June 2002
Environmental Assessment for Proposed Effluent Guidelines

and Standards for the Construction and Development

Category

June 2002

United States Environmental Protection Agency

Office of Water (4303T)

1200 Pennsylvania Avenue, NW

Washington, DC 20460

www.epa.gov/waterscience/guide/

[EPA-821-R-02-009]
Acknowledgments and Disclaimer

The Construction and Development Effluent Guidelines proposed rule and support documents

were prepared by the C&D Project Team: Eric Strassler, Project Manager; Jesse Pritts, P.E.,

Engineer; George Denning, Economist; Karen Maher, Environmental Assessor; and Michael G.

Lee, Attorney. Technical support for this Environmental Assessment was provided by Tetra

Tech, Inc.

Neither the United States government nor any of its employees, contractors, subcontractors or

other employees makes any warranty, expressed or implied, or assumes any legal liability or

responsibility for any third party's use of, or the results of such use of, any information,

apparatus, product or process discussed in this report, or represents that its use by such a third

party would not infringe on privately owned rights. Mention of trade names or commercial

products does not constitute endorsement by EPA or recommendation for use.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 i

 Contents

Section 1 Introduction and Background

1.1 Introduction .......................................................... 1-1

1.2 Organization of Environmental Assessment ................................. 1-2

1.3 Review of Regulatory History Related to C&D Industries ...................... 1-3

1.3.1 Clean Water Act ................................................. 1-3

1.3.1.1 NPDES Storm Water Permit Program .......................... 1-3

1.3.2 Other State and Local Government Storm Water Requirements ............ 1-4

Section 2 Categories of Reported Impacts and Pollutants

2.1 Introduction .......................................................... 2-1

2.2 Pollutants Associated with Construction and Land Development 

Storm Water Runoff .................................................... 2-2

2.2.1 Sediment ...................................................... 2-2

2.2.1.1 Sources of Sediment ....................................... 2-2

2.2.1.2 Receiving Waters Impacts ................................... 2-5

2.2.2 Metals ........................................................ 2-7

2.2.2.1 Sources of Metal Runoff .................................... 2-8

2.2.2.2 Metals Impacts on Receiving Waters .......................... 2-10

2.2.3 PAHs, and Oil and Grease ........................................ 2-11

2.2.3.1 Sources of PAHs, and Oil and Grease ........................ 2-11

2.2.3.2 Receiving Water Impacts ................................... 2-12

2.2.4 Pathogens .................................................... 2-13

2.2.4.1 Sources of Pathogens ...................................... 2-13

2.2.4.2 Receiving Water Impacts .................................. 2-15

2.3 Physical Impacts of Construction and Land Development Activities ............. 2-16

2.3.1 Hydrologic Impacts ............................................. 2-18

2.3.1.1 Increased Runoff Volume .................................. 2-19

2.3.1.2 Increased Flood Peaks ..................................... 2-22

2.3.1.3 Increased Frequency and Volume of Bankfull Flows ............. 2-22

2.3.1.4 Changes in Baseflow ...................................... 2-22

2.3.2 Impacts on Geomorphology/Sediment Transport ...................... 2-23

2.3.2.1 Increased Transport of Sediment ............................. 2-23

2.3.2.2 Decreased Sediment Transport .............................. 2-25

2.3.2.3 Increase in Size of Channel ................................. 2-26

2.3.3 Changes in Habitat Structure ...................................... 2-27

2.3.3.1 Embeddedness ........................................... 2-27

2.3.3.2 Large Woody Debris (LWD) ................................ 2-28
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 ii

2.3.3.3 Changes in Stream Features ................................. 2-29

2.3.4 Thermal Impacts ............................................... 2-29

2.3.5 Direct Channel Impacts .......................................... 2-30

2.3.5.1 Channel Straightening and Hardening/Reduction in 

First Order Streams ............................................. 2-30

2.3.5.2 Fish Blockages ........................................... 2-30

2.3.6 Site Differences in Physical Impacts ................................ 2-30

Section 3 Description of Assessment Methodology

3.1 Introduction .......................................................... 3-1

3.2 Methodology to Estimate Pollutant Loadings from Construction Runoff 

Water Discharges ...................................................... 3-1

3.3 Characterizing the Nation’s Stream Network ................................ 3-4

3.3.1 Characterizing the Stream Network within Developing Acreage ........... 3-9

3.3.2 Characterizing the Flow Conditions in Stream Network ................. 3-12

3.3.3 Converting Stream Miles into Impact Estimates ....................... 3-14

Section 4 Environmental Benefits Assessment of Evaluated Regulatory Options

4.1 Total Suspended Solids Loadings ......................................... 4-1

4.2 Total Suspended Solid In-Stream Concentrations ............................. 4-3

4.3 Miscellaneous Impacts .................................................. 4-4

Section 5 References ....................................................... 5-1

Appendices

A. Evaluating Pollutant Loadings from Construction Activities that Potentially Impact 

the Environment ...................................................... A-1

B. Inventorying of Streams Potentially Impacted by Construction Activities .......... B-1

C. Impacts of Construction Activity on Hydrology .............................. C-1

Tables

Table 1-1. Regulatory Options Evaluated for Controlling Discharges from 

Construction Activities ........................................... 1-2

Table 2-1. Studies of Soil Erosion as TSS From Construction Sites ................. 2-3

Table 2-2. Sources of Sediment in Urban Areas ................................. 2-4

Table 2-3. Source Area Concentrations for TSS in Urban Areas .................... 2-4
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 iii

Table 2-4. Sediment Impacts on Receiving Waters .............................. 2-6

Table 2-5. Metal Sources and Hot Spots in Urban Areas .......................... 2-9

Table 2-6. Metal Source Area Concentrations in Urban Areas .................... 2-10

Table 2-7. Metals Impacts on Receiving Waters ................................ 2-11

Table 2-8. Effects of PAHs and Oil and Grease on Receiving Waters ............... 2-13

Table 2-9. Percentage Detection of Giardia Cysts and Cryptosporidium Oocysts

in Subwatersheds and Wastewater Treatment Plant Effluent in the 

New York City Water Supply Watersheds ........................... 2-15

Table 2-10. Effects of Bacteria on Receiving Waters ............................. 2-16

Table 2-11. Physical Impacts on Streams ...................................... 2-17

Table 2-12. Hydrologic Differences Between a Parking Lot and a Meadow ........... 2-20

Table 2-13. Comparison of Bulk Density for Undisturbed Soils and Common 

Urban Conditions .............................................. 2-21

Table 3-1. Common Construction Erosion and Sediment Control BMPs ............. 3-2

Table 3-2. Site BMPs Evaluated by EPA for Effluent Guidelines Development ........ 3-3

Table 3-3. Results of the National Stream Survey ............................... 3-6

Table 3-4. Land Development Annually in Ecoregions ......................... 3-11

Table 3-5. Characterization of Stream Orders for Ecoregions ..................... 3-13

Table 3-6. Characterization of Stream Length by Flow Type for Ecoregions ......... 3-14

Table 3-7. Estimated Miles of Streams Potentially Affected by One Year’s 

Construction ................................................... 3-16

Table 3-8. Active Construction Site Runoff Scenarios for Option 1 and Option 2 ..... 3-18

Table 3-9. Runoff Coefficients for Land Uses ................................. 3-18

Table 3-10. Runoff EMCs for Acres Within a Watershed ......................... 3-20

Table 4-1. Regulatory Options Evaluated for Controlling Discharges from 

Construction Activities ........................................... 4-1

Table 4-2. Estimated TSS Loadings Reductions for Proposed Regulatory Options ...... 4-2

Table 4-3. Development Scenarios Used to Estimate Impacts of Regulatory Options .... 4-3

Table 4-4. Estimated Average In-Stream TSS Concentrations Reduction ............. 4-4

Figures

Figure 2-1. Ultimate Channel Enlargement .................................... 2-18

Figure 2-2. Altered Hydrograph in Response to Urbanization ..................... 2-19

Figure 2-3. Runoff Coefficient Versus Impervious Cover ........................ 2-20

Figure 2-4. Baseflow in Response to Urbanization: Nassau County, NY ............. 2-23

Figure 2-5. Increased Shear Stress from an Urban Hydrograph .................... 2-24

Figure 2-6. Sediment Production from Construction Sites ........................ 2-25

Figure 2-7. Drainage Network of Rock Creek, Maryland, Before and 

After Urbanization. ............................................. 2-26
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 iv

Figure 2-8. Channel Enlargement in Watts Branch, Maryland ..................... 2-27

Figure 2-9. Large Woody Debris as a Function of Watershed Imperviousness ........ 2-28

Figure 2-10. Stream Temperature Increase in Response to Urbanization .............. 2-29

Figure 3-1. Ecoregions for Stream Inventorying ................................. 3-5

Figure 3-2. Land Use Distribution of a Watershed ............................... 3-15
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

1. The term impact is used to denote negative conditions related to elevated concentrations of pollutants,

physical destruction or alteration of habitat by excessive flows, elevation of water temperature, and loss

of fish spawning access due to new road crossings

June 2002 1-1

Section 1 Introduction and Background 

1.1 Introduction

The U.S. Environmental Protection Agency (EPA) is proposing national effluent limitation

guidelines for the construction and development (C&D) category. By establishing national

standards, EPA intends to reduce the environmental impacts of construction site storm water

discharges. This environmental assessment has been prepared to support the proposed rule by

identifying and estimating the environmental benefits of implementing the proposal.

For purposes of the environmental assessment, construction is defined as the process by which

land is converted from one land use to another. Hence, construction impacts are a result of how

the land is converted, not a result of what the land becomes.1 Land development is defined in this

document as the conversion of land from a pre-development condition such as rural land use to a

post-development condition such as urban land use. The impacts from the land development

industry originate from the post-development condition (what the land use becomes), which

causes adverse environmental effects that were not present in the pre-development condition.

Adverse environmental impacts attributable to the C&D industries have been well documented

and include (but are not limited to) alteration of stream flow patterns, change in river channels,

and reduction in the water quality of receiving waters as a result of increased generation and

transport of sediment. Aquatic habitats also can be damaged as a result of reduced water quality

and altered hydrology. These environmental impacts can in turn cause additional environmental

and economic damage by increasing the frequency and magnitude of flooding events in

vulnerable areas. 

The purpose of this document is to describe the methods used to evaluate and quantify such

impacts as they occur under the current regulatory framework and might occur under the

proposed effluent guidelines. This report also presents estimates of the environmental benefits

that would accrue from implementation of the proposed technology controls. As discussed later

in the document, however, the environmental assessment and the associated Economic Analysis

of the proposed rule (EPA, 2002) only partially capture the full range of potential benefits that

would derive from implementing the proposed regulations. Not all categories of environmental

impacts from C&D activities can be quantified and therefore some are not amenable to

monetization procedures. These additional categories of environmental benefits are evaluated in

only a qualitative manner.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 1-2

The environmental assessment evaluates construction impacts for each of the three regulatory

options considered in the proposal. As shown in Table 1-1, these options range from no new

regulatory requirements (Option 3) to requirements for inspections and certifications of erosion

and sediment controls and implementation of new storm water pollution prevention plans for

certain sized sites.

Table 1-1. Regulatory Options Evaluated for Controlling Discharges

from Construction Activities

Option Description

Option 1 • Applicable to construction sites with one acre or more of disturbed land

• Operators required to:

- Inspect site throughout land disturbance period

- Certify that the controls meet the regulatory design criteria as

applicable

• Amend NPDES regulations at 40 CFR Part 122 (no new effluent

guideline regulations)

Option 2 • Applicable to construction sites with five acres or more of disturbed land

• Operators required to:

- Prepare storm water pollution prevention plan

- Design, install, and maintain erosion and sediment controls

- Inspect site throughout land disturbance period

- Certify that the controls meet the regulatory design criteria as

applicable

• Creates a new effluent guidelines category at 40 CFR Part 450 and

amends Part 122 regulations

Option 3 • No new regulatory requirements

The assessment, where appropriate, estimates reductions in environmental impacts attributable to

EPA’s proposed rule. To help the reader understand the estimated changes under the regulatory

proposal, the document also summarizes the regulatory framework currently in place.

1.2 Organization of Environmental Assessment

This document first provides background information on the current regulatory framework and

summarizes how the proposed regulation would alter this framework. Section 2 provides

additional background information on how the C&D industries affect the environment through

generation of pollutants in storm water runoff and alteration of hydrology. A detailed discussion

of the methodology used to estimate environmental impacts from the C&D industries is provided

in Section 3. Section 4 presents EPA’s estimates of environmental impacts of construction
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 1-3

activities under baseline conditions and under the various regulatory options evaluated for the

proposed rule. Section 5 provides the references used in the analysis. The appendices are

provided primarily for readers who seek further detail about how the methodology was

developed.

1.3 Review of Regulatory History Related to C&D Category

This subsection describes the federal and state regulations designed to control storm water

discharges from the C&D industries. It describes the regulatory framework that is currently in

place.

1.3.1 Clean Water Act

Congress adopted the Clean Water Act (CWA) to “restore and maintain the chemical, physical,

and biological integrity of the Nation’s waters” (Section 101(a), 33 U.S.C. 1251(a)). To achieve

this goal, the CWA prohibits the discharge of pollutants into navigable waters except in

compliance with the statute. CWA section 402 requires "point source" discharges to obtain a

permit under the National Pollutant Discharge Elimination System (NPDES). These permits are

issued by EPA regional offices or authorized State agencies.

