risk of waste constituents

being transported to ground water.

Since plants vary in their tolerance to

saline environments, plant selection also is

important. Some plant species, such as rye

grass, canary grass, and bromegrass, are only

moderately tolerant and exhibit decreased

growth and yields as salinity increases. Other

plants, such as barley and bermuda grass, are

more saline-tolerant species.

You should avoid applying high salt content waste as much as possible. For saline

wastes, a lower application rate, and thorough tilling or plowing can help dilute the

overall salt content of the waste by mixing it

with a greater soil volume. To avoid the

inhibited germination associated with saline

soils, it also can help to time applications of

high-salt wastes well in advance of seedings.

Sodic waste. SAR alone will not tell how

sodium in a waste will affect soil permeability;

it is important to investigate the EC of a waste

as well. Even if a waste has a high SAR, plants

might be able to tolerate this level if the waste

also has an elevated EC. As with saline waste,

for sodic waste select a coarser-textured soil to

help address sodium concerns. Adding gypsum (CaSO4) to irrigation water can also help

to reduce the SAR, by increasing soil calcium

levels. Although this might help address sodium-induced soil structure problems, if choosing to add constituents to alter the SAR, the

EC should also be monitored to ensure salinity levels are not increased too much.

H. Calcium Carbonate

Equivalent

Calcium carbonate equivalent (CCE) is

used to measure a waste’s ability to neutralize

soil acidity—its buffering capacity—as compared with pure calcium carbonate. Buffering

capacity refers to how much the pH changes

when a strong acid or base is added to a solution. A highly buffered solution will show

only a slight change in pH when strong acids

or bases are added. Conversely, if a solution

has a low buffering capacity, its pH will

change rapidly when a base or acid is added

to it. If a waste has a 50 percent CCE, it

would need to be applied at twice the rate of

pure calcium carbonate to achieve the same

buffering effect.

I. Pathogens

Potential disease-causing microorganisms

or pathogens, such as bacteria, viruses, protozoa, and the eggs of parasitic worms, might

be present in certain wastes. Standardized

Protecting Ground Water—Designing A Land Application Program 

7C-11

Source: Fipps, G. Managing Irrigation Water Salinity In the Lower Rio Grande Valley.

a

In units of mmhos/cm bdimensionless

Soil Characterization

Normal Saline Sodic Saline-Sodic

ECa < 4 and EC > 4 SAR> 13 EC > 4 and

SARb < 13 SAR > 13

Table 3

EC and SAR Levels Indicative of Saline, Sodic, and Saline-Sodic Soils
testing procedures are available to help determine whether a waste contains pathogens.

You should consider using such tests especially if your process knowledge indicates

that a waste might contain pathogens. Fecal

coliform bacteria can be quantified, for example, by using a membrane filtering technique,

which involves passing liquid waste through

a filter, incubating the filtrate (which contains

the bacteria) on a culture medium for 24

hours, and then counting the number of bacterial colonies formed.

How can I reduce pathogenic

risks?

Methods to reduce pathogenic risk include

disinfecting or stabilizing a waste prior to

land application. Examples of treatment

methods recognized for sewage sludge

stabilization are included in the sidebar.

Pathogens present a public health hazard if

they are transferred to food or feed crops,

contained in runoff to surface waters, or

transported away from a land application site

by vectors. If pathogen-carrying vectors are a

concern at a site, it is important to establish

measures to control them. For examples of

methods to control vectors, refer to Chapter

8–Operating the Waste Management System.

Additional information on pathogen reduction and methods to control vectors can be

obtained from 40 CFR 503.15 and 40 CFR

503.32 (EPA’s Sewage Sludge Rule.) A discussion of these alternatives is available in

EPA’s guidance document Land Application of

Sewage Sludge: A Guide for Land Appliers on

the Requirements of the Federal Standards for

the Use or Disposal of Sewage Sludge, 40 CFR

Part 503 (U.S. EPA, 1994a). 

The services of a qualified engineer might

be necessary to design an appropriate process

for reducing pathogens in a waste. You

should consult with the state to determine

whether there are any state-specific requirements for pathogen reductions for specific

waste types.

III. Measuring Soil

Properties

Physical, biological, and chemical characteristics of the soil are key factors in determining its capacity for waste attenuation. If

the soil is overloaded, rapid oxygen depletion, extended anaerobic conditions, and the

accumulation of odorous and phytotoxic

end-products can impair soil productivity

and negatively impact adjacent properties.

With proper design and operation, waste can

be successfully applied to almost any soil;

however, sites with highly permeable soil

(e.g., sand), highly impermeable soil (e.g.,

clay), poorly drained soils, or steep slopes

can present special design issues. Therefore,

it is advisable to give such sites lower priority

during the site selection process.

7C-12

Protecting Ground Water—Designing A Land Application Program 

What are methods for stabilizing

waste prior to land application?

The following methods, recommended

for stabilizing sewage sludge, can also be

useful for reducing pathogens in waste: 

• Aerobic digestion

• Air drying

• Anaerobic digestion

• Composting

• Lime stabilization

More detailed information on each of

these and other methods can be found

in EPA’s Control of Pathogens and Vector

Attraction in Sewage Sludge (U.S. EPA,

1992).
How can I evaluate the soil at a

site?

To help evaluate the soil properties of a

site, you should consult the U.S. Department

of Agriculture (USDA) soil survey for the

prospective area. These surveys provide information on properties such as soil type and

permeability. USDA has prepared soil surveys

for most counties in each state. To obtain a

copy of the survey for an area, contact the

Natural Resource Conservation Service offices,

the county conservation district, the state agricultural cooperative extension service, or local

health authorities/planning agency. These soils

surveys will help during site selection; however, conditions they describe can differ from

the actual soil conditions. 

Several guidance documents on soil surveys are also available from USDA. These

documents include the National Soil Survey

Handbook and the guide Soil Taxonomy: A

Basic System of Soil Classification for Making

and Interpreting Soil Surveys. The National Soil

Survey Handbook provides an abundance of

information including help on interpreting

soil surveys, a primer on soil properties and

soil quality, and guides for predicting the permeability of your soil. Both of these documents are available over the Internet and can

be obtained from <www.ftw.nrcs.usda.gov/

tech_ref.html>.

For more site-specific data on actual soil

conditions, you can sample and characterize

the soil. It might be desirable to have a qualified soil scientist perform this characterization, which often includes soil texture,

percentage of organic matter, depth to water

table, soil pH, and cation exchange capacity.

At a minimum, you should characterize samples from an upper soil layer, 0 to 6 inches,

and a deeper soil layer, 18 to 30 inches, and

follow established soil sampling procedures to

obtain meaningful results. If a detailed characterization is desired, or if it is suspected soil

types vary considerably, further subdivision of

soil horizons or collection of samples over a

greater variety of depths might be appropriate.

For more information about how to obtain

representative soil samples and to submit

them for analysis, you can consult EPA’s

Laboratory Methods for Soil and Foliar Analysis

in Long-Term Environmental Monitoring

Programs (U.S. EPA, 1995d), or state guides,

such as Nebraska’s Guidelines for Soil Sampling,

G91-1000.

Why are chemical and biological

properties of soil important?

Chemical and biological properties of the

soil, like those of the waste, influence the

attenuation of waste constituents. These

properties include pH, percentage of organic

matter, and cation exchange capacity. Affected

attenuation processes in the soil include

absorption, adsorption, microbial degradation, biological uptake, and chemical precipitation. For example, adsorption—the process

by which molecules adhere to the surface of

other particles, such as clay—increases as the

cation exchange capacity and pH of the soil

increase. Cation exchange capacity, in turn, is

dependent on soil composition, increasing as

the clay content of the soil increases.

Adsorption through cation exchange is an

important means of immobilizing metals in

the soil. Organic chemicals, on the other

hand, are negatively charged and can be

adsorbed through anion exchange, or the

exchange of negative ions. A soil’s capacity for

anion exchange increases as its pH decreases.

Why are physical properties of

soil important?

Physical properties of the soil such as texture, structure, and pore-size distribution affect

infiltration rates and the ability of soil to filter

or entrap waste constituents. Infiltration and

permeability rates decrease as clay content

Protecting Ground Water—Designing A Land Application Program 

7C-13
increases. Sites with soils with permeabilities

that are too high or too low have lower land

application potential. Soils with high permeability can allow wastes to move through without adequate attenuation. Soils with low

permeability can cause pooling or excessive

surface runoff during intense rainstorms.

Excessive runoff conditions can be compensated for somewhat by minimizing surface slope

during site selection. Soils with low permeability are also prone to hydraulic overloading.

The amount of liquid that can be assimilated by a soil system is referred to as its

hydraulic loading capacity. In addition to a

soil’s permeability, hydraulic loading capacity

is dependent on other factors such as climate, vegetation, site characteristics, and

other site-specific soil properties such as soil

type, depth to seasonally high water table,

slope and erodibility, water intake rate, and

underlying geology and hydrogeology.

Exceeding the hydraulic loading capacity of a

site, can lead to rapid leaching of waste constituents into ground water, reduction in biological activity, sustained anaerobic

conditions, soil erosion, and possible contamination of surface waters. It can also result

in excessive evaporation, which can cause

excessive odor and unwanted airborne emissions. In order to avoid hydraulic overloading at a site, application of liquid or

semi-liquid waste or wastewater should be

managed so uncontrolled runoff or prolonged

saturation of the soil does not occur.

An important indicator of soil properties is

its topography, which affects the potential for

soil erosion and contaminated surface-water

runoff. Soils on ridge tops and steep slopes

are typically well drained, well aerated, and

shallow. Steep slopes, however, increase the

likelihood of surface runoff of waste and of

soil erosion into surface waters. State guidelines, therefore, often specify the maximum

slopes allowable for land application sites for

various waste characteristics, application

techniques, and application rates. The agencies that regulate land application in a state

can provide specific guidance concerning

slopes. Soils on concave land and broad flat

lands, on the other hand, frequently are

poorly drained and can be waterlogged during part of the year. Soils in relatively flat

areas can have intermediate properties with

respect to drainage and runoff and could be

more suitable for land application.

IV. Studying the

Interaction of

Plants and

Microbes with

Waste

The next step in the design of a land

application unit is to consider the plants and

microbes at the site and how they will interact with the waste. This interaction includes

the uptake and degradation of waste constituents, the effects of the wastes on plant

and microbial growth, and changes that can

occur in plants or crops affecting their use as

food or feed. The uptake of nutrients by

plants and microbes on plant roots or in soil

affects the rate of waste assimilation and

biodegradation, usually increasing it. 

It might be necessary to conduct greenhouse or field studies or other tests of plants,

soil, and microbes to understand and quantify these interactions. You should consult with

the state agricultural department, the local

health department, and other appropriate

agencies if considering land application of

wastes containing designated ground-water

constituents or other properties that are

potentially harmful to food or feed crops.

Industry groups might also be able to provide information about plants with which

they have land application experience.

7C-14

Protecting Ground Water—Designing A Land Application Program 
A. Greenhouse and Field

Studies

State agricultural extension services, departments of environmental protection, or public

universities might have previous studies about

plant uptake of nutrients, especially nitrogen,

phosphorus, and potassium, but it is important to recognize that the results of studies

conducted under different conditions (such as

different waste type, application rate, plant

type, or climate) are only partially relevant to a

specific situation. Furthermore, most studies to

date have focused on relatively few plant

species, such as corn, and only a handful of

constituents, typically metals. Greenhouse

studies or pilot-scale field studies attempt to

model site-specific conditions by growing the

intended crops in soil from the prospective

application site. These studies are useful

because individual parameters can be varied,

such as plant type and waste application rate,

to determine the effects of each factor.

Additionally, greenhouse or field studies might

be required by some states to certify that a

waste has agricultural benefits. Generally, the

first point of contact for assistance with studies

is the state agricultural extension service. Many

state extensions can conduct these studies;

others might be able to provide guidance or

expertise but will recommend engaging a private consultant to conduct the studies.

How do I conduct greenhouse or

field studies?

Currently, no national guidelines exist for

conducting greenhouse or field studies,10 but

check to see if the state has guidance on

accepted practices. Working with a state agricultural extension service or a local university

will provide the benefit of their expertise and

experience with local conditions, such as

which plants are suitable for local soils and

climate. If a particular industry sector has a

large presence in a state, the state agricultural

extension service might have previous experience with that specific type of waste.

Greenhouse studies. Aside from their

smaller scale, greenhouse studies differ from

field studies primarily in that they are conducted indoors under controlled conditions,

while field studies are conducted under natural environmental conditions. A greenhouse

study typically involves distributing representative soil samples from the site into several

pots to test different application rates, application methods, and crops. Using several

duplicate pots for each rate, method, or crop

allows averaging and statistical aggregating of

results. It is also important to establish control pots, some with no waste and no plants,

others with waste but no plants (to observe

the extent to which waste assimilation effects

are due to soil and pre-existing microbes) and

still others with plants but without waste (as

a baseline for comparison with waste-amended plant growth).

To the

extent

feasible,

temperature,

moisture, and

other

parameters should simulate actual site conditions.

There should be a series of several duplicate

pots grown with each combination of plant

type, application rate, and other parameters.

Pots should be arranged to avoid environmental conditions disproportionately affecting

one series of pots. For example, you should

avoid placing a whole series of pots in a row

closest to a light source; instead, it is better to

place one pot from each of several series in

that row or randomize placement of pots.

The controlled greenhouse environment

allows the study of a wide range of waste-soil

Protecting Ground Water—Designing A Land Application Program 

7C-15

10 Based on conversations with Dr. Rufus L. Chaney and Patricia Milner, U.S. Department of Agriculture.
interactions without risking the loss of plants

due to weather, animal hazards, and other

environmental influences. At the same time,

this can introduce differences from actual

conditions. Root confinement, elevated soil

temperature, and rapidly changing moisture

levels, for example, can increase the uptake

of pollutants by potted plants compared to

uptake under field conditions.11

Field studies. Field studies, on the other

hand, can test application rates and crops on

plots at the actual proposed site. As with

greenhouse studies, duplicate plots are useful

for statistical purposes, and controls are

needed. Field study data can be more useful

because it more closely reflects real-world

conditions, but it also can be more difficult

to obtain because of uncontrollable circumstances such as flooding or unusual pest

damage that can occur at the time of the

study. Field studies also can be subject to siting, health and safety, and permitting

requirements.

Field studies also help determine the actual land area required for land application and

the quality of runoff generated. Soil and

ground-water monitoring help to confirm

that waste constituents are being taken up by

plants and not leaching into the ground

water. Results from field studies, however,

might not be duplicated on actual working

plots after multiple waste applications, due to

long-term soil changes. Crop yields also can

vary by as much as 15 to 25 percent under

field conditions, even with good fertility and

management.

Both greenhouse and field studies typically

include extensive sampling of waste, soil

before application, plants or representative

parts of plants, soil after application, growth

of plants, and, to the extent feasible, water.

You should sample soil at the surface and in

lower horizons using core sampling. Some

soil tests require mixing samples with water

to form a paste or slurry. Plant tissue tests

often require dry-weight samples, made by

drying cut plants at about 65°C. Water can

be collected in lysimeters (buried chambers

made from wide perforated pipe) and

removed using hand pumps.

The effects of waste on organisms in the

soil can also be monitored during greenhouse

and field studies. The literature suggests, that

the effects of waste on earthworms are a good

indicator of effects on soil organisms in general. It might be worthwhile, therefore, to

stock greenhouse pots or field study plots

with earthworms at the beginning of a study

and monitor the waste constituent levels and

the effects on the worms during and at the

end of the study. Although these brief studies

will not effectively model long-term exposure

to waste constituents, it is possible to gauge

short-term and acute effects.

B. Assessing Plant and

Microbial Uptake Rates

Plants. After performing studies, you

should measure the amounts of various

nutrients, metals, and other constituents in

tissue samples from plants grown in the

greenhouses or on test plots. This tells

approximately how much of these constituents the plants extracted from the soilwaste mix. By measuring plant-extracted

quantities under these various conditions,

you can determine a relationship between

7C-16

11 If a waste contains VOCs, ensure the possibility of VOCs accumulating within the enclosed greenhouse

is addressed.

Protecting Ground Water—Designing A Land Application Program 
plant type, application rate, and nutrient

extraction. From this, you can choose the

conditions which result in the desired uptake

rate while avoiding uptake of designated

ground-water constituents at undesirable

concentrations. Plant uptake is often measured as a ratio of the pollutant load found in

the plants to the pollutant load applied to the

land as illustrated below:

This ratio serves to place pollutant uptake

in the context of the original amount of pollutant applied.

In choosing plants for a land application

unit, you should also consider growing seasons

in relation to periods of waste application rate.

Specific waste application rates associated with

corresponding uptakes of nutrients by plants,

as indicated in greenhouse or field studies, are

applicable only during the growing phases covered by the study. At other times, waste application might be infeasible because plants are

not present to help assimilate waste, or because

plants are too large to permit passage of application equipment without sustaining damage.

Microbes. Certain microbes can biodegrade organic chemicals and other waste constituents. Some accomplish this by directly

using the constituents as a source of carbon

and energy, while others co-metabolize constituents in the process of using other compounds as an energy source. Aerobic microorganisms require oxygen to metabolize waste

and produce carbon dioxide and water as end

products. Anaerobic microbes function without oxygen but produce methane and hydrogen sulfide as end products. These gases can

present a safety risk as well as environmental

threats, and hydrogen sulfide is malodorous.

For these reasons, it is recommended that

you maintain conditions that favor aerobic

microbes.

For many microorganisms, these conditions include a pH of 6 to 8 and temperatures

of 10°C to 30°C. In addition, microbes might

be unable to transfer oxygen from soil efficiently if the moisture content is near saturation, or they might be unable to obtain

sufficient water if the soil is too dry. A water

content of 25 to 85 percent of the soil’s water

holding capacity is recommended in the literature. Oxygen generally is available through

diffusion from the atmosphere, but this

mechanism might provide insufficient oxygen

if there is too little pore space (less than 10

percent of soil volume) or if so much organic

matter is applied that oxygen is consumed

faster than it is replaced.

C. Effects of Waste on

Plant and Microbe

Growth

Greenhouse and field studies can tell what

effect the waste will have on plant growth patterns. A typical method of quantifying plant

growth is to state it in terms of biomass production, which is the dry weight of the cut

plants (or representative parts of the plants). If

the plants grown with waste applications

show greater mass than the control plants,12

the waste might be providing useful nutrients

or otherwise improving the soil. If the plants

grown with waste applied at a certain rate

Protecting Ground Water—Designing A Land Application Program 

7C-17

12 Trends detected in studies assume that results have been subjected to tests of statistical validity before

finding a trend significant.

μg pollutant

per

g dry plant tissue

kg pollutant

hectare
weigh less than the controls, some constituent(s) in the waste might be excessive at

the studied application rate. Comparing the

results from several different application rates

can help find the rate that maximizes growth

and avoids detrimental and phytotoxic effects.

Analyzing soil and water after plant growth

allows for a comparison between the planted

pots or plots against the control to discern the

differences due to plant action. If water samples show excessive nutrient (especially nitrogen) levels at a certain application rate, this

might indicate that the plants were unable to

use all the nutrients in the waste applied at

that rate, suggesting that the application was

excessive. If soil and water tests show that

constituents are consumed, and if other possible causes can be ruled out, microbes might

be responsible. Further investigation of

microbial action might involve sampling of

microbes in soil, counting their population,

and direct measurement of waste constituents

and degradation byproducts.

D. Grazing and Harvesting

Restrictions

If a waste might contain pathogens or designated ground-water constituents, and the

established vegetative cover on the land

application site is intended for animal consumption, it is important to take precautions

to minimize exposure of animals to these

contaminants. This is important because animals can transport pathogens and groundwater constituents from one site to another,

and can be a point of entry for waste constituents and pathogens into the food chain. 

If harvesting crops from a unit for use as

animal fodder, you should test plants for the

presence of undesirable levels of the designated ground-water constituents before feeding. Grazing animals directly on a unit is

discouraged by some states.13 If considering

direct grazing, you should consult with the

state to see if there are any restrictions on

this practice. Growing crops for human consumption on soil amended with waste calls

for even greater caution. In some states, this

practice is prohibited or regulated, and in

states where it is allowed, finding food

processors or distributors willing to purchase

such crops can be difficult.

When testing crops before feeding them

to animals, local agricultural extension services might be able to help determine what

levels are appropriate for animal consumption. If plant tissue samples or findings of a

fate and transport model indicate waste constituent levels inappropriate for animal consumption, it is important that you not use

harvested plants as fodder or allow grazing

on the site. Additionally, plants with high

constituent levels will probably be inappropriate for other agricultural use, and thus

would likely necessitate disposal of such

crops as a waste after harvest.

V. Considering

Direct Exposure,

Ecosystem

Impacts, &

Bioaccumulation

of Waste

You should evaluate the impacts that your

land application unit will have on direct

exposure and ecological pathways as well as

the potential for bioaccumulation of landapplied waste. During the land application

unit’s active life, direct human exposure to

waste or waste-amended soil is primarily a

risk to personnel involved in the operation.

You should follow OSHA standards and

ensure that personnel are properly trained

and use proper protective clothing and equip7C-18

13 Grazing can also be unwise due to potential effects on soil physical structure. The weight of heavy animals can compact soil, decreasing pore space, which can reduce the soil’s waste attenuation capacity.

Protecting Ground Water—Designing A Land Application Program 
ment when working onsite. You should limit

direct exposure to others through steps such

as access control and vehicle washing to prevent tracking waste and waste amended soil

off site. 

Access control will also limit exposure of

some animals. If crops will be used for animal

fodder or grazing, you should test harvested

fodder for the designated ground-water constituents before use and restrict grazing times.

After a site is closed, there might be long-term

access risks to future land uses and the general public. To minimize these risks, long-term

access controls or deed restrictions might be

appropriate. Consult Chapter 11—Performing

Closure and Post-Closure Care for further

information.

Direct exposure of native animals is often

impossible to control and might be an entry

point for the ground-water constituents into

the food chain. Worms, for example, might

be present in the soil and take in these constituents. Birds or other animals could then

consume the worms, bioaccumulate, or be

transported off site. Furthermore, animals can

ingest plants grown on waste-amended soil.

Therefore, you should also consider pathways

such as these in evaluating your plans for

land application.

VI. Accounting for

Climate

Local climate considerations should also

enter into your land application planning

process. For example, wastes that are high in

soluble salts are less appropriate and can have

deleterious effects in arid climates due to the

osmotic pressure from the salts inhibiting root

uptake of water. On the other hand, the downward movement of water in the soil is minimal

in arid climates, making the migration of waste

constituents to ground water less likely.

Climate also determines which plants can

grow in a region and the length of the growing season. If the local climate cannot support the plants that might be most helpful in

assimilating the particular constituents in a

given waste, the use of land application might

be limited to other crops at a lower application rate. If the climate dictates that the part

of the growing cycle during which land application is appropriate is short, a larger area for

land application might be necessary.

There are also operating considerations

associated with climate. Since waste should

not be applied to frozen or very wet soil, the

application times can be limited in cold or

rainy climates. In climates where the ground

can freeze, winter application poses particular

problems even when the ground is not frozen,

because if the ground freezes soon after application, the waste that remained near the soil

surface can run off into surface waters during

subsequent thaw periods. Waste nutrients are

also more likely to leach through the soil and

into the ground water following spring thaw,

prior to crop growth and nutrient uptake.

These problems can be partially solved by

providing sufficient waste storage capacity for

periods of freezing or rainy weather.

VII. Calculating An

Agronomic

Application Rate

The purpose of a land application unit

(i.e., waste disposal versus beneficial use)

helps determine the waste application rate

best suited for that unit. When agricultural

benefits are to be maximized, the application

rate is governed by the agronomic rate. The

objective for determining an agronomic application rate is to match, as closely as possible,

the amount of available nutrients in the waste

with the amount required by the crop. One

Protecting Ground Water—Designing A Land Application Program 

7C-19
example of an equation for calculating agronomic application rates is:

Agronomic application rate = (Crop nutrient uptake × Crop yield)-Nutrient credits

Where:

Crop nutrient uptake = Amount of nutrients absorbed by a particular crop. These

requirements are readily available from

your state and local Cooperative Extension

Offices

Crop yield = Amount of plant available for

harvest. Methods for calculating expected

yields include past crop yields for that

unit, county yield records, soil productivity tables, or local research.

Nutrient credits = Nitrogen residual from

past waste applications, irrigation water

nitrate nitrogen, nutrients from commercial fertilizer, and other nitrogen credits

from atmospheric deposition from dust

and ammonia in rainwater.

In addition, many states and universities

have developed their own worksheets or calculations for developing an agronomic application rate. You should check with your state

agency to see if you are subject to an existing

regulation. In setting a preliminary application rate the crop’s nitrogen requirements

often serve as a ceiling, but in some cases,

phosphorus, potassium, or salt content, rather

than nitrogen, will be the limiting factor. 

How do I determine the agronomic rate?

Computer models can help determine sitespecific agronomic rates. Modeling nitrogen

levels in waste and soil-plant systems can help

provide information about physical and

hydrologic conditions and about climatic

influences on nitrogen transformations.

Models recommended for use with sewage

sludge include Nitrogen Leaching and

Economic Analysis Package (NLEAP);

DECOMPOSITION; Chemicals, Run-Off, and

Erosion from Agricultural Management

Systems (CREAMS); and Ground-Water

Loading Effects of Agricultural Management

Systems (GLEAMS).14 NLEAP is a moderately

complex, field scale model that assesses the

potential for nitrate leaching under agricultural fields. NLEAP can be used to compare

nitrate leaching potential under different soils

and climates, different cropping systems, and

different management scenarios. The computer model DECOMPOSITION is specifically

designed to help predict sewage sludge nitrogen transformations based on sludge characteristics, as well as climate and soil properties

(organic matter content, mean soil temperature, and water potential). Finally, the

CREAMS and GLEAMS models, developed by

the USDA, are other potentially useful models

to assist with site-specific management of land

application operations. Additional computer

models include Cornell Nutrient Management

Planning System (NMPS), Fertrec Plus v 2.1,

and Michigan State University Nutrient

7C-20

14 All of these models are referenced in EPA’s Process Design Manual: Land Application of Sewage Sludge and

Domestic Septage (U.S. EPA, 1995b). According to that source, the NLEAP software, developed by

Shaffer et al., is included in the purchase of Managing Nitrogen for Groundwater Quality and Farm

Profitability by Follet, et al., which also serves as reference for information on parameters required for

nitrogen calculations. Four regional soil and climatic databases (Upper Midwest, Southern,

Northeastern, and Western) also are available on disk for use with NLEAP. These materials can be

obtained from: Soil Science Society of America Attn: Book Order Department, 677 S. Segoe Road,

Madison, WI 53711, 608/273-2021; Book $36.00; Regional Databases $10.00 each. Current updates of

the NLEAP program can be obtained by sending original diskettes to: Mary Brodahl, USDA-ARS-GPSR,

Box E, Fort Collins, CO 80522. Additional information on the DECOMPOSITION model, developed

by Gilmour and Clark, can be obtained from: Mark D. Clark, Predictive Modeling, P.O. Box 610,

Fayetteville, AR 72702. The CREAMS and GLEAMS models were developed by USDA.

Protecting Ground Water—Designing A Land Application Program 
Management v1.1.15 If assistance is required in

determining an appropriate agronomic rate for

a waste, you should contact the regional, state,

or county agricultural cooperative extensions,

or a similar organization.

VIII. Monitoring

Monitoring ground water can be helpful to

verify whether waste constituents have migrated to ground water. Some state, tribal, or

other regulatory authorities require groundwater monitoring at certain types of land

application units; you should consult with the

appropriate regulatory agency to determine

whether such a requirement applies to the

unit. Even if the unit is not required to monitor ground water, instituting a ground-water

monitoring program is recommended for

long-term, multiple application units where

wastes contain the designated ground-water

constituents. Such units are more likely to

pose a threat to ground water than are singleapplication units or units receiving waste

without these constituents. 

In most cases, lysimeters should be sufficient to monitor ground water. A lysimeter is

a contained unit of soil, often a box or cylinder in the ground which is filled with soil,

open on the top, and closed at the bottom, so

that the water that runs through it can be collected. It is usually more simple and economical to construct and operate than a

monitoring well. You can consult with a qualified professional to develop an appropriate

ground-water monitoring program for your

land application unit.

If ground-water results indicate unacceptable constituent levels, you should suspend

land application until the cause is identified.

You should then correct the situation that led

to the high readings. If a long-term change in

the industrial process, rather than a one-time

incident, caused the elevated levels, you

should reevaluate your use of land application. Adjusting the application rate, adding

pretreatment, or switching to another means

of waste management might be necessary.

After reevaluation, you should examine

whether corrective action might be necessary

to remediate the contaminated ground water.

You should pay particular attention to ensure

that applications are not exceeding the soil’s

assimilative capacity.

You should also consider testing soil samples periodically during the active life of a

land application unit. For this testing to be

meaningful, it is important that you first

determine baseline conditions by sampling

the soil before waste application begins. This

might already have been done in preparation

for greenhouse/field studies or for site characterization. Later, when applying waste to the

unit, you should collect and analyze samples

at regular intervals (such as annually or after

a certain number of applications). Consider

analyzing samples for macronutrients,

micronutrients, and any of the designated

ground-water constituents reasonably expected to be present in the waste. The location

and number of sampling points, frequency of

sampling, and constituents to be analyzed

will depend on site-specific soil, water, plant,

and waste characteristics. Local agricultural

extension services, which have experience

with monitoring, especially when coupled

with ground-water monitoring, can detect

contamination problems. Early detection

allows time to change processes to remedy

the problems, and to conduct corrective

action if necessary before contamination

becomes widespread.

Testing soils after the active life of a unit

ends might also be appropriate, especially if

the waste is likely to have left residues in the

soil. The duration of monitoring after closure,

like the location and frequency of monitoring

during active life, is site-specific and depends

on similar factors. For further information

Protecting Ground Water—Designing A Land Application Program 

7C-21

15 These models are referenced in the Northeast Regional Agricultural Engineering Cooperative

Extension’s Nutrient Management Software: Proceedings from the Nutrient Management Software

Workshop from December 11, 1996.
about testing soil after the active life of a unit

ends, refer to Chapte 11—Performing

Closure and Post-Closure Care.

IX. Odor Controls

Odors are sometimes a common problem

at land application facilities and an odor

management plan can allow facility managers

to respond quickly and effectively to deal

with odor complaints. A plan should involve

working to prevent odors from occurring,

working with neighbors to resolve odor complaints, and making changes if odors become

an unacceptable condition. The plan should

also identify the chemical odor constituents,

determine the best method for monitoring

odor, and develop acceptable odor thresholds. These odor management plans can be

stand-alone plans or part of your company’s

environmental management system. 

To effectively deal with odor complaints, it

is important to consider creating an odor

detection and response team to identify the

source of, and quickly respond to, potential

nuisance odor conditions. Document the

problem as well as how it was or was not

resolved, and notify facility managers as soon

as possible. Odor complaints should be documented immediately in terms of the odor’s

location, characteristics, the time and date,

existing meteorological conditions, suspected

specific source, information that indicates relative strength compared to other events, and

when during the day the odors are noticed. 

Measuring odors can be accomplished in

two manners: olfactometry and analytical.

The olfactometry method uses trained individuals who determine the strength of an

odor. Both of these methods have advantages

and disadvantages. Some of the advantages of

the olfactometry method are that it is accurately correlated with human response, it is

fast at providing a general chemical classification, and it is usually cost effective as a field

screening method. Disadvantages include the

requirement of highly trained individuals,

and it does not address the chemistry of the

odor problem. Analytical methods use gas

chromatographs and mass spectrophotometers to analyze vapor concentrations captured

from a sample. Some of the advantages of the

analytical method are that it allows detection

of odorants at levels near human detection, it

is precise and repetitive, and it provides

chemical specificity. Disadvantages include a

very high capital cost which might not accurately correlate with human responses. You

should contact your state for more information on odor management plans and measuring odors.

7C-22

Protecting Ground Water—Designing A Land Application Program 
Protecting Ground Water—Designing A Land Application Program 

7C-23

■ Use the framework to design and evaluate a land application program and to help determine a preliminary waste application rate.

■ Be familiar with waste parameters, such as total solids content, pH, organic matter, nutrients, carbon and nitrogen levels, salts, soil buffering capacity, and pathogens.

■ When examining potential application sites, give special consideration to physical and chemical

properties of soil, topography, and any site characteristics that might encourage runoff or odor.

■ Choose crops for the unit considering plant uptake of nutrients and constituents.

■ Account for climate and its effects.

■ Determine an agronomic application rate.

■ Evaluate ground-water and air risks from land application units and consider potential exposure

pathways.

■ Consider implementing a ground-water monitoring program and periodic sampling of unit soils. 

Designing a Land Application

Program Activity List
7C-24

Protecting Ground Water—Designing A Land Application Program 

Brandt, R.C. and K.S. Martin. 1996. The Food Processing Residual Management Manual. September.

Borrelli, J. and D. Brosz. 1986. Effects of Soil Salinity on Crop Yields.

Evanylo, G.K. and W. L. Daniels. 1996. The Value and Suitability of Papermill Sludge and Sludge

Compost as a Soil Amendment and Soilless Media Substitute. Final Report. Virginia Department of

Agriculture and Consumer Services. April.

Fipps, G. 1995. Managing Irrigation Water Salinity in the Lower Rio Grande Valley. <hermes.ecn.purdue.edu/sgml/water_quality/texas/b1667.ascii>.

Gage, J. 2000. Operating by Progressive Odor Management Plan. Biocycle Journal of Composting &

Recycling. Vol. 41 No. 6. June.

Idaho Department of Health and Welfare. 1988. Guidelines for Land Application of Municipal and

Industrial Wastewater. March.

Michigan Department of Natural Resources, Waste Characterization Unit. 1991. Guidance for Land

Application of Wastewater Sludge in Michigan. March.

Michigan Department of Natural Resources, Waste Characterization Unit. 1991. Guide to Preparing a

Residuals Management Plan. March.

Minnesota Pollution Control Agency. 1993. Land Treatment of Landfill Leachate. February.

Nagle, S., G. Evanylo, W.L. Daniels, D. Beegle, and V. Groover. Chesapeake Bay Regional Nutrient

Management Training Manual. Virginia Cooperative Extension Service. Crop & Soil Environmental

Sciences. Virginia Polytechnic Institute and State University. Blacksburg, VA. 1997.

Northeast Regional Agricultural Engineering Cooperative Extension. 1996. Nutrient Management

Software: Proceedings from the Nutrient Management Software Workshop. NRAES-100. December.

Northeast Regional Agricultural Engineering Cooperative Extension. 1996. Animal Agriculture and the

Environment: Nutrients, Pathogens, and Community Relations. NRAES-96. December.

Northeast Regional Agricultural Engineering Cooperative Extension. 1993. Utilization of Food

Processing Residuals. Selected Papers Representing University, Industry, and Regulatory Applications.

NRAES-69. March.

North Carolina Cooperative Extension Service. 1994. Soil facts: Careful Soil Sampling—The Key to

Reliable Soil Test Information. AG-439-30.

Resources
Protecting Ground Water—Designing A Land Application Program 

7C-25

Oklahoma Department of Environmental Quality. Title 252. Oklahoma Administrative Code, Chapter

647. Sludge and Land Application of Wastewater.

Rowell, D.L. 1994. Soil Science: Methods and Applications.

Striebig, B. and R. Giani. 2000. Briefing: The Odor Index and Its Use as a Management Tool for Biosolids

Land Application. Penn State University and Pennsylvania Department of Environmental Protection.

Texas Water Commission. 1983. Industrial Solid Waste Management Technical Guideline No. 5: Land

Application. December.

University of Nebraska Cooperative Extension Institute of Agriculture and Natural Resources. 1991.

Guidelines for Soil Sampling. G91-1000-A. February.

U.S. Department of Agriculture, Natural Resources Conservation Service. 1999. Agricultural

Phosphorus and Eutrophication. July.

U.S. Department of Agriculture, Natural Resources Conservation Service. 1999. Conservation Practices

Standard: Nutrient Management, Code 590. April.

U.S. Department of Agriculture, Natural Resources Conservation Service. 1999. Core Conservation

Practices, Part 2: Nutrient Management. August.

U.S. Department of Agriculture, Natural Resources Conservation Service. 1999. National Soil Survey

Handbook. September.

U.S. Department of Agriculture, Natural Resources Conservation Service. 1999. Soil Taxonomy: A Basic

System of Soil Classification for Making and Interpreting Soil Surveys. September.

U.S. EPA. 1995a. A Guide to the Biosolids Risk Assessments for the EPA Part 503 Rule. EPA832-B-93-

005. September.

U.S. EPA. 1995b. Process Design Manual: Land Application of Sewage Sludge and Domestic Septage.

EPA625-R-95-001. September.

U.S. EPA. 1995c. Process Design Manual: Surface Disposal of Sewage Sludge and Domestic Septage.

EPA625-R-95-002. September.

U.S. EPA. 1995d. Laboratory Methods for Soil and Foliar Analysis in Long-term Environmental

Monitoring Programs. EPA600-R-95-077.

Resources (cont.)
7C-26

Protecting Ground Water—Designing A Land Application Program 

Resources (cont.)

U.S. EPA. 1994a. Land Application of Sewage Sludge: A Guide for Land Appliers on the Requirements

of the Federal Standards for the Use or Disposal of Sewage Sludge, 40 CFR Part 503. EPA831-B-93-

002b. December.

U.S. EPA. 1994b. Guide to Septage Treatment and Disposal. EPA625-R-94-002. September.

U.S. EPA. 1994c. A Plain English Guide to the EPA Part 503 Biosolids Rule. EPA832-R-93-003.

September.

U.S. EPA. 1994d. Biosolids Recycling: Beneficial Technology for a Better Environment. EPA832-R-94-

009. June.

U.S. EPA. 1993. Domestic Septage Regulatory Guidance: A Guide to the EPA 503 Rule. EPA832-B-92-

005. September.

U.S. EPA. 1992. Control of Pathogens and Vector Attraction in Sewage Sludge. EPA625-R-92-013.

December.

U.S. EPA. 1990. State Sludge Management Program Guidance Manual. October.

U.S. EPA. 1983. Process Design Manual for Land Application of Municipal Sludge. EPA625-1-83-016.

October.

U.S. EPA, U.S. Army Corps of Engineers, U.S. Department of Interior, and U.S. Department of

Agriculture. 1981. Process Design Manual for Land Treatment of Municipal Wastewater. EPA625-1-81-

013. October.

U.S. EPA. 1979. Methods for Chemical Analysis of Water and Wastes. EPA600-4-79-020.

Viessman Jr., W. and M.J. Hammer. 1985. Water Supply and Pollution Control. 4th ed.

Washington State Department of Ecology. 1993. Guidelines for Preparation of Engineering Reports for

Industrial Wastewater Land Application Systems. Publication #93-36. May.

Webber, M.D. and S.S. Sing. 1995. Contamination of Agricultural Soils. In Action, D.F. and L.J.

Gregorich, eds. The Health of Our Soils.

Wisconsin Department of Natural Resources. 1996. Chapter NR 518: Landspreading of Solid Waste.

April.
Part V

Ensuring Long-Term Protection

Chapter 8

Operating The Waste Management System
Contents

I. An Effective Waste Management System ..................................................................................................8-1

II. Maintenance and Operation of Waste Management System Components ................................................8-2

A. Ground-Water Controls ..........................................................................................................................8-4

B. Surface-Water Controls ............................................................................................................................8-5

C. Air Controls ............................................................................................................................................8-5

III. Operational Aspects of a Waste Management System................................................................................8-7

A. Operating Plan ........................................................................................................................................8-7

B. Waste Analysis ........................................................................................................................................8-8

C. Waste Inspections ....................................................................................................................................8-8

D. Daily Cover..............................................................................................................................................8-9

E. Placing Wastes ......................................................................................................................................8-10

F. Sludge Removal......................................................................................................................................8-10

G. Climate Considerations ..........................................................................................................................8-11

H.Security Measures, Access Control, and Traffic Management..................................................................8-11

I. Providing Employee Training ................................................................................................................8-12

J. Emergency Response Plan and Procedures ............................................................................................8-14

K. Record Keeping ....................................................................................................................................8-16

L. Addressing Nuisance Concerns..............................................................................................................8-17

Operating the Waste Management System Activity List ................................................................................8-20

Resources ......................................................................................................................................................8-21
Ensuring Long-Term Protection—Operating the Waste Management System

8-1

I

mplementing a waste management system that achieves protective environmental operations requires incorporating

performance monitoring and measurement of progress towards environmental

goals. An effective waste management system

can help ensure proper operation of the many

interrelated systems on which a unit depends

for waste containment, leachate management,

and other important functions. If the elements

of an overall waste management system are not

regularly inspected, maintained, improved,

and evaluated for efficiency, even the bestdesigned unit might not operate efficiently.

Implementing an effective waste management

system can also reduce long- and short-term

costs, protect workers and local communities,

and maintain good community relations. 

I. An Effective

Waste

Management

System

Having an effective waste management system requires an understanding of environmental laws and an understanding of how to

comply with these laws. An effective waste

management system also requires that procedures be in place to monitor performance and

measure progress towards clearly articulated

and well understood environmental goals.

Lastly, an effective waste management system

involves operational procedures that integrate

continual improvements in waste management

operations to ensure continued compliance

with environmental laws. In addition to what

is discussed in this chapter, you can consider

reviewing and implementing, as appropriate,

the draft voluntary standards for good environmental practices developed by the

International Standards Organization (ISO).

The ISO 14000 series of standards identify

management system elements that are intended to lead to improved performance. These

include: a method to identify significant environmental aspects; a policy that includes a

Operating the Waste Management System

This chapter will help you:

• Develop a waste management system that includes procedures

for monitoring performance and measuring progress towards

environmental goals. The waste management system should

identify operational procedures that are necessary to achieve

those environmental goals and to make continual improvements in waste management operations.

This chapter will address the following

questions.

• What is an effective waste management

system?

• What maintenance and operational

aspects should be developed as part of

a waste management system?
8-2

Ensuring Long-Term Protection—Operating the Waste Management System

commitment to regulatory compliance, the

prevention of pollution, and continual

improvement; environmental objectives and

targets for all relevant levels and functions in

the organization; procedures to ensure performance, as well as compliance procedures to

monitor and measure performance; and a systematic management review process. 

The ISO 14000 series of standards include

a “specification” standard, ISO 14001. The

rest are standards that provide optional guidance for companies developing and implementing management systems and product

standards. The ISO 14001 specification standard contains only those requirements that

can be objectively audited for certification,

registration, and self-declaration purposes. For

more information about EPA’s involvement in

the ISO 14000 and 14001 standards, refer to

the ISO 14000 Resource Directory, October

1997, (U.S. EPA, 1997). Information on

obtaining the ISO 14000 series of standards is

provided in the text box above. An example of

an integrated EMS can be found at

<www.epa.gov/dfe/tools/iems.htm>.

II. Maintenance

and Operation of

Waste

Management

System

Components

All of the time and money invested in planning, designing, and developing a unit will be

jeopardized if proper operational procedures

are not carried out. Effective operation is

important for environmental protection, and

for reasons of economy, efficiency, and aesthetics. Operating control systems, therefore,

should be developed and maintained by the

facility operator to ensure efficient and protective operation of a waste management system.

These controls consist of the operator conducting frequent inspections, performing routine maintenance, reporting inspection results,

and making necessary improvements to keep

the system functioning. 

Unit inspections can help identify deterioration of or malfunction in control systems.

Surface impoundments should be inspected

Additional Information on

ISO 14000

The ISO 14000 series of standards are

copyrighted and can be obtained by contacting any of the following organizations:

American National Standards

Institute (ANSI)

1819 L Street, NW, 6th Floor

Washington, DC 20026

202 293-8020

<www.ansi.org>

American Society of Testing and

Materials (ASTM)

100 Bar Harbor Drive

West Conshohocken, PA 19428-2959

610 832-9585

<www.astm.org>

American Society for Quality

Control (ASQC)

611 East Wisconsin Avenue

P.O. Box 3005

Milwaukee, WI 53201

800 248-1946

<www.asqc.org>

NSF International

P.O. Box 130140

789 N. Dixboro Road

Ann Arbor, MI 48113-0140

800 NSF-MARK or 734 769-8010

<www.nsf.org>
Ensuring Long-Term Protection—Operating the Waste Management System

8-3

for evidence of overtopping, sudden drops in

liquid levels, ice formation, and deterioration

of dikes or other containment devices.

Overtopping, or the flowing of waste over the

top of the walls of an impoundment, can

occur as a result of insufficient freeboard,

wind or wave action, or other unusual conditions including the formation and movement

of ice within a surface impoundment which

can also puncture or tear synthetic liners. 

One method of protecting liners from ice

damage is to install a liner cover consisting of

sand and rip rap along the edge of the liner.

Another option is the use of a double liner

system. The higher cost of a double liner is

offset by reducing the need for rip rap and

offers enhanced ground-water protection.

Regardless of which method is implemented,

liner systems should be inspected for damage

and be repaired if necessary after periods of

ice formation. Also, make visual inspections

periodically to check waste levels, weather

conditions, or draining during periods of

heavy precipitation. In addition, it is important to consider devising a contingency plan

to reinforce dikes when failure is imminent.

Waste piles and landfills should be

inspected for adequate surface-water protection systems, leachate seeps, dust suppression

methods, and daily covers, where applicable.

Land application sites should be inspected for

adequate surface-water protection systems

and dust suppression methods, as applicable.

Inspections of pipes, monitoring of mechanical equipment, and safety, emergency, and

security devices will help to ensure that a

unit operates in a safe manner. In addition,

inspections often prevent small problems

from growing into more costly ones.

How should effective inspections

be conducted?

To help ensure that routine inspections are

performed regularly and consistently, consider

developing a written inspection schedule and

ensure that staff follow the schedule. The

schedule could state the type of inspections to

be conducted, the inspection methods to be

used, the frequency of the inspections, and a

plan of action highlighting preventative measures to address potential problems. Consider

conducting additional inspections after extraordinary site-specific circumstances, such as

storms or other extreme weather conditions.

Staff conducting the inspections should

look for malfunctioning or deteriorating

equipment, such as broken sump pumps,

leaking fittings, eroding dikes, or corroded

pipes or tanks; discharges or leaks from

valves or pipes; and operator errors. A written schedule for inspections should be maintained at the facility, and inspections should

be recorded in a log containing information

such as date of inspection, name of inspector,

conditions found, and recommended corrective action. Inspection personnel should be

familiar with the inspection log to identify

any malfunctions or deficiencies that remain

uncorrected from previous inspections. 

When designing an inspection form for a

unit, add appropriate items for the unit type.

You can check with the appropriate state regulatory agency to see if it has an inspection

form that can be used. For example, a landfill

form would include a section about waste

placement and a surface impoundment form

might have an entry for sufficient freeboard.

If ground water is monitored, you can make

ground-water monitoring part of the unit

inspection, and add check boxes for each

monitoring point to ensure that inspectors

collect samples from all monitoring points

according to the specified schedule. After an
8-4

Ensuring Long-Term Protection—Operating the Waste Management System

inspection, it is important that all inspection

reports are reviewed in a timely manner so

that any necessary repairs and improvements

can quickly be identified and implemented.

You should consult with your state agency to

help determine if improvements are necessary.

A. Ground-Water Controls

Ground-water protection controls, such as

ground-water monitoring systems, unit covers,

leachate collection and removal systems, and

leak detection systems should be incorporated

into the design and construction of a unit. 

Ground-water monitoring wells require

continued maintenance. A major reason for

maintenance is plugging of the gravel pack or

screen. (See Chapter 9–Monitoring

Performance for a discussion on the construction of ground-water monitoring wells.) The

most common plugging problems are caused

by precipitation of calcium or magnesium carbonates and iron compounds. Acid is most

commonly used to clean screens clogged with

calcium carbonate. In many instances, however, the cost of attempted restoration of a monitoring well can be more than the installation of

a new well. Because many wells are installed

in unconsolidated sand formations, silt and

clay can be pumped through the system and

cause it to fail. Silt and sand grains are abrasive and can damage well screens, pumps (if

present), flow meters, and other components. 

In some cases, the well can fill with sediment and must be cleaned out. The most frequent method of cleaning is to pull the pump

from the well, circulate clean water down the

well bore through a drop, and flush the sediment out. If large amounts of sediments are

expected to enter a monitoring well, consider

incorporating a sediment sump (also called a

silt trap or sediment trap) into the monitoring

well construction. The sump consists of a

blank section of pipe placed below the base of

the screen. Its purpose is to provide a catchtrap for fine sand and silt which bypasses the

filter pack and screen and settles out within

the well. This sediment collects within the

sump rather than within the screen, and therefore, does not reduce the functional screened

length of the well and minimizes the need for

periodic cleanouts of the screen. Regardless of

the type of ground-water monitoring well

installed, the well should be protected with a

cap or plug at the upper end to prevent condensation, rust, and dirt from entering into the

manhole or protective casing. In addition, it is

important to inspect the outer portion of the

wells to ensure that they have not been damaged by trucks or other unit operations, and to

ensure that the cap or plug is intact. 