Following enactment of the Federal Water Pollution Control Amendments of 1972 (Public Law

92-500, October 18, 1972), EPA and the States issued NPDES permits to thousands of

dischargers, both industrial (e.g. manufacturing, energy and mining facilities) and municipal

(sewage treatment plants). In accordance with the Act, EPA promulgated effluent limitation

guidelines and standards for many industrial categories, and these requirements are incorporated

into the permits.

The Water Quality Act of 1987 (Public Law 100-4, February 4, 1987) amended the CWA. The

NPDES program was expanded by defining municipal and industrial storm water discharges as

point sources. Industrial storm water dischargers, municipal separate storm sewer systems and

other storm water dischargers designated by EPA must obtain NPDES permits pursuant to

section 402(p) (33 U.S.C. 1342(p)).

1.3.1.1 NPDES Storm Water Permit Program

EPA's initial storm water regulations, promulgated in 1990, identified construction as one of

several types of industrial activity requiring an NPDES permit. These "Phase I" storm water

regulations require operators of large construction sites to apply for permits (40 CFR

122.26(b)(14)(x)). A large-site construction activity is one that:

• will disturb five acres or greater; or 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 1-4

• will disturb less than five acres but is part of a larger common plan of development or sale

whose total land disturbing activities total five acres or greater (or is designated by the

NPDES permitting authority); and

• will discharge storm water runoff from the construction site through a municipal separate

storm sewer system (MS4) or otherwise to waters of the United States.

The Phase II storm water rule, promulgated in 1999, generally extends permit coverage to sites

one acre or greater (40 CFR 122.26(b)(15)).

In addition to requiring permits for construction site discharges, the NPDES regulations require

permits for certain MS4s. The local governments responsible for the MS4s must operate a storm

water management program. The local programs regulate a variety of business activities that

affect storm water runoff, including construction.

1.3.2 Other State and Local Government Storm Water Requirements

States and municipalities may have other requirements for flood control, erosion and sediment

(E&S) control, and in many cases, storm water quality. Many of these provisions were enacted

before the promulgation of the EPA Phase I storm water rule. All states have laws for E&S

control, and these are often implemented by MS4s. A summary of existing state and local

requirements is provided in the Development Document (EPA, 2002a). Key control measures

used by states and municipal/regional authorities in these programs include:

• Storm water controls designed for peak discharge control

• Storm water controls designed for water quality control

• Storm water controls designed for flood control

• Specified depths of runoff for water quality control

• Percent reduction of loadings for water quality control (primarily solids and sediments)

• Numeric effluent limits for water quality control (primarily total suspended sediments,

settleable solids, or turbidity)

• Control measures for biological or habitat protection

• Control measures for physical in-stream condition controls (primarily streambed and stream

bank erosion).

Control measures used to reduce pollutants entering water bodies are commonly required during

the construction (land disturbance) phase. Post-construction requirements for pollutant

reductions are generally broader and more stringent. Typically, water quantity control measures

for peak discharges and runoff volume controls that apply to post-development conditions are not

required during the construction phase. 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-1

Section 2 Categories of Reported Impacts and Pollutants

2.1 Introduction

Construction and land development activities can generate a broad range of environmental

impacts by introducing new sources of contamination and by altering the physical characteristics

of the affected land area. In particular, these activities can result in both short- and long-term

adverse impacts on surface water quality in streams, rivers, and lakes in the affected watershed

by increasing the loads of various pollutants in receiving water bodies, including sediments,

metals, organic compounds, pathogens, and nutrients. Groundwater also can be adversely

affected through diminished recharge capacity. Other potential impacts include the physical

alteration of existing streams and rivers due to the excessive flow and velocity of storm water

runoff.

Construction activities typically involve excavating and clearing existing vegetation. During the

construction period, the affected land is usually denuded and the soil compacted, leading to

increased storm water runoff and high rates of erosion. If the denuded and exposed areas contain

hazardous contaminants, they can be carried at increased rates to surrounding water bodies by

storm water runoff. Although the denuded construction site is only a temporary state (usually

lasting less than 6 months), the landscape is permanently altered even after the land has been

restored by replanting vegetation. For example, a completed construction site typically has a

greater proportion of impervious surface than the predevelopment site, leading to changes in the

volume and velocity of storm water runoff. Changes in land use might also lead to new sources

of pollution, such as oils and metals from motor vehicles, nutrients and pesticides from landscape

maintenance, and pathogens from improperly installed or failing septic tanks. Increased

pollutant loads are particularly evident when land development takes place in previously

undeveloped environments. Together the short-term impacts from construction activities and the

long-term impacts of development can profoundly change the environment. 

The following subsections describe how pollutants associated with construction activities and

land development storm water discharges can adversely affect the environment. Potential effects

include impairment of water quality, destruction of aquatic life habitats, and enlargement of

flood plains. To the extent possible, this analysis distinguishes between environmental impacts

generated during construction and environmental impacts from post-development activities. 

Although in most cases the differences are in magnitude and duration (e.g., sediment runoff),

environmental impairment from such contaminants as pathogens are more likely to be associated

with the overall urbanization of a watershed than with the types of activities that take place

during construction. The discussion of environmental impacts first evaluates the impacts of

contaminated runoff and then focuses on the physical impacts of construction and land

development.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-2

2.2 Pollutants Associated With Construction and Land Development Storm Water

Runoff

This subsection describes pollutants associated with construction and land development storm

water runoff. The description does not represent the complete suite of contaminants that can be

found in the runoff but focuses instead on those that are the most prevalent and of greatest

concern to the environment. These pollutants include sediment, metals, poly-aromatic

hydrocarbons (PAHs), oil, grease, and pathogens.

2.2.1 Sediment

Sediment is an important and ubiquitous constituent in urban storm water runoff. Surface runoff

and raindrops detach soil from the land surface, resulting in sediment transport into streams. 

Sediment can be divided into three distinct subgroups: suspended solids, turbidity, and dissolved

solids. 

Total suspended solids (TSS) are a measure of the suspended material in water. The

measurement of TSS in urban storm water allows for estimation of sediment transport, which can

have significant effects locally and in downstream receiving waters. 

Turbidity is a function of the suspended solids and is a measure of the ability of light to penetrate

the water. Turbidity can exhibit control over biological functions, such as the ability of

submerged aquatic vegetation to receive light and the ability of fish to breathe dissolved oxygen

through their gills. 

Total dissolved solids are a measure of the dissolved constituents in water and are a primary

indication of the purity of drinking water. 

2.2.1.1 Sources of Sediment 

Construction Sites

Erosion from construction sites can be a significant source of sediment pollution to nearby

streams. A number of studies have shown high concentrations of TSS in runoff from

construction sites, and results from these studies are summarized in Table 2-1. One study,

conducted in 1986, calculated that construction sites are responsible for an estimated export of 80

million tons of sediment into receiving waters each year (Goldman, 1986, cited in CWP, 2000). 

On a unit area basis, construction sites export sediment at 20 to 1,000 times the rate of other land

uses (CWP, 2000).
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-3

Table 2-1. Studies of Soil Erosion as TSS From Construction Sites

Site

Mean Inflow

TSS

Concentration

(mg/L)

Source

Seattle, Washington 17,500 Horner, Guerdy, and Kortenhoff, 1990

SR 204 3,502 Horner, Guerdy, and Kortenhoff, 1990

Mercer Island 1,087 Horner, Guerdy, and Kortenhoff, 1990

RT1 359 Schueler and Lugbill, 1990

RT2 4,623 Schueler and Lugbill, 1990

SB1 625 Schueler and Lugbill, 1990

SB2 415 Schueler and Lugbill, 1990

SB4 2,670 Schueler and Lugbill, 1990

Pennsylvania Test Basin 9,700 Jarrett, 1996

Georgia Model 1,500 – 4,500 Sturm and Kirby, 1991

Maryland Model 1,000 – 5,000 Barfield and Clar, 1985

Uncontrolled Construction Site Runoff

(MD)

4,200 York and Herb, 1978

Austin, Texas 600 Dartiguenave, EC Lille, and Maidment,

1997

Hamilton County, Ohio 2,950 Islam, Taphorn, and Utrata-Halcomb, 1998

Mean TSS (mg/L) 3,681 NA

Post-Development Conditions as a Source of Sediment 

Sediment sources in urban environments include bank erosion, overland flow, runoff from

exposed soils, atmospheric deposition, and dust (Table 2-2). Streets and parking lots accumulate

dirt and grime from the wearing of the street surface, exhaust particulates, “blown-on” soil and

organic matter, and atmospheric deposition. Lawn runoff primarily contains soil and organic

matter. Source area monitoring data from Bannerman (1993), Waschbusch (2000), and Steuer

(1997) are shown in Table 2-3. Hot spots were identified for the transport of sediment from the

urban land surface, and they include streets, parking lots, and lawns.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-4

Table 2-2. Sources of Sediment in Urban Areas

Source Area Loading

Bank erosion • Up to 75 percent in California and Texas studies

Overland flow • Lawns - average value of geometric means from 4 studies: 201 mg/L

Runoff from areas with exposed soils • Average value: 3,640 mg/L

Blown-on material and organic

matter 

• May account for as much as 35 to 50 percent in urban areas

Bannerman et al., 1993; Dartinguenave et al., 1997; Schueler, 1987; Steuer et al., 1997; Trimble, 1997;

Waschbusch et al., 2000;

Table 2-3. Source Area Concentrations for TSS in Urban Areas

Source Area TSS

(mg/L)a

TSS

(mg/L)b

TSS (mg/L)c

Monroe

Basin

Harper

Basin

Commercial parking lot 110 58 51

High-traffic street 226 232 65

Medium-traffic street 305 326 51

Low-traffic street 175 662 68 69

Commercial rooftop 24 15 18

Residential rooftop 36 27 15 17

Residential driveway 157 173 34

Residential lawn 262 397 59 122

a

 Steuer et al., 1997.

b Bannerman et al., 1993.

c Waschbusch et al., 2000.

Parking lots and streets are responsible not only for high concentrations of sediment but also for

high runoff volumes. Normally about 90 percent of the water that falls on pavement is converted

to surface runoff, whereas roughly 5 to15 percent of the water that falls on lawns is converted to

surface runoff (Schueler, 1987). The source load and management model (SLAMM; Pitt and

Voorhes, 1989) evaluates runoff volume and concentrations of pollutants from different urban
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-5

land uses and predicts loads to the stream. When used in the Wisconsin and Michigan

subwatersheds, the model estimated that parking lots and streets were responsible for more than

70 percent of the TSS delivered to the stream (Steuer, 1997; Waschbusch et al., 2000). Because

basin water quality measurements were taken at pipe outfalls, bank erosion was not accounted for

in the studies. 

Sediment load is due to erosion caused by an increased magnitude and frequency of flows

brought on by urbanization (Allen and Narramore, 1985; Booth, 1990; Hammer, 1972; Leopold,

1968). Stream bank studies by Dartinguenave et al. (1997) and Trimble (1997) determined that

stream banks are large contributors of sediment in urban streams. Trimble (1997) used direct

measurements of stream cross sections, sediment aggradation, and suspended sediment to

determine that roughly 66.7 percent of the sediment load in San Diego Creek was a result of bank

erosion. Dartiguenave et al. (1997) used a GIS- based model developed in Austin, Texas, to

determine the effects of stream channel erosion on sediment loads. By effectively modeling the

pollutant loads on the land surface and by monitoring the actual in-stream loads at U. S.

Geological Survey (USGS) gauging stations, they were able to determine that over 75 percent of

the sediment load came from the stream banks. 

2.2.1.2 Receiving Waters Impacts

Sediment transport and turbidity can affect habitat, water quality, temperature, and pollutant

transport, and can cause sedimentation in downstream receiving waters (Table 2-4). Suspended

sediment and its resulting turbidity can reduce light for submerged aquatic vegetation. In

addition, deposited sediment can cover and suffocate benthic organisms like clams and mussels,

cover habitat for substrate-oriented species in urban streams, and reduce storage in reservoirs. 

Pollutants such as hydrocarbons and metals tend to bind to sediment and are transported with

storm flow (Crunkilton et al., 1996; Novotny and Chesters, 1989). Increased turbidity also can

cause stream warming by reflecting radiant energy (Kundell and Rasmussen, 1995). 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-6

Table 2-4. Sediment Impacts on Receiving Waters

Resource

Affected Impacts of Sediment Indicator Source

Streams

Loss of sensitive species and a decrease in

fish and macroinvertebrate diversity

communities

GA loss of sensitive

species at 25 NTU

Kundell and

Rasmussen, 1995

Clogging of gills and loss of habitat Leopold, 1973

Decreased flow capacity in streams

Maryland decreased

flow capacity. Increased

overbank flows

Barrett and Molina,

1998

Interference with water quality processes.