You also should inspect and maintain unit

covers to ensure that they are intact. For optimal performance, covers should be designed

to minimize permeability, surface ponding,

and the erosion of cover material. The cover

should also prevent the buildup of liquids

within the unit. Consult Chapter

11–Performing Closure and Post-Closure Care

for a more detailed discussion on maintaining

cover systems.

It is essential that all components of a

leachate collection and removal system and a

leak detection system be maintained properly.

The main components include the leachate

collection pipes, manholes, leachate collection

tanks and accessories, and pumps. You should

consider cleaning the leachate pipes once a

year to remove any organic growth and visually inspecting the manholes, tanks, and pumps

once a year as leachate can corrode metallic

parts. Annual inspections and necessary

repairs will prevent many future emergency

problems such as leachate overflow from the

tank due to pump failure. Maintain a record of

all repair activities as necessary to assess (or

claim) long-term warranties on pumps and

other equipment.
Ensuring Long-Term Protection—Operating the Waste Management System

8-5

In surface impoundments, monitor waste

liquid levels. An unexpected decrease in liquid levels can be an indication of a release

from the impoundment. If a surface

impoundment fails, it is important to discontinue adding waste to the impoundment and

contain any discharge that has occurred or is

occurring. Repair leaks as soon as possible. If

leaks cannot be stopped, empty the

impoundment if possible. If the size of the

unit or amount of waste present prohibits

emptying, see Chapter 9–Monitoring

Performance and consult with state officials

about beginning an assessment monitoring

program. Clean up any released waste (see

Chapter 10–Taking Corrective Action) and

notify the appropriate state authorities of the

failure and the remedial actions taken.

B. Surface-Water Controls

If a unit has a point source discharge, the

unit must have a National Pollutant

Discharge Elimination System (NPDES) permit (or equivalent) and, in some states, might

require a state discharge permit. Point source

discharges include the release of leachate

from a leachate collection or onsite treatment

system into surface waters, disposal of industrial waste into surface waters, or release of

surface-water runoff (e.g., storm water) that is

directed by a runoff control system into surface waters. Even if there are no point source

discharges, surface-water controls might be

necessary to prevent pollutants from being

discharged or leached into surface waters,

such as lakes and rivers. If a facility is discharging wastewater to a local publicly

owned treatment works (POTW), check with

the POTW and local regulatory authorities to

determine whether pretreatment standards

exist for the facility.

Soil erosion and sedimentation controls,

such as ditches, berms, dikes, drains, and silt

fences, should be incorporated into the

design and construction of a unit. Berms or

dikes are often constructed from earthen

materials, concrete, or other materials

designed to be safely traversed during inspection or monitoring activities. Vegetation also

is often used for erosion control. Trees or

other deep rooted vegetation, however,

should not be used near liners or other structures that could be damaged by roots. Grass

is often used for soil stabilization around surface impoundments. For a more detailed discussion of storm-water issues, consult

Chapter 6–Protecting Surface Water.

Most if not all of these surface-water controls should be inspected by the operator regularly, especially after large storm events.

Structures should be maintained as installed

and any structural damage should be repaired

as soon as possible to prevent further damage

or erosion. Any trapped sediments should be

removed and disposed of properly. Vegetative

controls frequently need watering after planting and during periods of intense heat or lack

of rain.

C. Air Controls

Gases, including methane, carbon dioxide,

and hydrogen, are often produced at waste

management units as byproducts of the

microbial decomposition of wastes containing

organic material. Additionally, volatile organic

compounds (VOCs) can be present in the

waste, and particulate emissions and dust can

be generated during unit operations. It is

important to analyze wastes carefully prior to

designing a waste management unit to determine what airborne emissions are likely to

come from these wastes. If airborne emission

controls are needed in the design of a unit,

maintenance of these controls should be considered as part of a waste management system. For further information on airborne

emission controls, consult Chapter 5–

Protecting Air Quality.
8-6

Ensuring Long-Term Protection—Operating the Waste Management System

Methane is a particular concern at some

waste management units. Methane is odorless

and can cause fires or explosions that can

endanger employees and damage structures

both on and off site. Hydrogen gas can also

form, and is also explosive, but it readily

reacts with carbon or sulfur to form methane

or hydrogen sulfide. Hydrogen sulfide can be

easily identified by its sulfur or “rotten egg”

smell. Methane, if not captured, will either

escape to the atmosphere or migrate underground. Underground methane can enter

structures, where it can reach explosive concentrations or displace oxygen, creating the

danger of asphyxiation. Methane in the soil

profile can damage the vegetation on the surface of the landfill or on the land surrounding

the landfill, thereby exposing the unit to

increased erosion. Finally, methane is a

potent “greenhouse” gas that contributes to

global warming.

Methane is explosive when present in the

ranges of 5 to 15 percent by volume in the

air. The 5 percent level is known as the lower

explosive limit (LEL) and 15 percent as the

upper explosive limit (UEL). At levels above

15 percent by volume, methane will not

explode when exposed to a source of ignition. Levels above the UEL remain a concern,

however, as methane will burn at these concentrations and can still cause asphyxiation.

In the event that methane gas levels exceed

25 percent of the LEL in facility structures or

other closed spaces, initiate safety measures,

such as evacuating the site and structures. In

such cases, or when the methane level

exceeds 25 percent of the LEL in the soil at a

monitoring point, implement a remediation

plan to decrease gas levels and prevent future

buildup of gases.

Gas control systems generally include

mechanisms designed to control gas migration and to minimize the venting of gas emissions into the atmosphere. Passive gas control

systems use natural pressure and convection

mechanisms to remove gas from the waste

management unit. Examples of passive gas

control system elements include ditches,

trenches, vent walls, perforated pipes surrounded by coarse soil, synthetic membranes,

and high moisture, fine-grained soil. Active

gas control systems use mechanical means to

remove gas from the unit. Gas extraction

wells are an example of an active gas control

system.

Gas monitoring and extraction systems

require regular maintenance to operate efficiently. As wastes settle over time, pipes can

fail and condensate outlets can become

blocked. Extracted gas is saturated, which

causes moisture to collect within the pipes.

Therefore, the condensate within the pipes

must be dealt with, otherwise it will affect the

pumping suction pressure. Since the plumbing on the top of the unit is quite involved,

develop and adhere to a gas maintenance

schedule to ensure the efficient operation of

gas systems.

If generated gas is not removed from a

unit, uplift pressure can cause bubbles within

the unit that displace the cover soil at the

surface. Gas bubbles also can decrease the

normal stress between the geomembrane and

its underlying material leading to slippage of

the geomembrane and all overlying materials.

This creates high tensile stresses evidenced by

folding at the toe of the slope and tension

cracks near the top.
Ensuring Long-Term Protection—Operating the Waste Management System

8-7

III. Operational

Aspects of a

Waste

Management

System

This section identifies and briefly discusses

some of the important operational aspects of

a waste management system, including developing an operating plan, performing waste

analyses and inspections, installing daily covers, placing wastes in a unit, removing

sludge, considering climate, implementing

security and access control measures, providing employee training, addressing nuisance

concerns, developing emergency response

plans and procedures, and maintaining

important records. Consider developing practices to ensure compliance with applicable

laws and regulations, to train workers how to

handle potential problems, and to ensure that

all necessary improvements or changes are

made to a waste management system. Proper

planning and implementation of these operating practices are important elements in the

efficient and protective operation of a unit. 

A. Operating Plan

An operating plan should serve as the primary resource document for operating a

waste management unit. It should include the

technical details necessary for a unit to operate as designed throughout its intended

working life. At a landfill, for example, the

operating plan should illustrate the chronological sequence for filling the unit, and it

should be detailed enough to allow the facility manager to know what to do at any point

in the active life of the unit.

An operating plan should include:

• A daily procedures component.

• Lists of current equipment holdings

and of future equipment needs.

• Procedures to inspect for inappropriate wastes and to respond when their

presence is suspected.

• Procedures for addressing extreme

weather conditions.

• Personnel needs and equipment utilization, including backup.

• Procedures to address emergencies,

such as medical crises, fires, and spills.

• Quality control standards.

• Record keeping protocols.

• Means of compliance with local,

state, and federal regulations.

The daily procedures component of the plan

outlines the day-to-day activities necessary to

place waste, operate environmental controls,

and inspect and maintain the waste management unit in accordance with its design. Daily

procedures should be concise enough to be circulated among all employees at the unit and

flexible enough to allow for any adjustments

necessary to accommodate weather variability,

changing waste volume, and other contingencies. You should revise and update daily procedures as needed to ensure the unit’s continued

safe operation within the parameters of the

overall operating plan.

Since a unit will likely operate for several

years, it is important that staff periodically

review the operating plan to refresh their

memories and to ensure long-term conformity with the plan. If modifications to the operating plan are necessary, the changes and the

date they were made should be noted within

the plan itself. Documented operating procedures can be crucial, especially if questions

arise in the future regarding the adequacy of

site construction and management.
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Ensuring Long-Term Protection—Operating the Waste Management System

B. Waste Analysis

To effectively manage waste and ensure

proper handling (e.g., preventing the mixing

of incompatible wastes, use of incompatible

liners or containers), knowledge of the chemical and physical composition of the wastes is

imperative. Determining waste characteristics

can be done by performing a comprehensive

waste analysis or through process knowledge.

To ensure that this information remains accurate, it might be necessary to repeat the

analysis whenever there is a change in the

industrial process generating the waste. For

further information, consult Chapter

2–Characterizing Waste.

C. Waste Inspections

The purpose of performing waste inspections is to identify waste that might be inappropriate for the waste management unit, and

to prevent problems and accidents before

they happen. Hazardous wastes, PCBs, liquids (in landfills and waste piles), and statedesignated wastes are prohibited from

disposal in units designated solely for industrial nonhazardous waste. Some states have

developed more stringent screening requirements that require a spotter to be present at a

unit to detect unauthorized wastes and to

weigh and record incoming wastes.

As part of a waste management system,

screening procedures should be implemented

to prevent inappropriate wastes from entering

a unit. For units receiving waste exclusively

from on site, only limited waste screening

might be necessary. For facilities receiving

waste from off site, screening procedures typically call for screening waste as it enters a

unit. Ideally, all wastes entering a unit should

be screened, but this is not always practical or

necessary. A decision might be made, therefore, to screen a percentage of incoming

waste. It might be practical to use spot inspections, such as checking random loads of waste

on a random day each week or every incoming load on one random day each month.

Base the frequency of random inspections on

the type and quantity of wastes expected to be

received, the accuracy and confidence desired,

and any state inspection requirements.

Inspections need to be performed prior to

placement of wastes in a unit.

Training employees to recognize inappropriate wastes during routine operations

increases the chances that inappropriate

waste arriving on non-inspection days will be

detected. Some indications of inappropriate

wastes are color, texture, or odor different

from those of the waste a unit normally

receives. Also, laboratory testing can be performed to identify different wastes.

A waste management system should

include procedures to address suspected

inappropriate waste. The procedures to

implement, when inappropriate wastes are

found, should include the following:

• Segregate the suspicious wastes.

• Use appropriate personal protective

equipment.

• Contact the part of the industrial

facility that generated the waste to

find out more about it.

An effective waste management system

relies on accurate knowledge of the waste

being handled.
Ensuring Long-Term Protection—Operating the Waste Management System

8-9

1 EPA is investigating the potential of bioreactor landfills as the concept applies to the operation of a

municipal landfill. The idea of a bioreactor landfill might be considered appropriate in select cases for

an industrial landfill at some time in the future.

2 In Pennsylvania a coproduct is defined as “materials which are essentially equivalent to and used in

place of an intentionally manufactured product or produced raw material and...[which present] no

greater risk to the public or the environment.”

• Contact laboratory support to analyze

the waste, if required.

• Call the appropriate state, tribal or

federal agencies in accordance with

the opertaing plan.

• Notify a response agency, if necessary.

Should liquids be restricted from

being placed in some units?

Bulk or containerized liquids should not

be placed in landfills or waste piles, as liquids

increase the potential for leachate generation.

Liquid waste includes any waste material

determined to contain free liquids as defined

by Method 9095 (also known as the paint filter test) in EPA’s Test Methods for Evaluating

Solid Waste, Physical/Chemical Methods (SW846). Sludges are a common waste that can

contain significant quantities of liquids. You

should consider methods such as drying beds

to dewater sludges prior to placement in

landfills and waste piles.1

D. Daily Cover

It might be necessary to apply a daily

cover to operating landfills and waste piles.

Covering the waste helps control nuisance

factors, such as the escape of odors, dust, and

airborne emissions, and can control the population of disease vectors where necessary.

Some cover materials, due to their ability to

hold moisture, can reduce the infiltration of

rain water, decreasing the generation of

leachate and the potential for surface-water

and ground-water contamination.

How is daily cover applied?

Covers most often consist of earthen material, although there are several alternative

daily covers being used in the industry today,

including coproducts,2 foam, geotextiles, and

plastic sheets or tarps. Examples of coproducts that have been used as daily cover

include granular wastes, automobile shredder

fluff, foundry sand, dewatered sludges, and

synthetic soils. When using coproduct covers

that can themselves contain contaminants,

ensure that run-on is either diverted before it

contacts the cover material or captured and

handled appropriately after contacting it.

Granular wastes used as daily cover should

be low in fine-grained particles to avoid waste

being transported by wind. Before using alternative covers, especially coproducts, you

should consult the state to determine what, if

any, regulations apply.

Daily cover should be applied after the

waste has been placed, spread, and compacted. Cover frequency is most often determined

by the type of industrial waste disposed of at

the landfill or waste pile. Frequent application of earthen material might be required if

undesirable conditions persist. A typical daily

soil cover thickness is 6 inches, but different

thicknesses might be sufficient. When using

earthen cover, it is important to avoid soils

with high clay content. Clay, due to its low

permeability, can block vertical movement of

water and channel it horizontally through the

landfill or waste pile. 

Inspect waste to ensure that hazardous

waste is not placed in a unit.
8-10

Ensuring Long-Term Protection—Operating the Waste Management System

Using alternative daily cover materials can

save valuable space in a waste management

unit. Some types of commercially available

daily cover materials include foam that usually is sprayed on the working face at the end

of the day, and geosynthetic products, such as

a tarp or fabric panel that is applied at the

end of the working day and removed at the

beginning of the following working day.

Some of these materials require specially

designed application equipment, while others

use equipment generally available at most

units. Criteria to consider when selecting an

alternative daily cover material include availability and suitability of the material, precipitation, chemical compatibility with waste,

equipment requirements, and cost.

E. Placing Wastes

To protect the integrity of liner systems,

the waste management system should prescribe proper waste placement practices. The

primary physical compatibility issue is puncture of the liner by sharp objects in the waste.

Ensure that the liner is protected from items

angular and sharp enough to puncture it.

Similarly, facility employees should be

instructed to keep heavy equipment off the

liner. Another physical compatibility issue is

keeping fine-grained waste materials away

from drainage layers that could be clogged by

such materials.

Differential settlement of wastes is another

problem that can be associated with waste

placement. To avoid differential settlement,

focus on how the waste is placed on the liner

material or on the protective layer above the

liner. Uneven placement of waste, or uneven

compaction can result in differential settlement of succeeding waste layers or of final

cover. Differential settlement, in turn, can lead

to ponding and infiltration of water and damage to liners or leachate collection systems. In

extreme cases, failure of waste slopes can

occur. To avoid these problems, it is important to ensure that waste is properly placed

and, if possible, compacted to ensure stability

of the final cover.

To protect liner integrity in lined surface

impoundments, consider placing an erosion

guard or a concrete pad on the liner at the

point where waste discharges into the unit.

Otherwise, pressure from the waste hitting

the liner can accelerate liner deterioration in

that area. Inlet pipes can also be arranged so

that liquid waste being discharged into the

unit is diffused upward or to the side.

Although inlet pipes can enter the surface

impoundment above the water level, the

point of discharge should be submerged to

avoid generating odor and disturbing the circulation of stratified ponds. Discharging liquid waste straight into the unit without

diffusion is not recommended as this can disrupt the intended treatment.

F. Sludge Removal

If significant amounts of sludge accumulate on the bottom of an impoundment, it

might be necessary to remove the sludge and

dispose of it periodically. There are two ways

to remove the sludge: dewater the cell and

remove the sludge after it has dried, or

dredge the impoundment. Many different

methods exist for dredging an impoundment.

Examples include a tanker truck outfitted

with a vacuum hose, manned and remote

dredges, and submersible pumps on steel

pontoons used as a floating dredge or

dragged on the pond bottom. You should

work with your state and sludge removal professionals to choose or create a method that

works best at your facility.

There are two main concerns regarding

sludge management: protecting the liner

while cleaning out sludge from the impoundment (if a liner is used) and properly disposing of any removed sludge. During dredging,
heavy equipment can damage the liner. You

can avoid this by selecting equipment and

methods that protect the liner during sludge

removal. Further, any sludge removed should

be evaluated and managed in an appropriate

manner, based on its chemical properties.

G. Climate Considerations

Waste management operations can be

affected by weather conditions, especially

rain, snow, or wind. Rainy or snowy weather

can create a variety of problems, such as hindered vehicle access and difficulty in spreading and compacting waste. To combat these

difficulties, consider altering drainage patterns, maintaining storm-water controls,

maintaining all-weather access roads (if

appropriate), or designating a wet-weather

disposal area.

Extremely cold conditions can prevent efficient excavation of soil from a borrow pit and

can also inhibit the spreading and compaction of soil cover on the waste. Freezing

temperatures can also inflict excessive wear

on equipment. To combat these problems,

you can use coarse-textured soil during winter operations, stockpile cover soil for winter

use, and protect cover soil with leaves, plastics, or other insulating materials.

Consider using special inclement weather

disposal areas during extreme wet and windy

weather. In wet weather, placing waste in a

part of the unit near the entrance reduces the

likelihood of trucks causing ruts on site roadways or being stranded in mud. Under windy

conditions, waste might need to be wetted or

placed in downwind areas of a unit to reduce

blowing waste or particulates.

H. Security Measures,

Access Control, and

Traffic Management

To prevent injury to members of the public, consider implementing security and

access control measures to block unauthorized entry to a unit. These measures can also

help to prevent scavenging, vandalism, and

illegal dumping of unauthorized wastes.

Providing access controls for the facility within which the unit is located is an example of

providing such measures for the unit.

Examples of access control measures

include fences, locked gates, security guards,

and surveillance systems; and natural barriers

such as, berms, trees, hedges, ditches, and

embankments. The site perimeter should be

clearly marked or fenced. Additionally, consider posting signs that warn of restricted access

and alert the public to the potential for harm

associated with heavy equipment operations.

How can onsite traffic best be

managed?

Even though access to the unit is limited,

it is important to provide clear transportation

routes for emergency response equipment to

access the waste management unit. Traffic

management is often overlooked as part of

waste management unit operations. Proper

traffic routing can help a unit operate more

smoothly and prevent injuries and deter

intruders. Access roads should be designed

and built to be safe and efficient, and blind

spots or unmarked intersections should be

minimized. They should also be located to

provide long-term service without requiring

relocation. Posting clear directional signs can

help direct traffic and reduce the potential for

vehicle accidents. Providing all-weather

access roads (if appropriate) and temporary

storage areas can improve waste transport to

and from a unit and allow equipment to

Ensuring Long-Term Protection—Operating the Waste Management System

8-11
8-12

Ensuring Long-Term Protection—Operating the Waste Management System

move about more freely. In addition, you can

consider imposing onsite speed limits or constructing speed bumps.

Access roads should be maintained properly at all times. Adequate drainage of road

beds is essential for proper operation of a

unit. Heavy, loaded vehicles traveling to and

from a unit deteriorate the roads on which

they travel. Equipment without rubber tires

should be restricted from the paved stretches

of roads as they can damage the roads.

Sufficient funds should be allocated up front

for the maintenance of access roads.

What are some other prudent

safety measures?

There are a number of safety considerations associated with ground-water monitoring wells. The tops of monitoring wells

should be clearly marked and accessible. In

traffic areas, posts and bumper guards around

monitoring wells can help protect aboveground installations from damage. Posts and

bumper guards come in various sizes and

strengths and are typically constructed for

high visibility and trimmed with reflective

tape or highly visible paint containing reflective material. 

Proper labeling of monitoring wells is also

important for several reasons. Monitoring

wells should be distinguished from underground storage tank fill lines, for example.

Also, different monitoring wells should be

distinguished from each other. Monitoring

wells, therefore, should be labeled on immovable parts of the well.

I. Providing Employee

Training 

One of the most important aspects of a

waste management system is employee training. Employees should be trained before their

initial assignment, upon changing assignments, and any time a new health or safety

hazard is introduced into the work area. A

good training program uses concrete examples to improve and maintain employee skill,

safety, and teamwork. Training can be provided by in-house trainers, trade associations,

computer programs, or specialized consultants. In some states, proactive safety and

training programs are required by law. 

What types of training can be

provided for employees? 

Safety is a primary concern because waste

management operations can present a variety

of risks to workers. In addition, employee

right-to-know laws require employers to provide training and information about safety

issues pertinent to a given occupation.

Furthermore, accidents can be expensive,

with hidden costs often amounting to several

times the apparent costs. Accidents at waste

management units can include injury from

explosions or fire, inhalation of contaminants

and dust, asphyxiation from poorly vented

leachate collection system manholes or tanks,

falls from vehicles, injury associated with

operating heavy earth-moving equipment,

exposure to extreme cold or heat, and onsite

traffic accidents.

To minimize risks to workers, it is recommended that you provide an ongoing

safety training program to ensure all staff

Classroom training helps familiarize employees

with operating procedures.
are properly and regularly trained on safety

issues. A safety training program should be

consistent with the requirements specified

by the U.S. Occupational Safety and Health

Administration (OSHA) and include initial

training and frequent refresher sessions on

at least the following topics:

• Waste management operations.

• Hazardous waste identification.

• Monitoring equipment operations.

• Emergency shut-off procedures.

• Overview of safety, health, and other

hazards present at the site.

• Symptoms and signs of overexposure

to hazards.

• Proper lifting methods, material handling procedures, equipment operation, and safe driving practices.

• Emergency response topics, such as

spill response, fire suppression, hazard analysis, and location and operation of emergency equipment.

• Requirements for personal protective

gear, such as hard hats, gloves, goggles, safety shoes, and high-visibility

vests.

Weave a common thread of teamwork into

every training program. Breaks in communication between site engineers and field operations personnel can occur. Bridging this gap is

an important step toward building an effective

unit team that can work together. Consider

periodic special training to update employees

on new equipment and technologies, to

improve and broaden their range of job-related

skills, and to keep them fresh on the basics.

Training can also include such peripheral topics as liability concerns, first aid, avoidance of

substance abuse, and stress management. 

Ensuring Long-Term Protection—Operating the Waste Management System

8-13

Sample Manager and

Supervisor Training Agenda

• Introduction

• Unit basics:

—Siting

—Waste containment

—Daily operations

• Owning and operating costs

• Machine types

• Equipment maintenance

• Maximizing airspace

• Labor management

• Production analysis

• Application of production rate data

• Budgets and data tracking:

—Operating budget

—Cover soil budget

—Airspace budget

• Waste handling techniques

• Waste management techniques

• Cover soil placement

• Safety issues and safety meetings

• Record keeping

• Emergency response plan

• State requirements for operation

Bolton, N. 1995. The Handbook of Landfill

Operations: a Practical Guide for Landfill

Engineers, Owners, and Operators. (ISBN 0-

9646956-0-X). Reprinted by permission.
How should training programs

be conducted?

You should keep records of the type and

amount of training provided to employees,

and obtain documentation (employee signatures) whenever training is given. Consider

establishing regular (at least monthly) safety

meetings, during which specific topics can be

addressed and employees can voice concerns,

ask questions, and present ideas. Keep meetings short and to the point, and steer discussion toward topics that are applicable to

those employees present. In addition, do not

waste time talking about issues not applicable to a site. If a site experiences extreme

weather conditions, develop safety meeting

topics that address weather-related safety.

Many safety-related videos are available and

can add variety to meetings. 

Closely monitor worker accident and

injury reports to try to identify conditions

that warrant corrective or preventive measures. In addition, it is wise to document all

safety meetings. Assistance in establishing a

safety program is available from insurance

companies with worker’s compensation programs, the National Safety Council, safety

consultants, and federal and state government

safety organizations. The overall cost of an

aggressive, preventive safety program is

almost certain to be offset by the savings from

a decrease in lost work time and injuries.

J. Emergency Response

Plan and Procedures

There are three major types of waste management emergencies: accidents, spills, and

fires/explosions. A waste management system

should include emergency response plans for

each of these scenarios that considers not

only the waste management unit but also all

surrounding facility areas. The plans should

be reviewed and revised periodically to keep

the procedures fresh in employees’ minds and

to reflect any changes in such items as the

unit operating procedures, facility operations,

physical and chemical changes in the wastes,

generated volumes, addition or replacement

of emergency equipment, and personnel

changes. If an emergency does arise, or if haz8-14

Ensuring Long-Term Protection—Operating the Waste Management System

Equipment Operator

Training Agenda

• Introduction

• Unit basics:

—Siting

—Waste containment

—Daily operations

• Heavy equipment types and applications:

—Scraper, dozer, and compactor

operations

—Support equipment

—Fluids

—Fueling, maintenance and its

hazards, and fuel spill prevention

• Cover operations:

—Types of cover soil

—Placement of cover soil

• Drainage control

• Surveying and staking

• Unit safety:

—Emergency response plans

—Safe operating techniques

• Owning and operating costs

Bolton, N. 1995. The Handbook of Landfill

Operations: a Practical Guide for Landfill

Engineers, Owners, and Operators. (ISBN 0-

9646956-0-X). Reprinted by permission.
ardous waste is inadvertently disposed of in a

unit, notify appropriate agencies, adjacent

land owners, and emergency response personnel, if needed. After emergency conditions

have been cleared, review the waste management system and revise it, if necessary, to prevent similar mishaps in the future. 

A facility might be required to prepare similar emergency response or contingency plans

under other regulatory programs [e.g., Spill

Prevention Control and Countermeasures and

Response Plan requirements (40 CFR Part

112.7(d) and 112.20-21); Risk Management

Program regulations (40 CFR Part 68); and

HAZWOPER regulations (29 CFR 1910.120)].

EPA encourages facilities to consolidate emergency response plans whenever possible to

elimante redundancy and confusion. The

National Response Team, chaired by EPA, has

prepared its Integrated Contingency Plan

Guidance (61 FR 28642; June 5, 1996) as a

model for integrating such plans.

How should an appropriate

emergency response plan be

developed?

An emergency response plan should consider the following:

• Description of types of emergencies that

would necessitate a response action.

• Names, roles, and duties of primary

and alternate emergency coordinators.

• Spill notification procedures.

• Who should be notified.

• Fire department or emergency

response telephone number.

• Hospital telephone number.

• Primary and secondary emergency

staging areas.

• Location of first aid supplies.

• Designation and training of several

first aid administrators.

• Location of and operating procedures

for all fire control, spill control, and

decontamination equipment.

• Location of hoses, sprinklers, or

water spray systems and adequate

water supplies.

• Description and listing of emergency

response equipment.

Ensuring Long-Term Protection—Operating the Waste Management System

8-15

Sample Laborer Training

Agenda

• Introduction

• Unit basics:

—Siting

—Waste containment

—Daily operations

• Traffic management and safety

• Interacting with the public

• Load segregation and placement

• Hazardous material identification procedure

• Unit equipment types and applications

• Cover operations

• Equipment maintenance

• Unit safety:

—Heavy equipment safety

—Traffic safety

—Personal protective equipment

• Emergency response plans

Bolton, N. 1995. The Handbook of Landfill

Operations: a Practical Guide for Landfill

Engineers, Owners, and Operators. (ISBN 0-

9646956-0-X). Reprinted by permission.
• Maintenance and testing log of emergency equipment.

• Plans to familiarize local authorities,

local emergency response organizations, and neighbors with the characteristics of the unit and appropriate

and inappropriate responses to various emergency situations.

• Information on state emergency

response teams, response contractors,

and equipment suppliers.

• Properties of the waste being handled

at the unit, and types of injuries that

could result from fires, explosions,

releases, or other mishaps.

• An evacuation plan for unit personnel (if applicable).

• Prominent posting of the above

information.

The emergency plan should instruct all

employees what to do if an emergency arises,

and all employees should be familiar with the

plan and their responsibilities under it. In

order to ensure that everyone knows what to

do in an emergency, EPA recommends conducting periodic drills. These practice responses could be planned ahead of time or

they could be unannounced. Either way, the

drills are treated as real emergencies and

serve to hone the skills of the employees who

might have to respond to actual emergencies.

The key to responding effectively to an emergency is knowing in advance what to do.

Communication is vital during an emergency and should be an inherent component

of any emergency response plan. Two-way

radios and bullhorns can prove invaluable in

the event of an emergency, and an alarm system can let employees know that an emergency situation is at hand. It is recommended

that you designate one or more employees

who will not be essential to the emergency

response to handle public affairs during a

major emergency. These employees should

work with the press to ensure that the public

receives an accurate account of the emergency.

K. Record Keeping 

Record keeping is a vital part of cost-effective, efficient waste management unit operations. Records should be maintained for an

appropriate period of time, but it is a good

idea to keep a set of core records indefinitely.

Some facilities have instituted policies that

records are to be maintained for up to 30

years while other facilities maintain records

for only 3 years. Some states have record

keeping requirements for certain waste management units and associated practices. You

should check with state authorities to determine what, if any, record keeping is required

by law and to determine how long records

should be kept. 

Besides being required by some states,

records help evaluate and optimize unit performance. Over time, these records can serve

as a valuable almanac of activities, as well as

a source of cost information to help fine tune

future expenditures and operating budgets.

Data on waste volume, for example, can

allow a prediction of remaining site life, any

special equipment that might be needed, and

personnel requirements. Furthermore, if a

8-16

Keeping accurate records is an essential part

of unit operations.

Ensuring Long-Term Protection—Operating the Waste Management System
facility is ever involved in litigation, accurate,

dated records can be invaluable in establishing a case.

What type of records should be

kept?

Operational records that should be maintained include the following, as appropriate:

• Waste analysis results.

• Liner compatibility testing (where a

liner system is considered appropriate).

• Waste volume.

• Location of waste placement, including a map.

• Depth of waste below the final cover

surface.

• Inventory of daily cover material

used and stockpile.

• Frequency of waste application.

• Equipment operation and maintenance statistics.

• Environmental monitoring data and

results.

• Inspection reports, including photographs.

• Design documents, including drawings and certifications.

• Cost estimates and other financial

data.

• Plans for unit closure and post-closure care.

• Information on financial assurance

mechanisms.

• Daily log of activities.

• Calendar of events.

Health and safety records that should be

maintained include the following:

• Personal information and work history

for each employee, including health

information such as illness reports.

• Accident records.

• Work environmental records.

• Occupational safety records, including safety training and safety surveys.

L. Addressing Nuisance

Concerns

Minimizing nuisances, such as noise, odor,

and disease vectors, is of great importance for

the health of personnel working in the industrial facility and of neighbors that live or work

near a unit. This section describes many of

the nuisance concerns typical of waste management units and offers measures to address

them. Measures besides those listed can also

be used to achieve the same objective.

How can noises be minimized?

Noise resulting from the operation of

heavy equipment can be a concern for waste

management units located near residential

areas. Noise can also disrupt animal habitats

and behavior. In addition, workers’ hearing

and stress levels can be adversely affected by

long-term exposure to noise. At waste management units where noise is a concern, limiting hours of operation can reduce potential

problems. Design access routes to minimize

the impact of site traffic noise on nearby

neighborhoods. Equipment should also be

maintained to minimize unnecessary noise,

and affected workers should wear ear protection (plugs or muffs). Berms, wind breaks, or

other barriers can be erected to help mute

sounds. OSHA has established standards for

occupational exposure to noise (see 29 CFR

§1910.95). 

Ensuring Long-Term Protection—Operating the Waste Management System

8-17
How can odor be minimized?

Increased urbanization has led to industrial facilities being situated in close proximity

to residential areas and commercial developments. This has resulted in numerous complaints about odors from industrial waste

management units and industrial processes

such as poultry processing, slaughtering and

rendering, tanning, and manufacture of

volatile organics. Some of the major sources

of odors are hydrogen sulfide and organic

compounds generated by anaerobic decomposition. The latter can include mercaptans,

indole, skatole, amines, and fatty acids. Odor

might be a concern at a unit, depending on

proximity to neighbors and the nature of the

wastes being managed. In addition to causing

complaints, odors can be a sign of toxic or

irritating gases or anaerobic conditions in a

unit that could have adverse health effects or

environmental impacts. Plan to be proactive

in minimizing odors, and establish procedures to respond to citizen complaints about

odor problems and to correct the problems.

Odors can be seasonal in nature and,

therefore, can often be anticipated. Some

odors at landfills, waste piles, and land application units arise either from waste being

unloaded or from improperly covered inplace waste. If odor from waste being

unloaded becomes a problem, it might be

necessary to place these loads in a portion of

the unit where they can be immediately covered with soil. At land application units,

quick incorporation or injection of waste can

help prevent odor. It also might be prudent to

establish a system whereby unit personnel are

notified when odorous wastes are coming to

the unit to allow them to prepare accordingly.

Odors from in-place waste can effectively be

minimized by maintaining the integrity of

cover material over everything but the currently active face. Proper waste compaction

also helps to control odors. Consider implementing gas controls if odors are associated

with gases generated from a unit.

If odors emanate from surface impoundments, there are several options available for

control, including biological and chemical

treatment. The type of treatment for an

impoundment should be determined on a

site-specific basis, taking into account the

chemistry of the waste. 

Practices to control odor are especially

important at land application units. If land

application is used, it is important to apply

waste at appropriate rates for site conditions,

and design and locate waste storage facilities

to minimize odor problems. Make it a priority

to minimize potential odors by applying

wastes as soon as possible after delivery and

incorporating wastes into the soil as soon as

possible after application. Cleaning trucks,

tanks, and other equipment daily (or more frequently, if necessary) can also help reduce

odor. Avoid applying waste when soils are wet

or frozen or when other soil or slope conditions would cause ponding or poor drainage.

Chapter 7 Section C– Designing a Land

Application Program presents information

concerning an odor management plan for land

application facilities.

Other methods of controlling odors

include:

• Covering or enclosing the unit.

• Adding chemicals such as chlorine,

lime, and ferric chloride to reduce

bacterial activity and oxidize many

products of anaerobic decomposition.

• Using biofilters.

• Applying a deep soil cover, whose

upper layers consist of silty soils or

soils containing a large percentage of

carbon or humic material.

• Applying a layer of relatively impermeable soil, so as to reduce gas gen8-18

Ensuring Long-Term Protection—Operating the Waste Management System
eration rates by reducing the amount

of rainfall water percolating into the

waste.

• Restoring landfill surface covers when

subsidence and cracks occur.

Choosing a method for controlling odors

involves a comprehensive understanding of

wastes and how they react under certain circumstances. Consult with state agencies to

determine the most effective odor control

method for the wastes in question.

In addition to these steps to control odor

generation, consider steps to manage those

odors that are generated. When designing a

waste management unit, consider installing

barriers such as walls, berms, embankments,

and dense plantings of trees set at right

angles to the flow of cold, odorous nighttime air. These measures can help to impede

the odor and dilute it through mixture with

higher layers of fresh air. Alternatively, consider placing an impermeable fence or wall

on top of a berm or embankment, on its

downwind side. This will increase odor

plume height, and odors will be diluted on

the steep downslope side of the barrier as a

result of turbulent mixing of air layers as the

cold air flows over it. Try to locate such barriers as close to the unit as possible.

Another design suggestion is to plant fastgrowing evergreen trees which have good

windbreak properties in buffer-zones around a

unit. In addition to dispersing odors, dense

plantings of evergreen trees will also help to

protect the unit itself from strong winds, reducing the possibility of windblown soil erosion.

How can disease vectors be 

controlled?

Disease vectors are animals or insects, such

as rodents, birds, flies, and mosquitos, that

can transmit disease to humans. Burrowing

animals, such as gophers, moles, and groundhogs, can also damage vital unit structures,

such as liners, final cover materials, drainage

ditches, and sedimentation ponds. As a result,

these animals can create costly problems.

Consider the following methods to control

disease vectors:

• Apply adequate daily cover. This simple action is often all that is needed

to control many disease vectors.

• Make sure the unit is properly

drained, reducing the amount of

standing water that acts as a breeding

medium for insects.

• As a last resort, or when the application of cover material is impractical,

consider using repellents, insecticides,

rodenticides, or pest reproductive control. Care must be taken to make sure

that pesticides are used only in accordance with specified uses and application methods. Follow the instructions

carefully when using these products.

Trapping animals might also be considered, but trapping alone rarely

eliminates the problem.

If land applying wastes, subsurface injection

and prompt incorporation of waste can help

control vectors. Both of these methods work

by using the soil as a barrier between the

waste and the vectors. If a waste storage facility exists, these can attract vectors as well and

should not be overlooked in the implementation of vector control. If vector problems arise

Ensuring Long-Term Protection—Operating the Waste Management System

8-19
■ Develop a waste management system identifying the standard procedures necessary

for a unit to operate according to its design throughout the intended working life.

■ Provide proper maintenance and operation of ground-water, surface-water, and air

controls.

■ Develop daily procedures to place waste, operate environmental controls, and inspect

and maintain the unit.

■ Review at a regular interval, such as annually, whether the waste management system

needs to be updated.

■ Develop a waste analysis procedure to ensure an understanding of the physical and

chemical composition of the waste to be managed.

■ Develop regular schedules for waste screening and for unit inspections.

■ If daily cover is recommended, select an appropriate daily cover and establish

processes for placing and covering waste.

■ Consider how operations can be affected by climate conditions.

■ Implement security measures to prevent unauthorized entry.

■ Provide personnel with proper training.

■ Establish emergency response procedures and familiarize employees with emergency

equipment.

■ Develop procedures for maintaining records.

■ Establish nuisance controls to minimize dust, noise, odor, and disease vectors. 

Operating the Waste Management

System Activity List

8-20

Ensuring Long-Term Protection—Operating the Waste Management System
Ensuring Long-Term Protection—Operating the Waste Management System

8-21

ASTM. 1993. Standard Practice for Maintaining Health and Safety Records at Solid Waste Processing Facilities.

E 1076-85.

Bagchi, A. 1994. Design, Construction, and Monitoring of Landfills. John Wiley & Sons Inc. 

Bolton, N. 1995. The Handbook of Landfill Operations: A Practical Guide for Landfill Engineers, Owners, and

Operators. Blue Ridge Solid Waste Consulting.

Robinson, W. 1986. The Solid Waste Handbook: A Practical Guide. John Wiley & Sons Inc.

U.S. EPA. 1997. ISO 14000 Resource Directory. EPA625-R-97-003.

U.S. EPA/National Response Team. 1996. The National Response Teams Integrated Contingency Plan

Guidance; Notice. (61 FR 28642; June 5, 1996).

U.S. EPA. 1998. CAMEO: Computer-Aided Management of Emergency Operations. EPA550-F-98-003.

U.S. EPA. 1995. Decision-Maker’s Guide to Solid Waste Management, Second Edition. EPA530-R-95-023.

U.S. EPA. 1995. State Requirements for Industrial Nonhazardous Waste Management Facilities. 

U.S. EPA. 1994. Seminar Publication: Design, Operation, and Closure of Municipal Solid Waste Landfills.

EPA625-R-94-008.

U.S. EPA. 1993. Solid Waste Disposal Facility Criteria: Technical Manual. EPA530-R-93-017.

U.S. EPA. 1991. Technical Resource Document: Design, Construction, and Operation of Hazardous and

Nonhazardous Waste Surface Impoundments. EPA530-SW-91-054.

U.S. EPA. 1989. Test Methods for Evaluating Solid Waste, Physical/Chemical Methods. SW-846. 

U.S. EPA. 1988. RCRA Inspection Manual. OSWER Directive 9938.2A.

U.S. EPA. 1988. Subtitle D of RCRA, “Criteria for Municipal Solid Waste Landfills” (40 CFR Part 258),

Operating Criteria (Subpart C). Draft/Background Document.

Resources
Part V

Ensuring Long-Term Protection

Chapter 9

Monitoring Performance
Contents

I. Ground-Water Monitoring ......................................................................................................................9 - 2

A. Hydrogeological Characterization ..........................................................................................................9 - 2

B. Monitoring Methods ..............................................................................................................................9 - 4

1. Conventional Monitoring Wells ........................................................................................................9 - 4

2. Direct-Push Ground-Water Sampling ................................................................................................9 - 4

3. Geophysical Methods ........................................................................................................................9 - 5

C. Number of Wells....................................................................................................................................9 - 6

D. Lateral and Vertical Placement of Wells..................................................................................................9 - 7

1. Lateral Placement ..............................................................................................................................9 - 7

2. Vertical Placement and Screen Lengths ..............................................................................................9 - 8

E. Monitoring Well Design, Installation, and Development........................................................................9 - 9

1. Well Design ......................................................................................................................................9 - 9

2. Well Installation ..............................................................................................................................9 - 12

3. Well Development ..........................................................................................................................9 - 12

F. Duration and Frequency of Monitoring ..............................................................................................9 - 13

G. Sampling Parameters............................................................................................................................9 - 13

H.Potential Modifications to a Basic Ground-Water Monitoring Program ................................................9 - 14

1. Duration and Frequency of Monitoring ..........................................................................................9 - 14

2. Sampling Parameters ......................................................................................................................9 - 16

3. Vadose-Zone Monitoring..................................................................................................................9 - 16

II. Surface-Water Monitoring ....................................................................................................................9 - 21

A. Monitoring Storm-Water Discharges ....................................................................................................9 - 22

B. Monitoring Discharges to POTWs........................................................................................................9 - 25

C. Monitoring Surface Water Conditions..................................................................................................9 - 26

III. Soil Monitoring ....................................................................................................................................9 - 28

A. Determining the Quality of Soil ..........................................................................................................9 - 29

B. Sampling Location and Frequency ......................................................................................................9 - 30

C. Sampling Equipment ..........................................................................................................................9 - 31

D. Sample Collection................................................................................................................................9 - 31

IV. Air Monitoring......................................................................................................................................9 - 32

A. Types of Air Emissions Monitoring ......................................................................................................9 - 33

1. Emissions Monitoring......................................................................................................................9 - 33

2. Ambient Monitoring ........................................................................................................................9 - 33

3. Fugitive Monitoring ........................................................................................................................9 - 34

4. Meteorological Monitoring ..............................................................................................................9 - 34
B. Air Monitoring and Sampling Equipment ............................................................................................9 - 36

1. Ambient Air Monitoring ..................................................................................................................9 - 36

2. Source Emissions Monitoring ..........................................................................................................9 - 37

C. Test Method Selection..........................................................................................................................9 - 38

D. Sampling Site Selection........................................................................................................................9 - 38

V. Sampling and Analytical Protocols and Quality Assurance and Quality Control ..................................9 - 39

A. Data Quality Objectives ......................................................................................................................9 - 41

B. Sample Collection................................................................................................................................9 - 41

C. Sample Preservation and Handling ......................................................................................................9 - 42

D. Quality Assurance and Quality Control ..............................................................................................9 - 42

E. Analytical Protocols ............................................................................................................................9 - 44

VI. Analysis of Monitoring Data, Contingency Planning, and Assessment Monitoring................................9 - 45

A. Statistical Approaches ..........................................................................................................................9 - 45

B. Contingency Planning..........................................................................................................................9 - 46

C. Assessment Monitoring........................................................................................................................9 - 46

Monitoring Performance Activity List..........................................................................................................9 - 48

Resources ..................................................................................................................................................9 - 50

Tables:

Table 1: Factors Affecting Number of Wells Per Location ..........................................................................9 - 9

Table 2: Potential Parameters for Basic Groundwater Monitoring ............................................................9 - 15

Table 3: Recommended Components of a Basic Ground-Water Monitoring Program ..............................9 - 16

Table 4: Comparison of Manual and Automatic Sampling Techniques ....................................................9 - 24

Table 5: Types of QA/QC Samples............................................................................................................9 - 43

Figures:

Figure 1: Cross-Section of a Generic Monitoring Well................................................................................9 - 5

Figure 2: Major Methods for In Situ Monitoring of Soil Moisture or Matrix Potential..............................9 - 18

Figure 3: Example Methods for Collecting Soil-Pore Samples ..................................................................9 - 19

Figure 4: Soil Gas Sampling Systems........................................................................................................9 - 20

Figure 5: Schematic Diagram of various Types of Sampling Systems........................................................9 - 36

Figure 6: Sampling Train..........................................................................................................................9 - 38

Contents
Ensuring Long-Term Protection—Monitoring Performance 

9-1

Monitoring the performance of

a waste management unit is

an integral part of a comprehensive waste management

system. A properly implemented monitoring program provides an

indication of whether a waste management

unit is functioning in accordance with its

design, and detects any changes in the quality

of the environment caused by the unit. The

detection information obtained from a monitoring program can be used to ensure that the

proper types of wastes are being managed in

the unit, discover and repair any damaged

area(s) of the unit, and determine if an alternative management approach might be

appropriate. By implementing a monitoring

program, facility managers can identify problems or releases in a timely fashion and take

the appropriate measures to limit contamination. Continued detection of contamination

in the environment could result in the implementation of more aggressive corrective

action measures to remediate releases.

This chapter highlights issues associated

with establishing a ground-water monitoring

program because most industrial waste management units need to have such a program.

The chapter also provides a discussion of air,

surface water, and soil monitoring that might

be applicable to some units managing industrial waste. You should consult with qualified

professionals, such as engineers and groundwater specialists,1 for technical assistance in

making decisions about the design and operation of a ground-water monitoring program. In

1 For the purpose of this chapter, a qualified “ground-water specialist” refers to a scientist or engineer

who has received a baccalaureate or post-graduate degree in the natural sciences or engineering and has

sufficient training and experience in ground-water hydrology and related fields as demonstrated by

state registration, professional certifications, or completion of accredited university programs that

enable that individual to make sound professional judgements regarding ground-water monitoring,

contaminant fate and transport, and corrective action.

Monitoring Performance

This chapter will help you:

• Carefully design and implement a monitoring program that is essential to evaluating whether a unit meets performance objectives and

whether there are releases to, and impacts on, the surrounding

environment that need to be corrected. 

• Design effective monitoring programs that protect the environment,

improve unit performance, and help reduce long-term costs and liabilities associated with industrial waste management. 

This chapter will address the following

questions.

• What site characterizations are needed to

develop an effective monitoring program?

• What are the basic elements of a monitoring program?

• How should sampling and analytical protocols be used in a monitoring program?

• What procedures should be used to

evaluate monitoring data?

• What elements of the basic monitoring

program can be modified to address

site conditions?
9-2

Ensuring Long-Term Protection—Monitoring Performance 

addition when questions arise concerning soil,

air, or surface-water monitoring, you should

also consult specialists in these areas as each

media requires different expertise. 

I. Ground-Water

Monitoring

The basic elements of a ground-water

monitoring program include:

• The monitoring method.

• The number of wells.

• Location and screened intervals of

wells.

• Well design, installation, and development.

• The duration and frequency of monitoring.

• Sampling parameters to be monitored.

The remainder of this section provides a

brief overview of the six basic elements of a

ground-water monitoring program, along

with a discussion of the importance of a

hydrogeological characterization.

A. Hydrogeological

Characterization

An accurate hydrogeological characterization is the foundation of an effective groundwater monitoring system. The goal of a

hydrogeological characterization is to acquire

site-specific data to enable the development

of an appropriate ground-water monitoring

program for a site. In some instances, a complete hydrogeological characterization might

not be necessary due to the type of unit

being considered, the type of waste being

managed, or the climate. The design of the

ground-water monitoring program should be

based upon the following site-specific data:

• The lateral and vertical extent of the

uppermost aquifer.

• The lateral and vertical extent of the

upper and lower confining units/layers.

• The geology at the waste management unit’s site, such as stratigraphy,

lithology, and structural setting.

• The chemical properties of the uppermost aquifer and its confining layers

Why is it important to use

a qualified professional?

• Site characterizations can be extremely

complex.

• Incorrect or incomplete characterizations could result in inaccurate detection of contamination in the ground

water due to improper placement of

ground-water monitoring wells and can

cost a significant amount of money.

Incorrect or incomplete characterizations could also result in the installation

of unnecessary monitoring wells at significant cost.

• You should always use a qualified professional to conduct site characterizations. Check to see if the professional

has sufficient training and experience in

ground-water hydrology and related

fields, as demonstrated by state registration, professional certification, or completion of accredited university

programs. These professionals should

be experienced at analyzing groundwater flow and contaminant fate and

transport and at designing groundwater monitoring systems. Ensure that

these professionals are familiar with the

contaminants in the waste and thoroughly check their references.
relative to local ground-water chemistry and wastes managed at the unit.

• Ground-water flow, including:

- The vertical and horizontal directions of ground-water flow in the

uppermost aquifer.

- The vertical and horizontal components of the hydraulic gradient in

the uppermost aquifer and any

hydraulically connected aquifer.

- The hydraulic conductivities of the

materials that comprise the uppermost

aquifer and its confining units/layers.

- The average linear horizontal velocity of ground-water flow in the

uppermost aquifer.

To perform a hydrogeological characterization and develop an understanding of a site’s

hydrogeology, a variety of sources and kinds

of information should be considered.

• Existing information. This can

include the history of the site, including documented records describing

wastes managed on site and releases.

This information can help you characterize the area of the waste management unit and better understand

background conditions. Some hydrogeological information might also

have been developed in the past, for

example during the siting process

(see Chapter 4–Considering the Site).

It might be useful to conduct literature reviews for research performed

in the area of the unit and examine

federal and state geological and environmental reports related to the site

or to the region where the site is to

be located. This review can often

assist in better understanding the

overall site geology and ground-water

flow beneath the unit.

• Site geology. A geologic unit is typically considered to be any distinct or

definable native rock or soil stratum.

Characterize thickness, stratigraphy,

lithology, and hydraulic characteristics of saturated and unsaturated geologic units and fill materials overlying

the uppermost aquifer, in the uppermost aquifer, and in the lower confining unit of the uppermost aquifer

using soil borings, drilling, or geophysical methods. Conventional soil

borings are typically used to characterize onsite soils through direct sampling. Geophysical equipment, such

as ground-penetrating radar, electromagnetic detection equipment, and

electrical resistivity arrays, can provide non-invasive measurements of

physical, electrical, or geochemical

properties of the site. Understanding

the different strata can help identify

the appropriate ground-water monitoring well locations and screen

depths. 

• Ground-water flow beneath the

site. Across the United States,

ground-water flow velocities range

from several feet to over 2,000 feet

per year. To determine hydraulic gradient and flow rate, you should

implement a water-level monitoring

program and estimate hydraulic conductivity. This program should

include measurements of seasonal

and temporal fluctuations in flow, the

effect of site construction and operations on ground-water flow direction,

and variations in ground-water elevation. Information on water-level

monitoring programs and procedures

for obtaining accurate water level

measurements can be found in EPA’s

Municipal Solid Waste Landfill Technical

Guidance Document (U.S. EPA, 1988).

Ensuring Long-Term Protection—Monitoring Performance 

9-3
9-4

Ensuring Long-Term Protection—Monitoring Performance 

The level of effort one employs to characterize a site sufficiently to design an adequate

ground-water monitoring system depends on

the geologic and hydrogeologic complexity of

the site. The complexity of a site should not be

assumed; a soil boring program can help

determine the complexity of a site’s hydrogeology. The American Society for Testing and

Materials’ (ASTM) Annual Book of ASTM

Standards2 provides more than 80 guides and

practices related to waste and site characterization and sampling. For additional information

on ground-water monitoring, see EPA’s

Ground-Water Monitoring: Draft Technical

Guidance (U.S. EPA, 1993a) and Solid Waste

Disposal Facility Criteria: Technical Manual (U.S.

EPA, 1993b).

B. Monitoring Methods

Ground-water monitoring usually involves

the installation of permanent monitoring wells

for periodic collection of ground-water samples. Waste constituent migration can be monitored by sampling ground water for either

contaminants or geophysical parameters.

Ground water also can be sampled through

semi-permanent conventional monitoring

wells or by temporary direct-push sampling.

Conventional monitoring wells, direct-push

sampling, and geophysical methods are

described below.

1. Conventional Monitoring Wells

The conventional monitoring well is the

most common type used to target a single

screened interval. Figure 1 presents an illustration of a single screened interval. Specific construction features are described in more detail

below. The conventional monitoring well is

semi-permanent, meaning it can be used for

sampling over an extended period of time and

should be located by professionally surveyed

reference points. To monitor more than one

depth at a single location, you should install

conventional monitoring wells in clusters or

with multilevel sampling devices. 

2. Direct-Push Ground-Water

Sampling

Using the direct-push technique, ground

water is sampled by hydraulically pressing

and/or vibrating a probe to the desired depth

and retrieving a ground-water sample through

the probe. The probe is removed for reuse

elsewhere after the desired volume of ground

water is extracted. It is important to clean the

probe with an appropriate decontamination

protocol after each use to avoid potential

cross-contamination.

What are the benefits of directpush sampling?

Given favorable geology, the direct-push

method of ground-water sampling can be a

simpler and less expensive alternative to conventional wells. Conventional monitoring

wells, because they are semi-permanent, generally cost more and take longer to install.

Direct-push technology, however, does not

provide a semi-permanent structure from

which to sample the ground water over an

extended period of time, as do conventional

wells. Also, some states only allow the use of

direct-push technology as an initial screening

technique or as a complement to conventional

monitoring wells.

In sandy aquifers, however, the direct-push

technology can be used to install a well similar

to a conventional monitoring well. Relatively

recent advances in direct-push technology use

pre-packed screens with grouts and seals

attached to a metal pipe that are driven into

the ground, forming an assembly similar to a

conventional well. The appropriate state

agency will be able to tell you whether directpush well installations are acceptable.

2 ASTM’s Annual Book of ASTM Standards is available in hard copy or on CD-ROM through ASTM’s online

bookstore at <www.astm.org>.
Ensuring Long-Term Protection—Monitoring Performance 

9-5

3. Geophysical Methods

Geophysical methods measure potential

changes in ground-water quality by measuring changes in the geophysical characteristics

of the sub-surface soils, and in some cases, in

the ground water itself. For example, increases in the levels of certain soluble metals in

ground water can change the resistive properties of the ground water, which can be measured using surface resistive technologies.

Similarly, changes in the resistive properties

of the vadose zone might indicate the migration of leachate toward ground water.

Figure 1. Cross-Section of a Generic Monitoring Well

Source: U.S. EPA, 1993a
9-6

Ensuring Long-Term Protection—Monitoring Performance 

Geophysical characteristics, such as DC-resistivity, electromagnetic induction, pH, and

temperature, can provide important preliminary indications of the performance of the

liner system design. You should consult with

the appropriate state agency regarding the

use of a geophysical method. (See Subsurface

Characterization and Monitoring Techniques

(U.S. EPA, 1993) for additional information

on the use of geophysical methods).

How useful is geophysical

method data?

Geophysical methods are more commonly

used to map the initial extent of contamination

at waste management units than for ongoing

monitoring. Initial monitoring data can guide

the placement of permanent monitoring wells

for ongoing monitoring. As discussed later,

geophysical methods, used in conjunction with

ground-water monitoring, can reduce the frequency of well sampling, which could reduce

monitoring costs. The usefulness of geophysical methods, however, will depend on the local

hydrogeology, the contaminant concentration

levels, and type of contaminants.

C. Number of Wells

It is recommended that a ground-water

monitoring system have a minimum of one

upgradient (or background) monitoring well,

and three downgradient monitoring wells to

make statistically meaningful comparisons of

ground-water quality. The upgradient or

background well(s) permit the assessment of

the background quality of onsite ground

water. The downgradient wells permit detection of any contaminant plumes from a waste

management unit. The actual number of

upgradient and downgradient wells will vary

from unit to unit depending on the actual

site-specific conditions. The actual number of

upgradient and downgradient monitoring

wells and their distribution will influence the

selection of appropriate statistical method. If

an insufficient number of background wells

are used, the use of an inter-well evaluation

might not be possible. Site-specific conditions that influence the number of upgradient

and downgradient wells include: 

• Geology of the waste management

unit site.

• Ground-water flow direction and

velocity, including seasonal and temporal fluctuations.

• Permeability or hydraulic conductivity of any water-bearing formations.

• Physical and chemical characteristics

of contaminants.

• Area of waste management unit.

The number of wells is dependent on the

lateral and vertical placement of monitoring

wells, which is determined by the geology

and hydrogeology of the site. Other factors

influencing the number of wells include the

number of potential contaminant migration

pathways; the spatial distribution of potential

contaminant migration pathways; and the

depth and thickness of stratigraphic horizons

that can serve as contaminant migration

pathways. The number of wells needed will

also vary according to the need for samples

from different depths in the aquifer. This is a

function of hydrogeologic factors and the

chemical and physical characteristics of contaminants. The next section provides a

detailed discussion of the lateral and vertical

placement of monitoring wells.

A larger number of monitoring wells might

be needed at sites with complex hydrogeology.

If a site has multiple waste management units,

use of a multi-unit ground-water monitoring

system can reduce the necessary number of

wells. You should consult with the appropriate

state agency when determining a site’s groundwater monitoring well requirements.
Ensuring Long-Term Protection—Monitoring Performance 

9-7

D. Lateral and Vertical

Placement of Wells

The lateral and vertical placement of monitoring wells is very site-specific. (Monitoring

wells should yield ground-water samples

from the targeted aquifer(s) that are representative of both the quality of background

ground water and the quality of ground water

at a downgradient monitoring point.) Locate

monitoring wells at the closest practicable

distance from the waste management unit

boundary to detect contaminants before they

migrate away from the unit. Early detection

provides a warning of potential waste management unit design failure and allows time

to implement appropriate abatement measures and potentially eliminate the need for

more extensive corrective action. It also

reduces the area exposed and can limit overall liability. 

1. Lateral Placement

Monitoring wells should be placed laterally

along the down-gradient edge of the waste

management unit to intercept potential contaminant migration pathways. Ground-water

flow direction and hydraulic gradient are two

major determining factors in monitoring well

placement. Placement of monitoring wells

should also take into account the number

and spatial distribution of potential contaminant migration pathways and the depths and

thickness of stratigraphic horizons that can

serve as contaminant migration pathways. In

homogeneous, isotropic hydrogeologic sites,

ground-water flow direction and hydraulic

gradient, along with the potential contaminant’s chemical and physical characteristics,

will primarily determine lateral well placement. In a more complex site where hydrogeology and geology are variable and

preferential pathways exist, (a heterogeneous,

anisotropic hydrogeologic site, for example)

the well placement determination becomes

more complex. Potential migration pathways

are influenced by site geology including

changes in hydraulic conductivity, fractured

or faulted zones, and soil chemistry. Humanmade features that influence ground-water

flow should also be considered. These features include ditches, filled areas, buried piping, buildings, leachate collection systems,

and other adjacent disposal units. 

Another point of consideration is seasonal

change in ground-water flow. Seasonal

changes in ground-water flow can result from

seasonal changes in precipitation patterns,

tidal influences, lake or river stage fluctuations, well pumping, or land use pattern

changes. At some sites it might even be possible that ground water flows in all directions

from a waste management unit. These contingencies might call for placement of monitoring wells in a circular pattern to monitor on

all sides of the waste management unit.

Seasonal fluctuations might cause certain

wells to be downgradient only part of the

time, but such configurations ensure that

releases will be detected.

Lateral placement of monitoring wells also

depends upon the chemical and physical

characteristics of a waste management unit’s

constituents. Consider potential contaminant

characteristics such as solubility, Henry’s law

constant, partition coefficients, specific gravity

(density), potential for natural attenuation and

the resulting reaction or degradation products,

and the potential for contaminants to degrade

confining layers. A dense non-aqueous phase

liquid (DNAPL), for instance, because of its

density might not necessarily migrate only in

the direction of the ground-water flow. The

presence of DNAPLs, therefore, can result in

placing wells in more locations than just the

normal downgradient sites.
9-8

Ensuring Long-Term Protection—Monitoring Performance 

2. Vertical Placement and Screen

Lengths 

Similar to lateral placement, vertical well

placement in the ground water around a

waste management unit is determined by

geologic and hydrogeologic factors, as well as

the chemical and physical characteristics of

the potential contaminants. The vertical

placement of each well and its screen lengths

will be determined by the number and spatial

distribution of potential contaminant migration pathways and the depth and thickness of

potential migration pathways. Site-specific

geology, hydrogeology, and constituent characteristics influence the location, size, and

geometry of potential contaminant plumes,

which in turn determine monitoring well

depths and screen lengths.

The chemical and physical characteristics

of potential contaminants from a waste management unit play a significant role in determining vertical placement. The specific

properties of a particular contaminant will

determine what potential migration pathway

it might take in an aquifer. The specific characteristics of a contaminant, such as its solubility, Henry’s law constant, partition

coefficients, specific gravity (density), potential for natural attenuation and the resulting

reaction or degradation products, and the

potential for contaminants to degrade confining layers, will all influence the vertical placement and screen lengths of a unit’s

monitoring wells. A DNAPL, for instance, will

sink to the bottom of an aquifer and migrate

along geologic gradients (rather than hydrogeologic gradients), thus a monitoring well’s

vertical placement should correspond with

the depth of the appropriate geologic feature.

LNAPLs (light non-aqueous phase liquids),

on the other hand, would move along the top

of an aquifer, and result in placement of wells

and wells screens at the surface of the aquifer.

Well screen lengths are also determined by

site- and constituent-specific parameters.

These parameters and the importance of taking vertically discrete ground-water samples,

factor into the determination of well screen

size. Highly heterogeneous (complex) geologic sites require shorter well screen lengths to

allow for the sampling of discrete migration

pathway. Screens that span more than a single

contaminant migration pathway can cause

cross contamination, possibly increasing the

extent of contamination. Shorter screen

lengths allow for more precise monitoring of

the aquifer or the portion of the aquifer of

concern. Excessively large well screens can

lead to the dilution of samples making contaminant detection more difficult. 

The depth or thickness of an aquifer also

influences the length of the well screen. Sites

with highly complex geology or relatively

thick aquifers might require multiple screens

at varying depths. Conversely, a relatively

thin and homogenous aquifer might allow for

fewer wells with longer screen lengths. Table

1 below summarizes the recommended factors to consider when determining the number of wells needed per sampling location.

You should consult with state officials on

the lateral and vertical placement of monitoring wells including well screening lengths. In

the absence of specific state requirements, it

is recommended that the monitoring points

be no more than 150 meters downgradient

from a waste management unit boundary, on

facility property, and placed in potential contamination migration pathways. This maximum distance is consistent with the approach

taken in many states in order to protect

waters of the state.
Ensuring Long-Term Protection—Monitoring Performance 

9-9

E. Monitoring Well Design,

Installation, and

Development

Ground-water monitoring wells are tailored to suit the hydrogeologic setting, the

type of constituents to be monitored, the

overall purpose of the monitoring program,

and other site-specific variables. You should

consult with the appropriate state agency and

qualified professionals to discuss the design

specifications for ground-water monitoring

wells before beginning construction. Figure 1

illustrates the design components that are discussed in this section. The Annual Book of

ASTM Standards includes guides and practices

related to monitoring well design, construction, development, maintenance, and decommissioning. EPA’s Handbook of Suggested

Practices for the Design and Installation of

Ground-Water Monitoring Wells (U.S. EPA,

1989) also contains this information.

1. Well Design

The typical

components of a

monitoring well

include a well

casing, a well

intake, a filter

pack, an annular

and surface seal,

and surface completion. Each of

these components is briefly

described below.

One Well per Sampling Location More Than One Well Per Sampling Location

 No light non-aqueous phase liquids Presence of LNAPLs or DNAPLs

(LNAPLs) or dense non-aqueous phase

liquids (DNAPLs) (immiscible liquid

phases)

 Thin flow zone (relative to screen Thick flow zones

length) Vertical gradients present

 Horizontal flow predominates

 Homogeneous isotropic uppermost Heterogeneous anisotropic uppermost aquifier, 

aquifier, simple geology complicated geology

- multiple, interconnected aquifiers

- variable lithology

- perched water zones

- discontinuous structures

 Discrete fracture zones in bedrock 

 Solution conduits, such as caves, in karst terrains

 Cavernous basalts

Table 1

Factors Affecting Number of Wells Per Location (CLUSTER)
9-10

3 A piezometer is a non-pumping well, generally of small diameter, used to measure the elevation of the

water table.

Ensuring Long-Term Protection—Monitoring Performance 

Well Casing

The well casing is a pipe which is installed

temporarily or permanently to counteract

caving and to isolate the zone being monitored. The well casing provides access from

the surface of the ground to some point in

the subsurface. The casing, associated seals,

and grout prevent borehole collapse and

interzonal hydraulic communication. Access

to the monitored zone is through the casing

and either the screened intake or the open

borehole. (Note: some states do not allow the

use of open borehole monitoring wells.

Check with the state agency to determine

whether this type of monitoring well design

is acceptable.) The casing thus permits piezometric head measurements and ground-water

quality sampling.

A well casing can be made of an appropriate rigid tubular material. The most frequently

evaluated characteristics that directly influence

the performance of casing material in groundwater monitoring applications are strength,

chemical resistance, and interference. The

monitoring well casing should be strong

enough to resist the forces exerted on it by the

surrounding geologic materials and the forces

imposed on it during installation. Casings

should exhibit structural integrity for the

expected duration of the monitoring program

under natural and man-induced subsurface

conditions. Well casing materials should also

be durable enough to withstand galvanic or

electrochemical corrosion and chemical degradation. Metallic casing materials are most subject to corrosion and thermoplastic casing

materials are most subject to chemical degradation. In addition, casing materials should

not exhibit a tendency to either sorb chemical

constituents from (i.e., take constituents out

of solution by either adsorption or absorption)

or leach chemical constituents into the water

that is sampled from the well. If casing materials sorb selected constituents, the waterquality sample will not be representative. 

The three most common types of casing

materials are fluoropolymer materials, including polytetrafluoroethylene (PTFE) and tetrafluoroethylene (TFE); metallic materials,

including carbon steel, galvanized steel, and

stainless steel; and thermoplastic materials,

including polyvinyl chloride (PVC) and acrylonitrile butadiene styrene (ABS). Threaded,

flush casing joints that do not require glue

should be used. Another option is the use of

PTFE tape or o-rings at the threaded joints.

Well Screen

A well screen is a filtering device used to

retain the primary or natural filter pack; it is

usually a cylindrical pipe with openings of a

uniform width, orientation, and spacing. It is

often important to design the monitoring well

with a well intake (well screen) placed opposite the zone to be monitored. The intake

should be surrounded by materials that are

coarser, have a uniform grain size, and have a

higher permeability than natural formation

material. This allows ground water to flow

freely into the well from the adjacent formation material while minimizing or eliminating

the entrance of fine-grained materials, such as

clay or sand, into the well. 

A well screen design should consider:

intake opening (slot) size, intake length,

intake type, and corrosion and chemicaldegradation resistance. Proper sizing of monitoring well intake openings is one of the most

important aspects of monitoring well design.

The selection of the length of a monitoring

well intake depends on the purpose of the

well. Most monitoring wells function as both

ground-water sampling points and piezometers3 for a discrete interval. To accomplish

these objectives, well intakes are typically 2

to 10 feet in length and only rarely equal or

exceed 20 feet in length. The hydraulic efficiency of a well intake depends primarily on

the amount of open area available per unit

length of intake. The amount of open area in
a well intake is controlled by the type of well

intake it is and its opening size. Many types

of well intakes have been used in monitoring

wells, including: the louvered (shutter-type)

intake, the bridge-slot intake, the machineslotted well casing, and the continuous-slot

wire-wound intake. 

Filter Pack

Filter pack is the material placed between

the well screen and the borehole wall that

allows ground water to flow freely into the

well while filtering out fine-grained materials.

It is important to minimize the distortion of

the natural stratigraphic setting during construction of a monitoring well. Hence, it

might be necessary to filter-pack boreholes

that are over-sized with regard to the casing

and well intake diameter. The filter pack prevents formation material from entering the

well intake and helps stabilize the adjacent

formation. The filter-pack materials should be

chemically inert to avoid the potential for

alteration of ground-water sample quality.

Commonly used filter-pack materials include

clean quartz sand, gravel, and glass beads.

You should check with the state regulatory

agency to determine if state regulations specify filter pack grain size, either in absolute

terms or relative to the grain size of the water

bearing zone, or a uniformity coefficient. 

The filter pack should generally extend

from the bottom of the well intake to approximately two to five feet above the top of the

well intake, provided the interval above the

well intake does not result in a hydraulic

connection with an overlying zone. To ensure

that filter pack material completely surrounds

the screen and casing without bridging, the

filter pack can be placed with a tremie pipe (a

small diameter pipe that carries the filter

pack material directly to the filter screen

without creating air pockets within the filter

pack). A layer of fine sand can also be placed

on top of the filter pack to minimize migration of annular seal material (see below) into

the filter pack.

Annular Seal

Annular space is the space between the

casing and the borehole wall. Any annular

space that is produced as a result of the

installation of well casing in a borehole provides a channel for vertical movement of

water and/or contaminants unless the space is

sealed. The annular seal in a monitoring well

is placed above the filter pack in the annulus

between the borehole and the well casing.

The seal serves several purposes: to provide

protection against infiltration of surface water

and potential contaminants from the ground

surface down the casing/borehole annulus; to

seal off discrete sampling zones, both

hydraulically and chemically; and to prohibit

vertical migration of water. Such vertical

movement can cause “cross contamination”

which can influence the representativeness of

ground-water samples. The annular seal can

be comprised of several different types of permanent, stable, low-permeability materials

including pelletized, granular, or powdered

bentonite; neat cement grout; and combinations of both. The most effective seals are

obtained by using expanding materials that

will not shrink away from either the casing or

the borehole wall after curing or setting.

Surface Seal

A surface seal is an above-ground seal that

protects a monitoring well from surface water

and contaminant infiltration. Monitoring wells

should have a surface seal of neat cement or

concrete surrounding the well casing and filling the annular space between the casing and

the borehole at the surface. The surface seal

can be an extension of the annular seal

installed above the filter pack, or it can be a

separate seal placed on top of the annular

Ensuring Long-Term Protection—Monitoring Performance 

9-11
9-12

Ensuring Long-Term Protection—Monitoring Performance 

seal. The surface seal will generally extend to

at least three feet away from the well casing at

the surface and taper down to the size of the

borehole within a few feet of the surface. In

climates with alternating freezing and thawing

conditions, the cement surface should extend

below the frost depth to prevent potential well

damage caused by frost heaving.

Surface Completions

Surface completions are protective casings

installed around the well casing. Two types of

surface completions are common for groundwater monitoring wells: above-ground completion, and flush-to- ground completion.

The primary purposes of either type of completion are to prevent surface runoff from

entering and infiltrating down the annulus of

the well and to protect the well from accidental damage or vandalism. 

In an above-ground completion, which is

the preferred alternative, a protective casing is

generally installed around the well casing by

placing the protective casing into the cement

surface seal while it is still wet and uncured.

The protective casing discourages unauthorized entry into the well, prevents damage by

contact with vehicles, and reduces degradation caused by direct exposure to sunlight.

The protective casing should be fitted with a

locking cap and installed so that there are at

least one to two inches clearance between the

top of the in-place, inner well, casing cap and

the bottom of the protective casing locking

cap when in the locked position. 

Like the inner well casing, the outer protective casing should be vented near the top

to prevent the accumulation and entrapment

of potentially explosive gases and to allow

water levels in the well to respond naturally

to barometric pressure changes. Additionally,

the outer protective casing should have a

drain hole installed just above the top of the

cement level in the space between the protective casing and the well casing. This drain

allows trapped water to drain away from the

casing. In high-traffic areas or in areas where

heavy equipment might be working, consider

the installation of additional protection such

as “bumper guards.” Bumper guards are

brightly-painted posts of wood, steel, or some

other durable material set in cement and

located within three or four feet of the well.

2. Well Installation

To ensure collection of representative

ground-water samples, the well intake, filter

pack, and annular seal need to be properly

installed. In cohesive unconsolidated material

or consolidated formations, well intakes

should be installed as an integral part of the

casing string by lowering the entire unit into

the open borehole and placing the well intake

opposite the interval to be monitored.

Centralizing devices are typically used to center the casing and intake in the borehole to

allow uniform installation of the filter pack

material around the well intake. In non-cohesive, unconsolidated materials there are other

standardized techniques to ensure the proper

installation of wells, such as the use of a casing hammer, a cable tool technique, the dualwall reverse-circulation method, or

installation through the hollow stem of a hollow-stem auger. 

3. Well Development

Monitoring well development is the

removal of fine particulate matter, commonly

clay and silt, from the geologic formation

near the well intake. If particulate matter is

not removed, as water moves through the formation into the well, the water sampled will

be turbid, and the viability of the water quality analyses will be impaired. When pumping

during well development, the movement of

water is unidirectional toward the well.

Therefore, there is a tendency for the particu-
lates moving toward the well to “bridge”

together or form blockages that restrict subsequent particulate movement. These blockages

can prevent the complete development of the

well capacity. This effect potentially impacts

the quality of the water entering the well.

Development techniques should remove such

bridges and encourage the movement of particulates into the well. These particulates can

then be removed from the well by bailer or

pump and, in most cases, the water produced

will subsequently be clear and non-turbid.

In most instances, monitoring wells

installed in consolidated formations can be

developed without great difficulty. Monitoring

wells also can usually be developed rapidly

and without great difficulty in sand and gravel deposits. However, many installations are

made in thin, silty, and/or clayey zones. It is

not uncommon for these zones to be difficult

to develop sufficiently for adequate samples

to be collected.

F. Duration and Frequency

of Monitoring

The duration of ground-water monitoring

will depend on the length of the active life of

the waste management unit and its post-closure care period. Continued monitoring after

a waste management unit has closed is

important because the potential for contaminant releases remains even after a unit has

stopped receiving waste. Monitoring frequency should be sufficient to allow detection of

ground-water contamination. This frequency

usually ranges from quarterly to annually. 

What site characteristics should

be evaluated to determine the

frequency of monitoring?

Ground-water flow velocity is important in

establishing an appropriate ground-water

monitoring frequency to ensure that samples

collected are physically and statistically independent. For example, in areas with high

ground-water flow velocity, more frequent

monitoring might be necessary to detect a

release before it migrates and contaminates

large areas. In areas with low flow velocity,

less frequent monitoring might be appropriate. It is important to analyze background

ground-water conditions, such as flow direction, velocity, and seasonal fluctuations to

help determine a suitable monitoring frequency for a site. You should consult with the

appropriate state agency to determine an

appropriate monitoring frequency. In the

absence of state requirements, it is recommended that semi-annual monitoring be conducted to detect contamination as part of a

basic monitoring program.

G. Sampling Parameters

Selection of parameters to be monitored in a

ground-water monitoring program should be

based on the characteristics of waste in the

management unit. Additional sampling and

analysis information can be found in EPA SW846 Test Methods for Evaluating Solid Waste (U.S.

EPA, 1986) and in ASTM’s standards. The

Annual Book of ASTM Standards also identifies

18 ASTM guides and practices for performing

waste characterization and sampling.

What are sampling parameters?

Analyzing a large number of ground-water

quality parameters in each sampling episode

can be costly. To minimize expense, select

only contaminants and geochemical indicators

that can be reasonably expected to migrate to

the ground water. These are called sampling

parameters. Sampling parameters should provide an early indication of a release from a

waste management unit. Once contamination

is detected, consider expanding the original

Ensuring Long-Term Protection—Monitoring Performance 

9-13
sampling parameters and monitor for additional constituents to fully characterize the

chemical makeup of the release.

What sampling parameters

should be used?

Due to the broad universe of industrial

solid waste, it is not possible to recommend a

list of indicator papameters that are capable

of identifying every possible release. It is recommended to begin by analyzing for a broad

range of parameters to establish background

ground-water quality, and then use the results

to select the sampling parameters to be monitored subsequently at a site. Table 2 lists

potential parameters for a basic ground-water

monitoring program, by different categories.

Modify these parameters, as appropriate, to

address site-specific circumstances. Your

knowledge of the actual waste streams or

existing analytical data is a preliminary guide

for what should be monitored, and leachate

sampling data is also useful to select or adjust

sampling parameters. Where there is uncertainty concerning the chemistry of the waste,

you should perform metal and organic scans

at a minimum. You should consult with the

appropriate state agency to ensure that appropriate sampling parameters are selected.

What are the minimum

components of a basic

monitoring program?

Table 3 summarizes the recommended

minimum components of a basic groundwater monitoring program described above.

Potential modifications to the basic monitoring program that might be appropriate based

on site-specific waste management unit conditions are discussed later in this chapter.

H. Potential Modifications

to a Basic Ground-Water

Monitoring Program

It might be appropriate to modify certain

elements of the basic ground-water monitoring

program described above to accommodate sitespecific circumstances. When using the IWEM

software to evaluate the need for a liner system,

if the recommendation is to use a composite

liner, then the basic ground-water monitoring

program should probably be enhanced. If the

recommendation using the software is that no

liner is appropriate, then it might be possible to

scale back some aspects of the basic groundwater monitoring program. 

Components that might be subject to modification include the duration and frequency

of monitoring, sampling parameters, and the

use of vadose zone monitoring. Possible modifications of these elements are discussed further below. You should consult with the

appropriate state officials on their requirements for ground-water monitoring programs.

In some states, a unit might be eligible for a

no-migration exemption from the state’s

ground-water monitoring requirements.

1. Duration and Frequency of

Monitoring

The duration of monitoring (active life

plus post-closure care) is not likely to be

modified in either a reduced or an enhanced

ground-water monitoring program.

Adjustments to the frequency of monitoring,

however, might be appropriate, based primarily on the mobility of contaminants and

ground- water velocity. For example, if the

sampling parameters are slow moving metals,

annual rather than semi-annual monitoring

might be appropriate. Conversely, quarterly

monitoring might be considered at a unit

with a rapid ground-water flow rate or a

9-14

Ensuring Long-Term Protection—Monitoring Performance 
Ensuring Long-Term Protection—Monitoring Performance 

9-15

Category Specific Parameters

Field-Measured Parameters Temperature

pH

Specific electrical conductance

Dissolved oxygen

Eh oxidation-reduction potential

Turbidity

Leachate Indicators Total organic carbon (TOC-filtered)

pH

Specific conductance

Manganese (Mn)

Iron (Fe)

Ammonium (NH4)

Chloride (Cl)

Sodium (Na)

Biochemical oxygen demand (BOD)

Chemical oxygen demand (COD)

Volatile organic compounds (VOCs)

Total Halogenated Compounds (TOX)

Total Petroleum Hydrocarbons (TPH)

Total dissolved solids (TDS)

Additional Major Water Quality Parameters Bicarbonate (HCO3)

Boron (Bo)

Carbonate (CO3)

Calcium (Ca)

Fluoride (Fl)

Magnesium (Mg)

Nitrate (NO3)

Nitrogen (disolved N2)

Potassium (K)

Sulfate (SO4)

Silicon (H2SiO4)

Strontium (Sr)

Total dissolved solids (TDS)

Minor and Trace Inorganics Initial background sampling of inorganics for which drinking water standards exist (arsenic, barium, cadmium,

chromium, lead, mercury, selenium, silver); ongoing monitoring of any constituents showing background near or

above drinking water standards.

Waste-Specific Constituents Selected based on knowledge of waste characteristics (initial metals and organic scans at a minimum).

Table 2

Potential Parameters for Basic Ground-Water Monitoring

(Potential Parameters Should be Selected Based on Site-Specific Circumstances)
mobile contaminant such as cyanide over a

permeable sand and gravel aquifer.

2. Sampling Parameters

The basic recommended ground-water

monitoring program already recommends the

use of a parameter list that is tailored to the

waste characteristics and site hydrogeology.

Where the use of the IWEM software indicates no liner is appropriate, it might be possible to reduce the list of parameters

routinely analyzed in downgradient wells to

only a few indicator parameters. More complete analysis would only be initiated if a significant change in the concentration of an

indicator parameter had occurred.

3. Vadose-Zone Monitoring

The vadose zone is the region between the

ground surface and the saturated zone.

Depending on climate, soils, and geology, it

can range in thickness from several feet to

hundreds of feet. Vadose-zone monitoring

can detect migration of contaminants before

they reach ground water, serving as an early

warning system if a waste management unit

is not functioning as designed. It can also

reduce the time and cost of remediation, and

the extent of subsequent ground-water monitoring efforts. 

If site conditions permit, it might be desirable to include vadose-zone monitoring as

part of the overall ground-water program. If

vadose-zone monitoring is incorporated, the

recommended number of ground-water monitoring wells would be determined by the

basic ground-water monitoring program, and

background quality would still need to be

characterized with ground-water monitoring.

The ground-water monitoring program

becomes a backup, however, with full use

only being initiated if contaminant migration

is detected in the vadose zone. The sections

9-16

Ensuring Long-Term Protection—Monitoring Performance 

Monitoring Component Recommended Minimum

Number of Wells Minimum 1 upgradient and 3 downgradient.4

Point of Monitoring Waste management unit boundary or out to 150 meters

down gradient of the waste management unit area.5

Duration of Monitoring Active life plus post-closure care. 

Frequency of Monitoring Semi-annual during active life.6

Sampling Parameters Metal and organic scans, use of indicators, leachate analysis,

and/or knowledge of the waste. See the categories listed in

Table 2.

Table 3 Recommended Components of a Basic Ground-Water Monitoring Program

4 The actual number of both upgradient and downgradient wells will vary from unit-to-unit and will

depend on the actual site-specific conditions.

5 Discussion of EPA’s rationale for the point of monitoring being out to 150 meters from a unit’s boundary can be found in 40 CFR Part 258 criteria.

6 Ground-water flow rate might dictate that more or less frequent monitoring might be appropriate. More

frequent monitoring might be appropriate at the start of a monitoring program to establish background.

Less frequent and/or reduced in scope monitoring might also be appropriate during the post-closure

care period.
below describe some of the commonly used

methods for vadose zone monitoring, vadose

zone characterization, and elements to consider in the design of a vadose zone monitoring system. 

Vadose-Zone Monitoring Methods

There are dozens of specific techniques for

indirect measurement and direct sampling of

the vadose zone. The more commonly used

methods with potential value for waste management units are described briefly below.

Soil-Water and Tension Monitoring

Measuring changes over time in soil-water

content or soil-water tension is a relatively

simple and inexpensive method for leak

detection. Periodic measurements of soil water

content or soil moisture tension beneath a

lined waste management unit, for example,

should show only small changes. Significant

increases in water content or decreases in

moisture tension would indicate a leak.

What method should be used to

measure soil moisture?

Soil-moisture characteristics can be measured in two main ways: 1) water content,

usually expressed as weight percentage, and

2) soil-moisture tension, or suction, which

measures how strongly water is held by soil

particles due to capillary effects. As soil-water

content increases, soil-moisture tension

decreases. Measurements will not indicate,

however, whether contaminants are present.

Figure 2 shows three major methods that

are available for insitu monitoring of soilmoisture changes. Porous-cup tensiometers

(Figure 2a) measure soil-moisture tension,

with the pressure measurements indicated by

using either a mercury manometer, a vacuum

gauge, or pressure transducers. Soil-moisture

resistivity sensors (Figure 2b) measure either

water content or soil-moisture tension,

depending on how they are calibrated. Timedomain reflectometry probes (Figure 2c)

measure water content using induced electromagnetic currents. For vadose-zone monitoring applications, the devices are usually

placed during construction of a waste management unit and electrical cables run to one

or more central locations for periodic measurement. The other commonly used method

for monitoring soil-water content is to use

neutron or dielectric probes. These require

placement of access tubes, through which

probes are lowered or pulled, and allow continuous measurement of changes in water

content along the length of the tubes. 

Soil-Pore Liquid Sampling

Sampling and analysis of soil-pore liquids

can determine the type and concentration of

contaminants that might be moving through the

vadose zone. Soil-pore liquids can be collected

by applying either a vacuum that exceeds the

soil moisture tension, commonly done using

vacuum or pressure-vacuum lysimeters, or by

burying collectors that intercept drain water.

Figures 3a and 3b illustrate different methods

for collecting soil-pore liquids.

Soil-Gas Sampling

Soil-gas sampling is a relatively easy and

inexpensive way to detect the presence or

movement of volatile contaminants and gases

associated with degradation of waste within a

Ensuring Long-Term Protection—Monitoring Performance 

9-17
waste management unit, such as carbon

dioxide and methane. Of particular concern

are gases associated with the breakdown of

organic materials and toxic organic compounds. Permanent soil-gas monitoring

installations consist of a probe point placed

above the water table, a vacuum pump which

draws soil-gas to the surface, and a syringe

used to extract the gas sample, as shown in

Figure 4a. Installing soil-gas probes at multiple levels, as shown in Figure 4b, allows

detection of downward or upward migration

of soil gases. It is important to note, however,

that the performance of soil-gas sampling can

9-18

Ensuring Long-Term Protection—Monitoring Performance 

Figure 2. Major Methods for In Situ Monitoring of Soil Moisture or Matrix Potential

(a) Three Types of Porous Cup Tensiometers, (b) Resistance Sensors, and (c) Time Domain Reflectometry

Probes 

Sources: (a) Morrison, 1983. (b) U.S. EPA, 1993. (c) Topp and Davis, 1985, by permission.
be limited by some types of soil, such as tight

clays or tight, saturated clays.

Vadose Zone Characterization

Just as the design of ground-water monitoring systems requires an understanding of

the ground-water flow system, the design of

vadose zone monitoring systems requires an

understanding of the vadose zone flow system. For example, in ground water systems,

hydraulic conductivity does not change over

time at a particular-location, whereas in the

vadose zone, hydraulic conductivity changes

with soil-water content and soil-moisture tension. To estimate the speed with which water

will move through the vadose zone, the relationship between soil-water content, soilmoisture tension, and hydraulic conductivity

should be measured or estimated.

Unsaturated zone numerical modeling programs, such as HYDRUS 2-D or Seep (2-D)

are designed to characterize the vadose zone.

Vadose-Zone Monitoring System Design

A vadose zone monitoring system combined with a ground-water monitoring system can reduce the cost of corrective

measures in the event of a release. Remedial

action is usually easier and less expensive if

employed before contaminants reach the

ground-water flow system. 

The design and installation of a vadose-zone

monitoring system are easiest with new waste

Ensuring Long-Term Protection—Monitoring Performance 

9-19

Figure 3. Example Methods for Collecting Soil-Pore Samples

(a) Vacuum Lysimeter, (b) Pressure-Vacuum Lysimeter

Source: ASTM, 1994. Copyright ASTM. Reprinted with permission.
management facilities, where soil-water monitoring and sampling devices can be placed

below the site. Relatively recent improvements

in horizontal drilling technology, however, now

allow installation of access tubes for soil-moisture monitoring beneath existing facilities.

Important factors in choosing the location and

depth of monitoring points in a leak-detection

network include: 1) consideration of the

potential area of downward leakage, and 2)

determination of the effective detection area of

the monitoring device. 

Cullen et al. (1995) suggest an approach

to vadose zone monitoring that includes the

following:

9-20

Ensuring Long-Term Protection—Monitoring Performance 

Figure 4. Soil Gas Sampling Systems

(a) Gas Sampling Probe and Sample Collection Systems, (b) Typical Installation of Nested Soil Gas Probes 

Source: Reprinted with permission from Wilson, et al., Handbook of Vadose Zone Characterization and

Monitoring, 1995. Copyright CRC Press, Boca Raton, Florida.
• Identification and prioritization of

critical areas most vulnerable to contaminant migration.

• Selection of indirect monitoring

methods that provide reasonably

comprehensive coverage and costeffective, early warning of contaminant migration.

• Selection of direct monitoring methods that provide diagnostic confirmation of the presence and migration of

contaminants.

• Identification of background monitoring points that will provide hydrogeologic monitoring data

representative of preexisting site conditions.

• Identification of a cost-efficient, temporal monitoring plan that will provide early warning of contaminant

migration in the vadose zone.

This approach is very similar to what is

described for the basic ground-water monitoring program.

II. Surface-Water

Monitoring

Controlling constituent discharges to surface water from industrial waste management

units is another component of responsible

waste management. Monitoring can be conducted for many purposes, such as:

• Characterizing surface-water conditions and identifying changes or

trends in water quality over time.

• Identifying existing or emerging

water quality problems.

• Identifying the types and amounts of

constituents present in the water body.

• Designing a pollution prevention program or establishing best management practices (BMPs).

• Determining whether surface-water

regulations and permit conditions are

being satisfied.

• Responding to emergencies, such as

accidental discharges or spills.

Some types of monitoring activities meet

several of these purposes simultaneously,

while others are specifically designed for one

purpose, such as to determine compliance

with permit conditions.

If your facility is subject to a federal, state,

or local permit that requires monitoring and

sampling, you must collect and analyze samples according to the permit requirements.

Otherwise, you should consider implementing a sampling program to monitor the quality of runoff, the performance of BMPs, and

any impacts on surface waters. For further

information on BMPs relating to surfacewater quality, refer to Chapter 6–Protecting

Surface Water. Implementation of BMPs,

along with regular maintenance inspections

and upkeep, will greatly reduce the potential

for surface-water contamination.

When establishing any type of sampling

and monitoring program, there are certain

common sense guidelines to follow.

Inadequate frequency of data collection and

incomplete monitoring might be useless

while high-frequency monitoring and sampling for numerous constituents can be costly

and could create a backlog of unusable data.

The following discussion summarizes what

you should consider when establishing sampling programs to effectively perform surface

water monitoring. 

Ensuring Long-Term Protection—Monitoring Performance 

9-21
A. Monitoring Storm-Water

Discharges

As discussed in Chapter 6–Protecting

Surface Water, NPDES permits establish limits on what constituents (and at what

amounts or concentrations) facilities may discharge to receiving surface waters. Some

waste management units, such as surface

impoundments, might have an NPDES permit to discharge wastewaters directly to surface waters. Other units might need an

NPDES permit for storm-water discharges.

An NPDES permit will also contain limits on

what can be discharged, monitoring and

reporting requirements, and other provisions

to ensure that the discharge does not impair

surface-water quality or human health. Due

to the variable nature of storm-water flows

during a rainfall event and the different analytical considerations for certain constituents,

the sampling requirements for different waste

management unit types and sampling locations will vary as well. The guidelines and

general sampling procedures outlined below

should be considered when developing a

storm-water sampling program to comply

with permit requirements or to monitor the

quality of runoff and determine the effectiveness of BMPs.

Sampling a representative storm. Using

climatic data, you can determine the average

rainfall depth and duration of rainfall events

at the waste management unit site. You

should sample during a representative storm

event. The representative storm should be

preceded by at least 72 hours of dry weather

and, when possible, should be between 50

and 150 percent of the average depth and

duration. The time to collect individual grab

samples is during the first flush (i.e., the first

30 minutes of the event), and composite

samples should then be collected over the

first 3 hours, or the entire event if less than 3

hours. These guidelines help ensure that constituents in the sampled runoff will not be so

concentrated or so dilute as to be unrepresentative of the overall runoff.

Determining the sample type. A grab

sample is a discrete, individual sample taken

within a short period of time, usually less

than 15 minutes. Analysis of a grab sample

characterizes the quality of a storm water-discharge at the time the sample was taken.

These types of samples can be used to characterize the maximum concentration of a

constituent in the discharge. 

A composite sample is a mixed or combined sample that is formed by combining a

series of individual and discrete samples of

specific volumes at specified intervals. These

intervals can be either time-weighted or flowweighted. Time-weighted composite samples

are collected and combined in proportion to

time, while flow-weighted composite samples

are combined in proportion to flow.

Composite samples characterize the quality

of a storm-water discharge over a specific

period of time, such as the duration of a

storm event. 

Determining the sample techniques.

Grab and composite samples can be collected

by either manual or automatic sampling techniques. Manual samples are simply collected

by hand, while automatic samples are collected by powered devices according to preprogrammed criteria. Both techniques have

advantages and disadvantages that need to be

weighed when choosing a sampling technique for a specific site. The advantages of

manual sampling include its appropriateness

for all constituents and its lower cost compared to automatic sampling. Manual sampling, however, can be labor intensive, can

expose personnel to potentially hazardous

conditions, and is subject to human error. 

The advantages of automatic sampling are

the convenience it offers, its minimum labor

requirements, its reduction of personnel

9-22

Ensuring Long-Term Protection—Monitoring Performance 
Ensuring Long-Term Protection—Monitoring Performance 

9-23

exposure to hazardous conditions, and its

low risk of human error. Unfortunately, automatic sampling is not suitable for all constituent types. Volatile organic compounds

(VOC), for example, can not be sampled

automatically due to the agitation during

sample collection. This agitation can cause

the VOC constituents to completely volatilize

from the sample. Other constituents such as

fecal streptococcus, fecal coliform, and chlorine might also not be amenable to automatic

sampling due to their short holding times.

Since sample temperature and pH need to be

measured immediately, the option for using

automatic sampling for these parameters is

limited as well. Automatic sampling can also

be expensive, and does require a certain

amount of training. Table 4 presents a comparison of manual and automatic sampling

techniques.

Sampling at the outfall point. Stormwater samples should be taken at a stormwater point source. A “point source” is

defined as any discernible, confined, and discrete conveyance. The ideal sampling location is often the lowest point in a drainage

area where a conveyance discharges, such as

the discharge at the end of a pipe or ditch.

The sample point should be easily accessible

on foot and in a location that will not cause

hazardous sampling conditions. You should

not sample during dangerous wind, lightning, flooding, or other unsafe conditions. If

these conditions are unavoidable during an

event, then the sampling should be delayed

until a less hazardous event occurs.

Preferably, the sampling location will be

located onsite, but if it is not, obtain permission from the owner of the property where

the discharge is located. Inaccessible discharge points, numerous small point discharges, run-on from other properties, and

infinite other scenarios can cause logistical

problems with sampling locations. If the discharge is inaccessible or not likely to be representative of the runoff, samples might need

to be taken at a point further upstream of the

discharge pipe or at several locations to best

characterize site runoff. 

Coordinating with the laboratory. It is

important to collect adequate sample volumes to complete all necessary analyses.

When testing for certain constituents, samples might need to be cooled or otherwise

preserved until analyzed to yield meaningful

results. Section 3.5 of EPA’s NPDES Storm

Water Sampling Guidance Document (U.S. EPA,

1992) contains information on proper sample

handling and preservation procedures.

Submitting the proper information to the laboratory is important in ensuring proper sample handling by the laboratory. Proper sample

documentation guidelines are outlined in

Section 3.7 of the NPDES Storm Water

Sampling Guidance Document. Coordination

with the laboratory that will be performing

the analysis will help ensure that these issues

are adequately addressed. 

You are required to follow all sampling

and monitoring requirements in an NPDES

permit. If there are no sampling requirements, analyze runoff for basic constituents,

such as oil and grease, pH, biochemical oxygen demand (BOD), chemical oxygen

demand (COD), total suspended solids

(TSS), phosphorus, and nitrogen, as well as

any other constituents known or suspected to

be present in the waste, such as heavy metals

or other toxic constituents. 

Additional sampling guidance can be

obtained from EPA’s NPDES Storm Water

Sampling Guidance Document (U.S. EPA,

1992) and Interim Final RCRA Facility

Investigation (RFI) Guidance: Volume III (U.S.

EPA, 1989). In addition, state and local environmental agencies also have guidance on

appropriate sampling methods.

There is a national system that provides

permitting information for facilities holding
9-24

Ensuring Long-Term Protection—Monitoring Performance 

Source: U.S. EPA, 1992.

Sample Method Advantages Disadvantages

Manual Grabs • Generally appropriate for all • Labor-intensive

constituents •Environment possibly dangerous to field personnel

• Minimum equipment required • Might be difficult to get personnel and equipment

to the storm water outfall within the first 30 

minutes of the event

• Possible human error

Manual Flow- • Generally appropriate for all • Labor-intensive

Weighted constituents •Environment possibly dangerous to field personnel

Composites • Minimum equipment required • Human error can have significant impact on 

(multiple grabs) sample representativeness

• Requires that flow measurements be taken during

sampling

Automatic Grabs • Minimizes labor requirements • Samples not collected for oil and grease, might 

• Low risk of human error not be representative

• Reduced personnel exposure to • Automatic samplers generally cannot properly 

unsafe conditions collect samples for VOC analysis

• Sampling can be triggered • Costly if numerous sampling sites require the 

remotely or initiated according to purchase of equipment

present conditions • Can require equipment installation and 

maintenance; can malfunction

• Can require operator training

• Might not be appropriate for pH and temperature

• Might not be appropriate for parameters with 

short holding times (e.g., fecal streptococcus,

fecal coliform, chlorine)

• Cross-contamination of aliquot if tubing/bottles 

not washed

Automatic Flow- • Minimizes labor requirements • Generally not acceptable for VOC sampling

Weighted • Low risk of human error • Costly if numerous sampling sites require the 

Composites • Reduced personnel exposure to purchase of equipment

unsafe conditions • Can require equipment installation and 

• Can eliminate the need for maintenance; can malfunction

manual compositing of aliquots • Can require operator training

• Sampling can be triggered remotely • Can require that flow measures be taken during 

or initiated according to onsite sampling

conditions • Cross-contamination of aliquot if tubing/bottles

not washed

Table 4

Comparison of Manual and Automatic Sampling Techniques
NPDES permits. This system is called the

Permits Compliance System (PCS) and it

allows users to retrieve information regarding

facilities holding NPDES permits, including

permit limits and actual monitoring data. You

can specify the desired information by using

any combination of facility name, geographic

location, standard industrial classification

(SIC) code, and chemical names. The PCS

database can be accessed at <www.epa.gov/

enviro/html/water.html#PCS>.

B. Monitoring Discharges

to POTWs

As discussed in the Chapter 6–Protecting

Surface Water, industrial facilities discharging

to a POTW might have to meet “pretreatment

standards.” If so,, they will be subject to certain requirements under a local pretreatment

program. The National Pretreatment Program

requires certain POTWs in defined circumstances to develop a local pretreatment program (see 40 CFR Section 403.8(a)). The

actual requirement for a POTW to develop

and implement a local program is a condition

of the POTW’s NPDES permit.