Affects transport of contaminants

MacRae and Marsalek,

1992

Wetlands 

 Deposition of sediment

High accretion rates in a

tidal wetland as a result

of sediment transport in

an urbanized watershed

Pasternack, 1998

Loss of sensitive species: amphibians,

plants

Loss of amphibian

species Horner, 1996

Loss of seven

wetland/SAV plant

species since European

development

Hilgartner, 1986

Reservoirs

Turbidity results in increased costs of

treatment for drinking water

more abatement costs at

>5 NTU McCutcheon et al.,

1993

 Sedimentation results in decreased storage 

Beaches 

Turbidity reduces aesthetic value

Kundell and

Rasmussen, 1995 

 Sedimentation can result in increased

accretion rates in wetlands and change

plant community structure 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

Table 2-4. Sediment Impacts on Receiving Waters

Resource

Affected Impacts of Sediment Indicator Source

June 2002 2-7

Estuaries

Sedimentation Pasternack, 1998

Turbidity Livingston, 1996

Reduced light attenuation can lead to a loss

of submerged aquatic vegetation (SAV)

Schiff, 1996

Mackiernan et al., 1996

SAV losses due to

sediments and

eutrophication

Short and WyllieEcheverria, 1996

SAV losses in NE Orth and Moore, 1983

Essential habitat

requirements for SAV

include light

attenuation, dissolved

inorganic nitrogen,

phosphorus and

chlorophyl-a

Stevenson et al., 1993

Loss of seven

wetland/SAV plant

species since European

settlement

Hilgartner, 1986

2.2.2 Metals 

Many toxic metals can be found in urban storm water, although only metals such as zinc, copper,

lead, cadmium, and chromium are of concern because of their prevalence and potential for

environmental harm. These metals are generated by motor vehicle exhaust, the weathering of

buildings, the burning of fossil fuels, atmospheric deposition, and other common urban activities.

Metals can bioaccumulate in stream environments, resulting in plant growth inhibition and

adverse health effects on bottom-dwelling organisms (Masterson and Bannerman, 1995).

Generally the concentrations found in urban storm water are not high enough for acute toxicity

(Field and Pitt, 1990). Rather, it is the cumulative effect of the concentration of these metals

over time and the buildup in the sediment and animal tissue that are of greater concern. 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-8

2.2.2.1 Sources of Metal Runoff

Construction Sites

Construction sites are not thought to be important sources of metal contamination. Runoff from

such sites could have high metals contents if the soil is already contaminated. Construction

activities alone do not result in metal contamination.

Post-Development Conditions as a Source of Metals 

Post-development conditions create significant sources of metal runoff in the urban environment,

including streets, parking lots, and rooftops. Table 2-5 summarizes the major sources of metal

runoff by metal type. Copper can be found in high concentrations on urban streets as a result of

the wear of brake pads that contain copper. A study in Santa Clara, California, estimated that 50

percent of the copper released is from brake pads (Woodward-Clyde, 1992). Sources of lead

include atmospheric deposition and diesel fuel, which are found consistently on streets and

rooftops. Zinc in urban environments is a result of the wear of automobile tires (an estimated 60

percent of the total zinc in the Santa Clara study), paints, and the weathering of galvanized

gutters and downspouts. Source area concentrations estimated by researchers in Wisconsin and

Michigan are presented in Table 2-6. Actual concentrations vary considerably, and highconcentration source areas vary from study to study. A study using SLAMM for an urban

watershed in Michigan estimated that most of the zinc, copper, and cadmium was a result of

runoff from urban parking lots, driveways, and residential streets (Steuer, 1997).
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-9

Table 2-5. Metal Sources and Hot Spots in Urban Areas

Metal Sources Hot Spots

Zinc Tires, fuel combustion, galvanized pipes and

gutters, road salts 

Estimate of 60% from tiresa

Parking lots, rooftops, and

streets

Copper Auto brake linings, pipes and fittings,

algacides, and electroplating 

Estimate of 50% from brake padsa

Parking lots, commercial

roofs, and streets

Lead Diesel fuel, paints, and stains Parking lots, rooftops, and

streets 

Cadmium Component of motor oil; corrodes from alloys

and plated surfaces

Parking lots, rooftops, and

streets

Chromium Found in exterior paints; corrodes from alloys

and plated surfaces

More frequently found in

industrial and commercial

runoff

a

 Woodward-Clyde, 1992 (Santa Clara, CA, study) 

Sources: Barr, 1997; Bannerman et al., 1993; Steuer, 1997
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-10

Table 2-6. Metal Source Area Concentrations in Urban Areas (in ug/L)

Source Area Diss.

Zinc

Total

Zinc

Diss.

Copper 

Diss.

Copper

Total

Copper 

Diss.

Lead

Diss.

Lead

Total

Lead

Total

Lead

Total

Lead

Citation (a) (b) (a) (b) (b) (a) (c) (a) (c) (b)

Commercial

parking lot 64 178 10.7 9 15 40 22

High-traffic

street

73 508 11.2 18 46 2.1 1.7 37 25 50

Mediumtraffic street 44 339 7.3 24 56 1.5 1.9 29 46 55

Low-traffic

street 

24 220 7.5 9 24 1.5 0.5 21 10 33

Commercial

rooftop 263 330 17.8 6 9 20 48 9

Residential

rooftop 188 149 6.6 10 15 4.4 25 21

Residential

driveway 27 107 11.8 9 17 2.3 52 17

Residential

lawn na 59 na 13 13 na na na

Basin outlet 23 203 7.0 5 16 2.4 49 32

na : not available

Sources: (a) Steuer 1997; (b) Bannerman 1993; (c) Waschbusch, 1996, cited in Steuer, 1997

2.2.2.2 Metals Impacts on Receiving Waters

Downstream effects of metal transported to receiving waters, such as lakes and estuaries, have

been studied extensively. Selected studies on metal impacts on receiving waters are summarized

in Table 2-7. Although evidence exists for the buildup of metals in deposited sediments in

receiving waters and for bioaccumulation in aquatic species (Bay et al., 2000; Livingston, 1996),

specific effects of these concentrations on submerged aquatic vegetation and other biota are not

well understood.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-11

Table 2-7. Metals Impacts on Receiving Waters

Resource

Affected Impacts of Metals Evidence

Streams

• Chronic toxicity due to in-stream concentrations

 and accumulation in sediment 

• Bioaccumulation in aquatic species 

• Acute toxicity at certain concentrations 

Chronic toxicity increased during longerduration studies, i.e., 7/14/21-day studies

(Crunkilton, 1996);

Delayed toxicity (Ellis, 1986/1987);

Baseflow toxicity (Mederios, 1983);

Resuspension of metals during storms

accounting for some toxicological effects

(Heaney and Huber, 1978);

Bioaccumulation in crayfish (Masterson &

Bannerman, 1994)

Reservoirs/

Lakes • Accumulation of metals in sediment 

Bioaccumulation levels in bottom-feeding

fish were found to be influenced by the metal

levels of the bottom sediments of storm water

ponds (Campbell, 1995).

Estuaries

• Accumulation of metals in sediment 

• Loss of SAV

Tampa Bay (Livingston, 1996);

San Diego (Schiff 1996);

SAV losses in northeast San Francisco Bay

(Orth and Moore, 1983)

2.2.3 PAHs, and Oil and Grease

Petroleum-based substances such as oil and grease and poly-aromatic hydrocarbons (PAHs) are

found frequently in urban storm water. Many constituents of PAHs and oil and grease, such as

pyrene and benzo[b]fluoranthene, are carcinogens and toxic to downstream biota (Menzie-Cura

and Assoc., 1995). Oil and grease and PAHs normally travel attached to sediment and organic

carbon. Downstream accumulation of these pollutants in the sediments of receiving waters such

as streams, lakes, and estuaries is of concern. 

2.2.3.1 Sources of PAHs, and Oil and Grease 

Construction Sites

Construction activities during site development are not believed to be major contributors of these

contaminants to storm water runoff. Improper operation and maintenance of construction

equipment at construction sites, as well as poor housekeeping practices (e.g., improper storage of

oil and gasoline products), could lead to leakage or spillage of products that contain

hydrocarbons, but these incidents would likely be small in magnitude and managed before offsite contamination could occur.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-12

Post-Development Conditions as a Source of PAHs, and Oil and Grease

In most storm water runoff, concentrations of PAHs and oil and grease are typically below 5

mg/L but concentrations tend to increase in commercial and industrial areas. Hot spots for these

pollutants in the urban environment include gas stations, commuter parking lots, convenience

stores, residential parking areas, and streets (Schueler, 1994). Schueler and Shepp (1993) found

concentrations of pollutants in oil/grit separators in the Washington Metropolitan area and

determined that gas stations had significantly higher concentrations of hydrocarbons and a

greater presence of toxic compounds than streets and residential parking lots. A study of source

areas in an urban watershed in Michigan (which excluded gas stations) showed that high

concentrations from commercial parking lots contributed 64 percent of the estimated

hydrocarbon loads (Steuer et al., 1997).

2.2.3.2 Receiving Water Impacts

Toxicological effects from PAHs and oil and grease are assumed to be reduced by their

attachment to sediment (lessened availability) and by photodegradation (Schueler, 1994). 

Evidence of possible impacts on the metabolic health of organisms exposed to PAHs and of

bioaccumulation in streams and other receiving waters does not exist (Masterson and

Bannerman, 1994; MacCoy and Black, 1998); however, crayfish from Lincoln Creek, analyzed

in the Masterson and Bannerman study, had a PAH concentration of 360 micrograms per

kilogram—much higher than the concentration known to be carcinogenic. The crayfish in the

control stream did not have detectable levels of PAHs. Known effects of PAHs on receiving

waters are summarized in Table 2-8. Long-term effects of PAHs in sediments of receiving

waters call for additional study.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-13

Table 2-8. Effects of PAHs and Oil and Grease on Receiving Waters

Resource

Affected Impacts of PAHs and Oil and Grease Citations

Streams

• Possible chronic toxicity due to in-stream

 concentrations and accumulation in sediment 

• Bioaccumulation in aquatic species 

• Acute toxicity at certain concentrations 

Bioaccumulation in crayfish tissue studies

(Masterson and Bannerman, 1994);

Potential metabolic costs to organisms

(Crunkilton et al., 1996);

delayed toxicity (Ellis, 1986/1987);

Baseflow toxicity (Mederios, 1983)

Reservoirs • Accumulation of PAHs in sediment 

Sediment contamination may result in a

decrease in benthic diversity and transfer of

PAHs to fish tissue (Schueler, 2000-CWP);

Elevated levels of PAHs found in pond

muck layer (Gavens et al., 1982)

Estuaries • Accumulation of PAHs in sediment 

• Potential loss of SAV

• Accumulation of PAHs in fish and shellfish

 tissue 

Tampa Bay (Livingston, 1996);

San Diego, San Francisco Bay (Schiff,

1996) 

2.2.4 Pathogens

Microbes, or living organisms undetectable by the naked eye, are commonly found in urban

storm water. Although not all microbes are harmful, several species such as the pathogens

Cryptosporidium and Giardia can directly cause diseases in humans (pathogens). The presence

of bacteria such as fecal coliform bacteria, fecal streptococci, and Escherichia coli indicates a

potential health risk (indicators). High levels of these bacteria may result in beach closings,

restrictions on shellfish harvest, and increased treatment for drinking water to decrease the risk of

human health problems. 

2.2.4.1 Sources of Pathogens

Construction Sites

Construction site activities are not believed to be major contributors to pathogen contamination

of surface waters. The only potential known source of pathogens from construction sites are

portable septic tanks used by construction workers. These systems, however, are typically selfcontained and are not connected to the land surface. Any leaks from them would likely be

identified and addressed quickly.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-14

Post-Development Conditions as a Source of Pathogen Runoff 

Coliform sources include pets, humans, and wild animals. Source areas in the urban

environment for direct runoff include lawns, driveways, and streets. Dogs have high

concentrations of coliform bacteria in their feces and have a tendency to defecate in close

proximity to impervious surfaces (Schueler, 1999). Many wildlife species also have been found

to contribute to high fecal concentrations. Essentially, any species that is present in significant

numbers in a watershed is a potential pathogen source. Source identification studies, using

methods such as DNA fingerprinting, have attributed high coliform levels to such species as rats

in urban areas, ducks and geese in storm water ponds, dogs, and even raccoons (Blankenship,

1996; Lim and Oliveri, 1982; Pitt et al., 1988; Samadapour and Checkowitz, 1998). 

Indirect surface storm water runoff sources include leaking septic systems, illicit discharges,

sanitary sewer overflows (SSOs), and combined sewer overflows (CSOs). These sources have

the potential to deliver high concentrations of coliforms to receiving waters. Illicit connections

from businesses and homes to the storm drainage system can discharge sewage or washwater into

receiving waters. Leaking septic systems are estimated to constitute 10 to 40 percent of all

systems. Inspection is the best way to determine whether a system is failing (Schueler, 1999). 

There is also evidence that these bacteria can survive and reproduce in stream sediments and in

storm sewers. During a storm event, they are resuspended and add to the in-stream bacteria load. 

Source area studies reported that end-of-pipe concentrations were an order of magnitude higher

than any source area on the land surface; therefore, it is likely that the storm sewer system itself

acts as a source (Bannerman, 1993; Steuer et al., 1997). Resuspension of fecal coliform bacteria

from fine stream sediments during storm events has been reported in New Mexico (NMSWQB,

1999). The sediments in the storm sewer system and in streams may be significant contributors

to the fecal coliform load. This area of research certainly warrants more attention to determine

whether these sources can be quantified and remediated.