Sampling is the most common method for

verifying compliance with pretreatment standards. Monitoring locations are usually designated by the local municipality administering

the pretreatment program and will be such

that compliance with permitted discharge

limits can be determined. Monitoring locations should be appropriate for waste stream

conditions, be representative of the discharge,

have no bypass capabilities, and allow for

unrestricted access at all times (see 40 CFR

Section 403.12).

EPA’s General Pretreatment Regulations

require POTWs to monitor each significant

industrial user (SIU) at least annually (see 40

CFR Section 403.8 (f)(2)(v)) and each SIU to

self-monitor semi-annually, although permits

issued by the local control authority might

require more frequent monitoring (see 40

CFR Section 403.12 (g) and (h)). The local

municipality will develop and implement

standard operating procedures and policies

that specify the sample collection and handling protocols in accordance with 40 CFR

Part 136.

Sampling for constituents such as pH,

cyanide, oil and grease, flashpoint, and VOCs

will require manual collection of grab samples (see 40 CFR Section 403.12 (b)(5)).

Similar to composite samples, grab samples

must be representative (see 40 CFR Section

403.12 (g)(4)) of the discharge and must be

collected from actively flowing waste streams.

Fluctuations in flow or the nature of the discharge might require collection and handcompositing of more than one grab sample to

accurately access compliance. Flow-weighted

composite samples are preferred over timeweighted composite samples, particularly

where the monitored discharge is intermittent

or variable. The local authorities can waive

flow-weighted composite sampling if an

industrial user demonstrates that flowweighted sampling is not feasible. In these

cases, time-weighted composite samples can

be collected (see 40 CFR Section 403.12

(b)(5)(iii)). Refer to EPA’s Industrial User

Inspection and Sampling Manual for POTWs

(U.S. EPA, 1994a) for additional information

on sample collection and analysis procedures

for the pretreatment program.

If you are subject to pretreatment requirements and must conduct sampling to demonstrate compliance, the requirements

established for your site by the local control

authority apply. These include following the

proper sample collection and handling protocols and being able to prove that you did so

(i.e., by keeping sampling records; noting

location, date, and time of sample collection;

maintaining chain of custody forms showing

the link between field personnel and the labEnsuring Long-Term Protection—Monitoring Performance 

9-25
oratory) (see 40 CFR Section 403.12(o)).

Consult EPA’s Introduction to the National

Pretreatment Program document (U.S. EPA,

1999) for further information on monitoring

requirements under the National

Pretreatment Program.

C. Monitoring Surface

Water Conditions

In order to determine if runoff from your

waste management unit is impacting adjacent

surface waters you might want to consider

establishing a surface-water quality monitoring program. Chemical, physical, and biological data can provide information about the

effectiveness of BMPs. The data collected will

help you to characterize any overall water

quality at the selected monitoring sites, identify problem areas, and document any

changes in water quality.

In designing your program, one of the

most important things to consider is what

types of parameters to monitor (chemical,

physical, and/or biological) that will enable

you to determine how your waste management unit might be impacting the aquatic

ecosystem. Determining where you should

set-up a monitoring station is also very

important and will depend on relevant

hydrologic, geologic, and meteorologic factors. For assistance and more information on

establishing water quality sampling stations

and a sampling program you should consult

with state and local water quality planning

agencies. Additional guidance on establishing

sampling and monitoring programs can be

obtained from EPA’s Volunteer Stream

Monitoring Document (U.S. EPA, 1997) and

Volunteer Lake Monitoring Document (U.S.

EPA, 1991). Monitoring can be conducted at

regular sites on a continuous basis (“fixed

station” monitoring); at selected sites on an

as needed basis or to answer specific questions (“intensive surveys”); on a temporary or

seasonal basis (e.g., during periods of intense

rainfall); or on an emergency basis (i.e., an

accidental spill or discharge).

Why is the monitoring taking

place? 

You should first determine the purpose of

establishing a surface-water monitoring program. Reasons for monitoring surface water

can include developing baseline characterization data prior to a waste management unit

being constructed, documenting water quality changes over time, screening for potential

water quality problems, determining the

effectiveness of BMPs, or determining the

impact of the waste management unit on surface waters.

How will the data be used? 

The data collected will help you to identify

constituents of concern, the impacts of pollution and pollution control activities (i.e.,

BMPs), and trends in water quality. Note that

the data you collect might also be useful to

regional or local water quality planning

offices that might already be collecting similar data in other parts of the watershed.

What parameters or conditions

will be monitored? 

The basic parameters that are indicators of

general water quality health, include dissolved

oxygen (DO), pH, total suspended solids

(TSS), nitrogen, hardness, temperature, and

phosphorous. In addition, you might choose

to monitor parameters that would indicate

whether the designated use (e.g., fisheries,

recreation) of the water body is being met (as

discussed in Chapter 6–Protecting Surface

Water). Further, based on the types of constituents associated with the waste management unit, you should also sample for

contaminants that would indicate whether

your surface-water protection measures are

9-26

Ensuring Long-Term Protection—Monitoring Performance 
functioning properly (e.g., heavy metals,

organics, or other materials associated with the

unit). In many cases, a few surrogate constituents can be selected instead of analyzing a

complete spectrum of constituents. For example, lead, zinc, or cadmium are often selected

to indicate pollution by toxic metals. Instead

of analyzing for every possible pathogenic

microorganism, total and fecal coliform bacteria analyses are commonly used to indicate

bacterial and viral contamination. Chemical

oxygen demand (COD) and total organic carbon (TOC) are used in high-frequency grab

sampling programs as indicators of pollution

by organics. 

Where should the monitoring

sites/stations be located? 

In order to determine if the waste management unit is having an impact on surface

water it is important to determine the quality

of the water upstream from the unit as well as

downstream. You should also consider the

number of sites to establish how accessible,

safe, and convenient potential sites are. In

addition, it is important to determine if potential sites are near tributary inflows, dams,

bridges, or other structures that might affect

the sampling results. You should also determine if you will establish permanent sampling

stations (i.e., structures or buildings) or if the

stations will simply be designated points within the watershed.

What sampling methods should

be used? 

You must decide how the samples will be

collected, what sampling equipment will be

used (e.g., automatic samplers or by hand),

what equipment preparation methods are

necessary (e.g., container sterilization, meter

calibration), and what protocols will be followed. Refer to Part II, Section A of this

chapter for a discussion of determining sampling methods. EPA’s SW-846 also provides

guidance on selecting the appropriate sampling methods.

When will the monitoring occur? 

You need to establish how frequently monitoring will take place, what time of year is

best for sampling, and what time of day is

best for sampling. Monitoring at the same

time of day and at regular intervals helps

ensure comparability of data over time. In

general, monthly chemical sampling and

twice yearly biological sampling are considered adequate to identify water quality

changes over time. If you are conducting biological sampling, it should be conducted at

the same time each year because of natural

seasonal variations in the aquatic ecosystem.

Note that the frequency of sampling should

be increased during the rainy season as this is

when contamination from waste management

units is expected to increase due to stormwater runoff. 

How can the quality of the data

collected be ensured? 

You should develop a quality assurance

plan to ensure that quality assurance and

quality control procedures are implemented

at all times. In addition, the personnel conducting the sampling should be properly

trained and consider how to manage the data

after the data have been collected.

Hydrologic and water quality information

is also collected and published regularly by

EPA and the U.S. Geological Survey (USGS).

Both agencies have computerized systems for

storing and retrieving information on water

quality that are available on the Internet.

Water quantity and flow data in streams is

also available from USGS which has offices in

every state. USGS also operates two national

stream water quality networks, the

Hydrologic Benchmark Network (HBN) and

Ensuring Long-Term Protection—Monitoring Performance 

9-27
the National Stream Quality Accounting

Network (NASQAN). These networks were

established to provide national and regional

descriptions of stream water quality conditions and trends, based on uniform monitoring of selected watersheds throughout the

United States, and to improve our understanding of the effects of the natural environment and human activities on water quality.

Stream water quality measurements are available for the approximate periods 1973 to

1995 for NASQAN and 1962 to 1995 for

HBN. For more information on how to

obtain this water quality information, visit

the USGS Web site at <water.usgs.gov/pubs/

FS/fs-014-00/index.html>.

III. Soil Monitoring

This section focuses primarily on establishing a soil monitoring program for land

application purposes. Much of the following

discussion concerning sampling methods,

protocols, and quality assurance and quality

control, however, also is applicable to soil

monitoring for corrective action site assessments. Part I of Chapter 10–Taking

Corrective Action outlines which parameters

to consider when performing soil investigations for corrective action purposes. For

more information on corrective action unit

assessments, refer to the North Carolina

Cooperative Extension Service’s Soil facts:

Careful Soil Sampling - The Key to Reliable Soil

Test Information (AG-439-30), the University

of Nebraska Cooperative Extension Institute

of Agriculture and Natural Resources’

Guidelines for Soil Sampling (G91-1000-A),

and EPA’s RCRA Facility Investigation

Guidance: Volume II: Soil, Ground Water and

Subsurface Gas Releases (U.S. EPA, 1989). As

discussed in Part I of this chapter, soil monitoring can be used to detect the presence of

waste constituents in the soil and track their

9-28

Ensuring Long-Term Protection—Monitoring Performance 

EPA’s Water Quality Data

Management Systems

EPA maintains two data management systems containing water quality information:

the Legacy Data Center (LDC) and STORET.

The LDC contains historical water quality

data dating back to the early part of the 20th

century and collected up to the end of 1998.

STORET (short for STOrage and RETrieval)

contains data collected beginning in 1999,

along with older data that has been properly

documented and migrated from the LDC. 

Both systems contain biological, chemical, and physical data on surface and

ground water collected by federal, state and

local agencies, Indian Tribes, volunteer

groups, academics, and others. All 50 states,

territories, and jurisdictions of the U.S. are

represented.

Each sampling result in these databases is

accompanied by information on where the

sample was taken (e.g., latitude, longitude,

state, county, Hydrologic Unit Code), when

the sample was gathered, the medium sampled (e.g., water, sediment, fish tissue), and

the name of the organization that sponsored

the monitoring. In addition, STORET contains information on why the data were

gathered; the sampling and analytical methods used; and the quality control checks

used when sampling, handling, and analyzing the data.

The LDC and STORET databases are

Web-enabled. With a standard Web browser, you can browse both systems interactively or create files to be downloaded to your

computer. For more information on the

LDC and STORET data management systems and how the water quality data can be

obtained visit EPA’s STORET Web site at

<www.epa.gov/storet>.
migration before they reach ground water.

Characterizing the soil properties at a land

application site can also help you determine

the application rates that will maximize waste

assimilation. 

To obtain site-specific data on actual soil

conditions, the soil should be sampled and

characterized. The number and location of

samples necessary for adequate soil characterization is primarily a function of the variability of the soils at a site. If the soil types occur

in simple patterns, a composite sample of

each major soil type can provide an accurate

picture of the soil characteristics. The depth

to which the soil profile is sampled, and the

extent to which each horizon is vertically

subdivided, will depend on the parameters to

be analyzed, the vertical variations in soil

character, and the objectives of the soil sampling program. You should rely on a qualified

soil scientist to perform this characterization.

Poorly conducted soil sampling can result in

an inaccurate soil characterization which

could lead to improper application of waste

and failure of the unit to properly assimilate

the applied waste.

A. Determining the Quality

of Soil

Soil quality is an assessment of how well

soil performs all of its functions, not just how

well it assimilates waste. Measuring crop yield,

nutrient levels, water quality, or any other single outcome alone will not give you a complete assessment of a soil’s quality. The

minerals and microbes in soil are responsible

for filtering, buffering, degrading, immobilizing, and detoxifying organic and inorganic

materials, including those applied to the land

and deposited by the atmosphere. Determining

the quality of a soil is an assessment of how it

performs all of these functions in addition to

waste assimilation. For assessing soil quality in

relation to land application units, it will be

Ensuring Long-Term Protection—Monitoring Performance 

9-29

Examples of Indicators of Soil Quality

Indicator Relationship to Soil Health 

Soil organic matter (SOM). Soil fertility, structure, stability, nutrient retention,

soil erosion.

PHYSICAL: soil structure, Retention and transport of water

depth of soil, infiltration and bulk and nutrients, habitat for 

density, water holding capacity. microbes, estimate of crop productivity potential,

compaction, water movement, porosity, workability.

CHEMICAL: pH, electrical Biological and chemical activity

conductivity, extractable nitrogen- thresholds, plant and microbial

phosphorous-potassium. activity thresholds, plant available nutrients and

potential for nitrogen and phosphorous loss.

BIOLOGICAL: microbial biomass, Microbial catalytic potential and 

carbon and nitrogen, potentially repository for carbon and

mineralizable nitrogen, soil nitrogen, soil productivity and

supplying potential, microbial respiration.

activity measure.
important for the soil to be able to filter the

waste constituents and cycle nutrients such as

carbon, nitrogen, and phosphorus. 

Measuring soil quality requires the use of

physical, chemical, and biological indicators,

which can be assessed by qualitative or quantitative techniques. After measurements are

collected, they can be evaluated by looking

for patterns and comparing results to measurements taken at a different time or field.

For more information, consult the Guidelines

for Soil Quality Assessment prepared by the

Soil Quality Institute of the Natural

Resources Conservation Service (formerly the

U.S. Soil Conservation Service).

B. Sampling Location and

Frequency

Prior to sampling, divide the land application unit into uniform areas, then collect representative samples from each area. These

divisions should be based upon soil type,

slope, degree of erosion, cropping history,

known crop growth differences, and any

other factors that might influence nutrient

levels in the soil. One recommended

approach is to divide the unit into areas no

larger than 20 acres and to collect at least

one sample from each of these areas. 

Each sample for a designated area consists

of a predetermined number of soil cores. A

soil core is an individual boring at one spot

in the field. The recommended number of

cores per sample are 15-20 cores for a surface soil sample and 6-8 cores for a subsurface sample. If using a soil probe, a single

core can be separated into its horizontal layers to provide samples for each layer being

analyzed. For example, a single core could be

divided into four predefined layers such as

surface soil, subsurface soil, and two deep

subsurface soil. For a designated area, all the

individual cores are combined according to

soil level and mixed to provide a composite

sample for the area. From the mixed cores a

composite subsample should be taken and

analyzed. Each grab sample can be analyzed

individually, rather than combined, as part of

a composite sample (discussed below), but

composite samples generally provide reliable

data for soil characterization.

Soil core grab samples can be collected at

random or in a grid pattern. Random collection generally requires the least amount of

time, but cores must be collected from the

entire area to ensure reliable site characterization. When performed properly, random

sampling will provide an accurate assessment

of average soil nutrient and constituent levels. While the preparation required for collecting core samples in a grid pattern can be

more costly and time consuming, it does

ensure that the entire area is sampled. An

advantage of grid sampling is the ability to

generate detailed nutrient level maps for a

land application unit. This requires analysis

of each individual grab sample from an area,

rather than compositing samples. Analyzing

each individual grab sample is time consuming and expensive, but software and computerized applicators are becoming available that

can use these data to tailor nutrient application to soil needs.

You should determine baseline conditions

by sampling the soil before waste application

begins. Subsequent sampling will depend on

land use and any state or local soil monitoring requirements. After waste is applied to

the land application unit, you should collect

and analyze samples at regular intervals, or

after a certain number of applications. You

should sample annually, at a minimum, or

more frequently, if appropriate. 

The frequency of sampling, the micronutrients, the macronutrients, and the constituents to be analyzed will depend on

site-specific soil, water, plant, and waste

9-30

Ensuring Long-Term Protection—Monitoring Performance 
characteristics. Local agricultural extension

services, which have experience with designing soil-sampling programs, can assist in this

area. Soil monitoring, especially when coupled with ground-water monitoring, can

detect contamination problems. Early detection allows changes to be made to the land

application process to remedy the problems

and to conduct corrective action if necessary.

Finally, soil testing after the active life of the

unit has ended is recommended to determine

if any residues remain in the soil. 

C. Sampling Equipment

There are a number of soil sampling

devices available. A soil probe or tube is the

most desirable, as it provides a continuous

core with minimal disturbance of the soil.

Sample cores from a soil probe can be divided by depth and provide surface, subsurface,

and deep subsurface samples from a single

boring. When the soil is too wet, too dry, or

frozen, however, soil probes are not very

effective. The presence of gravel in the soil

will also prevent the use of a soil probe.

When sampling excessively wet, dry, or

frozen soils, or soils with gravel, a soil auger

can be used in place of a soil probe. Because

of their tendency to mix soils from different

depths during sample collection, a soil auger

should only be used when the use of a soil

probe is not possible. A spade can also be

used for surface samples, but it is not effective for subsurface sampling. Post-hole diggers can be used for collecting deeper

subsurface samples, but they present the

same mixing problem as soil augers. EPA’s

Description and Sampling of Contaminated Soils:

A Field Pocket Guide (U.S. EPA, 1991) contains a description of various hand-held and

power-driven tube samplers. The guide also

outlines the recommended applications and

limitations for each sampling device.

D. Sample Collection

Initial soil characterization samples are

typically taken from each distinct soil horizon

down to a depth of 4-5 feet (120-150 cm).

For example, a single core sample might provide the following four horizon samples: surface (0-6 inches), subsurface (6-18 inches),

and two deep subsurface (18-30 inches and

30-42 inches). For subsequent evaluations, it

is important to sample more than just the

surface layer to determine if the land application rate is appropriate and that the quality of

soil is not being detrimentally affected.

Sampling subsurface layers will indicate

whether waste constituents are being

removed and assimilated as expected and are

not leaching into subsurface layers or the

groundwater. As a minimum practice, sample

at least the upper soil layer (0-6 inches) and

at least one deeper soil layer (e.g., 18-30

inches). You should consult the local agricultural extension service, the county agricultural agent, or other soil professionals for

recommended soil sampling depths for the

specific area in which your land application

unit is located.

Once the samples have been obtained,

they must be prepared for chemical analysis.

This typically is done by having the sample

air dried, ground, and mixed, and then

passed through a 2 millimeter sieve as soon

as possible after collection. If the samples are

to be analyzed for nitrate, ammonia, or

pathogens, then they should be refrigerated

under moist field conditions and analyzed as

soon as possible. For more information on

handling and preparing soil samples, refer to

the “General Protocol for Soil Sample

Handling and Preparation” section in EPA’s

Description and Sampling of Contaminated Soils:

A Field Pocket Guide (U.S. EPA,1991). ASTM

method D-4220 Practices for Preserving and

Transporting Soil Samples also addresses proper soil sample handling protocols.

Ensuring Long-Term Protection—Monitoring Performance 

9-31
The exact procedure for drying is not critical as long as contamination is minimized

and excessive temperatures are avoided. The

recommended drying procedure for routine

soil analysis is to dry the samples overnight,

using forced air at ambient temperatures.

Supplemental heating can be used, but it is

recommended that soil samples to be used

for routine analyses not be dried at greater

than 36°C. Microwave drying can alter the

analytical results and should be avoided.

Because soil is defined as having a particle

size of less than 2 millimeters, this sieve size

(# 10 mesh) is recommended for routine soil

testing. Commercial soil grinders and crushers, such as mortar and pestles, hammermills, or roller-crushers, are typically long

and motorized. The amount of coarse fragments common in some samples limits the

use of some of these. In general, it is desirable to get most of the sample to less than 2

mm with the least amount of grinding. If the

sample is to be analyzed for micronutrients,

all contact with metal surfaces should be

avoided during crushing and sieving unless it

has been clearly demonstrated that the metal

is not a source of contamination. Cross-contamination between samples can be avoided

by minimizing soil-particle carry over on the

crushing and sieving apparatus. For

macronutrient analysis, removal of particles

by brushing or jarring should be adequate. If

micronutrient or trace element analysis is to

be performed, a more thorough cleaning of

the apparatus by brushing or wiping between

samples might be required.

The bulk soil sample should be thoroughly homogenized by mixing with a spatula,

stirring rod, or other implement. As much of

the sample as possible should be loosened

and mixed together. No segregation of the

sample by aggregate size should be apparent

after mixing. You should dip into the center

of the mixed sample to obtain a subsample

for analysis.

Prior to sampling, all containers and

equipment that are to be used for soil collection (i.e., those that will come in contact

with the soil being sampled) should be

rinsed in warm tap water to remove any

residual soil particles from previous sampling

runs. They should then be rinsed with an

aluminum chloride solution. Avoid using

anhydrous aluminum chloride due to its violent reaction with water. A four percent

hydrogen chloride solution can also be used

if the soil is not to be analyzed for chlorine.

The containers and equipment should be

rinsed twice in distilled or deionized water

and allowed to dry prior to use.

You should obtain professional assistance

from qualified soil scientists and laboratories

to properly interpret the soil-sample results.

For more information about how to obtain

representative soil samples and submit them

for analysis, you can consult various federal

manuals, such as EPA’s Laboratory Methods

for Soil and Foliar Analysis in Long-Term

Environmental Monitoring Programs (U.S. EPA,

1995b), or state guides, such as Nebraska’s

Guidelines for Soil Sampling (G91-1000-A).

The following ASTM methods might also

prove useful when conducting soil sampling:

D-1452 Practice for Soil Investigation and

Sampling by Auger Borings; D-1586 Test

Method for Penetration Test and Split-Barrel

Sampling of Soils; D-1587 Practice for ThinWalled Tube Sampling of Soils; and D-3550

Practice for Ring-Lined Barrel Sampling of Soils.

IV. Air Monitoring

The development of appropriate air-monitoring data can be technically complex and

resource intensive. The Industrial Waste Air

(IWAIR) Model on the CD ROM version of

this Guide provides a simple tool that relies

on waste characterization information, rather

than actual air monitoring data, to evaluate

9-32

Ensuring Long-Term Protection—Monitoring Performance 
risks from VOC emissions at a unit. The airmodeling tool uses an emissions model to

estimate emissions from a waste management

unit based on the waste characterization. You

should review Chapter 5–Protecting Air

Quality, and the supporting background document developed for the IWAIR model to

understand the limitations of the model and

determine whether it is applicable to a specific unit. If the model is not appropriate for a

specific site or if it indicates that there is a

problem with VOC emissions, use an alternative (emissions) model that is more appropriate for the site or consider air monitoring to

gather more site-specific data. 

A. Types of Air Emissions

Monitoring

There are generally four different types of

air emissions monitoring: source, ambient,

fugitive, and indoor. Source, ambient, and

fugitive monitoring can provide data for use

in emission and dispersion modeling. In

addition, the monitoring of meteorological

conditions at sites is generally conducted

whenever source emissions or ambient monitoring is performed, as discussed below. As

the vast majority of industrial waste management units are located outdoors, indoor air

quality and monitoring issues typically will

not apply. Consequently, this guide does not

address this issue. For more information on

indoor air quality and monitoring visit the

Occupational Safety and Health

Administration’s (OSHA) Web site at

<www.osha-slc.gov/SLTC/indoorair

quality/index.html>.

1. Emissions Monitoring

Stationary-source emissions monitoring

involves the direct sampling of an air stream

in a duct, stack, or pipe that is the end source

of an emission release point. A stationary

source is an immobile unit from which air

pollutants are released. Examples include

incinerators, boilers, industrial furnaces,

landfills, waste piles, surface impoundments,

and other waste management units. The purpose of source sampling is to obtain as accurate a sample as possible of the material

entering the atmosphere. The major reasons

for which source testing is required are to

demonstrate compliance with regulations or

permit conditions, to collect engineering data

(e.g., to evaluate the performance of air pollution control equipment), to support performance guarantees (e.g., checking to confirm

that the air pollution control equipment is

meeting the guaranteed degree of performance), and to provide data for air modeling. 

2. Ambient Monitoring

The second type of air monitoring involves

ambient air monitoring at selected locations

around the waste management unit or site.

The data are used to monitor dispersion of

airborne contaminants to the surrounding

areas. Ambient testing usually involves

“fenceline” testing. Typically, the air is monitored at the four fenceline compass points. At

least one additional measuring station is

placed either in the predominant upwind (or

downwind) location or in a direct line

between your site and a neighboring facility

or property. The resulting data should yield

information concerning the concentration of

ambient emissions leaving your property

(minus the emissions from adjacent facilities).

In many areas of the country, several facilities share property boundaries delineated by a

fenceline. Since each facility is regulated

according to total emissions, it is critical that a

neighboring facility’s “drifting” emissions be

qualified and quantified. Depending on the

neighboring facility’s production rate, the

atmospheric conditions, and the seasonal climate, the neighboring facility’s emissions could

Ensuring Long-Term Protection—Monitoring Performance 

9-33
impact the operation of your facility. For

example, many facilities are required to continuously monitor downwind fenceline emission of hydrocarbons. If a neighboring facility’s

emissions of hydrocarbons or adjacent freeway

hydrocarbon emissions drift across your fenceline and combine with your own hydrocarbon

emissions, your total facility hydrocarbon

emission limit could be violated.

3. Fugitive Monitoring

Fugitive testing is a hybrid of ambient and

source testing and generally involves the

monitoring of either particulate or gaseous

emissions from sources open to the atmosphere. It can involve testing sources such as

valves, flanges, pumps, and similar equipment

and hardware for leaks, and it can include

quantifying emissions from open drums, open

vats, landfills, waste piles, and surface

impoundments such as lagoons, pits, and settling ponds. It is typically conducted using

one or more of the following techniques: use

of a handheld organic analyzer; “bagging” suspect sources for subsequent analysis; capturing and scrubbing fugitive emissions using a

floating flux chamber/summa canister; or

measuring particulate matter greater than or

less than 10 microns in diameter (PM10) following promulgated EPA test methods. 

Selection of the test method depends on

factors such as the type of emissions, source

type, temperature, pressure, constituent concentration, etc. (test methods are discussed

later in this chapter). For example, a plant

operator who suspects that a valve is leaking

might use a handheld organic analyzer to verify the presence of a leak. If the analyzer is

not able to quantify the concentration of the

leaking gas, then the bagging technique can

be employed. To determine the amount and

type of organic emissions escaping from a settling pond or wastewater treatment tank, a

floating flux chamber/summa canister might

be preferred. This is a box that isolates a portion of the pond to determine volumetric

flow. The box acts as a floating stack in which

emissions are captured into a canister for

analysis. For material transfer operations or

vehicular traffic from unpaved roads, it is

obviously not practical to use a handheld analyzer or to “bag” the source (especially something as large as a waste pile). In such cases of

particulate matter fugitive emissions, a highvolume ambient PM10 sampling system is

used, or the emissions are ducted through a

temporary stack for direct measurement using

a sampling train (see Figure 6).

4. Meteorological Monitoring

Another form of air monitoring measures

meteorological conditions at a site. Site-specific meteorological information can be collected for use in air emission and dispersion

modeling. This type of monitoring involves

measurement of wind speed, wind direction,

temperature, etc., and can be performed

when other offsite meteorological information might not adequately characterize the

weather conditions at the site. Local wind

systems are usually quite significant in terms

of the transport and dispersion of air constituents. Therefore, local meteorological

monitoring will most likely be important for

mountainous or hilly terrain (where solar

heating and radiational cooling influence

how wind moves) or for a site near a large

body of water (where the differential heating

of land and water can result in thermals and

subsidence over water). Also, the initial

direction of transport of constituents from

their source is determined by the wind

direction at the source. 

To make meteorological measurements,

three components are typically needed: a

detector or sensor, an encoder or digitizer,

and a data logger. Most detectors are analog,

providing a continuous output as a function

9-34

Ensuring Long-Term Protection—Monitoring Performance 
of varying meteorological conditions. The

output signal must then be sampled to produce a discrete digital record, using some sort

of encoder or analog-to-digital converter. The

resulting discrete series of data must be

recorded, often on magnetic tape, magnetic

disks, or optical disks. “Instrument system”

or “instrument package” is the name given to

the set of all three components listed above. 

Additional components might also be necessary including: an instrument platform, a

means of calibration, and display devices.

Platforms, such as a tower, can often hold

many instrument systems. Calibration against

known standards should be performed periodically during the measuring program, or

should be accomplished continuously as a

function of the sensor or instrument package.

All data must be calibrated. Finally, the measured values should be displayed on printers,

plotters, or video displays in order to confirm

the proper operation of the instrument.

A large variety of sensors have been developed to measure various meteorologic parameters. Direct sensors are ones that are

placed on an instrument platform to make in

situ measurements of the air at the location of

the sensor. Remote sensors measure waves

that are generated by, or modified by, the

atmosphere at locations distant from the sensor. These waves propagate from the generation or modification point back to the sensor.

Disadvantages of direct sensors include modification of the flow by the sensor or its platform and the requirement to physically

position the sensor where the measurement is

to be made. Disadvantages of remote sensors

include their size, cost, and complexity.

Advantages of direct sensors include sensitivity, accuracy, and simplicity. Advantages of

remote sensors include the fact that they can

quickly scan a large area while remaining stationary on the ground. 

Ensuring Long-Term Protection—Monitoring Performance 

9-35

Sensors Used To Measure

Meteorologic Parameters

The following types of sensors can be used to

monitor meteorological conditions at a site (note

that this list is not meant to be exhaustive):

Temperature—thermometers.

Direct sensors: Remote sensors:

wax thermostat microwave sounders

thermistor sodar

bimetallic strip thermistor

thermocouple

liquid (mercury or alcohol) in glass

radiometers 

Humidity—hygrometers.

Direct sensors: Remote sensors:

psychrometers lidar

hair hygrometer radar

chilled mirror (dew pointer)

hygristor

Wind—velocity (anemometers) and

direction (vanes).

Direct senors: Remote sensors:

cup Doppler radar

propellar

wind vane

bivane

Pressure—barometers and microbarographs.

Direct sensors:

aneroid elements

capacitive elements

mercury in glass

Remote sensors:

None that use wave propagation directly, but

some that measure temperature and velocity

fluctuations as mentioned above, and infer

pressure perturbations as residual from governing equations.

Radiation—radiometers.

Radiometers can be designed to measure radiation in specific frequency bands coming from

specific directions: radiometer, net radiometer,

pyranometer, and net pyranometer.
B. Air Monitoring and

Sampling Equipment

1. Ambient Air Monitoring

For ambient air monitoring, the principal

requirement of a sampling system is to obtain

a sample that is representative of the atmosphere at a particular place and time. The

major components of most sampling systems

are an inlet manifold, an air mover, a collection medium, and a flow measurement

device. The inlet manifold transports material

from the ambient atmosphere to the collection medium, or analytical device, preferably

in an unaltered condition. The inlet opening

can be designed for a specific purpose. All

inlets for ambient sampling must be rainproof. Inlet manifolds are made out of glass,

Teflon, stainless steel, or other inert materials

and permit the remaining components of the

system to be located at a distance from the

sample manifold inlet. The air mover (i.e.,

pump) provides the force to create a vacuum

or lower pressure at the end of the sampling

system. The collection medium for a sampling system can be a liquid or solid sorbent

for dissolving gases, a filter surface for collecting particles, or a chamber to contain an

aliquot of air for analysis. The flow device

measures the volume of air associated with

the sampling system. Examples of flow

devices include mass flow meters and

rotameters.

Gaseous Constituents

Sampling systems for gaseous constituents

can take several forms and might not necessarily have all four components as shown in

Figure 5. The sampling manifold’s only function is to transport the gas from the manifold

inlet to the collection medium. The manifold

must be made of nonreactive material and no

condensation should be allowed to occur in

the sampling manifold. The volume of the

manifold and the sampling flow rate determine the time required for the gas to move

from the inlet to the collection medium. This

residence time can be minimized to decrease

the loss of reactive species in the manifold by

keeping the manifold as short as possible. 

The collection medium for gases can be

liquid or solid sorbents, and evacuated flask,

9-36

Ensuring Long-Term Protection—Monitoring Performance 

Figure 5. Schematic Diagram of Various Types of Sampling Systems

Source: Fundamentals of Air Pollution.
or a cryogenic trap. Each design is an attempt

to optimize gas flow rate and collection efficiency. Higher flow rates permit shorter sampling times. Liquid collection systems take

the form of bubblers which are designed to

maximize the gas-liquid interface. However,

excessive flow rates can result in lower collection efficiency.

Diagram A is typical of many extractive

sampling techniques (e.g., SO2 in liquid sorbents and polynuclear aromatic hydrocarbons

on solid sorbents). Diagram B is used for

“open-face” filter collection, in which the filter is directly exposed to the atmosphere

being sampled. Diagram C is an evacuated

container used to collect an aliquot of air or

gas to be transported to the laboratory for

chemical analysis, (e.g., polished stainless

steel canisters are used to collect ambient

hydrocarbons for air toxic analysis). Diagram

D is the basis for many of the automated continuous analyzers, which combine the sampling and analytical processes in one piece of

equipment (e.g., continuous ambient air

monitors for SO2, O3, and NOx). 

Particulate Constituents

Sampling for particulate constituents in the

atmosphere involves a different set of parameters from those used for gases. Particles are

inherently larger than the molecules of N2 and

O2 in the surrounding air and behave differently with increasing diameter. When sampling for particulate matter in the atmosphere,

three pieces of information are of particular

interest: the concentration, the size, and the

chemical composition of the particles. Particle

size is important in determining adverse

effects and atmospheric removal processes. 

The primary approach is to separate the

particles from a known volume of air and

subject them to weight determination and

chemical analysis. The principle methods for

extracting particles from an airstream are filtration and impaction.7 All sampling techniques must be concerned with the behavior

of particles in a moving airstream. Care must

be taken to move the particles through the

manifold to the collection medium in an

unaltered form. Potential problems arise if

manifold systems are too long or too twisted.

Gravitational settling in the manifold will

remove a fraction of the very large particles.

Larger particles are also subject to loss by

impaction on walls at bends in a manifold.

Particles can also be subject to electrostatic

forces which will cause them to migrate to

the walls of nonconducting manifolds. Other

potential problems include condensation or

agglomeration during transit time in the manifold. These constraints require particulate

sampling manifolds to be as short as possible

and to have as few bends as possible.

2. Source Emissions Monitoring

For source emissions monitoring, the sampling system is tailored to the unique properties of the emissions from a particular

process. It is necessary to take into account

the specific process, the nature of the control

devices, the peculiarities of the source, and

the use of the data obtained. In source monitoring, the sample is obtained from a stack

that is discharging to the atmosphere using a

“sampling train”. A typical sample train is

shown in Figure 6. The figure shows the minimum number of components, but in some

systems the components can be combined.

Extreme care must be exercised to assure that

no leaks occur in the train and that the components of the train are identical for both calibration and sampling. Standard sampling

trains are specified for some tests.

Continuous emission monitors (CEMs) are

also available to monitor opacity and certain

gaseous emissions.

Ensuring Long-Term Protection—Monitoring Performance 

9-37

7 Filtration consists of collecting particles on a filter surface by three processes: direct interception, inertial impaction, and diffusion. Filtration attempts to remove a very high percentage of the mass and

number of particles by these processes. Any size classification is done by a preclassifier, such as an

impactor, before the particle stream reaches the surface of the filter
C. Test Method Selection

Correct method selection is both scientific

and subjective. Knowing when to utilize the

appropriate method for a given circumstance

is very important, since incorrect or inaccurate measurement can lead to incorrect

results. The test methods to be used for air

emission monitoring are typically specified

by applicable regulations; and the type of

facility will often determine the regulations or

standards which are applicable. In general,

most EPA test methods applicable to a facility

will be contained in the Code of Federal

Regulations (40 CFR Parts 60, 61, 63, and

51). Other test methods might be specified

by the EPA Office of Solid Waste or the

National Institute for Occupational Safety

and Health (primarily for indoor air monitoring). Additionally, some states and local air

pollution control agencies have their own test

methods that differ from EPA methods, the

use of which might be required in lieu of

EPA methods. The CFR specifies test methods for testing for numerous compounds and

various parameters necessary for determining

constituent concentrations and emission

rates. New regulations, however, are being

developed for many compounds that, as yet,

have no promulgated test methods. Air emission testing specialists or consultants can

often determine appropriate test methods for

most of these compounds. Usually, the testing involves adapting an existing method to

the constituent of interest. It is best to use an

existing method whenever possible. If using

an existing method is impractical, you can

develop a test method particular to that constituent to monitor for it. You should seek

the advice or assistance of a professional if

this is the case and consult your state and

local air quality offices. 

D. Sampling Site Selection

Sampling activities are typically undertaken

to determine the ambient air quality for compliance with air quality standards, to evaluate

the effectiveness of air pollution control techniques being implemented at the site, to evaluate hazards associated with accidental spills,

and to collect data for air emissions and dispersion modeling. The purpose or use of the

results of the monitoring program determines

the sampling site selection. The fundamental

reason for controlling air pollution sources is

to limit the concentration of contaminants in

9-38

Ensuring Long-Term Protection—Monitoring Performance 

Figure 6. Sampling Train

Source: Fundamentals of Air Pollution.
the atmosphere so that adverse effects do not

occur. Sampling sites should therefore be

selected to measure constituent levels close to

or representative of exposed populations of

people, plants, trees, materials, or structures.

As a result, ambient air monitoring sites are

typically located near ground level, about 3

meters above ground (Boubel, p. 192.), in a

place where the results are not influenced by a

nearby source such as a roadway. Sampling

sites might require electrical power and adequate protection (which can be as simple as a

fence). A shelter, such as a small building,

might be necessary. Permanent sampling sites

(when necessary) will require adequate heating and air conditioning to provide a stable

environment for the sampling and monitoring

equipment.

V. Sampling and

Analytical

Protocols and

Quality

Assurance and

Quality Control

The best designed monitoring program

will not provide useful data in the absence of

sound sampling and analytical protocols.

Sampling and analytical protocols are generally contaminant specific. A correctly

designed and implemented sampling and

analysis protocol helps ensure that sampling

results accurately represent media quality and

can be compared over time. The accurate

representation is demonstrated through statistical analysis.

Whether or not an established quality

assurance and quality control (QA/QC) program is required on a federal, state, or local

level, it is a good management practice to

develop and strictly implement such a plan.

The sampling protocol should incorporate

federal, state, and local QA/QC requirements.

Sampling QA/QC procedures detail steps for

collection and handling of samples. Sample

collection, preservation, shipment, storage,

Ensuring Long-Term Protection—Monitoring Performance 

9-39

EPA Test Methods 

EPA test methods are available for a

variety of compounds and parameters,

including but not limited to the following examples:

• Particulate Matter

• Volatile Organic Compounds (VOC)

• Sulfur Dioxide

• Nitrogen Oxide

• Visible Emissions

• Carbon Monoxide

• Hydrogen Sulfide

• Inorganic Lead

• Total Fluoride

• Landfill Gas (gas production flow

rate)

• Nonmethane Organic Compounds

(NMOC) (in landfill gases)

• Hydrogen Chloride

• Gaseous Organic Compounds

• Polychlorinated Dibenzo-p-dioxins

and Polychlorinated Dibenzofurans

• Stack Gas Velocity and Volumetric

Flow Rate

• Gas Analysis for Carbon Dioxide,

Excess Air, and Dry Molecular Weight

• Moisture Content in Stack Gases
and analysis should be performed in accordance with an approved QA/QC program to

ensure data of known quality are generated.

You should rely on qualified professionals

who are properly trained to conduct sampling. Poorly-conducted sampling can give

false evidence of a contamination problem or

can miss early warnings of contaminant

leaching. Erring in either direction is an

avoidable and costly mistake. 

At a minimum, you should include the

following in your sampling protocol: 

• Data quality objectives including lists

of important tracking parameters,

such as the date and name of samples.

• Sample collection procedures,

including description of sample collection methods, and lists of necessary field analyses.

• Instructions for sample preservation

and handling.

• Other QA/QC procedures such as

chain-of-custody.

• The name of the person who conducted the sampling.

Quality control operations are defined by

operational procedures and might contain the

following components for an air monitoring

program:

• Description of the methods used for

sampling and analysis.

• Sampling manifold and instrument

configuration.

• Appropriate multipoint calibration

procedures.

• Zero/span checks and record of

adjustments.

• Control specification checks and

their frequency.

• Control limits for zero, span, and

other control limits.

• The corrective actions to be taken

when control limits are exceeded.

• Preventative maintenance.

• Recording and validation of data.

• Documentation of quality assurance

activities.

States have developed guidance documents addressing sampling plans, protocols,

and reports. You should work with the state

to develop an effective sampling protocol. 

• You should consult with soil specialists at the state and local environmental/planning offices, your local

cooperative extension service office,

or the county conservation district

office before implementing a soil

monitoring program for your unit.

(For more information, visit the

USDA Cooperative State Research,

Education, and Extension Service

Web site at: <www.reeusda.gov/

1700/statepartners/usa.htm>).

These agencies likely will be able to

provide you with maps showing the

location and extent of soils, data

about the physical and chemical

properties of soils, and information

derived from the soil data about

9-40

Ensuring Long-Term Protection—Monitoring Performance 
potentialities and problems of use for

the soils in your area. You can also

consult the Natural Resources

Conservation Service (NRCS) Web

site at <www.wv.nrcs.usda.gov>.

The NRCS manages the national

cooperative soil survey program

which is a partnership of federal land

management agencies, state agricultural experiment stations, and state

and local agencies that provide soil

survey information necessary for

understanding, managing, conserving, and sustaining soil resources.

The NRCS maintains various on-line

databases that can help you to characterize local soil. 

• You should consult with air modeling

professionals, state and local air quality offices, EPA Regional air program

offices, or EPA’s Office of Air Quality

Planning and Standards (OAQPS) in

Research Triangle Park, North

Carolina, before implementing an air

monitoring program for your unit or

choosing alternative emission and

dispersion models to evaluate risks

associated with air emissions. For

information concerning emission test

methods, you can contact the

Emission Measurement Center (EMC)

within the Office of Air Quality

Planning and Standards. The EMC is

EPA’s point of contact for providing

expert technical assistance for EPA,

state, and local officials and industrial

representatives involved in emission

testing. The Center has produced

numerous methods of measuring air

constituents emitted from a multitude

of industries. A 24-hour automated

telephone information hotline known

as the “SOURCE” at 919 541-0200,

provides callers with a variety of

technical emission testing information. The SOURCE also includes connections to technical material

through an automatic facsimile link

and with technical staff during working hours. For more information concerning the EMC, visit EPA’s Web site

at: <www.epa.gov/ttn/emc>.

OAQPS also maintains the Support

Center for Regulatory Air Models

(SCRAM). The SCRAM Web site

<www.epa.gov/scram001> is a source

of information on various atmospheric dispersion (air quality) models that

support regulatory programs required

by the Clean Air Act. The computer

code, data, and technical documents

provided by SCRAM deal with mathematical modeling for the dispersion

of air constituents. Documentation

and guidance for these computerized

models are a major feature of the

Web site.

A. Data Quality Objectives

In any sampling and analysis plan, it is

important to understand the data needs for a

monitoring program. Tailoring sampling protocol and analytical work to data needs ensures

cost-efficient sampling. A sampling and analysis plan should specify: 1) clear objective, such

as what data are needed and how the data are

to be used, 2) target contaminants, and 3)

level of accuracy requirements for data to be

conclusive. Chapter 1 of EPA SW-846 Test

Methods for Evaluating Solid Waste (U.S. EPA,

1986) and ASTM Guide D5792 provide guidance on developing data quality objectives for

waste management activities. 

B. Sample Collection

Sample collection techniques should be

carefully designed to ensure sampling quality

and avoid cross-contamination or background

Ensuring Long-Term Protection—Monitoring Performance 

9-41
contamination of samples. (As an example of

some of the sample collection guidance available, Section A.4 of the Annual Book of ASTM

Standards lists guides for ground-water sampling.) You should consider the following factors when preparing for sample collection.

• Sample collection. The equipment

used to collect samples should be

appropriate for the monitoring parameters. Sampling equipment should

cause minimal agitation of the sample and reduce or eliminate contact

between the sample and environmental contaminants during transfer to

ensure it is representative.

• Field analysis. Some constituents or

parameters can be physically or chemically unstable and should be tested in

the field rather than waiting for shipment to a laboratory. Examples of

unstable parameters include pH,

redox (oxidation-reduction) potential,

dissolved oxygen, temperature, and

specific conductance. 

C. Sample Preservation

and Handling

Sample preservation and handling protocols are designed to minimize alterations of

the chemistry of samples between the time

the sample is collected and when it is analyzed. You should consider the following.

• Sample containers. To avoid altering

sample quality, transfer samples from

the sampling equipment directly into

a contaminant free container. SW846, identifies proper sample containers for different constituents and

media. Samples should not be combined in a common sample container

and then split later in the field.

• Sample preservation. The time

between sampling and sample analysis can range from several hours to

several weeks. Immediate sample

preservation and storage assists in

maintaining the natural chemistry of

the samples. The latest edition of

SW-846 provides specific preservation methods and holding times for

each constituent analyzed. SW- 846

recommends preservation methods,

such as pH adjustment, chemical

addition, and refrigeration.

• Sample transport. To document

sample possession from the time of

collection to the laboratory, include a

chain-of-custody record in every sample shipment. A chain-of- custody

record generally includes the date

and time of collection, signatures of

those involved in the chain of possession, time and dates of possession,

and other notations to trace samples.

D. Quality Assurance and

Quality Control

To verify the accuracy of field sampling

procedures, you should collect field quality

control samples, such as trip blanks, field

blank, equipment blanks, spilt samples,

blinds, and duplicates. Table 5 below summarizes these common types of QA/QC samples. Analyze quality control samples for the

required monitoring parameters. Other

QA/QC practices include sampling equipment calibration, equipment decontamination, and use of chain-of-custody forms.

ASTM Guide D-5283 Standard Practice for

Generation of Environmental Data Related to

Waste Management Activities: Quality Assurance

and Quality Control Planning and

Implementation provides guidance on QA/QC

9-42

Ensuring Long-Term Protection—Monitoring Performance 
Type of Sample Purpose Frequency

Ensuring Long-Term Protection—Monitoring Performance 

9-43

Table 5 Types of QA/QC Samples

Trip Blank

Used for volatile organic compounds (VOCs) only. Trip blanks

are prepared at the analyzing laboratory and transported to the field

with the empty vials to be used in

the VOC field sampling. They consist of a sealed vial filled with analyte-free water (i.e., de-ionized

water). The water should be the

same as the water the laboratory

will use in analyzing the actual

samples collected in the field, and

include any preservatives or additives that will be used. They are

handled, stored, and transported

in the exact same manner as the

field samples. Trip blanks should

never be opened in the field. 

Field Blank

A sample collected in the field by

filling a vial with analyte-free water

and all preservatives or additives

that will be added to actual samples. Field blanks should be prepared under the exact same

conditions in the same location as

actual samples either in the middle

or at the end of each sampling

episode. They also should be handled, stored, and transported in

the exact same manner as the actual samples.

Equipment Blank

A sample prepared by pouring

analyte-free water through or over

a decontaminated piece of sampling equipment. The blank

should be prepared on site.

Equipment blanks should be handled, stored, and transported in

the exact same manner as the actual samples.

Trip blanks provide a quality assurance test for detecting contamination

from improper sample container

(vial) cleaning prior to shipping to

the field, the use of contaminated

water in analyzing the samples in

the laboratory, VOC contamination

occurring during sample storage or

transport, and any other environmental conditions that could result

in VOC contamination of samples

during the sampling event. 

Field blanks are used to evaluate the

effects of onsite environmental contaminants, the purity of the preservatives and additives used, and general

sample collecting and container filling.

Equipment blanks are used to determine the effectiveness of the field

cleaning of sampling equipment.

Generally, they are necessary when

sampling equipment must be

cleaned in the field and reused for

subsequent sampling.

One trip blank for each cooler

used during a sampling episode

should be prepared for each

volatile organic method to be used

in the field. For example, if 2

volatile organic methods are to be

used over 2 days with samples

being sent to the lab at the end of

each day, then a total of 4 trip

blanks would be needed (i.e., Day

1: 1 cooler with samples from 2

methods = 2 trip blanks; Day 2: 1

cooler with samples from 2

methods = 2 trip blanks; total trip

blanks = 4).

One field blank should be

prepared for each parameter being

sampled and analyzed per day, or

at a rate of 5 percent of the

samples in a parameter group per

day, whichever is larger. For

example if 3 parameter groups

were to be sampled over 2 days

then 6 field blanks would be

required (i.e., 3 parameter groups

x 2 days = 6 field blanks).

At least one equipment blank

should be prepared for each piece

of equipment used in sampling

that must be field cleaned. Each

time an equipment blank is

required, a sample should be

prepared for each parameter group

being assessed. For example, if

samples are taken for 3 parameter

groups, and a piece of sampling

equipment requires cleaning then a

total of 3 equipment blanks will be

required for each required cleaning

(i.e., 1 piece of equipment x 3

parameter groups = 3 equipment

blanks per cleaning). 
planning and implementation for waste management activities. Chapter 1 of SW-846 also

provides guidance on QA/QC practices. 

E. Analytical Protocols

Monitoring programs should employ analytical methods that accurately measure the

constituents being monitored. SW-846 recommends specific analytical methods to test

for various constituents. Similarly, individual

states might recommend other analytical

methods for analysis. 

Ensure the reliability and validity of analytical laboratory data as part of the monitoring

program. Most facility managers use commercial laboratories to conduct analyses of samples; others might use their own internal

laboratories if they are equipped and qualified

to perform such analyses. In selecting an analytical laboratory, check for the following: laboratory certification by a state or professional

association for the type of analyses needed;

qualified lab personnel; good quality analytical equipment with back-up instrumentation;

a laboratory QA/QC program; proper lab documentation; and adherence to standard procedures for data handling, reporting, and record

keeping. Laboratory QA/QC programs should

describe chain-of-custody procedures, calibration procedures and frequency, analytical

9-44

Ensuring Long-Term Protection—Monitoring Performance 

Type of Sample Purpose Frequency

Table 5 Types of QA/QC Samples (cont.)

Split (Replicate) Sample

A sample that is divided into 2 or

more containers and sent for

analysis by separate laboratories.

Duplicates

Samples collected simultaneously

from the same source under identical conditions (e.g., same type of

sampling techniques and equipment).

Blinds

A sample prepared prior to a sampling episode by the laboratory or

an independent source. The blind

contains a specific amount of analyte known by the preparer, but

that is unknown to the analyst at

the time of analysis.

Split samples are used to assess sampling and analytical techniques.

Samples can be divided into portions (split) at different points in the

sampling and analysis process to

assess the precision of various components of the sampling and analysis

system. For example, a sample split

in the field (field replicate) is used to

assess sample storage, shipment,

preparation, analysis, and data

reduction. A sample split just prior

to laboratory analysis (analysis replicate) is used to assess the precision

of analytical instrumentation.

Duplicate samples are used to assess

the precision of sampling techniques

and laboratory equipment.

Blinds are used to validate the accuracy and precision of the analyzing

laboratories sample analyses. 

(No guidance on frequency

provided) 

(No guidance on frequency

provided)

(No guidance on frequency

provided)
standard operating procedures, and data validation and reporting procedures. A good

QA/QC program helps ensure the accuracy of

laboratory data.

VI. Analysis of

Monitoring Data,

Contingency

Planning, and

Assessment

Monitoring

Once monitoring data have been collected,

the data are analyzed to determine whether

contaminants are migrating from a waste management unit. You should develop a contingency plan to address the situations where

contamination is detected. 

A. Statistical Approaches

Statistical procedures should be used to

evaluate monitoring data and determine if

there is evidence of a release from a waste

management unit. Anomalous data can result

from sampling uncertainty, laboratory error, or

seasonal changes in natural site conditions.

Qualified statistical professionals can determine if statistically significant changes have

occurred or whether the quantified differences

could have arisen solely because of one of the

above-listed factors. Selecting the appropriate

statistical method is very important to avoid

generating false positive or false negatives. In

monitoring groundwater, for example, the

selection of the appropriate statistical method

will be contingent upon an adequate review

and evaluation of the background groundwater data. These data should be evaluated for

properties such as independence, trends,

detection frequency and distribution (e.g.,

normal or lognormal). Examples of two statistical approaches include inter-well (upgradient

vs. downgradient) or intra-well comparisons.

After consulting with the state agency and statistical professional and selecting a statistical

approach, continue to use the selected

method in all statistical analyses. Do not

switch to a different test when the first

method generates unfavorable results. 

What is important in selecting a

statistical approach?

An appropriate statistical approach will

minimize false positives or negatives in terms

of potential releases. The approach should

account for historical data, site conditions,

site operating practices, and seasonal variations. While there are numerous statistical

approaches used to evaluate monitoring data,

check with the state to determine if a specific

statistical approach is recommended.

Common methods for evaluating monitoring

data include the following statistical approaches: 

• Tolerance intervals. Tolerance intervals are statistical intervals constructed from data designed to contain a

portion of a population, such as 95

percent of all sample measurements. 

• Prediction intervals. These intervals

approximate future sample values

from a population or distribution

with a specific probability. Prediction

Ensuring Long-Term Protection—Monitoring Performance 

9-45
intervals can be used both for comparison of current monitoring data to

previous data for the same site.

• Control charts. These charts use historical data for comparison purposes

and are, therefore, only appropriate

for initially uncontaminated sites. 

There are many different ways to select an

appropriate statistical method. For more

detailed guidance on statistical methods for

ground-water contaminant detection monitoring, consult Addendum to Interim Final

Guidance Document on Statistical Analysis of

Ground-Water Monitoring Data at RCRA

Facilities (U.S. EPA, 1993); Guidance

Document on Statistical Analysis of GroundWater Monitoring Data at RCRA FacilitiesInterim Final Guidance (U.S. EPA, 1989); and

ASTM provisional guide PS 64- 96 in the

Annual Book of ASTM Standards.

B. Contingency Planning

Contingency plans identify the procedures

to follow if a statistically significant change in

one or more constituents has been detected.

A contingency plan should include procedures to determine whether a change in sample concentrations was caused by the waste

management unit or by unrelated factors;

procedures for developing and conducting an

assessment monitoring program; procedures

for remediating the waste management unit

to stop the release of contaminants; and a

determination of the magnitude of contamination that would require initiation of corrective action, such as a statistical exceedance of

an HBN, an MCL for surface or ground

water, or a site-specific risk-based number.

C. Assessment Monitoring

The purpose of assessment monitoring is

to evaluate the rate, extent, and concentrations of contamination. Once a statistically

significant change has been confirmed for

one or more of the sampling parameters, you

should determine whether the change was

caused by factors unrelated to the unit.

Factors unrelated to the unit that might cause

a change in the detected concentration(s) are:

• Contaminant sources other than the

waste management unit being monitored.

• Natural variations in the quality of

the media being monitored.

• Analytical errors.

• Statistical errors.

• Sampling errors.

If the change was caused by a factor unrelated to the unit, then additional measures

might not be necessary and the original monitoring program can be resumed. If, however,

these factors have been ruled out, you should

begin an assessment monitoring program.

You should consult with the state agency to

determine the type of assessment monitoring

to conduct at the unit. Assessment monitoring typically involves resampling at all sites,

and analyzing the samples for a larger list of

parameters than used during the basic monitoring program. More than one sampling

event might be necessary and additional

monitoring might need to be performed to

adequately determine the scope or extent of

any contamination. It is recommended that

you work with state officials to establish

background concentrations and protection

standards for all additional constituents that

were detected during assessment monitoring. 

If assessment monitoring results indicate

there is not a statistically significant change

in the concentrations of one or more of the

constituents over the established protection

standards, then you can resume the original

monitoring program. If, however, there is a

9-46

Ensuring Long-Term Protection—Monitoring Performance 
statistically significant change in any of these

constituents, consult with state officials to

identify the next steps. It might be necessary

to perform additional monitoring to characterize the nature and extent of the contamination and to notify persons who own or reside

on any land directly impacted by the contamination if it has migrated beyond the facility

boundary. 

Detection of contamination can be an indicator that the waste management unit’s containment system is not working properly.

During this assessment phase, component(s)

of the unit (cover, liner, or leachate collection

system) that are not working properly should

be identified and, if possible, remediated. For

example, sometimes sealing a hole in the

liner of a small surface impoundment can be

sufficient to stop the source of contamination.

Other times, more extensive response might

be required. One example could be the

extensive subsidence of a unit’s final cover

creating the need for repair. In some cases,

liner and leachate collection system repairs

might not be possible, such as in a large surface impoundment or a landfill with several

tons of waste already in place. If remediation

is not possible, consult with state officials

about beginning assessment monitoring and

consult Chapter 10–Taking Corrective Action.

Ensuring Long-Term Protection—Monitoring Performance 

9-47
You should consider the following for each media when developing a monitoring program for industrial

waste management units:

Ground Water

■ Perform a site characterization, including investigation of the site’s geology, hydrology, and subsurface hydrogeology to determine areas for ground-water monitoring; select parameters to be monitored based on the characteristics of the waste managed.

■ Identify qualified engineers and ground-water specialists to assist in designing and operating the

ground-water monitoring program.

■ Consult with qualified professionals to identify necessary program components including the monitoring well design, the number of monitoring wells, the lateral and vertical placement of the wells,

the duration and frequency of monitoring, and the appropriate sampling parameters.

■ Determine the appropriate method(s) of ground-water monitoring, including conventional well

monitoring, direct push sampling, geophysical monitoring, and vadose zone monitoring as possibilities.

■ Use qualified laboratories to analyze samples.

Surface Water

■ Collect and analyze samples according to the requirements of a site’s federal or state storm-water

permit.

■ If not subject to permit requirements, implement a storm-water sampling program to monitor the

quality of runoff and determine the effectiveness of BMPs.

■ If applicable, collect and analyze discharges to POTWs according to any requirements of a local

pretreatment program.

■ Implement a surface-water sampling program to monitor water quality and determine the effectiveness of BMPs.

■ Perform regular inspections and maintenance of surface-water protection measures and BMPs to

reduce the potential for surface-water contamination.

■ Use qualified laboratories to analyze samples.

Soil Monitoring

■ Determine the number and location of samples needed to adequately characterize soil according to

the variability of the soil at a site.

■ Follow established soil-sampling procedures to obtain meaningful results.

■ Use qualified laboratories to analyze samples.

Monitoring Performance Activity List 

9-48

Ensuring Long-Term Protection—Monitoring Performance 
Ensuring Long-Term Protection—Monitoring Performance 

9-49

■ Determine baseline soil conditions by sampling prior to waste application.

■ Collect and analyze samples at regular intervals to detect contaminant problems.

Air Monitoring

■ Use the Industrial Waste Air (IWAIR) Model to evaluate risks from VOC emissions.

■ Use an alternative emissions model if the IWAIR Model indicates a problem with VOC emission or

is not appropriate for your site.

■ If collecting air monitoring data, determine the type of monitoring necessary to evaluate the effectiveness of air pollution control techniques employed on site or for input into air emissions and

dispersion models.

■ Select the proper test methods.

■ Establish guidelines to ensure the quality of the data collected prior to implementing an air monitoring program.

■ Consult with air modeling professionals, state and local air quality offices, EPA regional air program offices, or EPA’s Office of Air Quality Planning and Standards before implementing an air

monitoring program or choosing an alternative emission model to evaluate risks.

■ Use qualified laboratories to analyze samples.

Sampling and Analytical Protocols QA/QC

■ Develop sample collection, preservation, storage, transport, and handling protocols tailored to data

needs, and establish quality assurance and quality control procedures to check the accuracy of the

monitoring samples.

■ Eliminate cross-contamination or background contamination of any samples by purging the wells,

using appropriate sampling equipment, and ensuring that any unstable parameters, such as pH,

dissolved oxygen, and temperature, have been tested at the site.

■ Identify the appropriate analytical methods and statistical approach for the sampling data including parametric analysis of variance (ANOVA), tolerance intervals, prediction intervals, and control

charts as possibilities.

■ Evaluate the need for assessment monitoring and abatement.

Monitoring Performance Activity List (cont.)
Site Characterization

American Society for Testing and Materials. 2001. Annual Book of ASTM Standards. ASTM.

American Society for Testing and Materials. 1994. ASTM Standards on Ground Water and Vadose Zone

Investigations, 2nd Edition. ASTM.

ASTM D-1452. 1980. Practice for Soil Investigation and Sampling by Auger Borings.

ASTM D-1586. 1984. Test Method for Penetration Test and Split-Barrel Sampling of Soils

ASTM D-1587. 1983. Practice for Thin-Walled Tube Sampling of Soils.

ASTM D-3550. 1988. Practice for Ring-Lined Barrel Sampling of Soils..

ASTM D-4220. 1989. Practices for Preserving and Transporting Soil Samples.

ASTM D-5792. 1995. Standard Practice for Generation of Environmental Data Related to Waste Management

Activities: Development of Data Quality Objectives.

Boulding, J.R. 1995. Practical Handbook of Soil, Vadose Zone, and Ground Water Contamination:

Assessment, Prevention and Remediation. Lewis Publishers.

CCME. 1994. Subsurface Assessment Handbook for Contaminated Sites, CCME EPC-NCSRP-48E, Canadian

Council of Ministers of the Environment.

Morrison, R.D. 1983. Groundwater Monitoring Technology. Timco Mfg. Inc.

Sara, M.N. 1994. Standard Handbook for Solid and Hazardous Waste Facility Assessments. Lewis Publishers.

Topp, G.C. and J.L. Davis. 1985. “Measurement of Soil Water Using Time-Domain Reflectometry (TDR): A

Field Evaluation,” Soil Science Society of America Journal. 49:19-24.

U.S. EPA. 1993. Subsurface Characterization and Monitoring Techniques: A Desk Reference Guide. Volume I:

Solids and Ground Water, Appendices A and B. EPA625-R-93-003a. 

U.S. EPA. 1993. Subsurface Characterization and Monitoring Techniques: A Desk Reference Guide. Volume II:

The Vadose Zone, Field Screening and Analytical Methods, Appendices C and D. EPA625- R-93-003b. 

Resources

9-50

Ensuring Long-Term Protection—Monitoring Performance 
Ensuring Long-Term Protection—Monitoring Performance 

9-51

U.S. EPA. 1988. Criteria for Municipal Solid Waste Landfills: Draft background Document. EPA530- SW88-042.

U.S. EPA. 1987. DRASTIC: A Standardized System for Evaluating Ground Water Pollution Potential Using

Hydrogeologic Settings. EPA600-2-87-035.

Wilson, L.G., L.G. Everett, and S.J. Cullen (eds.). 1995. Handbook of Vadose Zone Characterization and

Monitoring. Lewis Publishers.

Ground-Water Monitoring Well Design, Installation, and Development

Cullen, S.J. 1995. Vadose Zone Monitoring: Experiences and Trends in the United States. Ground Water

Monitoring Review 15(3):136-143.

Cullen, S.J., J.K. Kramer, and J.R. Luellen. 1995. A Systematic Approach to Designing a Multiphase

Unsaturated Zone Monitoring Network. Ground Water Monitoring Review 15(3):124-135.

Geoprobe Systems. 1996. Geoprobe Prepacked Screen Monitoring Well: Standard Operating Procedure.

Technical Bulletin No. 96-2000.

Hayes, J.P. and D.C. Tight. 1995. Applying Electrical Resistance Blocks for Unsaturated Zone Monitoring at

Arid Sites. Handbook of Vadose Zone Characterization and Monitoring. L.G. Wilson, L.G. Everett, and S.J.

Cullen (eds.). Lewis Publishers. pp. 387-399. 

Kramer, J.H., S.J. Cullen, and L.G. Everett. 1992. Vadose Zone Monitoring with the Neutron Moisture

Probe. Ground Water Monitoring Review 12(3):177-187.

Ohio Environmental Protection Agency. 1995. Technical Guidance Manual for Hydrogeologic

Investigations and Ground Water Monitoring.

Robbins, G.A. and M.M. Gemmell. 1985. Factors Requiring Resolution in Installing Vadose Zone

Monitoring Systems. Ground Water Monitoring Review 5:76-80.

U.S. EPA. 1993a. Ground-Water Monitoring: Draft Technical Guidance. EPA530-R-93-001.

U.S. EPA. 1993b. Solid Waste Disposal Facility Criteria: Technical Manual. Chapter 5. EPA530-R-93- 017.

U.S. EPA. 1991. Handbook: Ground Water. Volume II: Methodology. EPA625-6-90-016b. 

Resources (cont.)
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U.S. EPA. 1990. Handbook: Ground Water. Volume I: Ground Water and Contamination.

EPA625-6-90- 016a. 

U.S. EPA. 1989. Handbook of Suggested Practices for the Design and Installation of GroundWater Monitoring Wells. EPA600-4-89-034.

Sample Procedures

ASTM. D-5283. 1997. Standard Practice for Generation of Environmental Data Related to Waste

Management Activities: Quality Assurance and Quality Control Planning and Implementation.

Benson, R.C., R.A. Glaccum, and M.R. Noel. 1984. Geophysical Techniques for Sensing Buried

Wastes and Waste Migration. EPA600-7-84-064.

Bond, W.R. 1995. Case Studies of Vadose Zone Monitoring and Sampling Using Porous Suction

Cup Samplers. Handbook of Vadose Zone Characterization and Monitoring. L.G. Wilson, L.G.

Everett, and S.J. Cullen (eds.). Lewis Publishers. pp. 523-532.

Federal Remediation Technologies Roundtable. 2001. Field Sampling and Analysis Technologies

Matrix. Version 1.0. <www.frtr.gov/site>

Gibbons, R.D. 1990. Estimating the Precision of Ground-Water Elevation Data. Ground Water,

28, 357- 360.

Minnesota Pollution Control Agency. 1995. Ground Water Sampling Guidance: Development of

Sampling Plans, Protocols and Reports.

Texas Natural Resource Conservation Commission. 1994. TNRCC Technical Guidance:

Guidelines for Preparing a Ground-Water Sampling and Analysis Plan (GWSAP). 

Thomson, K.A. 1995. Case Studies of Soil Gas Sampling. Handbook of Vadose Zone

Characterization and Monitoring. L.G. Wilson, L.G. Everett, and S.J. Cullen (eds.). Lewis

Publishers. pp. 569-588.

U.S. EPA. 1995a. Ground Water Sampling—A Workshop Summary. EPA600-R-94-205.

U.S. EPA. 1995b. Laboratory Methods for Soil and Foliar Analysis in Long-term Environmental

Monitoring Program. EPA600-R-95-077

Resources (cont.)
Ensuring Long-Term Protection—Monitoring Performance 

9-53

U.S. EPA. 1995c. Low Flow Ground-Water Sampling. EPA540-S-95-504.

U.S. EPA. 1994a. Industrial User Inspection and Sampling Manual for POTWs. 

U.S. EPA. 1994b. Region VIII Guidance, Standard Operating Procedures for Field Sampling Activities. 

U.S. EPA. 1992. NPDES Storm Water Sampling Guidance Document. EPA833-B-92-001.

U.S. EPA. 1991. Description and Sampling of Contaminated Soils: A Field Pocket Guide. EPA625-12-

91-002

U.S. EPA. 1989. Interim Final RCRA Facility Investigation (RFI) Guidance: Volumes I-III. EPA530- SW89-031.

U.S. EPA. 1986. Test Methods for Evaluating Solid Waste—Physical/Chemical Methods. EPA SW-846,

3rd edition. PB88-239-233.

Surface Water Monitoring

Novotny, V., and H. Olem. 1994. Water Quality: Prevention, Identification, and Management of Diffuse

Pollution. Van Nostrand Reinhold.

U.S. EPA. 1999. Introduction to the National Pretreatment Program. EPA833-B-98-002.

U.S. EPA. 1997. Volunteer Stream Monitoring Document. EPA841-B-97-003.

U.S. EPA. 1991. Volunteer Lake Monitoring Document. EPA440-4-91-002.

Soil Monitoring

Delaware Cooperative Extension Service. 1995. Recommended Soil Testing Procedures for the

Northeastern United States. 2nd Edition. Northeastern Regional Publication No. 493.

North Carolina Cooperative Extension Service. 1994. Soil facts: Careful Soil Sampling - The Key to

Reliable Soil Test Information. AG-439-30.

Rowell, D.L. 1994. Soil Science: Methods and Applications.

Soil Quality Institute of the National Resources Conservation Service, USDA. 2001. Guidelines for Soil

Quality Assessment in Conservation Planning. <www.statlab.iastate.edu/survey/SQI/>

Resources (cont.)
9-54

Ensuring Long-Term Protection—Monitoring Performance 

University of Nebraska Cooperative Extension Institute of Agriculture and Natural Resources. 1991.

Guidelines for Soil Sampling. G91-1000-A. February. <www.ianr.unl.edu/pubs/soil/g1000.htm>

U.S. EPA. 1995d. Laboratory Methods for Soil and Foliar Analysis in Long-Term Environmental

Monitoring Programs. EPA600-R-95-077.

U.S. EPA. 1989. RCRA Facility Investigation Guidance: Volume II: Soil, Ground Water and Subsurface

Gas Releases. EPA530-SW-89-031

Air Monitoring 

Boubel, R. W., D. L. Fox, D. B. Turner, and A. C. Stern. 1994. Fundamentals of Air Pollution. 3rd

Edition. Academic Press.

Stull, Roland B. 1988. An Introduction to Boundary Layer Meteorology. Kluwer Academic Publishers.

Yoest, H. and R. W. Fitzgerald. February 1996. Chemical Engineering Progress. Stationary Source

Testing: The Fundamentals. 

U.S. EPA. 1993. Air/Superfund National Technical Guidance Study Series: Compilation of Information

on Real-time Air Monitoring for Use at Superfund Sites. EPA451-R-93-008. 

U.S. EPA. 1993. Air/Superfund National Technical Guidance Study Series: Volume 4: Guidance for

Ambient Air Monitoring at Superfund Sites, Revised. EPA451-R-93-007. 

U.S. EPA. 1990. Guidance on Applying the Data Quality Objectives Process for Ambient Air Monitoring

Around Superfund Sites (Stages 1 and 2). EPA450-4-90-005. 

U.S. EPA. 1990. Air/Superfund National Technical Guidance Study Series: Contingency Plans at

Superfund Sites Using Air Monitoring. EPA450-1-90-005. 

U.S. EPA. 1989. Air/Superfund National Technical Guidance Study Series, Volume 4: Procedures for

Dispersion Modeling and Air Monitoring for Superfund Air Pathway Analysis, Interim Report, Final.

EPA450-1-89-004.

U.S. EPA. 1986. Test methods for Evaluating Solid Waste. 3rd Edition. Office of Solid Waste and

Emergency Response. SW-846.

Statistical References

Davis, C.B. and McNichols, R.J. 1987. One-Sided Intervals for at Least p of m Observations from a

Normal Population on Each of r Future Occasions. Technometrics, 29, 359-370.

Resources (cont.)
Ensuring Long-Term Protection—Monitoring Performance 

9-55

Gibbons, R.D. 1994. Statistical Methods for Ground-Water Monitoring. John Wiley & Sons.

Gibbons, R.D. 1992. An Overview of Statistical Methods for Ground-Water Detection Monitoring at

Waste Disposal Facilities. In Ground-Water Contamination at Hazardous Waste Sites: Chemical Analysis.

S. Lesge and R.E. Jackson (eds.), New York: Marcel Dekker, Inc.

Gibbons, R.D., Dolan, D., Keough, H., O’Leary, K., and O’Hara, R. 1992. A Comparison of Chemical

Constituents in Leachate from Industrial Hazardous Waste and Municipal Solid Waste Landfills.

Proceedings of the Fifteenth Annual Madison Waste Conference, University of Wisconsin, Madison.

Gibbons, R.D., Gams, N.E., Jarke, F.H., and Stoub, K.P. 1992. Practical Quantitation Limits.

Chemometrics and Intelligent Laboratory Systems, 12, 225-235.

Gibbons, R.D. 1991. Some Additional Nonparametric Prediction Limits for Ground-Water Monitoring at

Waste Disposal Facilities. Ground Water, 29, 729-736.

Gibbons, R.D., Jarke, F.H., and Stoub, K.P. 1991. Detection Limits: For Linear Calibration Curves with

Increasing Variance and Multiple Future Detection Decisions. Waste Testing and Quality Assurance. 3,

ASTM, SPT 1075, 377-390.

Gibbons, R.D. and Baker, J. 1991. The Properties of Various Statistical Prediction Limits. Journal of

Environmental Science and Health. A26-4, 535-553.

Gibbons, R.D. 1991. Statistical Tolerance Limits for Ground-Water Monitoring. Ground Water 29.

Gibbons, R.D. 1990. A General Statistical Procedure for Ground-Water Detection Monitoring at Waste

Disposal Facilities. Ground Water, 28, 235-243.

Gibbons, R.D., Grams, N.E., Jarke, F.H., and Stoub, K.P. 1990. Practical Quantitation Limits.

Proceedings of Sixth Annual U.S. EPA Waste Testing and Quality Assurance Symposium. Vol. 1, 126-

142.

Gibbons, R.D., Jarke, F.H., and Stoub, K.P. 1989. Methods Detection Limits. Proceedings of Fifth Annual

U.S. EPA Waste Testing and Quality Assurance Symposium. Vol. 2, 292-319.

Gibbons, R.D. 1987. Statistical Prediction Intervals for the Evaluation of Ground-Water Quality. Ground

Water, 25, 455-465.

Resources (cont.)
Gibbons, R.D. 1987. Statistical Models for the Analysis of Volatile Organic Compounds in Waste

Disposal Facilities. Ground Water 25, 572-580.

Gilbert, R.O. 1987. Statistical Methods for Environmental Pollution Monitoring. Van Nostrand Reinhold,

New York.

Starks, T.H. 1988. Evaluation of Control Chart Methodologies for RCRA Waste Sites. U.S. EPA Technical

Report CR814342-01-3.

Patil, G.P. and Rao, C.R. eds, Elsevier. 1993. Handbook of Statistics, Vol 12: Environmental Statistics.

U.S. EPA. 1993. Addendum to Interim Final Guidance Document Statistical Analysis of Ground-Water

Monitoring Data at RCRA facilities. EPA530-R-93-003.

U.S. EPA. 1989. Guidance Document on Statistical Analysis of Ground-Water Monitoring Data at RCRA

Facilities–Interim Final Guidance.

9-56

Ensuring Long-Term Protection—Monitoring Performance 

Resources (cont.)
Part V

Ensuring Long-Term Protection

Chapter 10

Taking Corrective Action
Contents

I. Corrective Action Process........................................................................................................................10-1

A. Unit Assessment ....................................................................................................................................10-2

B. Unit Investigation ..................................................................................................................................10-4

1. Specific Considerations for Ground-Water Investigations ..................................................................10-5

2. Specific Considerations for Soil Investigations ..................................................................................10-6

3. Specific Considerations for Surface-Water Investigations ..................................................................10-6

4. Specific Consideration for Air-Release Investigations ........................................................................10-7

C. Interim Measures ..................................................................................................................................10-8

D. Evaluating Potential Corrective Measures ............................................................................................10-10

1. Meeting Cleanup Standards ............................................................................................................10-11

2. Evaluating Treatment Technologies ..................................................................................................10-12

3. Evaluating the Long- and Short-Term Effectiveness of the Remedy..................................................10-18

4. Evaluating the Effectiveness of Reducing or Eliminating the Source of Contamination....................10-19

5. Evaluating the Ease of Implementation............................................................................................10-19

6. Measuring the Degree to Which Community Concerns are Met ......................................................10-20

E. Implementing Corrective Measures ......................................................................................................10-20

1. Institutional Controls ......................................................................................................................10-20

2. Monitoring and Site Maintenance ....................................................................................................10-22

3. No Further Action and Site Closure ................................................................................................10-22

Taking Corrective Action Activity List ........................................................................................................10-23

Resources ....................................................................................................................................................10-24

Figures:

Figure 1. Corrective Action Process............................................................................................................10-2

Figure 2. Screening Process for Selecting Appropriate Treatment Technologies ........................................10-17

Tables:

Table 1 Factors To Consider in Conducting a Unit Assessment..................................................................10-3

Table 2 Chemical Characteristics................................................................................................................10-3

Table 3 Site Characteristics ........................................................................................................................10-4

Table 4 Potential Release Mechanisms for Various Unit Types ....................................................................10-7

Table 5 Examples of Interim Corrective Measures ......................................................................................10-8
Ensuring Long-Term Protection—Taking Corrective Action

10-1

E

ffective operation of a waste management unit involves checking

the performance of the waste management system components.

When components are not operating effectively or when a problem develops,

corrective action might be needed to protect

human health and the environment.

Corrective action involves identifying exposure pathways of concern, selecting the best

corrective measure to achieve the appropriate

cleanup standard, and consulting with state

and community representatives.

I. Corrective

Action Process

The purpose of a corrective action program

is to assess the nature and extent of the releases of waste or constituents from the waste

management unit(s); to evaluate unit characteristics; and to identify, evaluate, and implement appropriate corrective measures to

protect human health and the environment.

The overall goal of any corrective action

should be to achieve a technically and economically feasible cleanup standard at a specified point on the facility property. For new

facilities this point should be on facility property, no more than 150 meters from the waste

management unit boundary (as established in

Chapter 9–Monitoring Performance). Existing

facilities can either use this same 150 meter

monitoring point standard or work with their

state agencies to determine an alternate set of

acceptable monitoring and cleanup criteria.

Using the ground-water pathway as an example, the corrective action goal should be to

reduce constituent concentration levels to the

applicable maximum contaminant levels

(MCLs) or health based numbers at the moniTaking Corrective Action

This chapter will help you:

• Monitor the performance of a waste management unit and take

appropriate steps to remediate any contamination associated

with its operation. 

• Locate and characterize the source of any contamination. 

• Identify and evaluate potential corrective measures. 

• Select and implement corrective measures to achieve attainment

of the established cleanup standard. 

• Work closely with the state and community representatives.

This chapter will help address the following questions.

• What steps are associated with corrective action?

• What information should be collected

during investigations?

• What factors should be considered in

selecting an appropriate corrective measure?

• What is involved in implementing the

selected remedy?
10-2

Ensuring Long-Term Protection—Taking Corrective Action

toring point (i.e., for new units, no more than

150 meters from the waste management unit).

A corrective action program generally has

the components outlined here and in Figure

1 (and explained in greater detail below). The

detail required in each of these components

varies depending on the unit and its complexity and only those tasks appropriate for

your site should be conducted. We recommend that you coordinate with the state during all phases of corrective action.

• Perform a unit assessment to locate

the actual or potential source(s) of

the release(s) of contaminants based

on waste management unit monitoring information and the use of other

existing information.

• Perform a unit investigation to characterize the nature and extent of contamination from the unit and any

contamination that might be migrating beyond the facility boundary,

identify areas and populations threatened by releases from the unit, and

determine short- and long-term

threats of releases from the unit to

human health and the environment.

• Identify, evaluate, and implement

interim measures, if needed. Interim

measures are short-term actions

taken to protect human health and

the environment while a unit assessment or a unit investigation is being

performed or before a corrective

measure is selected.

• Identify, evaluate, and implement

corrective measures to abate the further spread of contaminants, control

the source of contamination, and to

remediate releases from the unit.

• Design a program to monitor the

maintenance and performance of any

interim or final corrective measures

to ensure that human health and the

environment are being protected.

A. Unit Assessment

Often the first activity in the corrective

action process is the unit assessment. A unit

assessment identifies potential and actual

releases from the unit and makes preliminary

determinations about release pathways, the

need for corrective action, and interim measures. If appropriate, evaluate the possibility

of addressing multiple units as the

corrective action

process proceeds.

Table 1 identifies a

number of factors

to consider during

a unit assessment.

Tables 2 and 3 present some useful

properties and

parameters that

define chemical

Unit Assessment

Unit Investigation

Interim Measures

Corrective Measures

Evaluation

Corrective Measures

Implementation

Figure 1 Corrective Action Process
Ensuring Long-Term Protection—Taking Corrective Action

10-3

Unit/Site Chemical Migration Evidence of Release Exposure

Characteristics Characteristics Pathways Potential

Table 1

Factors To Consider in Conducting a Unit Assessment

Contamination

Parameters

– Concentrations

– Depth and location of

contamination

Physical Parameters

– Geology

– Depth to ground water

– Flow characteristics

– Climate

Historical Information

– History of unit

– Knowledge of waste 

generation practices 

Type of waste

placed in the unit

Volatilization

parameters

Toxicological

characteristics

Physical and

chemical properties

Chemical class

Soil sorption/

degradation

parameters

Facility’s

geological

setting

Facility’s

hydrogeological

setting

Atmospheric

conditions

Topographic

characteristics

Manmade

features (e.g.,

pipelines,

underground

utility lines) 

Prior inspection reports

Citizen complaints

Monitoring data

Visual evidence, such as

discolored soil, seepage,

discolored surface water

or runoff

Other physical evidence

such as fish kills,

worker illness, or odors

Sampling data

Offsite water wells 

Proximity to

affected

population

Proximity to

sensitive

environments

Likelihood of

migration to

potential

receptors 

Property/Parameter Characteristics

Chemical properties Density, viscosity

Chemical class Acid, base, polar neutral, nonpolar neutral, inorganic

Chemical reactivity Oxidation, reduction, hydrolysis, polymerization, precipitation,

biotic/abiotic

Soil sorption parameters Cation exchange capacity, anion exchange capacity, soil/water

partition coefficient (Kd), octanol/water partition coefficient

(Kow)

Soil degradation parameters Half-life, intermediate products of degradation

Volatilization parameters Henry’s law constant, vapor pressure

Table 2

Chemical Characteristics
10-4

Ensuring Long-Term Protection—Taking Corrective Action

and site characteristics that you should consider when characterizing your site and environmental setting. 

A beginning step is to review available site

information regarding unit characteristics,

waste characteristics, contaminant migration

pathways, evidence of release, and exposure

potential. Much of this information should

have been gathered in the site assessment (see

Chapter 4–Considering the Site) and waste

characterization phases (see Chapter

2–Characterizing Waste). Conducting a visual

site inspection of the unit will re-affirm available information and enable you to note any

visual evidence of releases. If necessary, perform sampling to confirm or disprove suspected releases before performing an extensive unit

investigation.

B. Unit Investigation

A unit investigation is conducted after a

release from the operating unit has been confirmed. The purpose of the investigation is to

gather enough data to fully characterize the

nature, extent, and rate of migration of contaminants to determine and support the selection of the appropriate response action. It is

important to tailor unit investigations to specific conditions and circumstances at the unit

and focus on releases and potential pathways.

Although each medium will require specific

data and methodologies to investigate a

release, a general strategy for this investigation,

consisting of two elements, can be described

as follows.

• Collect and review monitoring data,

data which can be gathered from outside information sources on parameters affecting the release, or new

information such as aerial photography or waste characterization.

• Formulate and implement field investigations and sampling and analysis or

monitoring procedures designed to

verify suspected releases. Evaluate the

nature, extent, and rate of migration of

verified releases. Refer to Chapter

9–Monitoring Performance to help

design a monitoring program.

Detailed knowledge of source characteristics

is valuable in identifying constituents for

which to monitor, indicator parameters, and

Parameter/Information Characteristics

Contamination parameters Concentration in soil, water, and subsurface gas; depth and

location of contamination

Physical parameters Permeability, particle size distribution, organic matter, geology,

moisture content, flow characteristics, depth to ground water,

pH, wind directions, climate

Historical information History of the waste management unit, knowledge of waste

generation processes, waste quantity

Table 3

Site Characteristics

Additional information on performing unit assessments can be found in RCRA Facility Assessment

Guidance (U.S. EPA, 1986).
Ensuring Long-Term Protection—Taking Corrective Action

10-5

possible release pathways. It is also helpful in

linking releases to a particular unit.

Monitoring information collected by a program described in Chapter 9–Monitoring

Performance can be helpful. Waste and unit

characteristics can also provide information

for determining release rates and for determining the nature and scope of any corrective

measures which might be applied. Refer to

Chapter 2–Characterizing Waste for information on how to characterize a waste.

Unit investigations can result in significant

amounts of data, including the results of

chemical, physical, or biological analyses. This

can involve analyses of many constituents, in

different media, at various sampling locations,

and at different times. Data management procedures should be established to effectively

process these data such that relevant data

descriptions, such as sample numbers, locations, procedures, and methods, are readily

accessible and accurately maintained.

1. Specific Considerations for

Ground-Water Investigations

To facilitate ground-water investigations

consider the following parameters:

• Ability of the waste to be dissolved or

to appear as a distinct phase.

• Degradability of the waste and its

decomposition products.

• Geologic

and

hydrologic factors

which

affect the

release

pathway.

• Regional

and sitespecific

groundwater

flow

regimes

that might affect the potential magnitude of the release pathways and possible exposure routes. 

Exposure routes of concern include ingestion of ground water as drinking water and

near-surface flow of contaminated ground

water into basements of residences or other

Guidance on Performing

Unit Investigations

Additional guidance on performing

unit inspections can be found in the following EPA documents:

• RCRA Facility Investigation Guidance

Volume I: Development of an RFI Work

Plan and General Considerations for

RCRA Facility Investigations (U.S. EPA,

1989a)

• RCRA Facility Investigation Guidance

Volume II: Soil, Ground Water, and

Subsurface Gas Releases (U.S. EPA,

1989b)

• RCRA Facility Investigation Guidance

Volume III: Air and Surface Water

Releases (U.S. EPA, 1989c)

• RCRA Facility Investigation Guidance

Volume IV: Case Study Examples (U.S.

EPA, 1989d)

• Guidance for Conducting Remedial

Investigations and Feasibility Studies

Under CERCLA (U.S. EPA, 1988a)

• Draft Practical Guide for Assessing and

Remediating Contaminated Sites (U.S.

EPA, 1989f)

• Site Characterization for Subsurface

Remediation (U.S. EPA, 1991c)
10-6

Ensuring Long-Term Protection—Taking Corrective Action

structures. It is important to also address the

potential for the transfer of contaminants in

ground water to other environmental media

through processes such as discharge to surface

water and volatilization to the atmosphere.

Use existing ground-water monitoring information, where it exists, to determine the

nature, extent, and rate of contaminant release

from the unit(s) to the ground water.

Investigation of a suspected release might be

terminated based on results from an initial

monitoring phase if these results show that an

actual release has not, in fact, occurred. If,

however, contamination is found, you should

characterize the release through subsequent

monitoring to help determine the detailed constituent composition and concentrations, the

horizontal and vertical extent of the contaminant release, as well as its rate of migration as

appropriate to assess the risk. This should be

accomplished through direct sampling and

analysis and, when appropriate, can be supplemented by indirect means such as geophysical

assessment and fate and transport modeling.

2. Specific Considerations for Soil

Investigations

When performing soil investigations, consider the following parameters:

• Ability of the waste to be dissolved by

infiltrating precipitation.

• The waste’s affinity for soil particles.

• The waste’s degradability and its

decomposition products.

• Surface features such as topography,

erosion potential, land-use potential,

and vegetation.

• Stratigraphic/hydrologic features such

as soil profile, particle-size distribution,

hydraulic conductivity, pH, porosity,

and cation exchange capacity.

• Meteorological factors such as temperature, precipitation, runoff, and evapotranspiration. 

Relevant physical and chemical properties of

the soil should be assessed to help determine

potential mobility of any contaminants in the

soil. Also, consider the potential for transfer of

contaminants in the soil to other environmental

media such as overland runoff to surface water,

leaching to ground water, and volatilization to

the atmosphere. In addition, you should establish whether a potential release involved a

point source (localized) or a non-point source.

Point sources might include container handling

and storage areas, tanks, waste piles, and bulk

chemical transfer areas. Non-point sources

might include airborne particulate contamination originating from a land application unit

and widespread leachate seeps from a landfill.

Table 4 presents important mechanisms of contaminant release to soils for various unit types.

This information can be used to identify areas

for initial soil monitoring.

3. Specific Considerations for

Surface-Water Investigations

When conducting surface-water investigations, the following factors should be considered:

• The release mechanism, such as overtopping of an impoundment.
Ensuring Long-Term Protection—Taking Corrective Action

10-7

• The nature of the source area, such as

point or non-point.

• Waste type and degradability.

• Local climate.

• Hydrologic factors such as stream

flow conditions.

• The ability for a contaminant to accumulate in stream bottom sediments. 

Also, address the potential for the transfer

of contaminants in surface water to other

environmental media such as soil contamination as a result of flooding of a contaminated

creek on the facility property. 

During the initial investigation, particular

attention should be given to sampling runoff

from contaminated areas, leachate seeps, and

other similar sources of surface-water contamination, as these are the primary overland release

pathways for surface water. Releases to surface

water via ground-water discharge should be

addressed as part of the ground-water investigation for greater efficiency. See Chapter

9–Monitoring Performance, Section II: SurfaceWater Monitoring for information on proper

surface-water monitoring techniques.

4. Specific Consideration for AirRelease Investigations

The intent of an air-release investigation is

to determine any actual or potential effects at

a nearby receptor. This might involve emisUnit Type Release Mechanism

Surface impoundment Releases from overtopping

Leakage through dikes or unlined portions to surrounding soils

Landfill Migration of releases outside the unit’s runoff collection and containment

system

Seepage through underlying soils

Waste pile Migration of releases outside the unit’s runoff collection and containment

system

Seepage through underlying soils

Land application unit Migration of runoff outside the application area

Passage of leachate into the soil horizon

Table 4

Potential Release Mechanisms for Various Unit Types
10-8

Ensuring Long-Term Protection—Taking Corrective Action

sion modeling to estimate unit-specific emission rates, air monitoring to determine concentrations at a nearby receptor, emission

monitoring at the source to determine emission rates, and dispersion modeling to estimate concentrations at a nearby receptor. See

Chapter 9–Monitoring Performance, Section

IV: Air Monitoring for more information on

air monitoring and Chapter 5–Protecting Air

for more information on air modeling.

As in other media-specific investigations,

the first step is to collect, review, and evaluate

available waste, unit, environmental setting,

and release data. Evaluation of these data can

indicate the need for corrective measures or

that no further action is required. For example, the source might involve a large, active

storage surface impoundment containing

volatile constituents adjacent to residential

housing. Action, therefore, instead of further

studies, might be appropriate. Another case

might involve a unit in an isolated location,

where an acceptable modeling or monitoring

database indicates that the air release can be

considered insignificant and, therefore, further studies are not warranted. In many

cases, however, further release characterization might be necessary.

C. Interim Measures

Many cleanup programs recognize the

need for interim measures while site characterization is underway or before a final remedy is selected. Typically, interim measures are

used to control or abate ongoing risks before

final remedy selection. Examples of interim

measures for various types of waste management units and various release types are listed in Table 5. More information is available

through the RCRA Corrective Action Interim

Measures Guidance—Interim Final (U.S. EPA,

Unit/Release Interim Measure

Containers Overpack or redrum

Construct storage area

Move to new storage area

Segregation

Sampling and analysis

Treatment or storage

Temporary cover

Tanks Construct overflow/secondary containment

Leak detection or repair

Partial or complete removal

Surface Impoundments Reduce head

Remove free liquids and highly mobile wastes

Stabilize or repair side walls, dikes, or liner(s)

Temporary cover

Run-on or runoff control (diversion or collection devices)

Sample and analyze to document the concentration of constituents

Interim ground-water measures

Table 5

Examples of Interim Corrective Measures
Ensuring Long-Term Protection—Taking Corrective Action

10-9

Unit/Release Interim Measure

Landfills Run-on or runoff control (diversion or collection devices)

Reduce head on liner or leachate collection and removal system

Inspect leachate collection and removal system, or french drain

Repair leachate collection and removal system, or french drain

Temporary cap

Waste removal

Interim ground-water measures

Waste Piles Run-on or runoff control (diversion or collection devices)

Temporary cover

Waste removal

Interim ground-water measures

Soils Sampling or analysis

Removal and disposal

Run-on or runoff control (diversion or collection devices)

Temporary cap or cover

Ground Water Delineation or verification of gross contamination

Sampling and analysis

Interceptor trench, sump, or subsurface drain

Pump-and-treat

In situ treatment

Temporary cap or cover

Surface-Water Releases Overflow or underflow dams

(Point and Non-Point) Filter fences

Run-on or runoff control (diversion or collection devices)

Regrading or revegetation

Sample and analyze surface waters and sediments or point source discharges 

Gas Mitigation Control Barriers

Collection

Treatment

Monitoring

Particulate Emissions Truck wash (decontamination unit)

Revegetation

Application of dust suppressant

Other Actions Fencing to prevent direct contact

Sampling offsite areas

Alternate water supply to replace contaminated drinking water

Temporary relocation of exposed population

Temporary or permanent injunction 

Table 5

Examples of Interim Corrective Measures (cont.)
10-10

Ensuring Long-Term Protection—Taking Corrective Action

1988b) and RCRA Corrective Action

Stabilization Technologies (U.S. EPA, 1992b).

Interim measures can be separate from the

comprehensive corrective action plan, but

should be consistent with and integrated into

any longer term corrective measure. To the

extent possible, interim measures should not

seriously complicate the ultimate physical

management of wastes or constituents, nor

should they present or exacerbate a health or

environmental threat. 

D. Evaluating Potential

Corrective Measures

The corrective measure or measures selected should meet the corrective action goals,

such as a state or local cleanup standard, and

control or remove the source of contamination to reduce or eliminate further releases.

Most corrective measures fall into one of

three technology categories—containment

technologies, extraction or removal technologies, or treatment technologies. The performance objectives of the corrective measures

relate to source reduction, cleanup goals, and

cleanup timeframe. These measures might

include the repair or upgrade of existing unit

components, such as liner systems, leachate

collection systems, or covers. 

You should base selection of corrective

measures on the following considerations and

contact the state and community representatives before finalizing the selection:

• The ability to meet appropriate

cleanup standards.

• The appropriateness and effectiveness

of the treatment technology in relation to waste and site characteristics.

• The long- and short-term effectiveness

including economic, technical feasibility, and protectiveness of the remedy.

• The effectiveness of the remedy in

reducing further releases.

• The ease of implementing the remedy.

• The degree to which local community concerns have been addressed.

Potential Corrective

Measures

Additional guidance on potential corrective measures is available from the

following documents:

• Corrective Action: Technologies and

Applications (U.S. EPA, 1989c)

• Handbook: Stabilization Technologies for

RCRA Corrective Actions (U.S. EPA,

1991b)

• RCRA Corrective Action Stabilization

Technologies (U.S. EPA, 1992b)

• Pump-and-Treat Ground-Water

Remediation: A Guide for Decision

Makers and Practitioners (U.S. EPA,

1996c)

• Handbook: Remediation of

Contaminated Sediments (U.S. EPA,

1991a)

• Abstracts of Remediation Case Studies

(U.S. EPA, 1995)

• Bioremediation Resource Guide (U.S.

EPA, 1993)

• Groundwater Treatment Technology

Resource Guide (U.S. EPA, 1994a)

• Physical/Chemical Treatment Technology

Resource Guide (U.S. EPA, 1994b)

• Soil Vapor Extraction Treatment

Technology Resource Guide (U.S. EPA,

1994d)
1. Meeting Cleanup Standards

Work with your state and community representatives to establish risk-based cleanup

standards for the media of concern before

identifying potential corrective measures. For

example, if there is a statistically significant

increase of constituent concentrations over

background in the ground water, cleanup

standards would include reducing contaminant concentrations to the MCL or healthbased level at the point of monitoring. 

Several approaches have been developed to

identify appropriate cleanup standards. One of

the more recent approaches is the Risk-Based

Corrective Action (RBCA) standard developed

by some states and the American Society for

Testing and Materials (ASTM) Committee. The

RBCA standard provides guidance on how to

integrate ecological and human-health, riskbased, decision-making into the traditional

corrective action process described above.

RBCA is a decision-making process for the

assessment and response to chemical releases.

This standard is applicable to all types of

chemical-release sites, which can vary greatly

in terms of their complexity, physical and

chemical characteristics, and the risk they pose

to human health and the environment. RBCA

uses a tiered approach that begins with simple

analyses and moves to more complex evaluations when necessary. The foundation of the

RBCA process is that technical policy decisions

are identified in the front-end of the process to

ensure that data collected are of sufficient

quantity and quality to answer questions

posed at each tier of the investigation. The

RBCA standard is not intended to replace

existing regulatory programs, but rather to

provide an enhancement to these programs.

The RBCA process allows for a three-tiered

approach as described below. 

In recent years, many states have adopted

similar risk-based guidance or rules. The

Louisiana Department of Environmental

Quality, for instance, promulgated its Risk

Evaluation/Corrective Action Program

(RECAP) final rule, on June 20, 2000.

Likewise, the Texas Natural Resource

Conservation Commission (TNRCC) finalized

the Texas Risk Reduction Program in 1999

(Title 30 Texas Administrative Code (TAC)

Chapter 350). Your state and community representatives can tell you whether similar RBCA

standards exist in your state and the appropriateness of such an approach. ASTM also offers

two training courses on RBCA: Risk-Based

Corrective Action for Chemical Releases, and

Risk Based Corrective Action Applied at

Petroleum Release Sites. These courses are

open to all individuals from federal, state, tribal, and local regulatory agencies as well as professionals from the private sector.

RBCA Tier 1 Evaluation 

A Tier 1 evaluation classifies a site according to the urgency for corrective action using

broad measures of release and exposure. This

tier is used to identify the source(s) of the

chemical release, obvious environmental

impacts, potential receptors, and significant

exposure pathways. During a Tier 1 evaluation, site-specific contaminant concentrations

are compared against a standard table of riskbased screening levels (RBSLs) that have been

developed using conservative, nonsite-specific exposure assumptions. If a site’s contaminant concentrations are found to be above

the RBSLs, then corrective action or further

evaluation would be considered. Continued

monitoring might be the only requirement if

site-specific contaminant concentrations are

below the RBSLs. 

At the end of the Tier 1 evaluation, initial

corrective action responses are selected while

additional analysis is conducted to determine

final remedial action, if necessary. The standard includes an exposure scenario evaluation flowchart to help identify appropriate

Ensuring Long-Term Protection—Taking Corrective Action

10-11
10-12

Ensuring Long-Term Protection—Taking Corrective Action

receptors and exposure scenarios based on

current and projected reasonable land use

scenarios, and appropriate response actions.

Site conditions should also be compared to

relevant ecological screening criteria (RESC)

applicable to the site which might include

qualitative or quantitative benchmarks, comparison of site conditions to local biological

and environmental conditions, or considerations related to the exposed habitat areas. 