Giardia and Cryptosporidium in urban storm water are also a concern. There is evidence that

urban watersheds and storm events might have higher concentrations of Giardia and

Cryptosporidium than other surface waters (Stern, 1996). (See Table 2-9.) The primary sources

of these pathogens are humans and wildlife. Although Cryptosporidium is found in less than 50

percent of storm water samples, data suggest that high Cryptosporidium values may be a concern

for drinking water supplies. Both pathogens can cause serious gastrointestinal problems in

humans (Bagley et al., 1998). 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-15

Table 2-9. Percentage Detection of Giardia Cysts and Cryptosporidium Oocysts in

Subwatersheds and Wastewater Treatment Plant Effluent in the New York City

Water Supply Watersheds

Source Water Sampled 

(No. of sources/No. of samples) 

Percent Detection

Total

Giardia

Confirmed

Giardia

Total

Cryptosporidium

Confirmed

Cryptosporidium

Wastewater effluent (8/147) 41.5 12.9 15.7 5.4

Urban subwatershed (5/78) 41.0 6.4 37.2 3.9

Agricultural subwatershed (5/56) 30.4 3.6 32.1 3.6

Undisturbed subwatershed (5/73) 26.0 0.0 9.6 1.4

Source: Stern et al., 1996.

2.2.4.2 Receiving Water Impacts

Fecal coliform bacteria, fecal streptococci, and E. coli are consistently found in urban storm

water runoff. Their presence indicates that human or other animal waste is also present in the

water and that other harmful bacteria, viruses, or protozoans might be present as well. 

Concentrations of these indicator organisms in urban storm water are highly variable even within

a given monitoring site. Data for fecal coliform bacteria illustrate this variability: site

concentrations range from 10 to 500,000 most probable number per 100 milliliters

(MPN/100mL) (Schueler, 1999).

Concentrations in urban storm water typically far exceed the 200 MPN/100 mL threshold set for

human contact recreation. The mean concentration of fecal coliform bacteria in urban storm

water for 34 studies across the United States was 15,038 MPN/100mL (Schueler, 1999). 

Another national database of 1,600 samples (mostly Nationwide Urban Runoff Program data

collected in the 1980s), estimates the mean concentration at 20,000 MPN/100 mL (Pitt, 1998).

Fecal streptococci concentrations for 17 urban sites had a mean of 35,351 MPN/100 mL

(Schueler, 1999). Transport occurs primarily as a result of direct surface runoff, failing septic

systems, SSOs, CSOs, and illicit discharges. 

Human health can be affected by bacterial impacts on receiving waters when bacteria standards

for water contact recreation, shellfish consumption, or drinking water are violated. 

Epidemiological studies from Santa Monica Bay have documented frequent sickness in people

who swim near outfalls (SMBRP, 1996). Documented illnesses include fever, ear infections,

gastroenteritis, nausea, and flu-like symptoms. Table 2-10 describes the effects of bacteria and

protozoan problems on different receiving waters.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-16

Table 2-10. Effects of Bacteria on Receiving Waters

Resource

Affected Impacts of Bacteria Citations

Streams

• Human health issues More than 80,000 miles of streams and rivers

in non-attainment because of high fecal

coliform levels (USEPA, 1998a) 

Reservoirs • Contamination of water supply Increased treatment cost of drinking water due

to bacteria contamination (USEPA, 1996)

Beaches • Human health issues More than 4,000 beach closings or advisories 

(USEPA, 1998b)

Estuaries

• Closing of shellfish beds 

• Beach closings 

Nearly 4% of all shellfish beds restricted or

conditional harvest due to high bacteria levels 

(NOAA 1992);

More than 4,000 beach closings or advisories 

(USEPA, 1998b)

2.3 Physical Impacts of Construction and Land Development Activities

This subsection describes the physical impacts of construction activities and development

conditions, which include hydrologic, geomorphic, habitat structure, thermal, and direct channel

impacts. These impacts are most visible on the urban stream. Construction and land

development impacts on stream systems are described for each of these impact categories (Table

2-11). Site differences of these impacts are also noted. Because it is very difficult to

differentiate between physical impacts that occur during construction and impacts that result

from post-development conditions, the discussion addresses physical impacts from a broader

perspective. It does not differentiate between short-term effects arising and site construction

activities from long-term impacts of post-development conditions.

Physical changes are often precipitated by changes in hydrology that result when permeable rural

and forest land is converted to impervious surfaces like pavement and rooftops and relatively

impermeable urban soils. The conversion causes a fundamental change in the hydrologic cycle

because a greater fraction of rainfall is converted to surface runoff. This change in the basic

hydrologic cycle causes a series of other impacts (Table 2-11). The stream immediately begins

to adjust its size, through channel erosion, to accommodate larger flows. Streams normally

increase their cross-sectional area by incising, widening, or often both. This process of channel

response to increases in impervious surfaces accelerates sediment transport and destroys habitat.

In addition, urbanization frequently leads to alteration of natural stream channels, such as
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-17

straightening or lining with concrete or rock to transport water away from developed areas more

quickly. Finally, impervious surfaces also absorb heat, thereby increasing stream temperatures

during runoff events.

Table 2-11. Physical Impacts on Streams

Impact Class Specific Impacts Cause(s)

Hydrologic

• Increased runoff volume

• Increased peak flood flow

• Increased frequency of “bankfull” event

• Decreased baseflow

• Paving over natural surfaces

• Compaction of urban soils

Geomorphic • Sediment transport modified

• Channel area increase to accommodate

 larger flows

• Modified flows

• Channel modification

• Construction

Habitat

structure

• Stream embeddedness

• Loss of large woody debris

• Changes in pool/riffle structure

• Modified flows

• Stream channel erosion

• Loss of riparian area

Thermal • Increased summer temperatures • Heated pavement

• Storm water ponds

• Loss of riparian area

Channel

modification

• Channel hardening

• Fish blockages

• Loss of first and second order streams

 through storm drain enclosure

• Direct modifications to the stream

 system.

Figure 2-1 depicts the impacts of land development on the stream channel. At low levels of

imperviousness, the stream has a stable channel, contains large woody debris, and has a complex

habitat structure. As urbanization increases, the stream becomes increasingly unstable, increases

its cross-sectional area to accommodate increased flows, and loses habitat structure. In highly

urbanized areas, stream channels are often modified through channelization or channel

hardening. These physical changes are often accompanied by decreased water quality. 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-18

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

Imperviousness (%)

Enlargement Rati

o

Figure 2-1. Ultimate Channel Enlargement

(Claytor and Brown, 2000; MacRae and DeAndrea, 1999)

2.3.1 Hydrologic Impacts 

The increased runoff volume that results from land development alters the hydrograph, from its

predeveloped condition (Figure 2-2). The resulting hydrograph accommodates larger flows with

higher peak-flow rates. Because storm drain conveyance systems (e.g., curbs, gutters) improve

the efficiency with which water is delivered to the stream, the hydrograph is also characterized

by a more rapid time of concentration and peak discharge. Finally, the flow in the stream

between events can actually decrease because less rainfall percolates into the soil surface to feed

the stream as baseflow. The resulting hydrologic impacts include increased runoff volume,

increased flood peaks, increased frequency and magnitude of bankfull storms, and decreased

baseflow volumes.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-19

Figure 2-2. Altered Hydrograph in Response to Urbanization

(Schueler, 1987)

2.3.1.1 Increased Runoff Volume

Impervious surfaces and urban land use changes alter infiltration rates and increase runoff

volumes. Table 2-12 shows the difference in runoff volume between a meadow and a parking

lot. The parking lot produces approximately 15 times more runoff than a meadow for the same

storm event. Schueler (1987) demonstrated that runoff values increase significantly with the

impervious surfaces in a watershed (Figure 2-3). The increased volume of water from urban

areas is the greatest single cause of the negative impacts of urban storm water on receiving

waters. The volume causes channel erosion and loss of habitat stability, as well as an increase in

the total load of many pollutants such as sediment and nutrients.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-20

Table 2-12. Hydrologic Differences Between a

Parking Lot and a Meadow

Hydrologic or Water Quality

Parameter Parking Lot Meadow

Runoff coefficient 0.95 0.06

Time of concentration (minutes) 4.8 14.4

Peak discharge, 2-yr, 24-h storm (ft3

/s) 4.3 0.4

Peak discharge rate, 100-yr storm (ft3

/s) 12.6 3.1

Runoff volume from 1-in. storm (ft3

) 3,450 218

Runoff velocity @ 2-yr storm (ft/sec) 8 1.8

Key Assumptions: 2-yr, 24-hr storm = 3.1 in.; 100-yr storm = 8.9 in.

Parking Lot: 100% imperviousness; 3% slope; 200-ft flow length;

hydraulic radius = 0.03; concrete channel; suburban Washington ‘C’

values 

Meadow: 1% impervious; 3% slope; 200-ft flow length; good vegetative

condition; B soils; earthen channel 

Source: Schueler, 1987.

Figure 2-3. Runoff Coefficient Versus Impervious Cover

(Schueler, 1987).
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-21

Construction activities also cause fundamental modifications in native soils. The compaction of

urban soils and the removal of topsoil during construction decreases the infiltration capacity of

the soil, resulting in a corresponding increase in runoff (Schueler, 2000). The bulk density is a

measure of soil compaction, and Table 2-13 shows the values for different aspects of

urbanization. 

Table 2-13. Comparison of Bulk

Density for Undisturbed Soils and

Common Urban Conditions

Undisturbed Soil Type

or Urban Condition 

Surface Bulk Density

(grams/cubic

centimeter)

Peat 0.2 to 0.3 

Compost 1.0

Sandy Soils 1.1 to 1.3

Silty Sands 1.4

Silt 1.3 to 1.4

Silt Loams 1.2 to 1.5

Organic Silts/Clays 1.0 to 1.2 

Glacial Till 1.6 to 2.0

Urban Lawns 1.5 to 1.9

Crushed Rock Parking

Lot 

1.5 to 1.9

Urban Fill Soils 1.8 to 2.0

Athletic Fields 1.8 to 2.0

Rights of Way and

Building Pads (85%) 

1.5 to 1.8

Rights of Way and

Building Pads (95%)

1.6 to 2.1

Concrete Pavement 2.2

Note: Shading indicates “urban” conditions.

Source: Schueler, 2000.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-22

2.3.1.2 Increased Flood Peaks

Increased flow volume increases peak flows. Data from Sauer et al. (1983) suggest that peak

flow from large flood events (10-year to 100-year storm events) increases substantially with

urbanization. The paper presents results of a survey of urban watersheds throughout the United

States and predicts flood peaks based on watershed impervious cover and a “basin development

factor” that reflects watershed characteristics such as the amount of curb and gutter, and channel

modification. These data suggest that at 50 percent impervious cover, the peak flow for the 100-

year event can be as much as twice that in an equivalent rural watershed. Data from Seneca

Creek in Montgomery County, Maryland, suggest a similar trend. The watershed experienced

significant growth during the 1950s and 1960s. Comparison of gauge records from 1961 to 1990

to those from 1931 to 1960 suggests that the peak 10-year flow event increased from 7,300 to

16,000 cfs, an increase of more than 100 percent (Leopold, 1994).

2.3.1.3 Increased Frequency and Volume of Bankfull Flows

Stream channel morphology is more influenced by frequent (1- to 2-year) storm events, or

“bankfull” flows, than by large flood events. Hollis (1975) demonstrated that urbanization

increased the frequency and magnitude of these smaller-sized runoff events much more than the

larger events. Data from this study suggest that streams increase their 2-year bankfull discharge

by two to five times after development takes place. Many other studies have documented the

increase in flow associated with impervious cover. A study by Guay (1995) compared the 2-year

flows events before and after development in an urban watershed in Parris Valley, California, in

the 1970s and in the 1990s. The impervious level of 9 percent in the 1970s increased to 22.5

percent by the 1990s. The 2-year discharge more than doubled from 646 cfs to 1,348 cfs. A 13

percent change in impervious cover resulted in a doubling of the 2-year peak flow.

A significant impact of land development is the frequency with which the bankfull event occurs.

Leopold (1994) observed a dramatic increase in the frequency of the bankfull event in Watts

Branch, an urban subwatershed in Rockville, Maryland. This watershed also experienced

significant development between the 1950s and 1960s. A comparison of gauge records indicated

that the bankfull storm event frequency increased from two to seven times per year from 1958 to

1987. 

2.3.1.4 Changes in Baseflow

Land development results in a smaller recharge to groundwater and a corresponding decrease in

stream flow during dry periods (baseflow). Only a small amount of evidence, however,

documents this decrease in baseflow. Spinello and Simmons (1992) demonstrated that baseflow

in two urban Long Island streams went dry seasonally as a result of urbanization (Figure 2-4). 

Another study in North Carolina could not conclusively determine that urbanization reduced

baseflow in some streams in that area (Evett et al., 1994). It is important to note, however, that
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-23

groundwater flow paths are often complex. Water supplying baseflow feeding the stream can be

from deeper aquifers or can originate in areas outside the surface watershed boundary. In arid

and semiarid areas, watershed managers have reported that baseflow actually increases in urban

areas. Increased infiltration from people watering their lawns and return flow from sewage

treatment plants are two possible sources (Caraco, 2000). Recharge of clean groundwater is

important in these communities, and managers would rather see clean water infiltrated than

transported as surface water during storm events.