RBCA Tier 2 Evaluation 

The user might decide to conduct a Tier 2

evaluation after selecting and implementing

the appropriate initial response action to the

Tier 1 evaluation. The purpose of this tier is

to determine site-specific target levels (SSTLs)

and appropriate points of compliance when it

is determined that Tier 1 RBSLs have been

exceeded. While a Tier 2 evaluation is based

on similar screening levels as those used in

the Tier 1 evaluation, some of the generic

assumptions used in the earlier evaluation are

replaced with site-specific measurements to

develop the SSTLs. The intent of Tier 2 is to

incorporate the concept that measured levels

of contamination can decline over the distance from source to receptor. Thus, simple

environmental fate and transport modeling is

used to predict attenuation over that distance.

If site-specific contaminant concentrations are

above the SSTLs, corrective action is needed

and further analysis might be required.

RBCA Tier 3 Evaluation

A Tier 3 evaluation involves the same steps

as those taken during the Tier 1 and Tier 2

evaluations, except that a significant increase

in effort is employed to better define the

scope of the contamination. Actual levels of

contamination are compared to SSTLs that

are developed for this Tier. The Tier 3 SSTLs

differ from Tier 2 SSTLs in the level of

sophistication used to develop site-specific

measures of the fate and transport of contaminants. Where simplified, site-specific measures of the fate and transport are used in the

Tier 2 evaluation, much more sophisticated

models and data will be used in this Tier.

These models might rely on probabilistic

approaches and on alternative toxicity and

biodegradability data. 

2. Evaluating Treatment

Technologies

In nearly every phase of the corrective

action process, some information about treatment technologies is important. Many documents exist that describe candidate

technologies in detail and give their respective applicability and limitations. Below are

descriptions and examples of the three major

technology categories: containment, extraction, and treatment.

Containment technologies are used to stop

the further spread or migration of contaminants. Some examples of common containment techniques for constituents in

land-based units include waste stabilization,

solidification, and capping. Capping and

other surface-water diversion techniques, for

instance, can control infiltration of rainwater

to the contaminated medium. Typical ways to

contain contaminated ground-water plumes

include ground-water pumping, subsurface

drains, and barrier or slurry walls. These

ground-water containment technologies control the migration of contaminants in the

ground-water plume and prevent further dissolution of contaminants by water entering

the unit.

• Ground-water pumping. Groundwater pumping can be used to

manipulate and manage ground

water for the purpose of removing,

diverting, and containing a contaminated plume or for adjusting ground-
water levels to prevent plume movement. For example, pumping systems

consisting of a series of extraction

wells located directly downgradient

from a contaminated source can be

used to collect the contaminated

plume. The success of any contaminant capture system based upon

pumping wells is dependent upon

the rate of ground-water flow and the

rate at which the well is pumped.

Thus, the zone of capture for the

pumping system must be established.

• Subsurface drains. Subsurface

drains are essentially permeable barriers designed to intercept the

ground-water flow. The water is collected at a low point and pumped or

drained by gravity to the treatment

system. Subsurface drains can also be

used to isolate a waste disposal area

by intercepting the flow of uncontaminated ground water before it enters

into a contaminated site. Subsurface

drains are most useful in preliminary

containment applications for controlling pollutant migration, while a final

treatment design is developed and

implemented. They also provide a

measure of long-term protection

against residual contaminants following conclusion of treatment and site

closure. 

• Barrier walls. Low permeability barriers are used to direct the uncontaminated ground-water flow around a

particular site or to prevent the contaminated material from migrating

from the site. Barrier walls can be

made of a wide variety of materials,

as long as they have a lower permeability than the aquifer. Typical materials include mixtures of soil and

bentonite, mixtures of cement and

bentonite, or barriers of engineered

materials (sheet piling). A chemical

analysis of wall/contaminant compatibility is necessary for the final selection of materials. The installation of a

low permeability barrier usually

entails a great deal of earth moving,

requires a significant amount of land

area, and is expensive. Once in place,

however, it represents a long-term,

low maintenance system. 

Extraction or removal technologies physically remove constituents from a site.

Extraction techniques might remove the constituent of concern only, or the contaminated

media itself. For example, vapor extraction

might just remove the constituent vapors from

the soil, while excavation could remove all of

the contaminated soil. Extraction technologies

include excavation, pumping, product recovery, vapor extraction or recovery, and soil

washing.

Treatment or destruction technologies render constituents less harmful through physical, biological, chemical, and thermal

processes including ground-water treatment,

pH adjustment, oxidation and reduction,

bioremediation, and incineration. 

• Ground-water pump-and-treat is

one of the most widely used groundwater treatment technologies.

Conventional methods involve

Ensuring Long-Term Protection—Taking Corrective Action

10-13
pumping contaminated water to the

surface for treatment. Pump-andtreat systems are used primarily for

hydraulic containment and treatment

to reduce the dissolved contaminant

concentrations in ground water so

that the aquifer complies with cleanup standards or the treated water

withdrawn from the aquifer can be

put to beneficial use. A thorough,

three-dimensional characterization of

subsurface soils and hydrogeology,

including particle-size distribution,

sorption characteristics, and

hydraulic conductivity, provides a

firm basis for appropriate placement

of pump-and-treat wells. The following techniques can be useful in effectively designing and operating the

pump-and-treat system:

- Using capture zone analysis, optimization modeling, and data

obtained from monitoring the

effects of initial extraction wells to

identify the best locations for wells.

- Phasing the construction of extraction and monitoring wells so that

information obtained from the

operation of the initial wells

informs decisions about siting subsequent wells.

- Phasing pumping rates and the

operation of individual wells to

enhance containment, avoid stagnation zones, and ensure removal of

the most contaminated ground

water first.

• Chemical treatment is a class of

processes in which specific chemicals

are added to wastes or to contaminated media in order to achieve

detoxification. Depending on the

nature of the contaminants, the

chemical processes required might

include pH adjustment, lysis, oxidation, reduction, or a combination of

these. In addition, chemical treatment is often used to prepare for or

facilitate the treatment of wastes by

other technologies. 

- The function of pH adjustment is to

neutralize acids and bases and to

promote the formation of precipitates, which can subsequently be

removed by conventional settling

techniques. Typically, pH adjustment is effective in treating inorganic or corrosive wastes.

- Oxidation and reduction reactions

are utilized to change the chemical

form of a hazardous material, in

order to render it less toxic or to

change its solubility, stability, separability, or otherwise change it for

handling or disposal purposes. In

any oxidation reaction, the oxidation state of one compound is

raised (i.e., oxidized) while the oxidation state of another compound

is lowered (i.e., reduced). In the

reaction, the compound supplying

the oxygen (or chlorine or other

negative ion) is called the oxidizer

or oxidizing agent, while the compound accepting the oxygen (i.e.,

supplying the positive ion) is called

the reducing agent. The reaction

can be enhanced by catalysis, electrolysis, or photolysis.

- The basic function of lysis processes is to split molecules to permit

further treatment. Hydrolysis is a

chemical reaction in which water

reacts with another substance. In

the reaction, the water molecule is

ionized while the other compound

10-14

Ensuring Long-Term Protection—Taking Corrective Action
is split into ionic groups. Photolysis,

another lysis process, breaks chemical bonds by irradiating a chemical

with ultraviolet light. Catalysis uses

a catalyst to achieve bond cleavage.

• Biological treatment is a destruction

process relying primarily on oxidative

or reductive mechanisms. The two

types of biological treatment processes are aerobic and anaerobic. Aerobic

processes are oxidative processes and

are the most widely used. These

processes require a supply of molecular oxygen and include suspended

growth systems, fixed-film systems,

hybrid reactors, and in situ application. Anaerobic processes achieve the

reduction of organic matter to

methane and carbon dioxide in an

oxygen-free environment. The use of

biological treatment processes is

directed toward accomplishing

destruction of organic contaminants,

oxidation of organic chemicals

whereby the organic chemicals are

broken down into smaller constituents, and dehalogenation of

organic chemicals by cleaving a chlorine atom(s) or other halogens from a

compound. 

Biological processes can be used on a

broad class of biodegradable organic

contaminants. It should be noted,

however, that very high concentrations as well as very low concentrations of organic contaminants are

difficult to treat via biological

processes. Since microorganisms need

appropriate conditions in which to

function, you must provide an optimum environment, whether aboveground in a reactor or belowground

for an in situ application. The primary conditions which can affect the

growth of the microbial community,

in addition to providing them sufficient food (organic material), are pH,

temperature, oxygen concentration,

nutrients, and toxicity.

- Typically, a biological treatment system operates best when a waste

stream is at a pH near 7. However,

waste treatment systems can operate

(with some exceptions) between pH

values of 4 and 10. The exceptions

are aerobic systems in which

ammonia is oxidized to NOx as well

as anaerobic methane fermenting

systems. For these, the pH should

be between 6 and 8; outside this

range, efficiency will suffer.

- Waste treatment systems can function over a temperature range of 5°

to 60°C. Most waste treatment systems operate between 15° to 45°C

and use mesophilic organisms.

- Microorganisms need a certain

amount of oxygen not only to survive but also to control their reactions. Therefore, the residual

dissolved oxygen concentrations

should be maintained at approximately 2 mg/l or greater within a

typical liquid biotreatment system.

- The quantity of nutrients needed

depends on the biochemical oxygen

demand (BOD) of the waste. The

higher the BOD, the higher the number of cells produced and the greater

the quantity of nutrients required. 

- The presence of toxic substances

will obviously produce adverse conditions in a biological system.

Unfortunately, it is difficult to cite

specific toxic materials because toxicity depends on concentration.

Nutrients can be toxic in higher

Ensuring Long-Term Protection—Taking Corrective Action

10-15
concentrations and all types of

organic compounds which can be

used as food by bacteria can be

toxic if their concentrations are

high enough. Frequently, toxicity

concerns can be avoided by waste

dilution and microbe acclimation.

• Thermal treatment, or incineration,

is a treatment technology applicable

to the treatment of wastes containing

a wide range of organic concentrations and low concentrations of

water, metals, and other inorganics.

Incineration is the thermal decomposition of organic constituents via

cracking and oxidation reactions at

high temperatures that can be used

for detoxification, sterilization, volume reduction, energy recovery, and

by-product chemical recovery. A

well-designed and properly operated

incinerator will destroy all but a tiny

fraction of the organic compounds

contained in the waste. Incinerator

emission gases are composed primarily of carbon dioxide and water. The

type and quantity of other compounds emitted depends on the composition of the wastes, the

completeness of the combustion

process, and the air pollution control

equipment with which the incinerator is equipped. Incinerators are

designed to accept wastes of varying

physical forms, including gasses, liquids, sludges, and solids.

• Stabilization/solidification processes immobilize toxic or hazardous

constituents in a waste by changing

the constituent into immobile forms,

binding them in an immobile matrix,

or binding them in a matrix which

minimizes the waste material surface

exposed to solvent. Often, the immobilized product has a structural

strength sufficient to prevent fracturing over time. Solidification accomplishes the intended objective by

changing a non-solid waste material

into a solid, monolithic structure that

ideally will not permit liquids to percolate into or leach materials out of

the mass. Stabilization, on the other

hand, binds the hazardous constituents into an insoluble matrix or

changes the hazardous constituent to

an insoluble form. Other objectives

of solidification/stabilization processes are to improve handling of the

waste and produce a stable solid (no

free liquid) for subsequent use as a

construction material or for landfilling. Major categories of industrial

waste solidification/stabilization systems are cement-based processes.

Waste characteristics such as organic

content, inorganic content, viscosity,

and particle size distribution can

affect the quality of the final solidified product. These characteristics

inhibit the solidification process by

affecting the compatibility of the

binder and the waste, the completeness of encapsulation, and the development of preferential paths for

leaching due to spurious debris in

the waste matrix.

In selecting a treatment technology or set

of technologies, it is important to consider the

information obtained from the waste and site

characterizations, see Chapter

2–Characterizing Waste and Chapter

4–Considering the Site. For example, the

waste characterization should tell the location

of the waste and in what phase(s) the waste

should be expected to be found, (e.g., sorbed

to soil particles). Waste characterization information also allows for the assessment of the

leaching characteristics of the waste, its ability

10-16

1 U.S. EPA, 1991. Site Characterization for Subsurface Remediations.

Ensuring Long-Term Protection—Taking Corrective Action
to be degraded, and its tendency to react with

chemicals. The site characterization information should reveal important information

about subsurface flow conditions and other

physical characteristics, such as organic carbon content. You should use the information

from the waste and site characterizations to

select the appropriate treatment technology.

A screening process for selecting an appropriate technology is presented in Figure 2. In

some cases, a treatment train, a series of technologies combined together, might be appropriate.1 This step-by-step approach helps

ensure that technologies that might be applicable at a site are not overlooked. In addition,

the rationale for the elimination of specific

technologies will be available to justify decisions to interested parties.

Additional information regarding the use

and development of innovative treatment

technologies is available from EPA’s

Hazardous Waste Clean-up Information

(CLU-IN) Web site <clu-in.org>. This Web

site describes programs, organizations, publications, and other tools for all waste remediation stakeholders. Of particular interest is the

Remediation Technologies Screening Matrix

which is a user-friendly tool to screen for

technologies for a remediation project. The

matrix allows you to screen through 64 in

situ and ex situ technologies for either soil or

ground-water remediation. Variables used in

screening include contaminants, development

status, overall cost, and cleanup time. The

matrix can be accessed through CLU-IN or

directly from the Federal Remediation

Technologies Roundtable’s Web site

<www.frtr.gov/matrix2/top_page.html>. 

Another source of information is the Field

Analytic Technologies Encyclopedia (FATE)

developed by EPA’s Technology Innovation

Office (TIO), in collaboration with the U.S.

Army Corps of Engineers. FATE is an online

encyclopedia of information about technologies that can be used in the field to characterize contaminated soil and ground water,

monitor the progress of remedial efforts, and

in some cases, confirm sampling and analysis

for site closure. To access FATE visit:

<www.epa.gov/tio/chartext_tech.htm>. 

Ensuring Long-Term Protection—Taking Corrective Action

10-17

Figure 2

Recommended Screening Process for

Selecting Appropriate Treatment Technologies

Evaluate waste and site-specific information and

identify potential treatment technologies

Develop a conceptual design for each technology including:

• Process description

• Process flow diagram

• Layout drawing 

• Preliminary sizing of equipment, utility, and

land requirements

• Chemical requirements

• Expected residuals

Compare technologies using:

• Effectiveness and reliability of technology

meeting cleanup goals

• Beneficial and adverse effects on the environment

• Beneficial and adverse effects on human

health

• Ability to meet federal, state, and local government standards and gain public acceptance

• Capital, operating, and maintenance costs

Select most appropriate technology in consultation with state and community representatives

Obtain state approval
3. Evaluating the Long- and

Short-Term Effectiveness of

the Remedy

Evaluating the long- and short-term effectiveness of the remedy, involves analyzing the

risks associated with potential exposure pathways, estimates of potential exposure levels,

and the duration of potential exposure associated with the construction and implementation of the corrective measure. Because

waste characteristics vary from site to site,

the effect of a treatment technology with a

particular waste might be unknown. It is

important, therefore, to consider performing

a treatability study to evaluate the effectiveness of one or more potential remedies.

Spending the time and money up-front to

better assess the effectiveness of a technology

on a waste can save significant time and

money later in the process. To judge the

technical certainty that the remedy will attain

the corrective action goal, also consider

reviewing case studies where similar technologies have been applied.

It is also important to analyze the time to

complete the corrective measure, because it

directly impacts the cost of the remedy. It is

therefore important to carefully evaluate the

long-term costs of the remedial alternatives

and the long-term financial condition of the

facility. Consider including quality control

measures in the implementation schedule to

assess the progress of the corrective measure.

It is also important to determine the degree

to which the remedy complies with all

applicable state laws.

The Federal Remediation Technologies

Roundtable <www.frtr.gov> is at the forefront of the federal government’s efforts to

promote interagency cooperation to advance

the use of innovative remediation technologies. Roundtable member agencies include

EPA, the U.S. Department of Defense, the

U.S. Department of Energy, and the U.S.

Department of Interior. This group has prepared over 209 cost and performance reports

that can be accessed through CLU-IN 

<clu-in.org/remed1.cfm>. These reports

contained in the “Federal Remediation

Technologies Roundtable Case Studies” document results from completed full-scale hazardous waste site remediation projects and

several large-scale demonstration projects.

10-18

Ensuring Long-Term Protection—Taking Corrective Action

Treatability Studies

The four general types of treatability

studies are laboratory-scale, bench-scale,

pilot-scale, and field-scale.

• Laboratory-scale studies are small

scale screening studies that generate

qualitative information concerning

the general validity of a treatment

approach.

• Bench-scale studies are intermediate

studies conducted in the laboratory.

Bench scale studies are intended to

answer specific design, operation, and

cost questions, and are more detailed

than laboratory studies.

• Pilot-scale studies are large scale

experiments intended to provide

quantitative cost and design data.

They simulate anticipated full-scale

operational configurations as closely

as possible.

• Field-scale studies are large scale

studies intended to monitor the performance of treatment systems under

real world conditions at close to full

scale operations.

More information on treatability studies can be found in A Guide for

Conducting Treatability Studies Under

CERCLA (U.S. EPA, 1992a).
They are meant to serve as primary reference

sources, and they contain information on site

background and setting, contaminants and

media treated, technology, cost and performance, and points of contact for the technology application. 

EPA has also prepared an overview of

ground-water cleanup at 28 sites entitled

Groundwater Cleanup: Overview of Operating

Experience at 28 Sites (U.S. EPA, 1999a) that is

also available from CLU-IN. This overview

presents a range of the types of cleanups typically performed at sites with contaminated

ground water and summarizes information

about the remediation systems at the 28 sites.

Summarized information includes design,

operation, and performance of the systems;

capital, operating, and unit costs of the systems; and factors that potentially affect the cost

and performance of the systems. 

EPA’s TIO Web site <www.epa.gov/tio>

provides additional information about site

characterization and treatment technologies

for remediation. This Web site offers technology selection tools and describes programs,

organizations, and available publications.

Some of the available publications include

Abstracts of Remediation Case Studies, Volumes

1-4 (U.S. EPA, 2000a) which summarize 218

case studies of site remediation prepared by

federal agencies. Many of these publications

and links are also available through CLU-IN.

4. Evaluating the Effectiveness of

Reducing or Eliminating the

Source of Contamination

There are two major components of source

control that should be evaluated. First, if

source control consists of the removal, redisposal, or treatment of wastes, the volume of

wastes and residual materials should be

quantified and the potential to cause further

contamination evaluated. Second, engineering

controls intended to upgrade or repair deficient conditions at a waste management unit

should be quantified in terms of anticipated

effectiveness according to current and future

conditions. This evaluation should determine

what is technically and financially practicable.

Health considerations and the potential for

unacceptable exposure(s) to both workers

and the public can affect an evaluation.

5. Evaluating the Ease of

Implementation

The ease of implementing the proposed

corrective measure will affect its schedule. To

evaluate the ease of implementation of a specific corrective measure, it is important to

Ensuring Long-Term Protection—Taking Corrective Action

10-19

Selecting a Corrective

Action Specialist

Once it has been determined that corrective measures are necessary, you should

determine if in-house expertise is adequate

or if an outside consultant is necessary.

If a consultant is needed, determine if

the prospective consultant has the technical competence to do the work needed. A poor design for a recovery system,

unacceptable field procedures, lack of

familiarity with state requirements, or an

inadequate investigation might unnecessarily cost thousands of dollars and still

not complete the cleanup.

Some of the most important information to consider in selecting a consultant

is whether the consultant has experience

performing site investigations and remediations at similar sites, is familiar with

state regulations, has staff trained in the

use of field screening instruments, has

experience in monitoring well design

and installations, has established quality

assurance and quality control procedures, and can provide references.
consider the availability of technical expertise

and equipment, the ability to properly manage, dispose, or treat wastes generated by the

corrective measure, and the likelihood of

obtaining local permits and public acceptance for the remedy. Consider also the

potential for contamination to transfer from

one media to another as part of the overall

feasibility of the remedy. Cross-media

impacts should be addressed as part of the

implementation phase. Develop a correctivemeasure schedule identifying the beginning

and end periods of the permitting, construction, treatment, and source control measures. 

6. Measuring the Degree to

Which Community Concerns

are Met

Prior to selecting the corrective measure(s),

you should hold a public meeting to discuss

the results of the corrective action assessment

and to identify proposed remedies. Consider

notifying adjacent property owners via mail of

any identified contamination and proposed

remedies. You also should identify any public

concerns that have been expressed, via written public comments or from public meetings, about the facility’s contamination and

should address these concerns by the corrective measures being evaluated. The best remedy selected and implemented will be the one

that is agreed upon by the state or local regulatory agency, the public, and the facility

owner. Review Chapter 1–Understanding Risk

and Building Partnerships before selecting any

final remedies.

E. Implementing

Corrective Measures

The implementation of corrective measures encompasses all activities necessary to

initiate and continue remediation. During the

evaluation and assessment of the nature and

extent of the contamination, you should

decide whether no further assessment is necessary, whether institutional controls are necessary to protect human health and the

environment, whether monitoring and site

maintenance are necessary, and whether no

further action and closure are appropriate for

the unit.

1. Institutional Controls

Institutional controls are those controls

that can be utilized by responsible parties

and regulatory agencies in remedial programs

where, as part of the program, certain levels

of contamination will remain on site in the

soil or ground water. Institutional controls

can also be considered in situations where

there is an immediate threat to human

health. Institutional controls can vary in both

form and content. Agencies and landowners

can invoke various authorities and enforcement mechanisms, both public and private,

to implement one or more of the controls. A

10-20

Ensuring Long-Term Protection—Taking Corrective Action

Citizen Guides to

Treatment Technologies

EPA’s Technology Innovation Office

has developed a series of fact sheets that

explain, in basic terms, the operation

and application of innovative treatment

technologies for remediating sites. The

fact sheets address issues associated with

innovative treatment technologies as a

whole, bioremediation, chemical dehalogenation, in situ soil flushing, natural

attenuation, phytoremediation, soil

vapor extraction and air sparging, soil

washing, solvent extraction, thermal desorption, and the use of treatment walls.

English and Spanish versions of these

fact sheets can be downloaded from

CLU-IN <clu-in.org/remed1.cfm>.
state could adopt a statutory mandate, for

example, requiring the use of deed restrictions as a way of enforcing use restrictions

and posting signs. Commonly used institutional controls include deed restrictions, use

restrictions, access controls, notices, registry

act requirements, transfer act requirements,

and contractual obligations. Additional information on institutional controls is available at

EPA’s Office of Solid Waste and Emergency

Response Web site at <www.epa.gov/

oerrpage/superfund/action/

postconstruction/ic.htm>.

• Deed restrictions. These restrictions,

also called restrictive covenants, place

limits on the use and conveyance of

land. They inform prospective

owners/tenants of the environmental

status of the property and ensure longterm compliance with the institutional

controls. Typically, there are four

requirements for a promise in a deed

restriction: the conveyance of land must

be documented in writing; it should

precisely reflect the parties’ intentions

with respect to the scope and duration

of the restrictions; there should be

“privity of estate” so that it can be

enforced by states; and the promise

“touches and concerns the land.”

• Use restrictions. Use restrictions are

usually the heart of what is in a deed

restriction. Use restrictions describe

appropriate and inappropriate uses of

the property, in an effort to perpetuate the benefits of the remedial action

and ensure property use that is consistent with the applicable cleanup

standard. Such techniques also prohibit any person from making use of

the site in a manner that creates an

unacceptable risk of human or environmental exposure to the residual

contamination. Use restrictions

address uses that might disturb a

containment cap or any unremediated soils under the surface or below a

building. A prohibition on drinking

onsite or offsite ground water might

also be appropriate. Well restriction

areas can be a form of institutional

control by providing notice of the

existence of contaminants in ground

water and by prohibiting or conditioning the placement and use of any

or all wells within an area.

• Access controls. Access to any particular site can be controlled by either

fencing and gates, security, or posting

or warnings. A state might use the

following criteria to determine the

appropriate level and means of access

control: whether the site is located in

a residential or mixed-use neighborhood; proximity to sensitive land-use

areas including day care centers,

playgrounds, and schools; and

whether the site is frequently traversed by neighbors.

• Notices. Controls of this type generally provide notice of specific location

of contamination on site and disclose

any restrictions on access, use, and

development of part or all of the contaminated site to preserve the integrity of the remedial action. Types of

notices include record notice (notices

on land records), actual notice (direct

notice of environmental information

to other parties to a land transaction),

and notice to government authorities.

• Registry act requirements. Some

states have registry act programs that

provide for the maintenance of a registry of hazardous waste disposal sites

and the restriction of the use and

transfer of listed sites. When a site

appears on the registry, the owner

Ensuring Long-Term Protection—Taking Corrective Action

10-21
must comply with regulatory requirements in regard to use and transfer of

the site. The use of a site listed on

the registry can not be changed without permission from the state agency.

• Transfer act requirements. Some

states have transfer act programs that

require full evaluation of all environmental issues before or after the

transfer occurs. It might be that,

within such a program, institutional

controls can be established by way of

consent order, administrative order,

or some other technique that establishes implementation and continued

responsibility for institutional controls. A typical transfer act imposes

obligations and confers rights on parties to a land transaction arising out

of the environmental status of the

property to be conveyed. Transfer

acts impose information obligations

on the seller or lessor of a property.

That party must disclose general

information about strict liability for

clean-up costs as well as propertyspecific information, such as the

presence of hazardous substances,

permitting requirements and status,

releases, and enforcement actions

and variances.

• Contractual obligations. One system for ensuring future restrictions

on the use of a site, or the obligation

to remediate a site, is to require private parties to restrict use by contract. While this method is often

negotiated among private parties, it is

difficult, if not impossible, to institutionalize control over the process

without interfering with the abilities

and rights of private parties to freely

negotiate these liabilities. Another

avenue is for the landowner or

responsible party to obligate itself to

the state by contract. The state might

require a contractual commitment

from the party to provide long-term

monitoring of the site, use restrictions, and the means of continued

funding for remediation.

2. Monitoring and Site

Maintenance

In many cases, monitoring might need to

be conducted to demonstrate the effectiveness of the implemented corrective measures.

Consult with your state to determine the

amount of time that monitoring should be

conducted. Some corrective measures, such

as capping, hydraulic control, and other

physical barriers, can require long-term

maintenance to ensure integrity and continued performance. Upon completion and verification of cleanup goals, reinstitute your

original or modified ground-water monitoring program if the unit is still in active use. 

3. No Further Action and Site

Closure

When the corrective action goals have

been achieved, and monitoring and site

maintenance are no longer necessary to

ensure that this condition persists, reinstitute

your original or modified ground-water monitoring program if the unit is still in active

use. It might be necessary, however, to ensure

that any selected institutional controls remain

in place. Refer to Chapter 11–Performing

Closure and Post-Closure Care for additional

information on site closures.

10-22

Ensuring Long-Term Protection—Taking Corrective Action
Ensuring Long-Term Protection—Taking Corrective Action

10-23

Consider the following when developing a corrective action program for industrial waste management

units:

■ Locate the source(s) of the release(s) of contaminants and determine the extent of the contamination.

■ Consult with the state, community representatives, and qualified remedial experts when developing a corrective action program.

■ Identify and evaluate all potential corrective measures including interim measures. 

■ Select and implement corrective measures based on the effectiveness and protectiveness of the

remedy, the ease of implementing the remedy, and the degree that the remedy meets local community concerns and all applicable state laws.

■ Design a program to monitor the maintenance and performance of corrective measures to ensure

that human health and the environment are being protected.

Taking Corrective Action Activity List
10-24

Ensuring Long-Term Protection—Taking Corrective Action

ASTM. 1997. Standard Provisional Guide for Risk-Based Corrective Action (PS104). February.

ASTM. 1994. Emergency Standard Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites.

May.

Louisiana Department of Environmental Quality. 2000. Risk Evaluation/Corrective Action Program (RECAP)

June.

Texas Natural Resource Conservation Commission (TNRCC). 1999. Texas Risk Reduction Program, Title 30

Texas Administrative Code (TAC) Chapter 350.

Texas Natural Resource Conservation Commission (TNRCC). 1995. TNRCC Technical Guidance: Selecting an

Environmental Consultant/Corrective Action Specialist. February.

U.S. EPA. 2002. Draft Superfund Lead-Contaminated Residential Sites Handbook. OSWER 9285.7-50.

U.S. EPA. 2001a. Development of a Data Evaluation: Decision Support System for Remediation of Subsurface

Contamination. EPA600-R-01-044.

U.S. EPA. 2001b. Development of Recommendations and Methods to Support Assessment of Soil Venting

Performance and Closure. EPA600-R-01-070.

U.S. EPA. 2001c. Evaluation of the Protocol for Natural Attenuation of Chlorinated Solvents: Case Study at

the Twin Cities Army Ammunition Plant. EPA600-R-01-025.

U.S. EPA. 2001d.Handbook of Groundwater Protection and Cleanup Policies for RCRA Corrective Action.

EPA530-R-01-015.

U.S. EPA. 2001e. Multispecies Reactive Tracer Test in a Sand and Gravel Aquifer, Cape Cod, Massachusetts.

Parts I-II. EPA600-R-01-007a-b.

U.S. EPA. 2001f. Summary of the Phytoremediation State of the Science Conference, Boston Massachusetts,

May 1-2, 2000. EPA625-R-01-001a.

U.S. EPA. 2000a. Abstracts of Remediation Case Studies. Volume 4. EPA542-R-00-006.

U.S. EPA. 2000b. Statistical Estimation and Visualization of Ground-Water Contamination Data. EPA600-R00-034.

Resources
Ensuring Long-Term Protection—Taking Corrective Action

10-25

U.S. EPA. 1999a. Groundwater Cleanup: Overview of Operating Experience at 28 Sites. EPA542-R-99-

006.

U.S. EPA. 1999b. In Situ Permeable Reactive Barrier for the Treatment of Hexavalent Chromium and

Trichloroethylene in Ground Water: Volume 1 Design and Installation. EPA600-R-99-095a.

U.S. EPA. 1999c. In Situ Permeable Reactive Barrier for the Treatment of Hexavalent Chromium and

Trichloroethylene in Ground Water: Volume 2 Performance Monitoring. EPA600-R-99-095b.

U.S. EPA. 1999d. In Situ Permeable Reactive Barrier for the Treatment of Hexavalent Chromium and

Trichloroethylene in Ground Water: Volume 3 Multicomponent Reactive Transport Modeling. EPA600-R99-095c.

U.S. EPA. 1999e. Laser Fluorescence EEM Probe for Cone Penetrometer Pollution Analysis. EPA600-R-99-

041.

U.S. EPA. 1998a. Application of the Electromagnetic Borehole Flowmeter. EPA600-R-98-058.

U.S. EPA. 1998b. Permeable Reactive Barrier Technologies for Contaminant Remediation. EPA600-R-98-

125.

U.S. EPA. 1998c. Technical Protocol for Evaluating natural Attenuation of Chlorinated Solvents in Ground

Water, EPA600-R-98-128.

U.S. EPA. 1996a. A Citizen’s Guide to Innovative Treatment Technologies. EPA542-F-96-001.

U.S. EPA. 1996b. Corrective Action for Releases from Solid Waste Management Units at Hazardous Waste

Management Facilities: Advance Notice of Proposed Rulemaking. Fed. Reg. 61(85): 19,431- 19,464. May 1.

U.S. EPA. 1996c. Pump-and-Treat Ground-Water Remediation: A Guide for Decision-Makers and

Practitioners. EPA625-R-95-005.

U.S. EPA. 1995. Abstracts of Remediation Case Studies. EPA542-R-95-001.

U.S. EPA. 1994a. Groundwater Treatment Technology Resource Guide. EPA542-B-94-009.

U.S. EPA. 1994b. Physical/chemical Treatment Technology Resource Guide. EPA542-B-94-008.

Resources (cont.)
10-26

Ensuring Long-Term Protection—Taking Corrective Action

Resources (cont.)

U.S. EPA. 1994c. RCRA Corrective Action Plan. EPA520-R-94-004.

U.S. EPA. 1994d. Soil Vapor Extraction Treatment Technology Resource Guide. EPA542-B-94-007.

U.S. EPA. 1993. Bioremediation Resource Guide. EPA542-B-93-004.

U.S. EPA. 1992a. A Guide for Conducting Treatability Studies under CERCLA. EPA540-R-92-071.

U.S. EPA. 1992b. RCRA Corrective Action Stabilization Technologies Proceedings. EPA625-R-92-014.

U.S. EPA. 1991a. Handbook: Remediation of Contaminated Sediments. EPA625-6-91-028.

U.S. EPA. 1991b. Handbook: Stabilization Technologies for RCRA Corrective Action. EPA625-6-91- 026.

U.S. EPA. 1991c. Site Characterization for Subsurface Remediation. EPA625-4-91-026.

U.S. EPA. 1989a. RCRA Facility Investigation Guidance: Volume I: Development of an RFI Work Plan and

General Considerations for RCRA Facility Investigations. PB89-200-299.

U.S. EPA. 1989b. RCRA Facility Investigation Guidance: Volume II: Soil, Ground Water, and Subsurface Gas

Releases. PB89-200-299.

U.S. EPA. 1989c. RCRA Facility Investigation Guidance: Volume III: Air and Surface Water Releases. PB89-

200-299.

U.S. EPA. 1989d. RCRA Facility Investigation Guidance: Volume IV: Case Study Examples. PB89-200-299.

U.S. EPA. 1989e. Seminar Publication: Corrective Action: Technologies and Applications. EPA625-4-89-020.

U.S. EPA. 1989f. Practical Guide for Assessing and Remediating Contaminated Sites: Draft. 

U.S. EPA. 1988a. Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA.

Interim Final. EPA540-G-89-004.

U.S. EPA. 1988b. RCRA Corrective Action Interim Measures Guidance - Interim Final. EPA530-SW-88-029.

U.S. EPA. 1986. RCRA Facility Assessment Guidance. PB87-107769.
Part V

Ensuring Long-Term Protection

Chapter 11

Performing Closure and Post-Closure Care
Contents

I. Closure Plans ........................................................................................................................................11- 1

II. Selecting a Closure Method....................................................................................................................11- 3

III. Closure by Use of Final Cover Systems..................................................................................................11- 4

A. Purpose and Goal of Final Cover Systems ............................................................................................11- 4

B. Technical Considerations for Selecting Cover Materials ........................................................................11- 5

C. Components of a Final Cover ..............................................................................................................11- 8

D. Capillary-Break Final Covers ............................................................................................................11- 16

E. The Hydrologic Evaluation of Landfill Performance (HELP) Model ....................................................11- 17

F. Recommended Cover Systems ............................................................................................................11- 18

IV. Closure by Waste Removal ..................................................................................................................11- 21

A. Establishing Baseline Conditions ........................................................................................................11- 22

B. Removal Procedures............................................................................................................................11- 22

C. Disposal of Removed Wastes ..............................................................................................................11- 23

D. Final Sampling and Analysis ..............................................................................................................11- 23

V. Post-Closure Care Considerations When Final Cover Is Used..............................................................11- 24

A. Maintenance........................................................................................................................................11- 24

B. Monitoring During Post-Closure Care ................................................................................................11- 25

C. Recommended Length of the Post-Closure Care Period ......................................................................11- 25

D. Closure and Post-Closure Cost Considerations ..................................................................................11- 26

Performing Closure and Post-Closure Care Activity List ............................................................................11- 34

Resources ..................................................................................................................................................11- 35

Tables:

Table 1: Types of Layers in Final Cover Systems........................................................................................11- 9

Table 2: Types of Recommended Final Cover Systems ............................................................................11- 18

Table 3: Example Closure/Post-Closure Cost Estimate Form ..................................................................11- 27

Table 4: Sample Summary Cost Estimating Worksheet ..........................................................................11- 29

Table 5: Estimated Closure and Post-Closure Care Costs ........................................................................11- 31

Figures:

Figure 1: Regional Depth of Frost Penetration in Inches ..........................................................................11 - 6

Figure 2: Drainage Layer Configuration ................................................................................................11 - 11
Contents (cont.)

Figure 3: Geonet with Geotextile Filter Design for Drainage Layer ........................................................11 - 12

Figure 4: Passive Gas Venting System ....................................................................................................11 - 15

Figure 5: Active Gas Venting System......................................................................................................11 - 15

Figure 6: Example of a Capillary-Break Final Cover System ..................................................................11 - 17

Figure 7: Recommended Final Cover System For a Unit With a Double Liner or a Composite Liner ....11 - 19

Figure 8: Recommended Final Cover System For a Unit With a Single Clay Liner ................................11 - 19

Figure 9: Recommended Final Cover System For a Unit With a Single Clay Liner in an Arid Area ......11 - 20

Figure 10: Recommended Final Cover System For a Unit With a Single Synthetic Liner ......................11 - 20

Figure 11: Recommended Final Cover System For a Unit With a Natural Soil Liner ............................11 - 21
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-1

The overall goal of closure is to

minimize or eliminate potential

threats to human health and the

environment and the need for

future corrective action at the site.

If removing the wastes, containment devices,

and any contaminated subsoils from a unit,

the unit should be returned to an acceptable

risk level so that it is not a current or future

threat. If wastes will be left in place at closure, the unit should be closed in a manner

that also reduces and controls current or

future threats. Steps should also be taken to

avoid future disruptions to final cover systems and monitoring devices.

For post-closure care, the overall goal is to

minimize the infiltration of water into a unit

by providing maintenance of the final cover.

Maintenance should be continued until such

time as it is determined that care is no longer

necessary. Also, during post-closure care,

closed units should be monitored to verify

and document that no unacceptable releases

are occurring.

I. Closure Plans

A well-conceived closure plan is the primary resource document for the final stage in

the life of a waste management unit. The purpose of a closure plan is to consider all

aspects of the closure scenario. It should be

comprehensive so that staff who will implement it years after its writing will clearly

understand the activities it specifies. It also

needs to provide enough detail to allow calculation of closure and post-closure care costs

for determining how much funding needs to

be set aside for those activities. 

Performing Closure and Post-Closure Care

This chapter will help you:

• Provide closure and post-closure care as an integral part of a

unit’s overall design and operation. 

• Provide long-term environmental protection by reducing or eliminating potential threats and the need for potential corrective

action at the site. 

• Plan and accomplish the goals of closure and post-closure care by

requiring that adequate funding be set aside to cover the

planned costs of closure and post-closure care.

This chapter will help address the following questions.

• How do I develop a closure plan?

• What factors should I consider when

choosing a closure method?

• What are the components of a final

cover?

• What costs are associated with postclosure care?
11-2

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

What should be considered when

developing a closure plan?

You should tailor a closure plan to account

for the unique characteristics of the unit, the

waste managed in the unit, and anticipated

future land use. Each unit will have different

closure activities. Closing a surface impoundment, for example, involves removal of

remaining liquids and solidifying sludges

prior to placing a final cover on the unit.

The following information is important to

consider when developing a closure plan:

• Overall goals and objectives of closure.

• Future land use.

• Type of waste management unit.

• Types, amount, and physical state of

waste in the unit.

• Constituents associated with the wastes.

• Whether wastes will be removed or

left in place at closure.

• Schedule (overall and interim).

• Costs to implement closure.

• Steps to monitor progress of closure

actions, including inspections, maintenance, and monitoring (e.g., groundwater and leachate monitoring).

• Health and safety plans, as necessary.

• Contingency plans.

• Description of waste treatment or stabilization (if applicable).

• Final cover information (if applicable).

• Vegetation management.

• Run-on and runoff controls.

• Closure operations and maintenance.

• Erosion prevention and repair.

• Waste removal information (if applicable).

• Parameters to assess performance of

the unit throughout the post-closure

period. 

The plan should address the types of waste

that have been or are expected to be deposited

in the management unit and the constituents

that can reasonably be associated with those

wastes. The types of expected wastes will

affect both the design of the final cover and

the types of activities that should be undertaken during the post-closure care period.

Biodegradable waste, for example, can cause a

final cover to subside due to decomposition

and can also require gas management.

The closure plan should provide other

information that will address the closure strategy. If, for instance, a final cover is planned,

then the closure plan should consider seasonal precipitation that could influence the performance of both the cover and the

monitoring system. Information concerning

freeze cycles and the depth of frost permeation will provide supporting information

with which to assess the adequacy of the

cover design. Similarly, arid conditions should

be addressed to support a decision to use a

particular cover material, such as cobbles. 

The closure plan should address the closure

schedule, stating when closure is expected to

begin, and when closure is expected to be completed. You should consider starting closure

when the unit has reached capacity or has

received the last expected waste for disposal.

For units containing inorganic wastes, you

should complete closure as soon as possible

after the last expected waste has been received.

A period of 180 days is a good general guide

for completing closure, but the actual time

frame will be dictated by site-specific conditions. For units receiving organic wastes, more

time might be needed for the wastes to stabilize
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-3

prior to completing closure. Similarly, other

site-specific conditions, such as precipitation

or winter weather, can also cause delay in

completing closure. For these situations, you

should complete closure as soon as feasible.

You should also consult with the state agency

to determine if any requirements exist for closure schedules. 

Even within a waste management unit,

some areas will be closed on different schedules, with certain areas in partial closure,

while other areas continue to operate. The

schedules and partial closure activities (such

as intermediate cover) should be considered

in the closure plan. Although the processes

for closing such areas might not be different

than those for closing the unit as a whole, it

is still more efficient to integrate partial closure activities into the closure plan.

If the closure plan calls for the stabilization, solidification, or other treatment of

wastes in the unit before the installation of a

final cover, the plan should describe those

activities in detail. Waste stabilization, solidification, or other treatment has four goals:

• Removing liquids, which are ill-suited to supporting the final cover.

• Decreasing the surface area over

which the transfer or escape of contaminants can occur.

• Limiting the solubility of leachable

constituents in the waste.

• Reducing toxicity of the waste.

For closure strategies that will use engineering controls, such as final covers, the plan

should provide detailed specifications. This

includes descriptions of the cover materials in

each layer and their permeability as well as

any drainage and/or gas migration control

measures included in the operation of the

final cover. Also the plan should identify measures to verify the continued integrity of the

final cover and the proper operation of the gas

migration and/or drainage control strategies. 

If wastes will be removed at closure, the closure plan should estimate volumes of waste and

contaminated subsoil and the extent of contaminated devices to be removed during closure. It

should further state waste removal procedures,

establish performance goals, and address any

state or local requirements for closure by waste

removal. The plan should identify numeric

clean-up standards and existing background

concentrations of constituents. It also should

discuss the sampling plan for determining the

effectiveness of closure activities. Finally, it

should describe the provisions made for the disposal of removed wastes and other materials.

The closure plan should also provide a

detailed description of the monitoring that

will be conducted to assess the unit’s performance throughout the post-closure period.

These measurements include monitoring

leachate volume and characteristics to ensure

that a cover is minimizing infiltration. It is

important to include appropriate groundwater quality standards with which to compare ground-water monitoring reports. You

should develop the performance measures

section of the plan prior to completing closure. This section establishes the parameters

that will describe successful closure of the

unit. If limits on these parameters are exceeded, it will provide an early warning that the

final cover system is not functioning as

designed and that measures should be undertaken to identify and correct problems.

II. Selecting a

Closure Method

Factors to consider in deciding whether to

perform closure by means of waste removal

or through the use of a final cover include the

following:
11-4

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

• Feasibility. Is closure by waste

removal feasible? For example, if the

waste volumes are large and underlying

soil and ground water are contaminated, closure by total waste removal

might not be possible. If the unit is

contaminated, consult Chapter

10–Taking Corrective Action to identify

activities to address the contamination.

In some cases partial removal of the

waste might be useful to remove the

source of ground-water contamination.

• Cost-effectiveness. Compare the cost

of removing waste, containment

devices, and contaminated soils, plus

subsequent disposal costs at another

facility, to the cost of installing a final

cover and providing post-closure care.

• Long-term protection. Will the final

cover control, minimize, or eliminate

post-closure escape of waste constituents or contaminated runoff to

ground or surface waters to the extent

necessary to protect human health and

the environment?

• Availability of alternate site. Is an

alternate site available for final disposal or treatment of removed waste? You

should consult with the state agency

to determine whether alternate disposal sites are appropriate.

Sections III and V address closure by use of

final cover systems and associated post-closure

care considerations. Alternatively, Section IV

addresses closure by waste removal.

III. Closure by Use

of Final Cover

Systems

You might elect to close a waste management unit by means of a final cover system.

This approach is common for landfill units and

some surface impoundment units where some

waste is left in place. The choice of final cover

materials and design should be the result of a

careful review and consideration of all site-specific conditions that will affect the performance

of the cover system. If you are not knowledgeable about the engineering properties of cover

materials, you should seek the advice of professionals or representatives of state and local

environmental protection agencies. 

This section addresses the more important

technical issues that should be considered

when selecting cover materials and designing a

cover system. It discusses the various potential

components of final cover systems, including

the types of materials that can be used in their

design and some of the advantages and disadvantages of each. This section also examines

the interaction between the various components as they function within the system.

A. Purpose and Goal of

Final Cover Systems

The principal goals of final cover systems

are to:

• Provide long-term environmental protection of human health and the environment by reducing or eliminating

potential risk of contaminant release.

• Minimize infiltration of precipitation

into the waste management unit to

minimize generation of leachates within the unit by promoting surface

drainage and maximizing runoff.

• Minimize risk by controlling gas migration (as applicable), and by providing

physical separation between waste and

humans, plants, and animals.

• Minimize long-term maintenance needs.

The final cover should be designed to provide long-term protection and minimization of
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-5

leachate formation. Final cover systems can

be inspected, managed, and repaired to maintain long-term protection. For optimal performance, the final cover system should be

designed to minimize infiltration, surface

ponding, and the erosion of cover material.

To avoid the accumulation of leachate within

a unit, the cover system should be no more

permeable than the liner system. For example, if a unit’s bottom liner system is composed of a low-permeability material, such as

compacted clay or a geomembrane, then the

cover should also be composed of a low-permeability material unless an evaluation of

site-specific conditions shows an equivalent

reduction in infiltration. If the cover system is

more permeable than the liner, leachate will

accumulate in the unit. This buildup of liquids within a unit is often referred to as the

“bathtub effect.” In addition, since many

units can potentially generate gas, cover systems should be designed to control gas

migration. Proper quality assurance and quality control during construction and installation of the final cover are essential in order to

ensure that the final cover performs in accordance with its design. For general information on quality assurance during construction

of the final cover, refer back to the construction quality assurance section of Chapter 7,

Section B–Designing and Installing Liners.

Recommendations for the type of final cover

system to use will depend on the type of liner

and the gas and liquids management strategy

employed in a unit.

B. Technical Considerations

for Selecting Cover

Materials

Several environmental and engineering concerns can affect cover materials and should be

considered in the choice of those materials.

How can climate affect a final

cover?

Freeze and thaw effects can lead to the

development of microfractures in low permeability soil layers. These effects also can cause

the realignment of interstitial fines (silts and

clays), thereby increasing the hydraulic conductivity of the final cover. As a result, you

should determine the maximum depth of

frost penetration at a site and design covers

accordingly. In other words, barrier layers

should be below the maximum frost penetration depth. Information regarding the maximum frost penetration depth for a particular

area can be obtained from the Natural

Resource Conservation Service with the U.S.

Department of Agriculture, local utilities,

construction companies, local universities, or

state agencies. Figure 1 illustrates the regional

depth of frost penetration. You should ensure

that vegetation layers are thick enough that

low permeability soil layers in the final cover

are placed below the maximum frost penetration depth.

How can settlement and subsidence affect a final cover?

When waste decomposes and consolidates,

settlement and subsidence can result.

Excessive settlement and subsidence can significantly impair the integrity of the final

cover system by causing ponding of water on

the surface, fracturing of low permeability

infiltration layers, and failure of geomembranes. The degree and rate of waste settlement are difficult to estimate, but they should

be considered during design and development

of closure plans. Waste settlement should also

be considered when determining the timing of

closure. Steps should be taken to minimize

the degree of settlement that will occur after

the final cover system has been installed.
1 USDA Universal Soil Loss Equation: X = RKLSCP where: X = Soil loss (tons/acre/year); R = Rainfall erosion index; K = Soil erodibility index; L = Slope length factor; S = Slope gradient factor; C = Crop management factor; P = Erosion control practice. For minimal long-term care X < 2.0 tons/acre/year. 

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

How can erosion affect the performance of a final cover?

Erosion can adversely affect the performance of the final cover of a unit by causing

rills that require maintenance and repair.

Extreme erosion can lead to the exposure of

the infiltration layer, initiate or contribute to

sliding failures, or expose the waste.

Anticipated erosion due to surface-water

runoff for a given design criteria can be

approximated using the USDA Universal Soil

Loss Equation1 (U.S. EPA, 1989a). By evaluating erosion loss, you might be able to optimize the final cover design to reduce

maintenance through selection of the best

available soil materials. A vegetative cover not

only improves the appearance of a unit, but it

also controls erosion of the final cover. 

The vegetation components of the erosion

layer should have the following characteristics:

• Locally adapted perennial plants that

are resistant to various climatic

changes reasonably expected to occur

at the site.

• Roots that will not disrupt the lowpermeability layer.

• The ability to thrive in low-nutrient

soil with minimum nutrient addition.

• The ability to survive and function

with little or no maintenance.

Why are interfacial and internal

friction properties for cover components important?

Adequate friction between cover components, such as geomembrane barrier layers

and soil drainage layers, as well as between

any geosynthetic components, is needed to

prevent extensive slippage or interfacial shear.

Water and ice can affect the potential for

11-6

Figure 1. Regional Depth of Frost Penetration in Inches

Source: U.S. EPA, 1989a.
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-7

cover components to slip. Sudden sliding can

tear geomembranes or cause sloughing of

earthen materials. Internal shear can also be a

concern for composite or geosynthetic clay

liner materials. Measures to improve stability

include using flatter slopes or textured

geosynthetic membranes, geogrids designed

to resist slipping forces, otherwise reinforcing

the cover soil, and providing drainage.

Can dry soil materials affect a

final cover?

Desiccation, the natural drying of soil

materials, can have an adverse affect on the

soil layers compromising the final cover.

Although this process is most commonly

associated with layers of low permeability

soil, such as clay, it can cause problems with

other soil types as well. Desiccation causes

cracks in the soil surface extending downward. Cover layers are not very thick, and

therefore these cracks can extend through an

entire layer, radically changing its hydraulic

conductivity or permeability. Care should be

taken to detect desiccation at an early stage in

time to mitigate its damage. Also, the tendency for final covers to become dry makes root

penetration even more of a problem in that

plants respond to drought by extending their

root systems downward.

Can plants and animals have an

effect on a final cover?

When selecting the plant species to

include in the vegetative cover of a waste

management unit, you should consider the

potential for root systems to grow through

surface cover layers and penetrate underlying

drainage and barrier layers. Such penetration

will form preferential pathways for water

infiltration and compromise the integrity of

the final cover system. Similarly, the presence

of burrowing animals should be foreseen

when designing the final cover system. Such

animals can burrow in the surface layers and

can potentially breach the underlying barrier

layer. Strategies for mitigating the effects

described here are discussed below in the

context of protection layers composed of

gravel or cobbles.

Is it necessary to stabilize wastes?

Before installing a final cover, liquid or

semi-liquid wastes might need to be stabilized or solidified. Stabilization or solidification might be necessary to allow equipment

on the unit to install the final cover or to

ensure adequate support, or bearing capacity,

for the final cover. With proper bulk cover

technique, it might be feasible to place the

cover over a homogeneous, gel-like, semi-liquid waste. When selecting a stabilization or

solidification process, it is important to consider the effectiveness of the process and its

compatibility with the wastes. Performance

specifications for stabilization or solidification

processes include leachability, free-liquid content, physical stability, bearing capacity, reactivity, ignitability, biodegradability, strength,

permeability, and durability of the stabilized

and solidified waste. You should consider

seeking professional assistance to properly

stabilize or solidify waste prior to closure. 

Where solidification is not practical, you

should consider reinforcement and construction of a specialized lighter weight cover system over unstable wastes. This involves using

combinations of geogrids, geotextiles,

geonets, geosynthetic clay liners, and

geomembranes. For more detail on this practice, consult references such as the paper by

Robert P. Grefe, Closure of Papermill Sludge

Lagoons Using Geosynthetics and Subsequent

Performance, and the Geosynthetic Research

Institute proceedings, Landfill Closures:

Geosynthetics Interface Friction and New

Developments, cited in the Resources section.
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

How can wastes be stabilized?

Many stabilization and solidification

processes require the mixing of waste with

other materials, such as clay, lime, and ash.

These processes include either sorbents or

encapsulating agents. Sorbents are nonreactive and nonbiodegradable materials that soak

up free liquids to form a solid or near-solid

mass. Encapsulating agents enclose wastes to

form an impermeable mass. The following are

examples of some commonly used types of

waste stabilization and solidification methods. 

• Cement-based techniques. Portland

cement can use moisture from the

waste (sludge) for cement hydration.

The end product has high strength,

good durability, and retains waste

effectively.

• Fly ash or lime techniques. A combination of pozzolanic fly ash, lime,

and moisture can form compounds

that have cement-like properties.

• Thermoplastic techniques. Asphalt,

tar, polyolefins, and epoxies can be

mixed with waste, forming a semirigid solid after cooling.

• Organic polymer processes. This

technique involves adding and mixing

monomer with a sludge, followed by

adding a polymerizing catalyst. This

technique entraps the solid particles.

After evaluating and selecting a stabilization

or solidification process, you should conduct

pilot-scale tests to address issues such as safety, mix ratios, mix times, and pumping problems. Testing will help assess the potential for

an increase in waste volume. It will also help

to plan the production phase, train operators,

and devise construction specifications.

When conducting full-scale treatment

operations, options exist for adding and mixing materials. These options might include in

situ mixing and mobile plant mixing. In situ

mixing is the simplest technique, using common construction equipment, such as backhoes, excavators, and dump trucks. In situ

mixing is most suitable where large amounts

of materials are added to stabilize or solidify

the waste. The existing waste management

area, such as a surface impoundment, can be

used as the mixing area. The in situ mixing

process is open to the atmosphere, so environmental and safety issues, such as odor,

dust, and vapor generation, should be taken

into consideration. For mobile plant mixing,

wastes are removed from the unit, mechanically mixed with treatment materials in a

portable processing vessel, and deposited

back into the unit. Mobile plant mixing is

generally used for treating sludges and other

wastes with a high liquid content. 

C. Components of a Final

Cover

Cover systems can be designed in a variety

of ways to accomplish closure goals. This

flexibility allows a final cover design system

to integrate site-specific technical considerations that can affect performance. This section

discusses the potential components or layers

of a final cover system, their functions, and

appropriate materials for each layer. Since the

materials used in cover systems are the same

as those used in liner systems, refer to

Chapter 7, Section B–Designing and

Installing Liners for a more detailed discussion of the engineering properties of the various materials. 

Table 1 presents the types of layers and

typical materials that might exist in a final

cover. The minimum appropriate thicknesses

of each of the five types of layers depends

upon many factors including site drainage,

erosion potential, slopes, types of vegetative

cover, type of soil, and climate. 

11-8
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-9

What function does the surface

layer serve?

The role of the surface layer in the final cover

system is to promote the growth of native, nonwoody plant species, minimize erosion, restore

the aesthetics of the site, and protect the barrier

layer. The surface layer should be thick enough

so that the root systems of the plants do not

penetrate the underlying barrier layer. The vegetation on the surface layer should be resistant to

drought and temperature extremes, able to survive and function with little maintenance, and

also be able to maximize evapotranspiration,

which will limit water infiltration to the barrier

layer. It is recommended that you consult with

agriculture or soil conservation experts concerning appropriate cover vegetation. Finally, the

surface layer should be thick enough to withstand long-term erosion and to prevent desiccation and freeze/thaw effects of the barrier layer.

The recommended minimum thickness for the

surface layer is at least 12 inches. The state

agency can help to determine the appropriate

minimum thickness in cold climates to protect

against freeze-thaw effects.

What types of materials can be

used in the surface layer?

Topsoil has been by far the most commonly used material for surface layers. The principal advantages of using topsoil in the surface

layer include its general availability and its

suitability for sustaining vegetation. When topsoil is used as a surface layer, the roots of

plants will reinforce the soil, reduce the rate of

erosion, decrease runoff, and remove water

from the soil through evapotranspiration. To

achieve these benefits, however, the soil

should have sufficient water-holding capacity

to sustain plant growth. There are some concerns with regard to using topsoil. For example, topsoil requires ongoing maintenance,

especially during periods of drought or heavy

rainfall. Prolonged drought can lead to cracking in the soil, creating preferential pathways

for water infiltration. Heavy rainfall can lead to

erosion causing rills or gullies, especially on

newly-seeded or steeply sloping covers. If the

topsoil does not have sufficient water holding

capacity, it can not adequately support surface

plant growth, and evapotranspiration can

Layer Type of Layer Typical Materials

1 Surface (Erosion, Vegetative Cover) Topsoil, Geosynthetic Erosion Control Layer, 

Layer Cobbles

2 Protection Layer Soil, Recycled or Reused Waste Materials, Cobbles

3 Drainage Layer Sand and/or Gravel, Geonet or Geocomposite,

Chipped or Shredded Tires

4 Barrier (Infiltration) Layer Compacted Clay, Geomembrane, Geosynthetic Clay

Liner

5 Foundation/Gas Collection Layer Sand or Gravel, Soil, Geonet or Geotextile,

Recycled or Reused Waste Material 

Table 1

Types of Layers in Final Cover Systems

Source: Jesionek et al., 1995 
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

excessively dry the soils. In this case, irrigation

will be required to restore the water balance

within the soil structure. Topsoil is also vulnerable to penetration by burrowing animals.

Geosynthetic erosion control material can

be used as a cover above the topsoil to limit

erosion prior to the establishment of a mature

vegetative cover. The geosynthetic material can

include embedded seeds to promote plant

growth, and can be anchored or reinforced to

add stability on steeply sloped areas.

Geosynthetic material, however, does not

enhance the water-holding capacity of the soil.

In arid or semi-arid areas, therefore, the soil

might still be prone to wind and water erosion

if its water-holding capacity is insufficient.

Cobbles can be a suitable material for the

surface layer in arid areas or on steep slopes

which might hinder the establishment of vegetation. If they are large enough they will

provide protection from wind and water erosion without washout. Cobbles can also protect the underlying barrier layer from

intrusion by burrowing animals, but cobbles

might not be available locally, and their use

does not protect the underlying barrier layer

from water infiltration. Because cobbles create

a porous surface through which water can

percolate, they do not ordinarily support vegetation. Wind-blown soil material can fill

voids between cobbles, and plants can establish themselves in these materials. This plant

material should be removed, as its roots are

likely to extend into the underlying barrier

layer in search of water.

What function does the protection or biotic barrier layer serve?

A protection or biotic barrier layer can be

added below the surface layer, but above the

drainage layer, to protect the latter from

intrusion by plant roots or burrowing animals. This layer adds depth to the surface

layer, increasing its water storage capacity

and protecting underlying layers from freezing and erosion. In many cases, the protection layer and the surface layer are combined

to form a single cover layer. 

What types of materials can be

used in the protection layer?

Soil will generally be the most suitable

material for this layer, except in cases where

special design requirements exist for the protection layer. The advantages and disadvantages of using soil in the protection layer are

the same as those stated above in the discussion of the surface layer topsoil. Factors

impacting the thickness and type of soil to use

as a protection layer include freeze and thaw

properties and the interaction between the soil

and drainage layers. Other types of materials

that can be used in the protection layer

include cobbles with a geotextile filter, gravel

and rock, and recycled or reused waste.

Cobbles with a geotextile filter can form

a good barrier against penetration by plant

roots and burrowing animals in arid sites.

The primary disadvantage is that cobbles

have no water storage capacity and allow

water percolation into underlying layers.

Gravel and rock are similar to cobbles

since they can form a good barrier against

penetration by plant roots and burrowing animals. Again, this use is usually only considered for arid sites, because gravel and rocks

have no water storage capacity and allow

water percolation into underlying layers.

Recycled or reused waste materials such

as fly ash and bottom ash can be used in the

protection layer, when available. Check with

the state agency to verify that use of these

11-10
materials is allowable. The advantages of

using these materials in the protection layer

are that they store water that has infiltrated

past the surface layer, which can then be

returned to the surface through evapotranspiration, and that they offer protection

against burrowing animals and penetration by

roots. If planning to use waste material in the

protection layer, consider its impact on surface runoff at the unit’s perimeter. Design

controls to ensure runoff does not contribute

to surface-water contamination. Consult

Chapter 6–Protecting Surface Water for more

details on designing runoff controls.

What function does the drainage

layer serve? 

A drainage layer can be placed below the

surface layer, but above the barrier layer, to

direct infiltrating water to drainage systems at

the toe of the cover (see Figure 2) or to intermittent benches on long steep slopes. For

drainage layers, the thickness will depend on

the level of performance being designed and

the properties of available materials. For

example, some geonet composites, with a

thickness of less than 1 inch, have a transmissivity equal to a much thicker layer of aggregate or sand. The recommended thickness of

the high permeability soil drainage layer is 12

inches with at least a 3 percent slope at the

bottom of the layer. Based on standard practice, the drainage layer should have a

hydraulic conductivity in the range of 10-2 to

10-3 cm/sec. Water infiltration control through

a drainage layer improves slope stability by

reducing the duration of surface and protection layer saturation. In this role, the drainage

layer works with vegetation to remove infiltrating water from the cover and protect the

underlying barrier layer. If this layer drains

the overlying soils too well, it could lead to

the need for irrigation of the surface layer to

avoid desiccation. 

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-11

Figure 2. Drainage Layer Configuration

Source: U.S. EPA, 1991.
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

Another consideration for design of

drainage layers is that the water should discharge freely from the toe of the cover or intermittent benches. If outlets become plugged or

are not of adequate capacity, the toe of the

slope can become saturated and potentially

unstable. In addition, when designing the

drainage layer, you should consider using flexible corrugated piping in conjunction with

either the sand and gravel or the gravel with

geotextile filter material to facilitate the movement of water to the unit perimeter.

What materials can be used in

the drainage layer?

Sand and gravel are a common set of

materials used in the drainage layer. The

principal consideration in their use is the

hydraulic conductivity required by the overall

design. There can be cases in which the

design requires the drainage of a large

amount of water from the surface layer, and

the hydraulic properties of the sand and gravel layer might be insufficient to meet these

requirements. The advantages of using sand

and gravel in the drainage layer include the

ability to protect the underlying barrier layer

from intrusion, puncture, and temperature

extremes. The principal disadvantage to these

materials is that they are subject to intrusions

from the overlying protective layer that can

alter their hydraulic conductivity. Similarly,

fines in the sand and gravel can migrate

downslope, undermining the stability of the

cover slope. A graded filter or a geotextile filter can be used to separate and protect the

sand and gravel from intrusions by the overlying protection layer.

Gravel with a geotextile filter is also a

widely-used design, whose applicability can

be limited by the local availability of materials. The gravel promotes drainage of water

from the overlying layers, while the geotextile

filter prevents the clogging of granular

drainage layers. Again, be aware of the possibility that a gravel drainage layer might drain

overlying soils so well that irrigation of the

surface layer might become necessary. The

principal advantage to a gravel/geotextile

drainage layer is the engineering community’s

considerable body of knowledge regarding

their use as drainage materials. Other advantages include their ability to protect underlying layers from intrusion, puncture,

temperature extremes, and their common

availability. The geotextile filter provides a

cushion layer between the gravel and the

overlying protection layer.

Geonet and geotextile filter materials can

be used to form an effective drainage layer

directly above a compacted clay or geomembrane liner (see Figure 3). They are a suitable

alternative especially in cases where other

materials, such as sand and gravel, are not

locally available. The principal advantage is

that lightweight equipment can be used 

during installation, reducing the risk of damaging the underlying barrier layer.

The disadvantages associated with geonet

and geotextile materials are that they provide

little protection for the barrier layer against

extreme temperature changes, and there can

be slippage between the interfaces between

the geomembrane, geotextile, and low perme11-12

Figure 3. 

Geonet with Geotextile Filter Design

for Drainage Layer

Source: U.S. EPA, 1991.
ability soil barrier materials. The use of textured materials can be considered to address

slippage. Furthermore, problems can arise in

the horizontal seaming of the geotextile

drainage layer on long slopes.

Chipped or shredded tires are an additional option for drainage layer materials.

Chipped or shredded tires have been used for

bottom drainage layers in the past and might

be suitable for cover drainage layers as well.

One caution concerning the use of chipped

or shredded tires is possible metal contaminants, or pieces of metal that could damage a

geomembrane liner. You should consult with

the state agency to determine whether this

option is an acceptable practice.

What function does the barrier

layer serve?

The barrier layer is the most critical component of the cover system because it prevents water infiltration into the waste. It also

indirectly promotes the storage and drainage

of water from the overlying protection and

surface layers, and it prevents the upward

movement of gases. This layer will be the least

permeable component of the final cover system. Typically, the hydraulic conductivity of a

barrier layer is between 10-9 to 10-7 cm/sec.

What types of materials can be

used in the barrier layer?

Single compacted clay liners (CCLs) are

the most common material used as barrier

layers in final cover systems. CCL popularity

arises largely because of the local availability

of materials and the engineering community’s

extensive experience with their use. Drying

and subsidence are the primary difficulties

posed by CCLs. When the clay dries, cracks

appear and provide preferential pathways

along which water can enter the waste, promoting leachate formation, waste decomposition, and gas formation (when methane

producing waste is present). Dry waste material and gas formation within the unit contribute to drying from below, while a range of

climatological conditions, including drought,

can affect CCLs from above. Even with

extremely thick surface and protection layers,

CCLs can still undergo some desiccation.

Clay liners are also vulnerable to subsidence within the waste unit. This problem

can first manifest itself during liner construction. As the clay is compacted with machinery, the waste might not provide a stable,

even foundation for the compaction process.

This will make it difficult to create the evenly

measured lifts comprising the liner. As waste

settles over time, depressions can form along

the top of the CCL. These depressions put

differential stresses on the liner, causing

cracks which compromise its integrity. For

instance, a depression of only 5 to 11 inches

across a 6-foot area can be sufficient to crack

the liner materials.

Single geomembrane liners are sheets of

a plastic polymer combined with other ingredients to form an effective barrier to water

infiltration. Such liners are simple and

straightforward to install, but they are relatively fragile and can be easily punctured

during installation or by movement in surface

layer materials. The principal advantage of a

geomembrane is that it provides a relatively

impermeable barrier with materials that are

generally available. It is not damaged by temperature extremes and therefore does not

require a thick surface layer. The geomembrane is more flexible than clay and not as

vulnerable to cracking as a result of subsidence within the unit. The principal disadvantage is that it provides a point of potential

slippage at the interface with the cover soils.

Such slippage can tear the geomembrane,

even if it is anchored.

Single geosynthetic clay liners (GCLs)

are composed of bentonite clay supported by

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-13
geotextiles or geomembranes held together

with stitching or adhesives. These liners are

relatively easy to install and have some selfhealing capacity for minor punctures. They

are easily repaired by patching. The main disadvantages include low shear strength, low

bearing capacity, vulnerability to puncture

due to relative thinness, and potential for

slippage at interfaces with under- and overlying soil materials. When dry, their permeability to gas makes GCLs unsuitable as a barrier

layer for wastes that produce gas, unless the

clay will be maintained in a wet state for the

entire post-closure period.

Geomembrane with compacted clay liners (CCLs) can be used to mitigate the shortcomings of each material when used alone. In

this composite liner, the geomembrane acts to

protect the clay from desiccation, while providing increased tolerance to differential settlement within the waste. The clay acts to

protect the geomembrane from punctures and

tearing. Both components act as an effective

barrier to water infiltration. The principal disadvantage is slippage between the geomembrane and surface layer materials.

Geomembrane with geosynthetic clay liners (GCLs) can also be used as a barrier layer.

As with geomembrane and CCL combinations,

each component serves to mitigate the weakness of the other. The geosynthetic material is

less vulnerable than its clay counterpart to

cracking and has a moderate capacity to selfheal. The geomembrane combined with the

GCL is a more flexible cover and is less vulnerable to differential stresses from waste settlement. Neither component is readily affected by

extreme temperature changes, and both work

together to form an effective barrier layer. For

more information on the properties of geosynthetic clay liners, including their hydration

after installation, refer to Chapter 7, Section

B–Designing and Installing Liners. The potential disadvantage is slippage between the upper

and lower surfaces of the geomembrane and

some types of GCL and other surface layer

materials. The geomembrane is still vulnerable

to puncture, so placement of cover soils is

important to minimize such damage. 

Textured geomembranes can be used to

increase the stability of cap side slopes.

Textured geomembranes are nearly identical

to standard “smooth” geomembranes differing

only in the rough or textured surface that has

been added. This textured surface increases

the friction between the liner and soils and

other geosynthetics used in the cap, and can

help prevent sliding failures. In general, textured geomembranes are more expensive than

comparable “smooth” geomembranes.

Using textured geomembranes allows cap

designers to employ steeper slopes which can

increase the available airspace in a waste

management unit, and therefore increase its

capacity. Textured geomembranes also help

keep cover soil in place improving overall

liner stability on steep slopes. The degree to

which textured geomembranes will improve

frictional resistance (friction coefficients/friction angles) will vary from site-to-site

depending upon the type of soil at the site

and its condition (e.g., moisture content).

Textured geomembranes are manufactured

by two primary methods. Some textured

geomembranes have a friction coating layer

added to standard “smooth” geomembranes

through a secondary process. Others are textured during the initial production process,

meaning textured layers are coextruded as

part of the liner itself. Textured geomembranes can be textured on one or both sides.

Textured geomembranes are seam-welded

by the same technologies as standard

geomembranes. Due to their textured surface,

however, seam welds can be less uniform

with textured liners than with normal liners.

Some textured geomembranes have smooth

edges on the top and bottom of the sheet to

allow for more uniform seam welding. 

11-14

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care
What function does the gas collection layer serve?

The role of the gas collection layer is to

control the migration of gases to collection

vents. This collection layer is a permeable

layer that is placed above the foundation

layer. It is often used in cases where the foundation layer itself is not the gas collection

layer. For more information on Clean Air Act

requirements for managing gas from landfills

and other waste management units, refer to

Chapter 5–Protecting

Air Quality.

Gas control systems

generally include mechanisms designed to control gas migration and

to help vent gas emissions into the atmosphere. Systems using

natural pressure and

convection mechanisms

are referred to as passive

gas control systems (see

Figure 4). Examples of

passive gas control system elements include

ditches, trenches, vent

walls, perforated pipes

surrounded by coarse

soil, synthetic membranes, and high moisture, fine-grained soil.

Systems using mechanical means to remove gas

from the unit are

referred to as active gas

control systems. Figure

5 illustrates an active

gas system. Gas control

systems can also be

used as part of corrective action measures

should the concentration of methane rise to dangerous levels. As

with all aspects of a waste containment system, construction quality assurance plays a

critical role in the success of a gas management system. 

Gas extraction wells are an example of

active gas control systems. For deep wells,

the number, location, and extent of the pipe

perforations are important. Also, the depth of

the well must be kept safely above the liner

system beneath the waste. For continuous gas

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-15

Figure 4. Passive Gas Venting System

Source: Robinson, W., ed. 1986. The Solid Waste Handbook: A Practical

Guide. Reprinted by permission of John Wiley & Sons, Inc.

Figure 5. Active Gas Venting System

Source: Robinson, W., ed. 1986. The Solid Waste Handbook: A Practical

Guide. Reprinted by permission of John Wiley & Sons, Inc.
collection layers beneath the barrier layer,

continuity is important for both soils and

geosynthetics. 

Knowing the rate of gas generation is

essential to determining the quantity of gas

that can be extracted from the site. Pumping

an individual well at a greater vacuum will

give it a wider zone of influence, which is

acceptable, but obviously there are points of

diminishing marginal returns. Larger suction

pressures influence a larger region but

involve more energy expended in the pumping. Pumping at greater vacuum also increases the potential for drawing in atmospheric

air if the pumping rate is set too high.

Significant air intrusion into the unit can

result in elevated temperatures and even

underground fires. You should perform routine checks of gas generation rates to better

ensure that optimal pumping rates are used.

The performance of gas extraction systems

is affected by the following parameters,

which should be considered when designing

and operating gas systems:

• Daily cover, which inhibits free

movement of gas.

• Sludge or liquid wastes, which affect

the ease at which gas will move.

• Shallow depth of unit, which makes

it difficult to extract the gas, because

atmospheric air will be drawn in

during the pumping.

• Permeability of the final cover, which

affects the ability of atmospheric air

to permeate the wastes in the unit.

What types of materials can be

used in the gas collection layer?

Sand and gravel are the most common

materials used for gas collection layers. With

these materials, a filter might be needed to

prevent infiltration of materials from the barrier layer. Geotextile and geosynthetic

drainage composites also can make suitable

gas collection layers. In many cases, these can

be the most cost-effective alternatives. The

same disadvantages exist with these materials

in the gas collection layer as in other layers,

such as slippage and continuity of flow.

With a geomembrane in the final cover

barrier system, uplift pressures will be exerted unless the gas is quickly and efficiently

conveyed to the wells, vents, or collection

trenches. If this is not properly managed,

uplift pressure will either cause bubbles to

occur, displacing the cover soil and appearing at the surface, or decrease the normal

stress between the geomembrane and its

underlying material. This problem has led to

slippage of the geomembrane and all overlying materials creating high tensile stresses

evidenced by folding at the toe of the slope

and tension cracks near the top.

D. Capillary-Break Final

Covers 

The capillary-break (CB) approach is an

alternative design for a final cover system

(see Figure 6). This system relies on the fact

that for adjacent layers of fine- and coarsetextured material to be in water-potential

equilibrium, the coarse-grained material

(such as crushed stone) will tend to have a

much lower water content than the finegrained material (such as sand). Because the

conductivity of water through a soil decreases

exponentially with its water content, as a soil

becomes more dry, its tendency to stay dry

increases. Therefore, as long as the strata in a

capillary break remain unsaturated (remain

above the water table), the overlying fine-textured soil will retain nearly all the water and

the coarse soil will behave as a barrier to

water percolation due to its dryness. Since

this phenomenon breaks down if the coarse

layer becomes saturated, this alternative

11-16

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care
cover system is most appropriate for semiarid

and desert environments.

What types of materials are used

in capillary-break covers?

The CB cover system typically consists of

five layers: surface, storage, capillary-break,

barrier, and foundation. The surface, barrier,

and foundation layers play the same role in

the cover system as described above. The

storage layer consists of fine material, such as

silty sand. The capillary-break, or coarse,

layer consists of granular materials, such as

gravel and coarse sand. A fabric filter is often

placed between the coarse and fine layers. 

E. The Hydrologic

Evaluation of Landfill

Performance (HELP)

Model

The relative performance of various cover

designs can be evaluated with the Hydrologic

Evaluation of Landfill Performance (HELP)

model, developed by the U.S. Army Corps of

Engineers Waterway Experiment Station for

EPA. The HELP model was designed specifically to support permit writers and engineers

in evaluating alternative landfill designs, but

it can also be used to evaluate various final

cover designs.

The HELP model integrates runoff, percolation, and subsurface-water flow actions into

one model. The model can be used to estimate the flow of water across and through a

final cover. To achieve this, the HELP model

uses precipitation and other climatological

information to partition rainfall and snow

melt into surface runoff, evaporation, and

downward infiltration through the barrier

layer to the waste. 

The HELP model essentially divides a

waste management unit into layers, each

defined in terms of soil type, which is related

to the hydraulic conductivity of each. Users

fill in data collection sheets that request specific information on the layers and climate,

and this information is input to the model. In

performing its calculations, the model will

take into account the reported engineering

properties of each layer, such as slope,

hydraulic conductivity, and rates of evapotranspiration, to estimate the amount of precipitation that can enter the waste unit

through the final cover. To use the HELP

model properly, refer to the HELP Model

User’s Guide and documentation (U.S. EPA,

1994b; U.S. EPA, 1994c). The model itself,

the User’s Guide, and supporting documentation can be obtained from the U.S. Army

Corps of Engineers Web site at

<www.wes.army.mil/el/elmodels>.

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-17

Figure 6. Example of a Capillary-Break Final

Cover System 

Adapted from <www.hanford.gov/eis/hraeis/

eisdoc/graphics/fige-1.gif>
F. Recommended Cover

Systems

The recommended final cover systems correspond to a waste management unit’s bottom liner system. A unit with a single

geomembrane bottom liner system, for example, should include, at a minimum, a single

geomembrane in its final cover system unless

an evaluation of site-specific conditions can

show an equivalent reduction in infiltration.

Table 2 summarizes the minium recommend11-18

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

* Please consult with your state regulatory agency prior to constructing a final cover.

a The final selection of geomembrane type, thickness, and drainage layer requirements for a final cover

should be design-based and consultation with your state agency is recommended.

b This recommended thickness is for high permeability soil material with at least a 3 percent slope at the

bottom of the layer. Some geonet composites, with a minimal thickness of less than 1 inch, have a

transmissivity equal to a much thicker layer of aggregate or sand. 

c Thickness might need to be increased to address freeze/thaw conditions.

Type of Bottom Liner Recommended Cover System Thickness Hydraulic Conductivity

Layers (From top layer down)a (In inches) (In cm/sec)

Double Liner Surface Layer 12 not applicable

Drainage Layer 12b 1×10-2 to 1x10-3

Geomembrane 30mil(PVC)

60mil (HDPE) —

Clay Layer 18 less than 1×10-5

Composite Liner Surface Layer 12 not applicable

Drainage Layer 12b 1×10-2 to 1x10-3

Geomembrane 30 mil (PVC)

60 mil (HDPE) —

Clay Layer 18 less than 1×10-5

Single Clay Liner Surface Layer 12 not applicable

Drainage Layer 12b 1×10-2 to 1x10-3

Clay Layer 18 less than 1×10-7

Single Clay Liner in Cobble Layer 2-4 not applicable

an Arid Area Drainage Layer 12b 1×10-2 to 1x10-3

Clay Layer 18 less than 1×10-7

Single Synthetic Liner Surface Layer 12 not applicable

Drainage Layer 12b 1×10-2 to 1x10-3

Geomembrane 30 mil (PVC)

60 mil (HDPE) —

Clay Layer 18 less than 1×10-5

Natural Soil Liner Earthen Material 24c No more permeable than

base soil

Table 2: Minimum Recommended Final Cover Systems*
ed final cover systems based on the unit’s bottom liner system. While the recommended

minimum final cover systems include closure

layer component thicknesses and hydraulic

conductivity, the cover systems can be modified to address site-specific conditions. In

addition, you should consider whether to

include a protection layer or a gas collection

layer. Figures 7 through 11 display recommended minimum final cover systems. 

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-19

Figure 7. Recommended Final Cover System for a Unit With a Double or Composite Liner

Figure 8. Recommended Final Cover System for a Unit With a Single Clay Liner
11-20

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

Figure 9. Recommended Final Cover System for a Unit With a Single Clay Liner in an Arid Area

Figure 10. Recommended Final Cover System for a Unit With a Single Synthetic Liner
While these recommendations include the

use of compacted clay, a facility manager

might want to consider the use of a geomembrane barrier layer in addition to, or in place

of, a compacted clay barrier layer. Subsidence

of a final cover constructed with a compacted

clay barrier layer can allow precipitation to

enter the closed unit and increase leachate

production. The use of a geomembrane in

place of compacted clay might be more cost

effective. Due to cracking or channeling or

continued subsidence, post-closure care of a

compacted clay barrier layer can be more

expensive to maintain than a geomembrane

barrier layer. A geomembrane barrier layer

can also accommodate more subsidence without losing its effectiveness. 

IV. Closure by

Waste Removal

Closure by waste removal is a term that

describes the removal and decontamination

of all waste, waste residues, contaminated

ground water, soils, and containment devices.

This approach is common for waste piles and

some surface impoundments. Removal and

decontamination are complete when the constituent concentrations throughout the unit

and any areas affected by releases from the

unit do not exceed numeric cleanup levels.

You should check with the state agency to see

if it has established any numeric cleanup levels or methods for establishing site-specific

levels. In the absence of state cleanup levels,

metals and organics should be removed to

either statistically equivalent background levels or to maximum contaminant levels

(MCLs) or health-based numbers (HBNs)2

.

Metals and organics might have different

cleanup levels, but they both should be based

on either local background levels or on

health-based guidelines. 

Future land use considerations can also be

important in determining the appropriate

level of cleanup. One tool that can be used to

help evaluate whether waste removal is

appropriate at the site is the risk-based corrective action (RBCA) process described in

Chapter 10–Taking Corrective Action. The

RBCA process provides guidance on integrating ecological and human health risk-based

decision-making into the traditional corrective action process. 

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-21

2 To learn about the regulatory and technical basis for MCLs, access the Integrated Risk Information System

(IRIS), a database of human health effects that can result from exposure to environmental contaminants,

at <www.epa.gov/iris>. Call the EPA Risk Information Hotline at 513 569-7254 for more information.

Figure 11. Recommended Final Cover System for a Unit With a Natural Soil Liner
A. Establishing Baseline

Conditions

A good management practice is to establish

the baseline conditions for a waste management unit. Baseline conditions include the

background constituent concentrations at a

site prior to waste placement operations.

Identifying the types of contaminants that

might be present can provide an indication of

the potential contamination resulting from the

operation of a unit and the level of effort and

resources that can be required to reach closure. Naturally-occurring elevated background

levels that are higher than targeted closure levels might be encountered. In such cases, consult with the state agency to determine

whether these elevated background levels are a

more appropriate targeted cleanup level. The

identification of potential contaminants will

also provide a guideline for selecting sampling

parameters. If constituents other than those

initially identified are discovered through subsequent soil and water sampling, this might

indicate that contaminants are migrating from

another source.

In some cases, waste contaminants might

have been present at a site before a waste

management unit was constructed, or they

might have migrated to the site from another

unrelated source. In these situations, closure

by waste removal can still proceed, provided

that any contamination originating from the

closing unit is removed to appropriate

cleanup levels. You should determine whether

additional remediation is required under

other federal or state laws, such as the

Resource Conservation and Recovery Act

(RCRA), the Comprehensive Environmental

Response, Compensation, and Liability Act

(CERCLA), or state cleanup laws.

How are baseline conditions

established?

Initial soil and ground-water sampling

around, within, and below a unit will serve

to identify baseline conditions. Sampling can

detect contaminant levels that exceed background levels or federal, state, or local

health-based benchmarks. Contact local environmental protection officials for guidance on

the number and type of samples that should

be taken. If the initial round of sampling

does not reveal any contaminant levels that

exceed benchmarks, you should proceed

with the removal of waste and the restoration

of the unit. If the sampling does reveal contamination that exceeds the benchmarks, you

should consider ways to remediate the site in

compliance with federal, state, or local

requirements.

B. Removal Procedures

Proper removal procedures are vital to the

long-term, post-closure care of a unit and

surrounding land. Properly removing waste

can minimize the need for further maintenance, thereby saving time and money and

facilitating reuse of the land. You should perform closure by waste removal in a manner

that prevents the escape of waste constituents

to the soil, surface water, ground water, and

atmosphere. After removing the waste, you

should remove all equipment, liners, soils,

and any other materials containing waste or

waste residues. Removal verification should

include specifics as to how it will be determined that residues, equipment, liners, and

soils have been removed to baseline conditions. Finally, the land should be returned to

the appearance and condition of surrounding

land areas to the extent possible consistent

with the closure and post-closure plans.

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Ensuring Long-Term Protection—Performing Closure and Post-Closure Care
Should a plan for waste removal

procedures be prepared?

The waste removal process should be fully

described in a closure plan. The removal

process description should address estimates

of the volumes and types of waste and contaminated equipment or structures to be

removed during closure. It should also

include the types of equipment to be used,

the removal pattern, and the management of

loading areas. The closure plan should also

detail steps to be taken to minimize and prevent emissions of waste during closure activities. For example, if activities during closure

include loading and transporting waste in

trucks, the closure plan should describe the

steps that will be taken to minimize air emissions from windblown dust. Proper quality

assurance and quality control during the

waste removal process will help ensure that

the removal proceeds in accordance with the

waste removal plan. A key component of the

waste removal procedure is the consideration

of proper disposal or treatment methods for

any wastes or contaminated materials.

C. Disposal of Removed

Wastes

When a unit is closed by removing waste,

waste residues, contaminated ground water,

soils, and containment devices, you should

ensure that disposal of these materials is in

compliance with state law. If the composition

of the waste can not be determined using

process knowledge, you should test it using

procedures such as those described in Chapter

2–Characterizing Waste. Then consult with the

state agency to determine which requirements

might apply to the waste.

D. Final Sampling and

Analysis

The purpose of final sampling and analysis

is to ensure that target cleanup levels have

been achieved. While initial sampling is

intended to establish baseline levels of contaminants, final sampling is used more as a

safeguard to make sure levels have not

changed. It is important to conduct a final

sampling, in addition to the initial sampling,

because removal actions can increase the contaminant levels at the site, and sometimes

contamination is overlooked in the initial

baseline sampling event. Refer to Chapter

9–Monitoring Performance for a detailed discussion of sampling and analysis procedures.

How should the sampling data

be used?

The results of this sampling event should

be compared to the results of the baseline

event, and any discrepancies should be

noted. The results can be compared to performance measures established at the beginning of the closure process with state or local

regulators. Closure plans incorporating waste

removal should include a sampling and

analysis plan for the initial and final sampling

and analysis efforts. The plan should specify

procedures to ensure that sample collection,

handling, and analysis will result in data of

sufficient quality to plan and evaluate closure

activities. The sampling and analysis plan

should be designed to define the nature and

extent of contamination at, or released from,

the closing unit. The level of detail in the

sampling and analysis plan should be commensurate with the complexity of conditions

at the closing unit.

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-23
V. Post-Closure Care

Considerations

When Final

Cover Is Used

For units that will close with a final cover,

the following factors should be considered:

• Routine maintenance of the unit’s systems, including the final cover,

leachate collection and removal systems, run-on and runoff controls, gas

and ground-water monitoring systems, and surface-water and gas quality monitoring where appropriate.

• The names and telephone numbers

of facility personnel for emergencies.

• Mechanisms to ensure the integrity of

the final cover system, such as posted

signs or notifications on deeds.

• The anticipated uses of the property

during the post-closure period.

• The length of the post-closure care

period.

• Costs to implement and conduct

post-closure care.

• Conditions that will cause post-closure care to be extended or shortened.

A. Maintenance

After the final cover is installed, some

maintenance and repair likely will be necessary to keep the cover in good working condition. Maintenance can include mowing the

vegetative cover periodically and reseeding, if

necessary. Repair the cover when erosion or

subsidence occurs. Maintaining healthy vegetation will ensure the stability of slopes,

reduce surface erosion, and reduce leachate

production by increasing evapotranspiration.

A regular schedule for site inspections of

maintenance activities during the post-closure

period, as well as prompt repair of any problems found at inspection, can help ensure the

proper performance of the cover system.

Maintenance of the proper thickness of surface and drainage layers can ensure long-term

minimization of leachate production and protection of geomembranes, if present.

What maintenance and repair

activities should be conducted

after the final cover has been

installed?

In the case of damage to the final cover,

you should determine the cause of damage so

that proper repair measures can be taken to

prevent recurrence. For example, if the damage is due to erosion, potential causes might

include the length and steepness of slopes,

insufficient vegetation growth due to poor

planting, or uneven settlement of the waste.

Sedimentation basins and drainage swales

should be inspected after major storms and

repaired or cleaned, as necessary.

Components of the leachate collection and

removal system, such as leachate collection

pipes, manholes, tanks, and pumps should

also receive regular inspection and maintenance. If possible, flush and pressure-clean

the collection systems on a regular basis to

reduce sediment accumulation and to prevent clogging caused by biological growth.

The manholes, tanks, and pumps should be

visually inspected at least annually, and

valves and manual controls should be exercised even more frequently, because leachate

can corrode metallic parts. Repairs will help

prevent future problems, such as leachate

overflow from a tank due to pump failure.

You should inspect and repair gas and

ground-water monitoring wells during the

post-closure period. Proper operation of

11-24

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care
monitoring wells is essential to determine

whether releases from a closed waste management unit are occurring. For example,

ground-water monitoring wells should be

inspected to ensure that they have not been

damaged by vehicular traffic or vandalism.

Physical scraping or swabbing might be necessary to remove biological clogging or

encrustation from calcium carbonate deposits

on well screens.

B. Monitoring During PostClosure Care

Post-closure care monitoring should

include the leachate collection system, surface-water controls, the ground-water monitoring system where appropriate, and gas

controls where appropriate. Post-closure

monitoring will serve as your main source of

information about the integrity of the final

cover and liners. A reduction in the intensity

(i.e., frequency) and scope of monitoring

might be warranted after some period of time

during post-closure care. Conversely, an

increase in intensity and scope might become

necessary due to unanticipated problems.

What should be considered when

monitoring post-closure leachate,

ground water, and gas?

The quantity of leachate generated should

be monitored, as this is a good indicator of

the performance of the closure system. If the

closure system is effective, the amount of

leachate generated should decrease over time.

In addition, the concentration of contaminants in leachate should, in time, reach an

equilibrium. An abrupt decline in the contaminant concentration could mean that the

cover has failed, and surface water has

entered the waste and diluted the leachate.

To ensure leachate has not contaminated

ground-water supplies, you should sample

ground water regularly. Regular ground-water

monitoring detects changes, or the lack thereof, in the quality of ground water. For a more

detailed discussion, consult Chapter 9–

Monitoring Performance.

As no cover system is impermeable to gas

migration, and if gas production is a concern

at the unit, you should install gas monitoring

wells around the perimeter of the unit to

detect laterally moving gas. If geomembranes

are used in a cover, more gas can escape laterally than vertically. Gas collection systems

can also become clogged and stop performing

properly. Therefore, you should periodically

check gas vents and flush and pressure-clean

those vents not working properly.

C. Recommended Length

of the Post-Closure Care

Period

The overall goal of post-closure care is to

provide care until wastes no longer present a

threat to the environment. Threats to the environment during the post-closure care period

can be evaluated using leachate and groundwater monitoring data to determine whether

there is a potential for migration of waste constituents at levels that might threaten human

health and the environment. Ground-water

monitoring data can be compared to drinking

water standards or health-based criteria to

determine whether a threat exists.

Leachate volumes and constituent concentrations can also be used to show that the

unit does not pose a threat to human health

and the environment. The threats posed by

waste constituents in leachate should be evaluated based on the potential release of

leachate to ground and surface waters.

Consequently, you should consider doing

post-closure care maintenance for as long as

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-25
11-26

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

that potential exists. Individual post-closure

care periods can be long or short depending

on the type of waste being managed, the

waste management unit, and a variety of sitespecific characteristics. You should contact

the appropriate state agency to determine

what post-closure period it recommends. In

the absence of any state guidance on the

appropriate length of the post-closure period,

consider a minimum of 30 years. 

D. Closure and Post-Closure

Cost Considerations

The facility manager of a closed industrial

unit is responsible for that unit. To ensure

long-term protection of the environment, you

should account for the costs of closure and

post-closure care when making initial plans.

There are guidance documents available to

help plan for the costs associated with closing

a unit. For example, guides produced by the

R.S. Means Co. provide up-to-date cost estimates for most construction-related work,

such as moving soil, and material and labor

for installing piping. Table 3 also presents an

example of a closure/post-closure cost estimate form. Table 4 presents a sample summary cost estimating worksheet to assist in

determining the cost of closure. Also you

should consider obtaining financial assurance

mechanisms so that the necessary funds will

be available to complete closure and post-closure care activities if necessary. Financial

assurance planning encourages internalization

of the future costs associated with waste management units and promotes proper design

and operating practices, because the costs for

closure and post-closure care are often less

for units operated in an environmentally protective manner. You should check with the

state agency to determine whether financial

assurance is required and what types of

financial assurance mechanisms might be

acceptable. 

The amount of financial assurance that

might be necessary is based on site-specific

estimates of the costs of closure and post-closure care. The estimates should reflect the

costs that a third party would incur in conducting closure and post-closure activities.

This recommendation ensures adequate funds

will be available to hire a third party to carry

out necessary activities. You should consider

updating the cost estimates annually to

account for inflation and whenever changes

are made to the closure and post-closure

plans. For financial assurance purposes, if a

state does not have a regulation or guidance

regarding the length of the post-closure care

period, 30 years could be used as a planning

tool for developing closure and post-closure

cost estimates. 

Financial assurance mechanisms do not

force anyone to immediately provide full

funding for closure and post-closure care.

Rather, they help to ensure the future availability of such funds. For example, trust

funds can be built up gradually during the

operating life of a waste management unit. By

having an extended “pay-in” period for trust

funds, the burden of funding closure and

post-closure care will be spread out over the

economic life of the unit. Alternatively, consider the use of a corporate financial test or

third-party alternative, such as surety bonds,

letters of credit, insurance, or guarantees.

What costs can be expected to

be associated with the closure of

a unit?

The cost of constructing a final cover or

achieving closure by waste removal will

depend on site-specific activities. You should

consider developing written cost estimates

before closure procedures begin. For closure

by means of a final cover, the cost of constructing the final cover will depend on the

complexity of the cover profile, final slope
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-27

* Developed from New Jersey Department of Environmental Protection, Bureau of Landfill Engineering

Landfill Permits.

Provisions Total Closure Total Post- Total Closure/

Costs Yrs. ( - ) Closure Costs Post-Closure 

Yrs. ( - ) Costs Yrs. ( - )

i Soil Erosion and Sediment Control Plan NA

ii Final Cover NA

iii Final Cover Vegetation NA

iv Maintenance Program for Final Cover and NA

Final Cover Vegetation

v Maintenance Program for Side Slopes NA

vi Run-On and Runoff Control Program NA

vii Maintenance Program for Run-On and Runoff NA

Control System

viii Ground-water Monitoring Wells NA

ix Maintenance Program for Ground-water NA

Monitoring Wells

x Ground-water Monitoring NA

xi Methane Gas Venting or Evacuation System NA

xii Maintenance Program for Methane Gas NA

Venting or Evacuation System

xiii Leachate Collection and/or Control System NA

xiv Maintenance Program for Leachate Collection NA

and/or Control System

xv Facility Access Control System NA

xvi Maintenance Program for Facility Access NA

Control System

xvii Measures to Conform the Site to NA

Surrounding Area

xviii Maintenance Program for Site Conformance NA

Measures

xix Construction Quality Assurance and NA

Quality Control

TOTAL COSTS

Table 3: Example Closure/Post-Closure Cost Estimate Form* (All Costs Shown in ($000)
11-28

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

Provisions Total Post- Year Year Year Year Year Year Year 

Closure Costs #1 #2 #3 #4 #5 #6 #7

i Soil Erosion and Sediment Control 

Plan NA

ii Final Cover NA

iii Final Cover Vegetation NA

iv Maintenance Program for Final Cover 

and Final Cover Vegetation

v Maintenance Program for Side Slopes

vi Run-On and Runoff Control Program NA

vii Maintenance Program for Run-On 

and Runoff Control System

viii Ground-water Monitoring Wells NA

ix Maintenance Program for Groundwater Monitoring Wells

x Ground-water Monitoring

xi Methane Gas Venting or Evacuation NA

System 

xii Maintenance Program for Methane 

Gas Venting or Evacuation System

xiii Leachate Collection and/or Control NA

System 

xiv Maintenance Program for Leachate 

Collection and/or Control System

xv Facility Access Control System NA

xvi Maintenance Program for Facility 

Access Control System

xvii Measures to Conform the Site to NA

Surrounding Area 

xviii Maintenance Program for Site 

Conformance Measures

xix Construction Quality Assurance and NA

Quality Control 

TOTAL COSTS

Table 3: Example Closure/Post-Closure Cost Estimate Form (Cont’d)
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-29

Worksheet generated from CostPro©: Closure and Post-Closure Cost Estimating Software. Available from

Steve Jeffords of Tetra Tech EM Inc., 404 225-5514, or 285 Peach Tree Center Avenue, Suite 900,

Atlanta, GA, 30303.

Table 4: Sample Summary Cost Estimating Worksheet

Summary Worksheet for Landfills 

Activity

Some of the activities listed below are routine. The owner or operator Worksheet Cost

might elect or be required to conduct additional activities. Italic type Number 

denotes worksheets for estimating the costs of those additional activities 

1 Installation of Clay Layer LF-3 $

2 Installation of Geomembrane LF-4 $

3 Installation of Drainage Layer LF-5 $

4 Installation of Topsoil LF-6 $

5 Establishment of Vegetative Cover LF-7 $

6 Installation of Colloid Clay Liner LF-8 $

7 Installation of Asphalt Cover LF-9 $

8 Decontamination DC-1 $

9 Sampling and Analysis SA-2 $

10 Monitoring Well Installation MW-1 $

11 Transportation TR-1 $

12 Treatment and Disposal TD-1 $

13 Subtotal of Closure Costs (Add lines 1 through 12)

14 Engineering Expenses (Engineering expenses are typically 10% of closure $

costs, excluding survey plat, certification of closure, and post-closure care.)

15 Survey Plat LF-10 $

16 Certification of Closure LF-11 $

17 Subtotal (Add engineering expenses and cost of the survey plat, certification of $

closure, and post-closure care to closure costs [Add lines 12 through 16])

18 Contingency Allowance (Contingency allowances are typically 20% of closure costs, 

engineering expenses, cost of survey plat, cost of certification of closure, and 

post- closure care.) $

19 Post-Closure Care PC-1 $

TOTAL COST OF CLOSURE (Add lines 17, 18, and 19) $
contours of the cover, whether the entire unit

will be closed (or partial closures), and other

site-specific factors. For example, the components of the final cover system, such as a gasvent layer or a biotic layer, will affect costs. In

addition, closure-cost estimates would also

include final-cover vegetation, run-on and

runoff control systems, leachate collection

and removal systems, ground-water monitoring wells, gas-monitoring systems and controls, and access controls, such as fences or

signs. Closure costs might also include construction quality assurance costs, engineering

fees, accounting and banking fees, insurance,

permit fees, legal fees, and, where appropriate, contingencies for cost overruns, reworks,

emergencies, and unforeseen expenses.

For closure by means of waste removal,

closure costs would include the costs of

removal procedures, decontamination procedures, and sampling and analysis. Closure

cost estimates should also consider the costs

for equipment to remove all waste, transport

it to another waste management unit, and

properly treat or dispose of it. In addition,

fugitive dust emission controls, such as dust

suppression practices, might need to be

included as a closure cost. Table 5 presents

example estimates of average closure costs for

typical closure activities. It also presents estimates of typical post-closure care costs discussed in more detail below.