Figure 2-4. Baseflow in Response to Urbanization:

Nassau County, NY

(Spinello and Simmons, 1992)

2.3.2 Impacts on Geomorphology/Sediment Transport 

Changes in hydrology, combined with additional sediment sources from construction and

modifications to the stream channel, result in changes to the geomorphology of stream systems. 

These impacts include increased, and sometimes decreased, sediment transport and channel

enlargement to accommodate larger flows.

2.3.2.1 Increased Transport of Sediment

The increased frequency of bankfull (1- to 2-year) storms causes more “effective work” (as

defined by Leopold), causing greater sediment transport and bank erosion to take place within

the channel. For the same storm event, the increased volume results in a greater amount of total

stress above the critical shear stress required to move bank sediment (Figure 2-5). This effect is
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-24

compounded by the fact that smaller, more frequent storm events also cause flows in excess of

the stress required to move sediment.

Figure 2-5. Increased Shear Stress from an Urban Hydrograph

(Schueler, 1987)

The result of this change in effective work on stream banks is increased channel erosion. Studies

in California (Trimble, 1997) and Austin, Texas (Dartinguenave et al., 1997) suggest that 60 to

75 percent of the sediment transport in urban watersheds is from channel erosion as compared to

estimates of between 5 percent and 20 percent for rural streams (Collins et al., 1997; Walling and

Woodward, 1995). If the sediment is not deposited in the channel at obstructions, it is

transported downstream to receiving waters such as lakes, estuaries, or rivers. The result can be

reduced storage and habitat due to the filling of these water bodies.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-25

The clearing and grading of land for new construction at the outset of urbanization is another

source of sediment in urban streams. Figure 2-6 (from Leopold, 1968) illustrates the difference

in sediment from uncontrolled and controlled construction sites.

Figure 2-6. Sediment Production from Construction Sites

(Leopold, 1968)

2.3.2.2 Decreased Sediment Transport 

Decreased sediment transport off the land surface itself can result after urbanization as natural

drainage and first-order channels are replaced by storm drains and pipes (Figure 2-7). Channel

erosion downstream might result when any export of sediment is not replaced by diminished

upstream sediment supply. Ultimately, after significant erosion has taken place, the downstream

channel will have adjusted to its post-development flow regime and sediment transport will be

reduced. Hence, the stability of the land surface and the piping of drainage channels limit storm

water’s exposure to sediment and reduce the sediment supply.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-26

Figure 2-7. Drainage Network of Rock Creek, Maryland

Before and After Urbanization

(Dunne and Leopold, 1978)

2.3.2.3 Increase in Size of Channel 

Channels increase their cross-sectional area to respond to higher and more frequent urban flows. 

In post-development urban watersheds, the increase in frequency of this channel-forming event

normally causes sediment transport to be greater than sediment supply. The channel widens

(and/or downcuts) in response to this change in sediment equilibrium (Allen and Narramore,

1985; Booth, 1990 Hammer, 1977; Morisawa and LaFlure, 1979;). Some research suggests that

over time channels will reach an “ultimate enlargement,” relative to a predeveloped condition,

and that impervious cover can predict this enlargement ratio (MacRae and DeAndrea, 1999). 

This was shown in Figure 2-3, which depicted the relationship between ultimate stream channel

enlargement and impervious cover for alluvial streams, based on data from Texas, Vermont, and

Maryland. Figure 2-8 shows the channel expansion that has taken place and is projected to occur

in Watts Branch near Rockville, Maryland, in response to urbanization.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-27

0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30 35 40 45

C ross S ection S tations (ft) - Looking D ow nstream

E levation (ft-m sl)

Historic Section

Current Section

Bankfull Depth

Ultimate Section ?

Historic cross-section

Current cross-section

 Ultim ate cross-section ?

Figure 2-8. Channel Enlargement in Watts Branch, Maryland (Schueler, 1987) 

Note: Cross sections have been overlaid for illustration purposes only. Actual sections do not share the same datum. 

Stream channels expand by incision, widening, or both. Incision occurs when the stream downcuts and the channel expands in the vertical direction. Widening occurs when the sides of the

channel erode and the channel expands horizontally. Either method results in increased transport

of sediment downstream and degradation of habitat. Channel incision is often limited by grade

control from bedrock, large substrate, bridges, or culverts. These structures impede the

downward erosion of the stream channel and limit incision. In substrates such as sand, gravel,

and clay, however, stream incision can be of greater concern (Booth, 1990). 

Channel widening more frequently occurs when streams have grade control and the stream cuts

into its banks to expand its cross-sectional area. Urban channels frequently have artificial grade

control due to the frequent culverts and road crossings. These are often areas where sediment

can accumulate as a result of undersized culverts and bridge crossings.

2.3.3 Changes in Habitat Structure

Land development results in many changes in habitat structure, including embeddedness,

decreased riffle/pool quality, and loss of large woody debris (LWD). Increased sedimentation

due to clearing and grading during construction resulting from bank erosion can significantly

reduce the amount of habitat for substrate-oriented species. 

2.3.3.1 Embeddedness 

Increased sediment transport from construction and land development can fill the interstitial

spaces between rocks and riffles, which are important habitat for macroinvertebrates and fish
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-28

species, such as darters and sculpins. The stream bottom substratum is a critical habitat for trout

and salmon egg incubation and embryo development (May et al., 1997).

2.3.3.2 Large Woody Debris (LWD)

The presence and stability of LWD is a fundamental habitat parameter. LWD can form dams and

pools, trap sediment and detritus, provide stabilization to stream channels, dissipate flow energy,

and promote habitat complexity (Booth et al., 1996). For example, depending on the size of the

woody debris and the stream, the debris can create plunge, lateral, scour, and backwater pools,

short riffles, undercut banks, side channels, and backwaters, and create different water depths

(Spence et al., 1996). The runoff generated in urban watersheds from small storms can be

enough to transport LWD. Maxted et al. (1994) found that woody debris were typically buried

under sand and silt in urban streams. In addition, the clearing of riparian vegetation limits an

important source of large woody debris. Horner et al. (1996) present evidence from the Pacific

Northwest (Figure 2-9) that LWD in urban streams decreases with increased imperviousness.

Figure 2-9. Large Woody Debris as a Function of Watershed Imperviousness

(Horner et al., 1996)
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-29

2.3.3.3 Changes in Stream Features

Habitat diversity is a key factor in maintaining a diverse and well-functioning aquatic

community. The complexity of the habitat results in increased niches for aquatic species.

Sediment and increases in flow can reduce the residual depths in pools and decrease the diversity

of habitat features such as pools, riffles, and runs. Richey (1982) and Scott et al. (1986) reported

an increase in the prevalence of glides and a corresponding altered pool/riffle sequence due to

urbanization. 

2.3.4 Thermal Impacts

Summer in-stream temperatures have been shown to increase significantly (5 to 12 degrees) in

urban streams because of direct solar radiation, runoff from heat-absorbing pavement, and

discharges from storm water ponds (Galli, 1991). Increased water temperatures can prevent

temperature-sensitive species from surviving in urban streams. Figure 2-10 shows the increase in

water temperature resulting from urbanization.

Figure 2-10. Stream Temperature Increase in Response to Urbanization

(Galli, 1991)

Water temperature in headwater streams is strongly influenced by local air temperatures. Galli

(1991) reported that stream temperatures throughout the summer are higher in urban watersheds,

and the degree of warming appears to be directly related to the imperviousness of the

contributing watershed. Over a 6-month period, five headwater streams in the Maryland

Piedmont that have different levels of impervious cover were monitored. Each urban stream had
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-30

mean temperatures that were consistently warmer than that of a forested reference stream, and

the size of the increase appeared to be a direct function of watershed imperviousness. Other

factors, such as a lack of riparian cover and ponds, were also shown to amplify stream warming,

but the primary contributing factor appeared to be watershed impervious cover.

2.3.5 Direct Channel Impacts

2.3.5.1 Channel Straightening and Hardening/Reduction in First-Order Streams

Channel straightening and hardening includes the addition of riprap or concrete to the channel,

the straightening of natural channels, and the piping of first-order and ephemeral streams.

Although this conversion process often becomes necessary to control runoff from urbanized

areas, adverse impacts often occur downstream. In a national study of urban watersheds in 269

gauged basins, Sauer et al. (1983) determined that channel straightening and channel lining

(hardening)—along with the percentage of curbs and gutters, streets, and storm sewers—were the

dominant land use variables affecting storm flow. These variables all affect the efficiency with

which water is transported to the stream channel. Maintaining this efficiency increases the

velocities needed for storm water to exceed critical shear stress velocities, eroding the channel. 

These factors also considerably degrade any natural habitat for stream biota.

2.3.5.2 Fish Blockages

Infrastructure associated with urbanization—such as bridges, dams, and culverts—can have a

considerable effect on the ability of fish to move freely upstream and downstream in the

watershed. This in turn can have localized effects on small streams, where nonmigratory fish

species can be inhibited by the blockage from recolonizing areas after acutely toxic events. 

Anadromous fish species such as shad, herring, salmon, and steel head also can be blocked from

making the upstream passage that is critical for their reproduction. 

2.3.6 Site Differences in Physical Impacts

Site differences that can affect physical impacts include location of the impervious surfaces,

presence of vegetation, and soil type within the watershed. Location of the impervious

development can be instrumental in the timing of runoff in a watershed. If the development is at

the bottom of the watershed, peak flow from the urbanized area will likely have passed

downstream before the flow peaks from the upper watersheds reach the urbanized area (Sauer et

al., 1983). Vegetation can reduce channel erosion from storm flows. A study in British

Columbia showed that meander bends with vegetation were five times less likely to experience

significant erosion from a major flood than similar non-vegetated meander bends (Beeson and

Doyle, 1995). The types and porosity of soils are also important in determining runoff

characteristics from the land surface and erosion potential of the channels. Allen and Narramore
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 2-31

(1985) showed that channel enlargement in chalk channels was from 12 to 67 percent greater

than in shale channels near Dallas, Texas. They attributed the differences to greater velocities

and shear stress in the chalk channels.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-1

Section 3 Description of Assessment Methodology 

3.1 Introduction

This section describes EPA’s methodology to assess the environmental impacts of the

construction and development category. The methodology was used by EPA to quantify the

potential environmental and economic benefits that would result from implementation of the

proposed regulatory options. These quantified benefits are enumerated in Section 4 of this

document. 

The methodology described in this section focuses on impacts related to pollutant loadings

discharged from construction sites. EPA used total suspended solids (TSS) to indicate pollutantrelated benefits for proposed options.

3.2 Methodology to Estimate Pollutant Loadings from Construction Runoff Water

Discharges 

EPA’s methodology for estimating construction site pollutant loadings builds upon the

methodology used in the Economic Analysis of the Final Phase II Storm Water Rule (USEPA,

1999). This report (referred to herein as the Phase II EA): 

• Estimated the annual number of construction sites or starts covered under Phase I and

Phase II programs

• Developed detailed “model construction sites” to represent a range of construction site

types, sizes and locations to estimate national construction site TSS loadings (3 site sizes, 5

slopes, and 15 climatic regions)

• Estimated suspended solids loadings with and without a suite of BMPs. 

The Phase II EA estimated that in the absence of any controls, construction sites on average

generate approximately 40 tons of TSS per acre per year. In addition, the Phase II EA estimated

that properly designed, installed and maintained erosion and sediment (E&S) control BMPs, in

combination, can potentially achieve a 90 to 95 percent reduction in sediment runoff. The suite

of E&S BMPs evaluated in EPA’s Phase II EA is shown in Table 3-1.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-2

Table 3-1. Common Construction Erosion and

Sediment Control BMPs

BMP Description Erosion Controla Sediment Controlb

Silt Fence Yes

Runoff Diversion Yes

Mulch Yes

Seed and Mulch Yes

Construction Entrance Yes

Stone Check Dam Yes

Sediment Trap Yes

Sediment Pond Yes

a. Erosion controls are those distributed throughout the site to help

retain soil in place. 

b. Sediment controls are intended to intercept eroded soils preventing

runoff from the construction site.

The analysis conducted by EPA indicates that environmental benefits would be achieved by

implementing procedures that ensure good E&S practices and that establish design criteria and

installation for construction site BMPs. The suite of BMPs considered by EPA in its effluent

guidelines development is presented in Table 3-2.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-3

Table 3-2. Site BMPs Evaluated by EPA For Effluent Guidelines

Development

BMP Description Application Rationale

Design/Installation Criteria

Sediment Basins Standardization to 3,600 cubic feet of storage per watershed acre for

sites  10 acres.

Sediment Traps Applicable to sites  10 acres.

Mulch Mulching of any denuded surface would be required within 2 weeks of

final grade.

PAMa

PAM would be used as a temporary stabilization method until final

cover can be installed. EPA assumed that PAM is appropriate for 20

percent of construction sites.

Site Administration BMPs

E&S Site Inspections

and Certification

(a) Certify completion of SWPPP,

(b) Certify installation of BMPs,

(c) Conduct inspections every 14 days,

(d) Remove sediment from basins and traps periodically, and

(e) Certify that the site has been stabilized prior to filing NOT.

a

 PAM: Polyacrylamide

Implementing these BMPs as part of the proposed Option 1 is expected to achieve benefits due

to: 

• Higher installation rates because certification would be required;

• Certification of BMP implementation that creates a verifiable record of site E&S controls;

• Higher BMP maintenance frequency due to proposed inspection requirements.