What costs can be expected to be

associated with post-closure care?

After a waste management unit is closed,

you should conduct monitoring and maintenance to ensure that the closed unit remains

secure and stable. Consider the costs to conduct post-closure care and monitoring for

some period of time, such as 30 years (in the

absence of a state regulation or guidance). If a

unit is successfully closed by means of waste

removal, no post-closure care costs would be

expected. Post-closure care costs should

include both annual costs, such as monitoring, and periodic costs, such as cap or monitoring well replacement.

For units closed by means of a final cover,

you should consider the costs for a maintenance program for the final cover and associated vegetation. The more frequent the timing

of the maintenance activities, the greater your

post-closure care costs will be. This program

might include repair of damaged or stressed

vegetation, and maintenance of side slopes.

Costs to maintain the run-on and runoff control systems, leachate collection and removal

systems, and ground-water and gas monitoring wells should also be expected. In addition, sampling, analysis, and reporting costs

should be factored into the post-closure cost

estimates. See Table 5 above for estimates of

post-closure care costs.

Post-closure costs should be updated

annually as a record of actual unit costs is

developed. Some costs, such as erosion control and ground-water sampling, might be

reduced over time as the vegetation on the

cover matures and a meaningful amount of

monitoring data is accumulated. Due to sitespecific conditions, a shorter or longer postclosure period might be determined to be

appropriate.

How can long-term financial

assurance for a unit be obtained?

Different examples of financial assurance

mechanisms include trust funds, surety bond,

insurance, guarantee, corporate guarantees,

and financial tests. Trust funds are a method

whereby cash, liquid assets, certificates of

deposit, or government securities are deposited into a fund controlled by a trustee, or state

agency. The trust fund amount should be such

that the principal plus accumulated earnings

over the projected life of the waste management unit would be sufficient to pay closure

11-30

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-31

Closure Activity Cost Estimate

Estimated average total landfill closure cost $4,000,000 1

Complete site grading $1,222/acre 2

Landfill capping

Total (all capping materials & activities) $80,000 – $100,000/ acre 3

Compacted clay cap $5.17/cubic yard of clay 2

Geosynthetic clay liner cap $16,553/acre 2

Leachate collection and treatment $0.05 – $0.15/gallon 3

$0.25/gallon 2

Reclamation of area (applying 2.5 feet of top soil and seeding) $10,200/acre 3

Install ground-water monitoring wells $2,400/well 4

Install methane monitoring wells (if applicable) $1,300/well 4

Install perimeter fence $13/linear foot 4

Repair/replace perimeter fence $2.20/linear foot 2

Construct surface-water structures $1/linear foot 4

Table 5. Example Estimated Closure and Post-Closure Care Costs

Post-Closure Activity Cost Estimate

(based on 30 year post-closure care period) 

Estimated average total landfill post-closure care cost $1,000,000 1

Conduct annual inspections $22,000/facility/year 4

$15,000/facility/year 2

Maintain leachate collection systems $60,000 2

Conduct Post-closure ground-water monitoring $15,000 – $25,000/year 3

(sampling and analysis) $12,000/well 4

Conduct methane monitoring $7,200/well 4

Maintain perimeter fence $12/linear foot 4

Maintain surface-water structures $1/linear foot 4

Remove perimeter fence (at end of post-closure care period) $2/linear foot 4

1 ICF Incorporated. Memo to Dale Ruhter, September 11, 1996

ICF’s data show that total closure and post-closure care costs are dependent upon the size of the landfill.

The size ranges and corresponding cost estimates were used to calculate the estimated average total costs.
and post-closure care costs. Surety bond,

insurance, and guarantee are methods to

arrange for a third party to guarantee payment for closure and post-closure activities if

necessary. A financial test is a standard, such

as an accounting ratio, net worth, bond rating, or a combination of these standards, that

measures the financial strength of a firm. By

passing a financial test, it is determined that

one has the financial strength to pay for closure and post-closure costs.

A more detailed explanation of these

examples and other potential financial assurance mechanisms is provided below. These

mechanisms can be used individually or in

combination. This Guide, however, does not

recommend specific, acceptable, financial

assurance mechanisms. 

• Trust funds. A trust fund is an

arrangement in which one party, the

grantor, transfers cash, liquid assets,

certificates of deposit, or government

securities into a fund controlled by a

special “custodian,” the trustee, who

manages the money for the benefit of

one or more beneficiaries. The trust

fund should be dedicated to closure

and post-closure care activities.

Payments are made annually into the

fund so that the full amount for closure and post-closure care accumulates before closure and post-closure

care activities start. A copy of the

trust agreement, which describes

how the funds will be used to pay for

closure and post-closure care activities, should be placed in the waste

management unit’s operating record.

• Surety bond. A surety bond guarantees performance of an obligation,

such as closure and post-closure

care. A surety company is an entity

that agrees to answer for the debt or

default of another. Payment or performance surety bonds are acceptable

in the event an owner or operator

fails to conduct closure and post-closure care activities. If you use a surety bond or letter of credit, you

should establish a standby trust fund

(essentially the same as a trust fund).

11-32

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

2 Oklahoma Department of Environmental Quality. Table 5.2 Closure Cost Estimate and Table 5.3 Post

Closure Estimate from Chapter 5 of Solid Waste Financial Assurance Program Report. December 2000.

3 Jeffrey H. Heath “Landfill Closures: Balancing Environmental Protection with Cost,” MSW Management.

January/February 1996. pp. 66-70.

4 Wyoming Department of Environmental Quality, Solid and Hazardous Waste Division. Solid Waste

Guideline #12: Participation in the State Trust Account. May 1994.

Size Range Cost 

(tons per day) (in 2000 dollars)

50 – 125 $2,700,000

126 – 275 $5,100,000

276 – 563 $8,300,000

564 – 1125 $11,800,000

Subtitle D Landfill Closure Costs

Size Range Cost 

(tons per day) (in 2000 dollars)

50 – 125 $820,000

126 – 275 $980,000

276 – 563 $1,400,000

564 – 1125 $1,700,000

Subtitle D Landfill Post-Closure Care Costs

Notes for Table 5
In most cases, a standby trust fund is

established with an initial nominal

fee agreed to by the owner or the

operator and the trustee. Further

payments into this fund are not

required until the standby trust is

funded by a surety company. The

surety company should be listed as

an acceptable surety in Circular 570

of the U.S. Department of Treasury. 

• Letters of credit. A letter of credit is

a formalized line of credit from a

bank or another institution on behalf

of an owner or operator. This agreement states that it will make available

to a beneficiary, such as a state, a specific sum of money during a specific

time period. The letter of credit

should be irrevocable and issued for

1 year. The letter of credit should

also establish a standby trust fund.

• Insurance. An insurance policy is

basically a contract through which

one party guarantees another party

monies, usually a prescribed amount,

to perform the closure or post-closure care in return for premiums

paid. The policy should be issued for

a face amount at least equal to the

current cost estimate for closure and

post-closure care. The face amount

refers to the total amount the insurer

is obligated to pay; actual payments

do not change the face amount. 

• Corporate financial test. Corporate

financial tests are a method for an

owner and operator to self-guarantee

that they have the financial resources

to pay for closure and post-closure

costs. These tests might require that a

company meet a specified net worth,

a specified ratio of total liabilities to

net worth, and a specified net working capital in the United States.

Implicit in using a financial test is a

reliance on Generally Accepted

Accounting Principles (GAAP) to provide fairly represented accounting

data. Your financial statements should

be audited by an independent certified public accountant. If the accountant gives an adverse opinion or a

disclaimer of opinion of the financial

statements, you should use a different

financial assurance mechanism.

• Corporate guarantee. Under a corporate guarantee, a parent company

guarantees to pay for closure and

post-closure care, if necessary. The

parent company should pass a financial test to show that it has adequate

financial strength to provide the

guarantee. A financial test is a way

for guarantors to use financial data to

show that their resources are adequate to meet closure and post-closure care costs. The guarantee should

only be used by firms with adequate

financial strength.

• Other financial assurance mechanisms. If you consider other financial

assurance mechanisms, you should

talk to your state to see if the mechanism is acceptable. 

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-33
11-34

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

You should consider the following while developing closure and post-closure care activities for industrial

waste management units.

■ Develop a closure and post-closure plan, specifying the activities, unit type, waste type, and schedule

of the closure.

■ If using a final cover to accomplish closure:

— Include the specifications for the final cover in the closure plan.

— Determine whether the waste will need stabilization or solidification prior to constructing the final

cover.

— Address site-specific factors that can affect cover performance.

— Select the appropriate materials to use for each layer of the final cover.

— Evaluate the effectiveness of the final cover design using an appropriate methodology or modeling

program.

— Establish a maintenance plan for the cover system.

— Establish a program for monitoring the leachate collection system, ground-water quality, and gas

generation during the post-closure period.

— Ensure proper quality assurance and quality control during final cover installation and post-closure monitoring.

■ If accomplishing closure by waste removal:

— Include estimates of the waste volume, contaminated soils and containment structures to be

removed during closure.

— Establish baseline conditions and check to see if the state requires numeric cleanup levels.

— Develop removal procedures.

— Develop a sampling and analysis plan.

— Ensure proper quality assurance and quality control during sampling.

■ Determine what post-closure activities will be appropriate at the site.

■ Estimate the costs of closure and post-closure care activities and consider financial assurance mechanisms to help plan for these future costs. 

Performing Closure and PostClosure Care Activity List
Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

11-35

ASTM. D-3987-85. Standard Test Method for Shake Extraction of Solid Waste with Water.

ASTM. Standard Methods for Examination of Water and Wastewater.

ASTM, APHA, AWWA, & WPCF. Standard Test Methods for Examination of Water and Wastewater.

Bagchi, A. 1994. Design, Construction, and Monitoring of Landfills. John Wiley & Sons Inc.

Florida Department of Environmental Protection. Solid Waste Section. 1995. Municipal Solid Waste Landfill

Alternate Design Closure Guidance. 

Geosynthetic Research Institute. 1990. Landfill Closures: Geosynthetics Interface Friction and New

Developments. GRI Proceedings.

Grefe, R. P. 1989. Closure of Papermill Sludge Lagoons Using Geosynthetics and Subsequent Performance.

Presented at the Twelfth Annual Madison Waste Conference. September.

Heath, Jeffrey H. 1996. “Landfill Closures: Balancing Environmental Protection with Cost,” MSW

Management. January/February. pp. 66-70.

ICF Incorporated. 1996. Memorandum to U.S. EPA: Updated Closure and Post-Closure Cost Estimates for

Subtitle C. (Nevin and Brawn to Ruhter, September 11, 1996).

Jesionek, K.S., R.J. Dunn, and D.E. Daniel. 1995. Evaluation of Landfill Final Covers. Proceedings Sardinia

95, Fifth International Landfill Symposium. October.

Koerner, R.M. and D.E. Daniel. 1997. Final Covers for Solid Waste Landfills and Abandoned Dumps.

Oklahoma Department of Environmental Quality. 2000. Chapter 5 of Solid Waste Financial Assurance

Program Report.

New Jersey Department of Environmental Protection and Energy. 1994. Technical Manual for Division of Solid

Waste Management Bureau of Landfill Engineering Landfill Permits.

Texas Natural Resource Conservation Commission. Industrial & Hazardous Waste Division. 1993. Closure

Guidance Documents (Draft). September.

Texas Natural Resource Conservation Commission. Industrial Solid Waste Management. 1984. “Closure and

Post-Closure Estimates.” <ftp://ftp.tnrcc.state.tx.us/pub/bbs1/ihwpslib/tg10.doc>. October.

Resources
11-36

Ensuring Long-Term Protection—Performing Closure and Post-Closure Care

U.S. EPA. 1996. Test Methods for Evaluating Solid Waste Physical/Chemical Methods. SW-846.

U.S. EPA. 1995. Decision-Maker’s Guide to Solid Waste Management, Second Edition. EPA530-R-95-023.

U.S. EPA. 1994a. Design, Operation, and Closure of Municipal Solid Waste Landfills. EPA625-R-94-008.

U.S. EPA. 1994b. The Hydrologic Evaluation of Landfill Performance (HELP) Model: Users Guide for

Version 3. EPA600-R-94-168a. 

U.S. EPA. 1994c. The Hydrologic Evaluation of Landfill Performance (HELP) Model: Engineering

Documentation for Version 3. EPA600-R-94-168b.

U.S. EPA. 1993. Solid Waste Disposal Facility Criteria: Technical Manual. EPA530-R-93-017.

U.S. EPA. 1991. Seminar Publication: Design and Construction of RCRA/CERCLA Final Covers. EPA625-

4-91-025.

U.S. EPA. 1990. Sites for Our Solid Waste: a Guidebook for Effective Public Involvement. EPA530-SW-90-

019.

U.S. EPA. 1989a. Seminar Publication: Requirements for Hazardous Waste Landfill Design, Construction,

and Closure. EPA625-4-89-022.

U.S. EPA. 1989b. Technical Guidance Document: Final Covers on Hazardous Waste Landfills and Surface

Impoundments. EPA530-SW-89-047.

U.S. EPA. 1988. Guide to Technical Resources for the Design of Land Disposal Facilities. EPA625-6-88-

018.

U.S. EPA. 1979. Method for Chemical Analysis of Water and Wastes. EPA600-4-79-020.

Washington Department of Ecology, Hazardous Waste and Toxics Reduction Program. 1994. Guidance for

Clean Closure of Dangerous Waste Facilities.

Wyoming Department of Environmental Quality, Solid and Hazardous Waste Division. 1994. Solid Waste

Guideline #12: Participation in the State Trust Account.

Resources (cont.)
Glossary

G-1

24-hour, 25-year a rainfall event of 24 hours duration and of such a magnitude that it 

storm event has a 4 percent statistical likelihood of occurring in any given year.

acceptance and methods used to evaluate the performance of geomembranes. While the

conformance testing specific ASTM test methods vary depending on geomembrane type, recommended acceptance and conformance testing for geomembranes

includes evaluation of thickness, tensile strength and elongation, and

puncture and tear resistance testing, as appropriate.

access controls measures, such as fences or security guards, used to restrict entry to a site.

active gas control mechanical means, such as a vacuum or pump, to forcibly remove gas 

systems from a waste management unit.

adsorption the process by which molecules of gas, liquid, or dissolved solids adhere

to the surface of other particles, such as activated carbon or clay.

aerobic processes a biochemical process or condition occurring in the presence of oxygen.

agronomic rate in land application, a waste application rate designed to provide the

amount of nitrogen needed by a crop or vegetation to attain a desired

yield, while minimizing the amount of nitrogen that will pass below the

root zone of the crop or vegetation to ground water.

anaerobic processes a biological process that reduces organic matter to compounds such as

methane and carbon dioxide in an oxygen-free environment.

anchor trench a long, narrow ditch along the perimeter of a unit cell in which the edges

of a geomembrane are buried or secured.

annular seal impermeable material used to prevent infiltration of surface water and

contaminants into the space between the borehole wall and the groundwater well casing.

attenuation the process by which a compound is reduced in concentration over time

through chemical, physical, and biological processes such as adsorption,

degradation, dilution, and transformation.

Atterberg limits a soil’s plastic limit (percent moisture at which soil transitions from solid

to plastic) and its liquid limit (percent moisture at which soil transitions

from plastic to liquid); useful in characterizing soil plasticity when designing liners with clay soils.

Glossary
Glossary

G-2

barrier (infiltration) in a final cover system, a layer preventing water infiltration into the

waste, indirectly promoting the storage and drainage of water from the

overlying protection and surface layers, and preventing the upward

movement of gases. 

barrier walls low permeability partitions used to direct uncontaminated ground-water

flow around a disposal site or to prevent contaminated material from

migrating from a site.

bathtub effect the buildup of leachate within a unit that occurs when the cover system

is more permeable than the liner. Leachate accumulates due to the infiltration rate through the cover system exceeding the exfiltration rate

through the liner system.

bench-scale a study used to evaluate the effectiveness of one or more potential

treatability study treatment remedies. It establishes the validity of a technology and generates data indicating the remedy’s potential to meet performance goals.

berm a raised flow diversion structure made from compacted earth or rock fill

and used to buttress a slope and prevent run-on from entering a waste

management unit.

best management measures used to reduce or eliminate contaminant releases to the 

practices (BMPs) environment. BMPs can take the form of a process, activity, or physical

structure.

bioaccumulation the uptake and concentration of substances, such as waste constituents,

by exposed organisms. This phenomenon has the potential to cause high

concentrations especially in the tissues of higher predators.

biochemical oxygen the amount of oxygen consumed in the biological processes that break 

demand (BOD) down organic matter (typically measured in mg oxygen per L waste or

leachate). 

biodegradable significant component of waste used in land application. Carbon-based

organic matter material derived from biological organisms; eventually decomposed by

microbes into nontoxic products often useful as plant nutrients.

(Compare to synthetic organic compounds.)

biological treatment a process relying primarily on oxidative or reductive mechanisms initiated by microorganisms to stabilize or de-toxify a waste or leachate.

Biological treatment can rely either on aerobic or anaerobic processes.

Glossary (cont.)
Glossary

Glossary (cont.)

G-3

blanks samples of ground water, air, or other media, collected to determine

background contaminants in the field; used for comparison purposes

when analyzing monitoring data.

borrow pit a location where soils are excavated for use as fill or for compaction

into liners.

buffer zone an area between waste management units and other nearby properties,

such as schools. Buffer zones provide time and space to shield surrounding properties from ongoing activities and disruptions associated

with waste management activities.

calcium carbonate a measure of a waste’s ability to neutralize soil acidity—its buffering 

equivalent (CCE) capacity—compared to pure calcium carbonate.

capillary-break (CB) an alternative design for a final cover system that exploits the relative 

approach differences in porosity between soil types to inhibit water infiltration.

carbon to nitrogen in land application, the ratio of the relative quantities of these two 

ratio elements in a waste. Carbon is associated with the biodegradable

organic matter in a waste, and the carbon to nitrogen ratio reflects the

level of inorganic nitrogen available in the soil for plant growth.

cation exchange the ability of a soil to take up and give off positively charged ions—a 

capacity process which affects the movement of metals in soil.

chain-of-custody a document tracking possession of samples from the time of collection 

record through laboratory analysis. A chain-of-custody record generally

includes the date and time of collection, signatures of those involved

in the chain of possession, time and dates of possession, and other

notations to allow tracking of samples.

chemical oxygen a measure of the oxygen equivalent of the organic matter in a waste 

demand (COD) or leachate that is susceptible to oxidation by a strong chemical oxidant such as chromate. COD is used to determine the degree of contamination of a waste or leachate that is not readily biodegradable (see

biochemical oxygen demand.)

chemical seaming the use of solvents, cement, or an adhesive to join panels or rolls of a

liner. Chemical seaming processes include chemical fusion and adhesive seaming.

chemical treatment a class of processes in which chemicals are added to wastes or to contaminated media to reduce toxicity, mobility, or volume.
Glossary

Glossary (cont.)

G-4

closure termination of the active life of a waste management accompanied by

one of the following measures: 1) use of engineered controls, such as a

final cover, and post-closure care activities to maintain and monitor

the controls, or 2) removal of waste and contaminated containment

devices and soils.

closure plan a document describing the procedure envisioned for the termination of

a waste management unit’s active life. Topics addressed often include

future land use, whether wastes will be removed or left in place at closure, closure schedule, steps to monitor progress of closure actions,

contingency plans, and final cover information.

collection and an area that retains runoff long enough to allow solids/particles that 

sedimentation basin are suspended in and being transported by surface water to settle out

by gravity.

compacted clay a hydraulic barrier layer composed of natural mineral materials 

liner (CCL) (natural soils), bentonite-soil blends, and other materials placed and

compressed in layers called lifts.

construction quality a planned series of observations and tests of unit components, such as 

assurance (CQA) liners, as they are being built. CQA is designed to ensure that the components meet specifications. CQA testing, often referred to as acceptance inspection, provides a measure of final product quality and its

conformance with project plans and specifications.

construction quality an ongoing process of measuring and controlling the characteristics of 

control (CQC) unit components, such as liners, in order to meet manufacturer’s or

project specifications. CQC inspections are typically performed by the

contractor to provide an in-process measure of construction quality

and conformance with the project plans and specifications, thereby

allowing the contractor to correct the construction process if the quality of the product is not meeting the specifications and plans.

control charts a statistical method of evaluating ground-water monitoring data using

historical data for comparison purposes. Appropriate only for initially

uncontaminated wells.

corrective action the process of taking appropriate steps to remediate any contamination.

critical habitat areas which are occupied by endangered or threatened species and

which contain physical or biological features essential to the proliferation of the species.
Glossary

Glossary (cont.)

G-5

daily cover a level of soil and/or other materials applied at the end of a day after

waste has been placed, spread, and compacted. Covering the waste

helps control nuisance factors, such as the escape of odors, dust, and

airborne emissions, and can limit disease vectors.

deed restriction a notation on a property’s deed or title placing limits and conditions

on the use and conveyance of the property.

design storm event a storm of an intensity, volume, and duration predicted to recur once

in a given number of years, whose effects you are designing a system

or structure to withstand. (See 24-hour, 25-year storm event.)

destructive testing the removal of a sample from a liner seam or sheet to perform tests to

assess quality.

dilution/attenuation DAFs are used to measure the difference in the concentration of waste 

factor (DAF) constituents found in the leachate released from a waste management

unit at the source and the same leachate subsequently arriving at a

receptor well. DAF is defined as the ratio of the leachate concentration

at the source to the receptor well concentration.

direct-push sampling a method of sampling ground water by hydraulically pressing and/or

vibrating a probe to the desired depth and retrieving a ground-water

sample through the probe. The probe is removed for reuse after the

desired volume of ground water is extracted.

diversion dike a raised land feature built to channel or control the flow of run-on and

runoff water around and within a waste management unit.

downgradient well a ground-water monitoring installation built to detect contaminant

plumes from a waste management unit. In the absence of specific state

requirements, monitoring points should be no more than 150 meters

downgradient from your waste management unit boundary and placed

in potential contamination migration pathways.

drainage layer in a final cover system, a stratum that directs infiltrating water to

drainage systems at the toe of the cover. The drainage layer can be

placed below the surface or protection layer, but above the barrier

layer.

electrical conductivity the ability of a sample to carry an electrical charge. Used in land 

(EC) application to estimate the total dissolved solids content of a soil or waste.

emergency response procedures to address major types of waste management unit 

plan emergencies: accidents, spills, and fires/explosions.
Glossary

Glossary (cont.)

G-6

environmental justice the practice of identifying and addressing, as appropriate, disproportionately high and adverse human health or environmental effects of

waste manage ment programs, policies, and activities on minority and

low-income populations.

environmental stress imperfections or failures in a liner caused by environmental factors 

cracks before the liner is stressed to its stated maximum strength.

EPA’s Composite EPACMTP is a ground-water fate and transport model. It simulates 

Model for Leachate subsurface fate and transport of contaminants leaching from the 

Migration with bottom of a waste management unit and predicts concentrations of 

Transformation those contaminants in a downstream receptor as well.

Products (EPACMTP)

erosion layer (see surface layer.)

expansive soils soils that lose their ability to support a foundation when subjected to

certain natural events, such as heavy rain, or human-caused events,

such as explosions.

fate and transport a methodology which examines numerous waste and site characterismodeling tics to determine how waste constituents move through the environment, how they are degraded or changed, and where they end up.

fault a failure that occurs in a geologic material, such as rock, when tectonic,

volcanic, or other stresses exceed the material’s ability to withstand them.

field study in land application, a scientific investigation of waste, soil, and plant

interaction conducted under natural environmental conditions.

(Compare to greenhouse study.)

filter pack in a ground-water monitoring well, a quantity of chemically inert

material such as quartz sand, that prevents material from surrounding

geological formations from entering the well intake and helps stabilize

the adjacent formation. Might be necessary in boreholes that are oversized with regard to the casing and well intake diameter.

final cover a system of multiple layers of soil; engineered controls, such as liners; and/

or other materials placed atop a closed waste management unit. Typically

improves aesthetics, prevents erosion, blocks roots and burrowing animals,

collects and drains incoming water, provides a barrier between waste and

the environment, and collects gas generated within the unit.

financial assurance a funding instrument, such as a bond or trust, that provides or 

mechanism guarantees sufficient financial resources for the closure and post-closure care of a unit in the event the owner or operator is unable to pay.
Glossary

Glossary (cont.)

G-7

fines silt and clay-sized particles.

100-year floodplain a relatively flat, lowland area adjoining inland and coastal waters that

is susceptible to inundation during a 100-year flood. A 100-year flood

is a large magnitude occurrence with a 1 percent chance of recurring

in any given year.

foundation/gas in a final cover system, a stratum of permeable material such as sand 

collection layer or gravel that controls the migration of gases to collection vents and

supports overlying strata.

freeboard depth (capacity) intended to remain unused above the expected highest

liquid level in a liquid storage facility, such as a surface impoundment.

freeze-thaw cycles climatic changes in which water enters a small crack in a material,

expands upon freezing, and thereby expands the crack; the process

then repeats itself and the crack progressively grows. It can increase

the hydraulic conductivity of low permeability soil layers or damage

geomembranes in final covers.

fugitive dust solid particulate matter, excluding particulate matter emitted from

exhaust stacks, that become airborne directly or indirectly as a result

of human activity.

fugitive emission dust suppression at a waste management unit through measures such 

control as watering or chemical dust suppression.

gabion a structure formed from crushed rock encased in wire mesh and used

to check erosion and sediment transport.

gas migration the lateral and/or vertical movement of gas through a waste management

unit or its cover systems; can convey methane or other dangerous gases

to other sites or buildings if gas monitoring is not implemented.

geogrid plastic material manufactured into an open, lattice-like sheet configuration and typically used as reinforcement; designed with apertures or

openings sized to allow strike through of surrounding rock and soil.

geomembrane a synthetic sheet composed of one or more plastic polymers with ingredients such as carbon black, pigments, fillers, plasticizers, processing

aids, cross- linking chemicals, anti-degradants, and biocides.

Geomembranes are used as hydraulic barriers in liner and cover systems.

geophysical measurement of changes in the geophysical characteristics of 

monitoring subsurface soils, and in some cases, in the ground water itself, to

determine potential changes in ground-water quality.
Glossary

Glossary (cont.)

G-8

geosynthetic clay a factory-manufactured, hydraulic barrier typically consisting of 

liner (GCLs) bentonite clay (or other very low permeability materials), supported by

geotextiles and/or geomembranes held together by needling, stitching,

or chemical adhesives.

geotextile a woven, nonwoven, or knitted synthetic fabric used as a filter to prevent the passing of fine-grained material such as silt or clay. A geotextile can be placed on top of a drainage layer to prevent the layer from

becoming clogged with fine material.

gravel soil particles unable to pass through the openings of a U.S. Number 4

sieve, which has 4.76 mm (0.2 in.) openings.

greenhouse study in land application, a scientific investigation of waste, soil, and plant

interaction conducted under controlled indoor conditions. (Compare

to field study.)

ground-water a borehole in soil outfitted with components typically including a 

monitoring well casing, an intake, a filter pack, and annular and surface seals; used to

collect ground water from one or more soil layers for sampling and

analysis.

ground-water The objectives of a ground-water monitoring program are to measure 

monitoring program the effectiveness of a waste management unit’s design; to detect changes,

or the lack thereof, in the quality of ground water caused by the presence of a waste management unit; and to provide data to accurately

determine the nature and extent of any contamination that might occur.

ground-water a ground-water remediation technology in which contaminated water 

pump-and-treat is pumped to the surface for treatment.

ground-water a scientist or engineer who has received a baccalaureate or postspecialist graduate degree in the natural sciences or engineering and has sufficient training and experience in ground-water hydrology and related

fields as demonstrated by state registration, professional certifications,

or completion of accredited university programs that enable that individual to make sound professional judgements regarding ground-water

monitoring, contaminant fate and transport, and corrective action.

health-based number a concentration limit for a waste constituent. The HBN is derived from

(HBN) reference doses or reference concentrations that estimate the maximum

daily exposure to a waste constituent through a specific pathway (i.e.,

ingestion) that would be without appreciable risk of deleterious effects

during a lifetime.

hydraulic the velocity at which a fluid, such as leachate, flows through a material, 

conductivity such as a compacted clay liner.
Glossary

Glossary (cont.)

G-9

hydraulic loading in land application, the quantity of liquid or aqueous waste that can be

capacity assimilated per unit area by the soil system.

hydraulic in land application, the application of waste in excess of the liquid or 

overloading water handling capacity of a soil; can result in ponding, anaerobic

waste degradation, and odors.

hydrogeologic study and quantification of a site’s subsurface features to determine

characterization ground-water flow rate and direction; necessary for an effective

ground-water monitoring program.

Hydrologic an EPA model that evaluates the relative performance of various final

Evaluation of Landfill cover designs, estimates the flow of water across and through a final 

Performance (HELP) cover, and determines leachate generation rates.

infiltration the entry of precipitation, ground water, waste, or other liquid into a

soil layer or other stratum.

in-situ soil geological material already present at a site; known as an in-situ liner

when used as a barrier layer in place of imported soil or synthetic

materials.

institutional control a measure that can be used by responsible parties and regulatory agencies to prevent use of or access to a site in a remedial program where,

as part of the program, certain levels of contamination will remain on

site in the soil or ground water. Can also be considered in situations

where there is an immediate threat to human health; can include deed

restrictions, restrictive covenants, use restrictions, access controls,

notices, registry act requirements, transfer act requirements, and contractual obligations.

interfacial shear the friction or stress between components, such as a compacted clay

liner and a geomembrane, that occurs on side slopes of waste management units. When the interfacial shear is inadequate, a weak plane can

form on which sliding can occur. The shift in components can compromise liner and cover performance, negatively affecting unit stability. 

interim measure in corrective action, a step taken to control or abate ongoing risks

before final remedy selection.

internal shear a stress that can lead to tearing of liner or cover components when

overlying or underlying pressure upon a liner or cover exceeds its ability to withstand this stress.

ISO 14000 voluntary set of standards for good environmental practices developed 

procedures by the International Standards Organization (ISO), also known as

Environmental Management Standards (EMS).
Glossary

Glossary (cont.)

G-10

karst terrain areas containing soluble bedrock, such as limestone or dolomite, that

have been dissolved and eroded by water, leaving characteristic physiographic features including sinkholes, sinking streams, caves, large

springs, and blind valleys.

land application (see land application unit.)

land application unit a waste management unit in which waste (such as sludge or wastewater) is spread onto or incorporated into the land to amend the soil

and/or treat or dispose of the waste.

landfills a waste management unit in which waste is compacted in engineered

cells for permanent disposal, usually covered daily.

leachate liquid (usually water) that has percolated through waste and taken

some of the waste or its constituents into solution.

leachate the concentration (usually in mg/L) of a particular waste constituent in 

concentration the leachate.

leachate collection a system of porous media, pipes, and pumps that collect and convey 

and removal system leachate out of a unit and/or control the depth of leachate above a liner.

leachate testing used to characterize waste constituents and their concentrations, and

to estimate the potential amount and/or rate of the release of waste

constituents under worst case environmental conditions.

leak detection also known as a secondary leachate collection and removal system; a

system (LDS) redundant leachate collection and removal system to detect and capture leachate that escapes or bypasses the primary system. Sudden

increases in leachate captured by an LDS can indicate failure of a primary leachate collection and removal system.

lifts layers of compacted natural mineral materials (natural soils), bentonite-soil blends, and other materials that compose a liner or other

compacted stratum.

liner a hydraulic barrier, such as compacted clay or a geomembrane, used to

restrict the downward or lateral escape of waste, waste constituents,

and leachate. Liners accomplish this by physically impeding the flow

of leachate and/or by adsorbing or attenuating pollutants.

in-situ soil geological material already present at a site; known as an in-situ liner

when used as a barrier layer in place of imported soil or synthetic

materials.
Glossary

Glossary (cont.)

G-11

single liner a hydraulic barrier consisting of one soil layer, one geomembrane, or

any other individual barrier without a second barrier to impede contaminants that might breach it.

composite liner a liner consisting of both a geomembrane and a compacted clay layer

(or a geosynthetic clay liner).

double liner a hydraulic barrier between a waste management unit and the natural

environment, consisting of primary (top) and secondary (bottom) levels. Each level can consist of compacted clay, a geomembrane, or a

composite (consisting of a geomembrane and a compacted clay layer

or GCL).

liquefaction occurs when vibrating motions caused by an earthquake turn saturated

sand grains in the soil into a viscous fluid, diminishing the bearing

capacity of the soil and possibly leading to foundation and slope failures.

lithology the description of geological materials on the basis of their physical

and chemical characteristics.

lower explosive the minimum percentage of a gas by volume in the air that is necessary 

limit (LEL) for an explosion. This level is 5 percent for methane.

lysimeter a device used to measure the quantity or rate of water movement

through or from a block of soil or other material. It collects soil-pore

liquids by applying a vacuum that exceeds the soil moisture tension;

usually a buried chamber made from wide perforated pipe.

material balances used to calculate all input and output streams, such as the annual

quantities of chemicals transported to a facility and stored, used, or

produced at a facility, and released or transported from a facility as a

commercial product or by-product or a waste. Material balances can

assist in determining concentrations of waste constituents where analytical test data are limited.

Maximum Achievable national standards that regulate major sources of hazardous air 

Control Technology pollutants. Each MACT standard specifies particular operations, 

(MACT) standards processes, and/or wastes that are covered. If a facility is covered by a

MACT standard, it must be permitted under Title V.

maximum the maximum permissible level of a contaminant in water delivered to 

contaminant level any user of a public water system.

(MCL)
Glossary

Glossary (cont.)

G-12

molding water for natural soils, the degree of saturation of the soil liner at the time of 

content compaction; influences the engineering properties, such as hydraulic

conductivity, of the compacted material.

Monte Carlo analysis an iterative process involving the random selection of model parameter

values from specified frequency distributions, followed by simulation

of the system and output of predicted values. The distribution of the

output values can be used to determine the probability of occurrence

of any particular value given the uncertainty in the parameters. In this

guidance, used to predict a statistical distribution of exposures and

risks for a given site.

National Ambient Air airborne emission limits set by EPA as authorized by the Clean Air Act.

Quality Standards EPA has designated NAAQS for the following criteria pollutants: 

(NAAQS) ozone, sulfur dioxide, nitrogen dioxide, lead, particulate matter, and

carbon monoxide.

National Emission national standards regulating 188 hazardous air pollutants listed in

Standards for Section 112(b) of the Clean Air Act Amendments of 1990.

Hazardous Air 

Pollutants (NESHAP)

numeric clean-up a state corrective action requirement mandating that a site be cleaned 

standard up such that concentrations of a waste constituent do not exceed a set

level.

operating plan a document that specifies methods of running a waste management

unit, such as standard waste-handling practices, management and

maintenance activities, employee training, and emergency plans; based

on comprehensive knowledge of the chemical and physical composition of the waste managed, unit type, operational schedules, and monitoring performed at the unit.

overland flow land application of liquid waste by irrigation methods; can lead to 

(“flood”) application increased surface runoff of waste if not properly managed and, therefore, is regulated by some states and localities.

parametric analysis a method of statistical analysis that attempts to determine whether 

of variance (ANOVA) different monitoring wells have significantly different average constituent concentrations.

particulate matter a mixture of solid particles and liquid droplets suspended in the 

(PM) atmosphere that can cause a variety of respiratory problems, carry

adsorbed pollutants far from their source, impair visibility, and stain or

damage surfaces, such as buildings or clothes, on which it settles.
Glossary

Glossary (cont.)

G-13

passive gas control a gas control system using natural pressure and convection 

system mechanisms to control gas migration and to help vent gas emissions

into the atmosphere; can include ditches; trenches; vent walls; perforated pipes surrounded by coarse soil; synthetic membranes; and high

moisture, fine-grained soil.

pathogens potentially disease-causing microorganisms, such as bacteria, viruses,

protozoa, and the eggs of parasitic worms.

peak flow period the phase of a storm event when flood waters are at their highest level.

pH A measure of acidity or alkalinity equal to the logarithm of the reciprocal of hydrogen ion (H+) concentration in a medium. pH is represented on a scale of 0 to 14; 7 represents a neutral state, 0 represents the

most acid, and 14 the most alkaline.

pH adjustment the neutralization of acids and bases (alkaline substances) and promotion of the formation of precipitates, which can subsequently be

removed by conventional settling techniques.

piezometer a well installed to monitor hydraulic head of ground water or to monitor ground-water quality.

pilot-scale a small study to evaluate the effectiveness of and determine the 

treatability study potential for continued development of one or more potential remedies; typically conducted to generate information on quantitative performance, cost, and design issues.

plasticity parameters describing a material’s ability to behave as a moldable 

characteristics material.

plume an elongated and mobile column or band of a contaminant moving

through the subsurface.

point of monitoring the location(s) where ground-water is sampled; should be appropriate

for site conditions and located at waste management boundary or out

to 150 meters downgradient of the waste management unit area.

post-closure care monitoring of a closed waste management unit to verify and document

that unacceptable releases from the unit are not occurring. The overall

goal is to ensure that waste constituents are contained until such time

as containment is no longer necessary.
Glossary

Glossary (cont.)

G-14

prediction intervals a statistical method of approximating future sample values from a population or distribution with a specific probability; used with groundwater monitoring data, both for comparison of downgradient wells to

upgradient wells (interwell comparison) and for comparison of current

well data to previous data for the same well (intrawell comparison).

process knowledge an understanding of industrial processes used to predict the types of

waste generated and to determine the mechanism by which they are

generated.

protection layer a stratum in a final cover system that protects the drainage layer from

intrusion by plant roots or burrowing animals; located below the surface layer and above the drainage layer.

public involvement dialogue between facility owners and operators and public to share

information, identify and address issues and concerns, and provide

input into the decision-making process.

public notice a document, announcement, or information release that publicizes a

meeting, decision, operational change, or other information of interest

to the public; usually provides the name and address of the facility

owner and operator and information about the issue being publicized.

puncture resistance the degree to which a material, such a liner, will resist rupture by

jagged or angular materials which might be placed above or below it.

quality assurance in ground-water sampling, steps for collection and handling of 

and quality control ground-water samples to ensure accurate results. In liner construction, 

(QA/QC) procedures steps to ensure that liners are installed according to design and will

perform specifications.

rational method a method for calculating the volume of storm water runoff. The rational method approximates the surface water discharge from a watershed

using a runoff coefficient, the rainfall intensity, and the drainage area.

receptor a person or other organism that might be exposed to waste constituents, especially an organism whose exposure is addressed by a fate

and transport analysis; or, a downgradient ground-water monitoring

well that receives ground water which has passed near a waste management unit.

recycling the process of collecting, processing, and reusing waste materials.

redox (oxidation- the capacity of a medium to raise the valence state of molecules (such 

reduction) potential as metals), add oxygen, or remove hydrogen (oxidation); or to lower the

valence state of molecules, remove oxygen, or add hydrogen (reduction).
Glossary

Glossary (cont.)

G-15

riprap rock cover used to protect soil in dikes or channels from erosion.

risk-based corrective an approach to corrective action that integrates the components of

action (RBCA) traditional corrective action with alternative risk and exposure assessment practices. States and ASTM have developed RBCA as a three

stage process.

runoff storm water that flows from a waste management unit to surface waters.

run-on storm water that falls directly on a waste management unit or flows

toward the unit from adjoining areas.

saline soil soil with excessive salt concentrations.

sampling parameters for monitoring, those items for which ground water samples will be tested,

such as waste constituents reasonably expected to migrate to the ground

water and other geochemical indicators of contaminant migration.

seaming process the joining of panels or rolls of a liner using thermal, chemical, or

other methods compatible with the properties of the liner material.

seismic impact zone an area having a 10 percent or greater probability that the maximum

horizontal acceleration caused by an earthquake at the site will exceed

0.1g in 250 years. g is a unit of force equal to the force exerted by

gravity on a body at rest and used to indicate the force to which a

body is subjected when accelerated.

setback the placing of a waste management unit or one of its components

some distance from an adjoining property, a geologic feature, or other

feature that could affect the unit or be affected by the unit. (Compare

to buffer zone.)

shear strength for soils, the internal resistance per unit area that a soil mass can offer

to resist failure and sliding along any plane inside it; in liner design,

indicates the degree to which stability problems and desiccation cracks

are likely to occur in liner material (such as clay).

silt fence a barrier consisting of geotextile fabric supported by wooden posts;

slows the flow of water and retains sediment as water filters through

the geotextile.

slip for soils, to slide downhill in mass movements such as avalanches,

land slides, and rock slides; can be caused by inherent properties of

the soil or by cutting or filling of slopes during construction.
Glossary

Glossary (cont.)

G-16

slippage movement of a geomembrane liner due to a lack of adequate friction

between the liner and the soil subgrade or between any geosynthetic

components. 

sodic soil soil with excessive levels of sodium ions (Na+) relative to divalent ions,

such as calcium (Ca2+) and magnesium (Mg2+).

soil gas sampling collection of gas from soil pores to detect the presence or movement of

volatile contaminants and gases, such as carbon dioxide and methane,

that are associated with waste degradation.

soil-pore liquids fluids present in spaces between soil particles in the vadose zone; can

be collected to determine the type and concentration of contaminants

that might be moving within the vadose zone.

soil water content the ratio of the weight of water to the weight of solids in a given volume of soil; usually stated as a percentage and can be greater than 100

percent for very soft clays.

soil water tension a measure of the strength of capillary effects holding water between

soil particles; decreases as soil water content increases, so decreases in

soil water tension beneath a lined waste management unit might indicate the presence of leachate due to a leaking liner.

solidification the conversion of a non-solid waste into a solid, monolithic structure 

processes that ideally will not permit liquids to percolate into or leach materials

out of the mass; used to immobilize waste constituents.

soluble salts materials that could dissolve in or are already in solution in your

waste. Major soluble salts include calcium, magnesium, sodium, potassium, chloride, sulfate, bicarbonate, and nitrate.

Source Loading and an urban nonpoint source water quality model developed by the 

Management Model University of Alabama at Birmingham; useful for designing run-on and 

(SLAMM) runoff controls.

source reduction the prevention or reduction of waste at the point of generation.

spill prevention and procedures for avoiding accidental releases of waste or other 

response contaminants and promptly addressing any releases that occur.

stabilization process a means of immobilizing waste constituents by binding them into an

insoluble matrix or by changing them to insoluble forms.
Glossary

Glossary (cont.)

G-17

standard operating established, defined practices for the operation of a waste management 

procedures unit; useful in maintaining unit safety and protection of human health

and the environment; should be recorded in an operating plan to facilitate employees’ familiarity.

storm water pipes, ditches, swales, and other structures or landforms that carry, 

conveyances divert, or direct run-on and/or runoff.

Storm Water EPA computer model capable of simulating the movement of 

Management Model precipitation and pollutants from the surface through pipe and 

(SWMM) channel networks, storage treatment units, and finally to surface water;

used in the design of run-on and runoff controls.

stratigraphy characterization of the origin, distribution, and succession of geologic

strata, such as soil and rock layers.

subsidence lowering of the land surface due to factors such as excessive soil loading, compaction of soil owing to high moisture content, or reduction

in waste volume due to degradation; can significantly impair the

integrity of the final cover system by causing ponding of water on the

surface, fracturing of low permeability infiltration layers, and failure of

geomembranes.

sump a low point in a liner system constructed to gravitationally collect

leachate from either the primary or secondary leachate collection system.

surface completion the part of a ground-water monitoring well constructed at or just

above ground level, often consisting of a protective outer casing

around the inner well casing, fitted with a locking cap; discourages

vandalism and unauthorized entry into the well, prevents damage by

contact with vehicles, reduces degradation caused by direct exposure

to sunlight, and prevents surface runoff from entering and infiltrating

the well.

surface a natural or manmade topographic depression, excavation, or diked 

impoundment area designed to hold liquid waste.

surface layer in a final cover system, a stratum that promotes the growth of native,

nonwoody plant species, minimizes erosion, restores the aesthetics of

the site, and protects the barrier layer.

surface seal neat cement or concrete surrounding a ground-water monitoring well

casing and filling the space between the casing and the borehole at the

surface; protects against infiltration of surface water and potential contaminants from the ground surface.
Glossary

Glossary (cont.)

G-18

synthetic organic man-made carbon compounds used in a variety of industrial and 

molecules agricultural processes, sometimes hazardous, and unlike biodegradable

organic matter, not necessarily biodegradable, or if biodegradable, not

necessarily broken down into nonhazardous byproducts.

Synthetic The SPLP is currently used by several state agencies to evaluate the 

Precipitation leaching of TC hazardous constituents from wastes and can be used to 

Leaching Procedure assess the risks posed by wastes placed in a landfill and subject to acid 

(SPLP) rain. The SPLP is designed to determine the mobility of both organic

and inorganic analytes present in liquids, soils, and wastes.

tear resistance the ability of a material, such as a geomembrane, to resist being split

due to stresses at installation, high winds, or handling.

tensile behavior the tendency of a material to elongate under strain.

tensiometer an instrument that measures soil water tension.

terraces and benches earthen embankments with flat tops or ridges and channels; used to

hold moisture and minimize sediment loadings in runoff.

test pad in liner design, a small-scale replica of a liner system used to verify

that the materials and methods tested will yield a liner that provides

the desired hydraulic conductivity.

thermal seaming the use of heat to join panels or rolls of a liner.

Title V operating established by the Clean Air Act, these permits are required for any 

permits facility emitting or having the potential to emit more than 100 tons per

year of any air pollutants, as defined by Section 302(g) of the Clean

Air Act. Permits are also required for all sources subject to MACT or

NSPS standards.

toe the lower endpoint of a slope.

tolerance interval a statistical interval constructed from data designed to contain a portion of a population, such as 95 percent of all sample measurements;

used to compare data from a downgradient well to data from an

upgradient well.

topography the physical features (configuration) of a surface area including relative

elevations and the position of natural and constructed features.

total dissolved solids the sum of all ions in solution.

(TDS)
Glossary

Glossary (cont.)

G-19

total solids content the sum of suspended and dissolved solids in a liquid waste, usually

expressed as a percentage.

Toxicity The TCLP is most commonly used by EPA and state agencies to 

Characteristic evaluate the leaching potential of wastes, and to determine toxicity. 

Leaching Procedure The TCLP quantifies the extractability of certain hazardous 

(TCLP) constituents from solid waste under a defined set of laboratory conditions. It evaluates the leaching of metals, volatile and semi-volatile

organic compounds, and pesticides from wastes.

ultraviolet resistance the degree to which a material, such as a geomembrane, can resist degradation and cracking from prolonged exposure to ultraviolet radiation.

unstable area a location susceptible to human-caused or natural events or forces,

such as earthquakes, capable of impairing the integrity of a waste management unit.

upgradient well a ground-water monitoring installation built to measure background

levels of contamination in ground water at an elevation before it

encounters a waste management unit.

upper explosive the maximum percentage of a gas by volume in the air that will permit 

limit an explosion. This level is 15 percent for methane; at higher percentages, non- explosive burning is still possible.

use restrictions stipulations describing appropriate and inappropriate future uses of a

closed site, in an effort to perpetuate the benefits of the remedial

action and ensure property use that is consistent with the applied

clean-up standard.

vadose zone the soil (or other strata) between the ground surface and the saturated

zone; depending on climate, soils, and geology, can be very shallow or

as deep as several hundred feet.

vegetative cover layer (see surface layer.)

volatile organic carbon compounds which tend to evaporate at low to moderate 

compounds (VOCs) temperatures due to their low vapor pressure.

waste pile a noncontainerized accumulation of solid, nonflowing waste that is

used for treatment or storage.
Glossary

waste reduction waste reduction practices include source reduction, recycling and reuse,

and treatment of waste constituents. Waste reduction minimizes the

amount of waste that needs to be disposed of in the first place, and limits the environmental impact of those wastes that actually are disposed.

water content (see soil water content.)

well casing in a ground-water monitoring well, the pipe or tube lowered into the

borehole as the outer wall of the well; supports the sides of the hole

and prevents water from entering or leaving the well other than by

normal ground-water flow.

well intake a perforated segment of a ground-water monitoring well designed to 

(well screen) allow ground water to flow freely into the well from an adjacent geological formation while minimizing or eliminating the entrance of finegrained materials such as clay or sand.

well purging procedures for removing stagnant water from a ground-water monitoring 

methods well and its filter pack before collecting a sample; employed to ensure

collection of samples that accurately represent current ground-water

quality.

wellhead protection the most easily contaminated zone surrounding a wellhead; officially 

area (WHPA) designated for protection in many jurisdictions to prevent public

drinking water sources from becoming contaminated.

wetlands areas, such as tidal zones, marshes, and bottomland forests, that are

inundated or saturated by surface or ground water at a frequency or

duration sufficient to support, and that under normal circumstances

do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.

working face the area of a waste management unit, especially a landfill, where waste

is currently being placed and compacted.

zoning local government classification of land into areas designated for different use categories, such as residential, commercial, industrial, or agricultural; used to protect public health and safety, maintain property

values, and manage development.

Glossary (cont.)

G-20