In addition, Option 2 is expected to achieve additional benefits due to:

• Shorter no-control periods due to more timely application of erosion BMPs;

• Standardization of design/sizing criteria (Codification of BMP designs under Option 2

would result in higher removal efficiencies).

Under the proposed options EPA estimates increased efficiency, as measured by the pounds of

eroded material retained on construction sites, to range from 5 to 15 percent for Option 1 and 20

percent for Option 2. The lower and upper percentages of net performance for Option 1 yield

upper and lower bounds of reductions in construction site loadings discharged to the

environment, respectively. These ranges indicate potential additional reductions in suspended
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-4

solid discharges as a result of regulatory implementation, and do not account for states with

equivalent construction programs and for acres not covered by the proposed guidelines. To

account for these two factors, EPA developed additional steps to lower its estimates of TSS

loadings reductions.

For Option 2, EPA also reduced the estimated loadings to discount sites between 1 and 5 acres in

size. These sites would not be regulated under proposed Option 2 effluent guidelines, and

constitute approximately 15 percent of annually developed acreage. EPA discounted TSS

loadings reductions estimates by 15 percent to account for the fact that these sites would not be

affected by Option 2.

As detailed in Appendix A, EPA performed an evaluation of state construction general permits

and regulations to estimate the percentage of national acreage developed annually that is

currently covered under regulation that is equivalent to or exceeds the proposed option levels.

EPA evaluated states, focusing on those with annual developed acreage greater than 50,000

acres. Overall, EPA estimated that approximately 41 percent of developing acreage is currently

subject to regulatory requirements equivalent to or exceeding those under Options 1 and 2. EPA

surveyed the following four proposed requirements:

1. 3,600 cubic feet per acre storage requirement for sediment basins on sites  10 acres

2. Certification of BMPs at installation

3. 14-day or more frequent inspection

4. 14-day cover for erosion and dust control.

To account for states currently performing at or above the levels designated under Option 1and 2,

EPA reduced estimated TSS loading estimates by 41 percent to remove states with equivalent

programs. The results of EPA’s loadings assessment are provided in Section 4.

3.3 Characterizing the Nation’s Stream Network

To evaluate environmental impacts related to stream size and length, EPA characterized stream

densities in 19 "ecoregions" for the contiguous United States (Figure 3-1). Detailed

methodologies are explained in Appendix B. The 19 ecoregions were developed based on the

stream density of large river systems, a relatively coarse assessment. Next, EPA performed a

characterization or inventory to estimate a typical stream density within each region, and to

define a statistically “standard” watershed for each ecoregion. EPA first determined the stream
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

1

 Stream Order is a hierarchal ordering of streams based on the degree of branching. A first order stream

is an unbranched or unforked stream. Two first-order streams flow together to make a second-order

stream; two second- order streams combine to make a third-order stream. First-order watersheds in

EPA’s ecoregion-specific standard watersheds occupy between 20 and 50 acres.

June 2002 3-5

network based on stream orders1, assessing approximately 100,000 acres in each ecoregion. The

analysis estimated the average number, acreage, slope, and length of streams, as well as the ratio

of stream orders and their drainage area. EPA used those data to estimate the total stream miles

in each ecoregion’s standard watershed. Because EPA focused on land development, regional

stream densities were established through spatial and statistical averaging of actual stream

networks at the developing fringe of existing metropolitan areas.







 

























	

	

 











Figure 3-1. Ecoregions for Stream Inventorying

Only one metropolitan area was analyzed for each ecoregion because of the extensive amount of

data processed to define stream networks based on 30 meter digital elevation data for 100,000

acres.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-6

EPA’s stream inventory focused on relatively small watersheds that terminate in a small

perennial stream (e.g., a fourth-order stream in the mid-Atlantic area). Intermittent and small

perennial streams are expected to be the water bodies most adversely affected by the activities of

the construction and land development industry. Less emphasis was placed on the inventory and

evaluation of larger perennial rivers (i.e., greater than fifth-order in the mid-Atlantic area)

because they potentially have more pollutant sources and isolating the benefits of the proposed

effluent guidelines in these water bodies could potentially be difficult.

The results of EPA’s assessment of stream information in each of the 19 ecoregion standard

watersheds are presented in Table 3-3. In general, whenever EPA determined it should to

estimate impacts related to the total mileage of streams located within a defined acreage, EPA

used these values to convert the acreage to stream miles on the basis of stream order. 

Information in the table (i.e., number and stream length) was also used to scale-up the impacts on

a stream order basis.

Table 3-3. Results of the National Stream Survey

EcoRegionReach

Order

Number

of

Segments

Analyzed

General

Ratio of

Stream

Orders*

 Average

Segment

Length, ft

Average

Slope of

River, ft/ft

 Average

Watershed

Acreage per

Segment 

Drainage Area

Ratio of Upstream

Channels to the

Downstream

Channel**

1

1 608 87 428 3.06% 53.07 0

2 104 15 1,078 1.75% 273.35 5.15

3 22 3 3,323 1.07% 1,597.67 5.84

4 7 1 6,914 0.81% 6,425.88 4.02

2

1 742 82 499 11.25% 45.78 0

2 166 18 1,185 7.37% 228.24 4.99

3 34 4 2,801 5.25% 1,194.55 5.23

4 9 1 4,297 4.51% 4,434.78 3.71

3

1 829 92 423 3.11% 53.08 0

2 179 20 1,017 2.00% 266.69 5.02

3 35 4 2,307 1.29% 1,316.02 4.93

4 9 1 9,367 0.62% 8,283.03 6.29
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

Table 3-3. Results of the National Stream Survey

EcoRegionReach

Order

Number

of

Segments

Analyzed

General

Ratio of

Stream

Orders*

 Average

Segment

Length, ft

Average

Slope of

River, ft/ft

 Average

Watershed

Acreage per

Segment 

Drainage Area

Ratio of Upstream

Channels to the

Downstream

Channel**

June 2002 3-7

4

1 961 120 309 2.81% 29.55 0

2 209 26 591 1.62% 129.62 4.39

3 45 6 1,259 1.03% 556.92 4.3

4 8 1 6,411 0.50% 4,417.34 7.93

5

1 862 86 434 0.52% 57.35 0

2 201 20 825 0.40% 398.05 6.94

3 47 5 1,751 0.28% 2,119.32 5.32

4 10 1 3,835 0.17% 6,114.79 2.89

6

1 961 120 371 4.37% 29.55 0

2 209 26 779 3.20% 138.31 4.68

3 45 6 1,372 2.45% 554.87 4.01

4 8 1 4,724 1.13% 3,369.25 6.07

7

1 862 86 351 6.22% 42.56 0

2 201 20 954 3.21% 229.2 5.39

3 47 5 2,028 1.81% 1,096.47 4.78

4 10 1 5,850 0.84% 5,447.43 4.97

8

1 638 80 302 1.08% 27.43 0

2 141 18 612 0.72% 123.19 4.49

3 35 4 1,340 0.52% 580.24 4.71

4 8 1 3,058 0.31% 2,112.57 3.64

9

1 645 81 356 0.43% 27.31 0

2 123 15 631 0.50% 127.26 4.66

3 28 4 2,170 0.34% 845.78 6.65

4 8 1 7,322 0.14% 5,134.48 6.07
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

Table 3-3. Results of the National Stream Survey

EcoRegionReach

Order

Number

of

Segments

Analyzed

General

Ratio of

Stream

Orders*

 Average

Segment

Length, ft

Average

Slope of

River, ft/ft

 Average

Watershed

Acreage per

Segment 

Drainage Area

Ratio of Upstream

Channels to the

Downstream

Channel**

June 2002 3-8

10

1 1,238 88 306 3.35% 30.89 0

2 275 20 742 2.05% 158.44 5.13

3 59 4 1,421 1.27% 691.2 4.36

4 14 1 4,392 0.70% 4,339.58 6.28

11

1 1,050 105 353 3.71% 30.89 0

2 198 20 859 2.04% 158.44 5.13

3 41 4 1,595 1.29% 691.2 4.36

4 10 1 3,241 0.81% 4,339.58 6.28

12

1 960 80 376 14.71% 34.1 0

2 215 18 801 9.29% 155.93 4.57

3 50 4 2,162 5.95% 867.6 5.56

4 12 1 3,054 4.15% 3,082.49 3.55

13

1 753 63 272 22.47% 21.96 0

2 161 13 587 14.88% 107.42 4.89

3 43 4 1,311 9.97% 497.52 4.63

4 12 1 6,152 3.77% 3,738.79 7.51

14

1 933 72 427 5.78% 37.21 0

2 194 15 865 3.50% 171.65 4.61

3 44 3 1,635 2.38% 720.88 4.2

4 13 1 2,073 1.35% 2,563.73 3.56

15

1 1,424 129 381 3.86% 31.84 0

2 290 26 697 2.29% 143.06 4.49

3 58 5 1,469 2.05% 545.11 3.81

4 11 1 3,315 1.07% 2,680.10 4.92
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

Table 3-3. Results of the National Stream Survey

EcoRegionReach

Order

Number

of

Segments

Analyzed

General

Ratio of

Stream

Orders*

 Average

Segment

Length, ft

Average

Slope of

River, ft/ft

 Average

Watershed

Acreage per

Segment 

Drainage Area

Ratio of Upstream

Channels to the

Downstream

Channel**

June 2002 3-9

16

1 1,009 72 463 8.12% 39.77 0

2 224 16 1,064 5.09% 191.81 4.82

3 53 4 2,170 3.92% 888.83 4.63

4 14 1 4,309 2.56% 4,293.71 4.83

17

1 464 77 464 20.60% 57.02 0

2 79 13 1,605 14.51% 395.06 6.93

3 21 4 3,018 9.47% 1,823.06 4.61

4 6 1 5,392 4.27% 6,881.95 3.77

18

1 251 84 381 3.86% 31.84 0

2 50 17 697 2.29% 143.06 4.49

3 13 4 1,469 2.05% 545.11 3.81

4 3 1 3,315 1.07% 2,680.10 4.92

19

1 457 65 463 8.12% 39.77 0

2 102 15 1,064 5.09% 191.81 4.82

3 27 4 2,170 3.92% 888.83 4.63

4 7 1 4,309 2.56% 4,293.71 4.83

Notes:

A stream “segment” is a single stream reach between upstream and downstream confluence points.

* The “General Ratio of Stream Orders” value indicates the number of streams of “X” order found in a single

fourth order watershed. 

** The “Drainage Area Ratio of Upstream Channels to the Downstream Channel” indicates the ratio of

drainage areas based on full watershed area of each stream order.

3.3.1 Characterizing the Stream Network within Developing Acreage

Although the information contained in the table can be used to convert acreage into estimated

stream miles for the 19 ecoregions it is not sufficient to estimate the number of stream miles
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-10

contained within the land area developed each year. To calculate that estimate, EPA first

estimates the number of acres developed and the geographic region in which the developing acres

are located. EPA used geographically linked annual development rates in the U.S. from the

National Resources Inventory (NRI) (USDA, 2000). The NRI captures data on land cover and

use, soil erosion, prime farmland soils, wetlands, habitat diversity, selected conservation

practices, and related resource attributes at more than 800,000 scientifically selected sample sites. 

NRI estimated the development rate for hundreds of individual watersheds that cover the

contiguous states. To estimate the annual development rate for each of the 19 ecoregions, EPA

summed the development rates of all watersheds within the boundary of each ecoregion.

The NRI was used for assessing the impacts of the construction and land development industry

because it provides a consistent and periodic national assessment of land development trends and

employs a standard methodology for the entire nation. In addition, the NRI also provides

information on land use prior to development (e.g., the acres of farm land converted into

residential use). EPA’s analysis of the most current NRI information available (rates of land

development from 1992 to 1997) is shown in Table 3-4, which shows that the current rate of land

development is approximately 2 million acres per year.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-11

Table 3-4. Land Development Annually in Ecoregions

(Adapted from USDA, 2000)

Ecoregion

Acres

Developed

Annually

Percent of

National Total

Miles of Streams

Within Developed

Acres

1 64,236 2.9% 134

2 91,015 4.1% 303

3 34,424 1.6% 61

4 338,378 15.2% 957

5 67,107 3.0% 137

6 127,511 5.7% 387

7 42,321 1.9% 82

8 252,790 11.4% 1,075

9 330,635 14.9% 805

10 326,850 14.7% 686

11 97,386 4.4% 181

12 249,748 11.3% 757

13 35,090 1.6% 113

14 38,822 1.7% 152

15 11,093 0.5% 42

16 57,947 2.6% 149

17 28,799 1.3% 58

18 12,592 0.6% 47

19 12,607 0.6% 32

Totals 2,219,352 6,160

Values provided indicate total acres developed. Approximately, sites  1

acres constitute 2 percent of acres developed, and sites between 1 and 5 acres

constitute 15% of the acres developed.

Table 3-4 also provides EPA’s estimate of the miles of stream contained within the acres

developed annually. When estimating the total miles of stream per ecoregion by stream order,

EPA first estimated the number of fourth-order watersheds developed. For example, in
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-12

ecoregion 19, the number of acres developed annually (12,607) was divided by the number of

acres in a fourth-order watershed (4,293) to yield the number of developed watersheds (2.9). 

This number was then multiplied by the average number of feet per fourth-order stream (4,309)

and by the stream order ratio (1) to yield the number of feet of fourth-order streams in developed

areas (12,496). In order to find the total number of stream feet for the ecoregion, these steps are

repeated for third, second and first order streams and the sum taken of each order of stream feet. 

3.3.2 Characterizing the Flow Conditions in Stream Network

Table 3-5 shows the estimated division of perennial and intermittent streams by stream order for

each ecoregion. The designations provided in Table 3-5 are based on best professional judgment. 

EPA notes that third- and fourth-order streams in relatively arid areas of the nation could be

perennial due to small dams and lakes; however, the analysis assumes they are intermittent in

nature.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-13

Table 3-5. Characterization of Stream Orders for Ecoregions

Ecoregion 1st Order 2nd Order 3rd Order 4th Order

1 I I I I

2 I I I I

3 I I I P

4 I I P P

5 I I P P

6 I I P P

7 I I P P

8 I I P P

9 I I P P

10 I I P P

11 I I P P

12 I I P P

13 I I I I

14 I I I I

15 I I P P

16 I I P P

17 I I P P

18 I I I I

19 I I P P

20 I I P P

P = Perennial; I = Intermittent

EPA estimated the total miles of intermittent and perennial streams based on a cross-product of

information on Tables 3-3, 3-4 and 3-5 (total stream lengths by order, ecoregion development

rates, and perennial/intermittent assumptions, respectively). The results of this calculation are

shown in Table 3-6.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-14

Table 3-6. Characterization of Stream Length by Flow Type

for Ecoregions

Ecoregion Geographic Name

Baseline Conditions

Perennial

Stream Miles

Intermittent

Stream Miles

1 Midwest 0 134

2 Southwest Arid 0 303

3 Southwest 7 54

4 Coastal Atlantic 196 762

5 Atlantic Shoreline 25 112

6 North Florida 77 310

7 South Florida 19 63

8 New England 197 878

9 Appalachia 198 608

10 Great Lakes Region 147 539

11 Mississippi Outlet 38 143

12 Mississippi West 159 598

13 Upper Midwest & Dakotas 0 113

14 Midwest Central 0 152

15 Pacific Coastal Region 8 34

16 Southern California 32 117

17 Willamette Valley 13 45

18 Eastern Washington 0 47

19 Sierras 7 25

Total 1,123 5,036

3.3.3 Converting Stream Miles into Impact Estimates

Inventorying stream information for each of the ecoregions and estimating the miles of stream

contained within urbanizing acreage provides a basis for estimating impacts that are proportional
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-15

to stream length. EPA developed data sets which indicate stream type (perennial or intermittent),

stream order, and location (ecoregion). The data, however, are not sufficiently customized at the

local/regional level to permit detailed environmental modeling of stream impacts on an ecoregion

basis. Hence, EPA estimated environmental changes at the national level.

Table 3-6 shows national and ecoregion-specific estimates of the river miles contained within the

acres developed annually, if all acres developed were within a single watershed. Additional

adjustment is necessary to account for the fact that development is not consolidated in a single

land mass but rather is dispersed among areas not currently under construction. See Figure 3-2.

To estimate the miles of streams potentially impacted under baseline conditions, EPA considered

a range of assumptions about the ratio of construction to non-construction area within

watersheds. As shown in Figure 3-2, EPA assumed that an area of 10 times larger than the total

area under construction is also impacted from runoff from construction in addition to runoff from

urban areas, forests and agriculture.

Land Use Type Distribution Across Watershed

Existing Urban Area (25% Under Scenario 1)

Farm/Pasture Area (32.5% Under Scenario 1)

Forested Area (32.5% Under Scenario 1)

Construction This Year (10% Under Scenario 1)

Stream Channels

Figure 3-2. Land Use Distribution of a Watershed.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-16

Given this assumption, a construction rate of 2.2 million constructed acres per year means that

streams dispersed in 22 million acres of land area are potentially impacted by construction site

runoff in combination with runoff from urban, forested and farm land. Based on EPA’s

assessment of stream lengths contained in the 19 ecoregions and the rates of development in each

ecoregion, EPA estimates that roughly 10,000 perennial stream miles and 36,000 intermittent

stream miles are potentially affected by construction site runoff annually (Table 3-7).

Table 3-7. Estimated Miles of Streams Potentially Affected

by One Year’s Construction

Ecoregion Geographic Name

2.2 Million Acres 

(Acreage Constructed

Annually )

22 Million Acres 

(Assumed Land Area

Containing Acreage

Constructed Annually )

Perennial

Stream Miles

Intermittent

Stream Miles

Perennial

Stream Miles

Intermittent

Stream Miles

1 Midwest - 107 0 1,070

2 Southwest Arid - 242 0 2,420

3 Southwest 7 43 70 430

4 Coastal Atlantic 196 609 1,960 6,090

5 Atlantic Shoreline 25 90 250 900

6 North Florida

7 South Florida

8 New England 197 702 1,970 7,020

9 Appalachia 198 486 1,980 4,860

10 Great Lakes Region 147 431 1,470 4,310

11 Mississippi Outlet

12 Mississippi West 159 478 1,590 4,780

13 Upper Midwest & Dakotas - 91 0 910

14 Midwest Central - 121 0 1,210

15 Pacific Coastal Region 8 27 80 270

16 Southern California 32 93 320 930

17 Willamette Valley 13 36 130 360
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

Table 3-7. Estimated Miles of Streams Potentially Affected

by One Year’s Construction

Ecoregion Geographic Name

2.2 Million Acres 

(Acreage Constructed

Annually )

22 Million Acres 

(Assumed Land Area

Containing Acreage

Constructed Annually )

Perennial

Stream Miles

Intermittent

Stream Miles

Perennial

Stream Miles

Intermittent

Stream Miles

June 2002 3-17

18 Eastern Washington - 38 0 380

19 Sierras 7 20 70 200

Total 989 3,614 9,890 36,140

Notes:

• EPA assumed that all streams within fourth-order watersheds are intermittent in regions 1, 2, 13, 14, and 18. 

• Total values reflect a 20 percent reduction in intermittent stream miles to account for streams that are

expected to be converted into below grade pipe systems. Values also discount stream miles in Ecoregions 6, 7,

and 11 because these systems are greatly influenced by man-made channel networks and natural wetland

systems (i.e., are less hierarchal in nature).

EPA then developed a simple stream model to assess potential changes in TSS concentrations

during wet-weather periods for the estimated 61 thousand miles of streams receiving discharges

from construction sites annually. EPA evaluated three development scenarios to estimate the

range of potential TSS reductions in streams within watersheds experiencing construction runoff,

as shown in Table 3-8. The three development scenarios are intended to represent low,

moderate, and high levels of urbanization, over which construction activities are superimposed.

EPA used a simple mass balance approach to estimate in stream TSS concentrations, as follows:

1. Estimate the average annual runoff from each land use condition, from construction

acreage affected, and not affected by proposed guideline options. 

2. Estimate the average annual TSS loading from each land use condition, based on EPAestimated or literature reported event mean concentration (EMC) for TSS.

3. Estimate national average change in the in-stream concentration of TSS using land use

fractions given in each of the three scenarios in Table 3-8. This assessment is performed

for all 2.2 million acres developed annually, based on the total estimated runoff volume in

a single (typical) rainfall year.

Table 3-8, also shows the allocation of regulated construction sites for Options 1 and 2. Under

Option 1, approximately 0.2 percent of the watershed is assumed to be covered by construction

sites less than 1 acres in size. The runoff from these acres is not affected by Option 1 proposed
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-18

requirements. Under Option 2, approximately 1.7 percent of the watershed is assumed to be

covered by construction sites less than 5 acres in size. The runoff from these acres are not

affected by Option 2 proposed requirements. Runoff coefficients (Table 3-9) indicate the portion

of rainfall that leaves the area as runoff. The remainder is assumed to infiltrate into the ground or

evaporate. Values were selected based on EPA estimates of percent imperviousness, values

reported in literature, and best professional judgement. 

Table 3-8. Active Construction Site Runoff Scenarios

for Option 1 and Option 2

Land Use Conditions

Land Use Coverage Scenarios 

Low

Urbanization

Moderate

Urbanization

High

Urbanization

Existing Urban Area 25.0% 50.0% 75.0%

Forested 32.6% 20.1% 7.6%

Farm 32.6% 20.1% 7.6%

Sites Regulated Under Option 1 9.80% 9.80% 9.80%

Sites Not Affected by Option 1 0.20% 0.20% 0.20%

Sites Regulated Under Option 2 8.27% 8.27% 8.27%

Sites Not Affected by Option 2 1.73% 1.73% 1.73%

Table 3-9. Runoff Coefficients for

Land Uses

Land Use Conditions Runoff Coefficients

Existing Urban Area 0.46

Forested 0.05

Farm 0.15

Constructiona 0.80

a. Includes sites regulated under Option 1, not

affected by Option 1, regulated under Option 2, and

not affected by Option 2.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

2 EPA defined a “typical rainfall year” as having a total rainfall depth within 10 percent of the average

for the ecoregion, and not containing a single rainfall event with greater than a 2-year storm.

June 2002 3-19

EPA’s simple in-stream model estimates the potential reduction in TSS concentration during

wet-weather periods. EPA’s approach does not taken into account the contributions of base flow

and base flow loads (i.e., that entering streams due to groundwater) during wet-weather periods. 

Excluding this base flow results in an overestimation of actual TSS concentrations.

Because rainfall conditions affect the results of EPA’s assessment, an evaluation of

approximately 30 years of rainfall records for 1,200 rainfall gauges was performed to identify a

typical rainfall year for each of the 19 ecoregions.2 Based on this evaluation, EPA estimated that

the national average rainfall depth falling on construction sites is approximately 34.8 inches per

year. This estimate is a weighted average, based on the acres developed in each ecoregion.

Table 3-10 presents the event mean concentrations (EMCs) used by EPA to estimate the range of

TSS loadings. In selecting EMC values, EPA used values from the literature that would help

create reasonable upper and lower bound estimates. High and low effectiveness estimates for

construction site effluent concentrations were matched with lower bound and upper bound

EMCs, respectively, for other land uses. For example, lower bound and upper bound EMC

values for urban runoff (141 and 224 mg/L) were assumed to bracket urban concentrations, and

to indicate TSS annual loadings. Only forested area EMCs were held constant for both lower and

upper bound estimates. In terms of annual TSS yield, EPA’s assumed EMCs for urban areas

correspond to 0.26 and 0.41 tons per acre per year. Annual TSS yield for farm/pasture, equates

to 0.15 and 3.0 tons per acre per year (Corsi et al., 1997; Novotny and Chesters, 1981; Horner et

al., 1986; Horner, 1992; and Sonzogni et al., 1980).

EPA assumed that construction sites not affected by the proposed effluent guidelines would

discharge TSS in concentrations similar to those estimated under baseline conditions. This

assumption may overestimate TSS loadings estimates associated with Option 2 for sites between

1 and 5 acres. The results of EPA’s simple national in stream model, based on the data and

assumptions described above, are provided in Section 4.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 3-20

Table 3-10. Runoff EMCs for Acres Within a Watershed

(TSS in mg/L)

Land Use Condition

Lower Bound Upper Bound

Option 1 Option 2 Option 1 Option 2

Urban Area 141 141 224 224

Forested/Pasture 152 152 152 152

Farm 254 254 5,071 5,071

Regulated Construction Sites 2,613 1,843 6,529 5,081

Construction Sites Not Affected by

Regulations 3,765 3,765 6,914 6,914

Notes:

• Urban TSS Concentrations are from USEPA, 1993

• Option 1 high and low effectiveness assumes construction BMPs are installed/operated so

resulting capture of TSS generation is 80 and 50% of TSS generation, respectively.

• Option 2 high and low effectiveness assumes construction BMPs are installed/operated so

resulting capture of TSS generation is 90 and 70% of TSS generation, respectively.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 4-1

Section 4 Environmental Benefits Assessment of Evaluated Regulatory

Options

This section presents the Agency’s estimates of the environmental benefits that would result from

implementation of erosion and sediment controls during construction activities. EPA evaluated 3

regulatory options for controlling discharges from active construction sites. Table 4-1 describes

each of the options. 

Table 4-1. Regulatory Options Evaluated for Controlling Discharges

from Construction Activities

Option Description

Option 1 • Applicable to construction sites with one acre or more of disturbed land

• Operators required to:

- Inspect site throughout land disturbance period

- Certify that the controls meet the regulatory design criteria as applicable

• Amend NPDES regulations at 40 CFR Part 122 (no new effluent guideline regulations)

Option 2 • Applicable to construction sites with five acres or more of disturbed land

• Operators required to:

- Prepare storm water pollution prevention plan

- Design, install, and maintain erosion and sediment controls

- Inspect site throughout land disturbance period

- Certify that the controls meet the regulatory design criteria as applicable

• Creates a new effluent guidelines category at 40 CFR Part 450 and amends Part 122

regulations

Option 3 • No new regulatory requirements

The following subsections present Agency estimates of regulatory conditions for suspended

solids loadings and resulting improvements to the environment, including stream habitat.

4.1 Total Suspended Solids Loadings

Construction projects involve a series of temporary activities (e.g., land clearing, grubbing,

building), and, with the exception of large-scale facilities, these projects generally have a

duration of less than a year. During the construction period, erosion and sediment control (ESC)

BMPs are employed to minimize pollutant discharges. 

EPA used three criteria as a basis for selecting which pollutants to use as indicators of

construction site pollutant loadings: (1) pollutants that correlate strongly with the construction
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 4-2

activities, (2) toxic pollutants should be considered only if dissolved concentrations are high, and

(3) proposed effluent guidelines would significantly reduce loadings from current levels. Based

on these criteria, EPA selected eroded soils/sediment loadings (e.g., measured by TSS and14 

turbidity) as the indicator of construction site pollutant loadings. Other runoff constituents are

either present in low concentrations or account for such a small proportion of the total discharge

that conventional treatment would not prove effective in removing additional levels beyond that

attained in treating the suspended solid component. 

Table 4-2 presents EPA’s estimates of construction site loadings reductions under Options 1, 2

and 3 in terms of tons of TSS per year.

Table 4-2. Estimated TSS Loadings Reductions for

Proposed Regulatory Options 

Option 1 Option 2 Option 3

Lower bound

estimates

Incremental Percent TSS

captured by BMPs

5% 25% 0

Annual reductions (tons) 2,637,569 11,126,639 a 0

Upper bound

estimates

Incremental Percent TSS

captured by BMPs 

15% 25% 0

Annual reductions (tons) 7,912,707 11,126,639 a 0

a. Option 2 reductions were reduced by approximately 15 percent to account for sites between

1 and 5 acres in size not covered by this option.

As shown in the table, EPA estimates that under Option 1, construction sites would increase the

removal rate of TSS by approximately 5 to 15 percent. The projected increase in net

performance of construction site BMPs under Option 2 is about 25 percent. These estimates

were developed using the Agency's engineering judgement, but are based on the following

assumptions:

• Regulatory options would require that sediment ponds are certified at the time of

installation to ensure they are built as designed

• Implementation of the proposal would result in more effective selection, installation and

O&M of ESC BMPs due to inspection and certification of site activities.

• Option 2 would result in shorter duration of exposure for un-managed denuded areas

The regulatory options loadings were generated using three factors: total annual number of acres

developed, tons per year of suspended solids per acre of land undergoing development, and
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 4-3

incremental improvement in BMP performance under the regulatory options. As described in

Section 3, NRI data were used to estimate that approximately 2.2 million acres are developed

annually and the estimate of 40 tons per acre generation of TSS at construction sites was based

on the Phase II Storm Water Economic Assessment (EPA, 1999). 

Estimated annual sediment loadings reductions from implementation of EPA’s proposed

alternatives range from 0 tons (Option 3: no new regulations) to approximately 11 million tons

per year for Option 2. 

4.2 Total Suspended Solid In-Stream Concentrations 

Although the Agency did not attempt to quantify aquatic losses (e.g., fish kills, habitat loss), it

did estimate how construction loadings impact in-stream concentration levels of TSS in receiving

water bodies.

Because in-stream concentrations of TSS result from mixtures of point and nonpoint sources that

cannot cannot be readily separated, EPA estimated in-stream TSS concentrations for three

different land use scenarios that assumed 10 percent of the land area was under construction and

90 percent was distributed among three types of land uses: forest, farm and urban. As shown in

Table 4-3, the land use scenarios were developed to characterize different levels of urbanization,

ranging from 25 percent urban in scenario 1 to 75 percent urban in scenario 3. EPA’s analysis

does not assess in-stream settling and resuspension. In addition, there are other sources of TSS

that have not been included in the analysis, such as loads resulting from commercial point source

discharges and loads resulting from increased stream bank erosion related to higher stream flow

rates and velocities in urbanizing water bodies. TSS loadings (section 4.1) were used in

conjunction with different event mean concentration (EMC) values, runoff coefficients, and ESC

BMP efficiency rates to generate TSS in-stream concentrations, as described in section 3.3.3. 

Table 4-3. Development Scenarios Used to Estimate Impacts

of Regulatory Options

Development Scenario Land Use Proportions

1. Low Urbanization 25% Urban, 10% Construction, 32.5% Farm, 32.5% Forest

2. Moderate Urbanization 50% Urban, 10% Construction, 20% Farm, 20% Forest

3. High Urbanization 75% Urban, 10% Construction, 7.5% Farm, 7.5% Forest

Different land use scenarios were evaluated because of the differences in TSS characteristics that

result as land becomes developed from rural to urban conditions. The high urban conditions

contribute the lowest levels of TSS while the low urbanization contribute the highest levels of
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 4-4

TSS. This can be explained by the fact that forest and farm practices generate higher levels of

sediment runoff and urbanized areas create more storm water runoff, diluting TSS

concentrations.

Table 4-4 shows the estimated concentration reductions in TSS from the regulatory options. 

Reductions in TSS concentrations under Option 1 are estimated to range from 68 to 348 mg/L. 

TSS concentrations under Option 2 would decrease from 276 to 489 mg/L. The larger reductions

from regulatory Option 2 reflect the more stringent proposed requirements resulting in higher

ESC BMP effectiveness. Reductions from the lower bound comparisons are higher than

reductions in the upper bound comparisons.

Table 4-4. Estimated Average In-Stream TSS Concentrations Reduction,

mg/L

Development Scenario

High Effectiveness Estimates Low Effectiveness Estimates

Option 1 Option 2 Option 1 Option 2

1. Low Urbanization 348 489 116 466

2. Moderate Urbanization 258 363 86 346

3. High Urbanization 205 289 68 276

Note: The results provided in this table could overestimate the differences between the effects of

high and low urbanization because the study did not include discharges from commercial point

sources or from increased stream bank erosion resulting from increased stream flow rates and

velocities in urbanized areas. If these factors had been included, the concentrations under high

urbanization would likely have been significantly higher.

4.3 Miscellaneous Impacts

Sites under construction have hydrologic responses that differ from those under pre-development

conditions; both the peak discharge and duration of high discharges increase dramatically.

(Appendix C describes hydrologic changes caused by construction and the effects of commonly

employed sedimentation ponds on site discharge.) As a result, EPA believes that construction

sites increase the potential for flooding of downstream areas above the levels found in the predevelopment condition. Both Options 1 and 2 are expected to reduce flooding potential by

ensuring the installation and maintenance of sedimentation ponds (if already present) that retain

site runoff and help minimize flooding potential.

Poor ESC BMP implementation has an adverse impact on aesthetics of affected water bodies

lowering the visual quality of streams and lakes by creating high turbidity levels. Sediment
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 4-5

enriched runoff from failing construction site ESC BMPs convey sediment to adjacent land

creating a visual nuisance and sometimes requiring clean up. Although EPA did not estimate the

environmental or economic benefits associated with improvements in these conditions, EPA

believes that both Option 1 and 2 would reduce these impacts significantly by requiring closer

tracking of ESC BMP operation, problem identification, and problem resolution.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 5-1

Section 5 References

Allen, P. and R. Narramore. 1985. Bedrock Controls on Stream Channel Enlargement with

Urbanization, North Central Texas. Water Resources Bulletin. 21(6): 1037-1048. 

Bagley et al. 1998. Sources and Fate of Giardia Cysts and Cryptosporidium Oocysts in Surface

Waters. Journal of Lake and Reservoir Management. 14(2-3):379-392.

Bannerman, R.; D. Owens; R. Dodds; and N. Hornewer. 1993. Sources of Pollutants in

Wisconsin Stormwater. Water Science and Technology. 28(3-5): 241-259.

Barfield, B. J. and M. J. Clar. 1985. Development of New Design Criteria for Sediment Traps

and Basins. Prepared for Maryland Department of the Environment, Water Resources

Administration, Sediment and Stormwater Division. Annapolis, MD. 33pp. 

Barr, R. 1997. Maryland NPDES Phase I Monitoring Data. Maryland Department of the

Environment. Baltimore, MD.

Barrett, M. and J. Molina. 1998. Comparison of Filtration Systems and Vegetated Controls for

Stormwater Treatment. 3rd International Conference on Diffuse Pollution. August 31 -

September 4, 1998. Scottish Environment Protection Agency. Edinburgh, Scotland.

Bay S. and J. Brown. 2000. Assessment of MTBE Discharge Impacts on California Marine

Water Quality. Prepared for State Water Resources Control Board. Southern California

Coastal Water Research Project. Westminster, California.

Beeson, C. and P. Doyle. 1995. Comparison of Bank Erosion at Vegetated and Non-vegetated

Bends. Water Resources Bulletin. 31(6).

Blankenship, K. 1996. Masked Bandit Uncovered in Water Quality Theft. Bay Journal. Vol 6.

No. 6. Alliance for the Chesapeake Bay, Baltimore, MD.

Booth, D. 1990. Stream Channel Incision Following Drainage Basin Urbanization. Water

Resources Bulletin. 26(3): 407-417.

Booth, D. , D. Montgomery, and J. Bethel. 1996. Large Woody Debris in the Urban Streams of

the Pacific Northwest. In Effects of Watershed development and Management on

Aquatic Systems . L. Roesner (ed.) Engineering Foundation Conference. Proceedings. 

Snowbird, UT. August 4-9, 1996. Pp. 178-197. 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 5-2

Brown, E. and R. Claytor. 2000. Draft Watershed Assessment Study for Watts Branch. Watts

Branch Watershed Plan. City of Rockville, MD. Center for Watershed Protection.

Ellicott City, MD.

Campbell, K. R. 1995. “Concentrations of “Heavy Metals Associated with Urban Runoff in Fish

Living in Stormwater Ponds.” Archives of Environmental Contamination and Toxicology

27: 352-356.

Caraco D. S. 2000. "The Dynamics of Urban Stream Channel Enlargement." Article No. 19 in

The Practice of Watershed Protection. 2000. Center for Watershed Protection, Ellicott

City, MD. http://www.stormwatercenter.net

Center for Watershed Protection. 2000. The Practice of Watershed Protection: Techniques for

Protecting Our Nation’s Streams, Lakes, Rivers and Estuaries. Ellicott City, MD.

Collins, A., D. Wallings, and G. Leeks. 1997. Source Type Ascription for Fluvial Suspended

Sediment Based on a Quantitative Composite Fingerprinting Technique. Catena 29:1-27.

Corsi, S. R., D. J. Graczyk, D. W. Owens, and R. T. Bannerman. 1997. Unit-Area Loads of

Suspended Solids and Total Phophorus from Small Watersheds in Wisconsin. USGS

Fact Sheet FS-195-97.

Crunkilton, R. et al. 1996. Assessment of the Response of Aquatic Organisms to Long-term

Insitu Exposures of Urban Runoff. In: Effects of Watershed Development and

Management on Aquatic Ecosystems: Proceedings of an Engineering Foundation

Conference. Snowbird, UT.

Dartiguenave, C. M., I. ECLille and D. R. Maidment. 1997. Water Quality Master Planning for

Austin. CRWR Online Report 97-6.

Dunne, T., and L.B. Leopold. 1978. Water in Environmental Planning.W.H.. Freeman and Co.,

New York. 818 pp. 

Ellis, J. 1986. “Pollutional Aspects of Urban Runoff.” In: Urban Runoff Pollution. eds., H. C.

Torno, J. Marsalek and M. Desbordes. Springer-Verlag, Berlin. 

Evett, et al. 1994. Effects of Urbanization and Land Use Changes on Low Stream Flow. North

Carolina Water Resources Research Institute, Report No. 284. 66 pp. 

Field R. and R. Pitt 1990. Urban Storm-induced Discharge Impacts: US Environmental

Protection Agency Research Program Review. Water Science and Technology. Vol. (22)

10-11.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 5-3

Gavens, A., D. Revitt and J. Ellis. 1982. “Hydrocarbon Accumulation in Freshwater Sediments

of an Urban Catchment.” Hydrobiologia. (91): 285-292.

Galli, J. 1991. "Thermal Impacts Associated with Urbanization and Stormwater Management

Best Management Practices." Publication No. 91701. Metropolitan Washington Council

of Governments. Washington, D.C. 188 pp. http://www.mwcog.org

Guay, J. 1996. Effects of Increased Urbanization from 1970's to 1990's on Storm Runoff

Characteristics in Perris Valley, CA. USGS Water Resources Investigations Report. 95-

4273. 

Hammer, T. 1972. “Stream Channel Enlargement Due to Urbanization.” Water Resources

Research 8(6): 1530-1540.

Heany, J. and W. Huber. 1978. Nationwide Assessment of Receiving Water Impacts from Urban

Storm Water Pollution. U.S. Environmental Protection Agency, Cincinnati, OH.

Hilgartner, W. 1986. Human Actions in the Watershed Reflected in Historical Estuarine

Changes. Coastlines. Issue 6.2.

Hollis, F. 1975. The Effects of Urbanization on Floods of Different Recurrence Intervals. 

Water Resources Research, 11:431-435. 

Horner, et al. 1996. Watershed Determinates of Ecosystem Functioning. In: Effects of Watershed

Development and Management on Aquatic Ecosystems. Roesner, L.A. (editor). Snowbird

Utah. August 4-9, 1996. Engineering Foundation.

Horner, R. R., J. J. Skupien, E.H. Livingston and H.E. Shover. 1992. Water Quality Impacts of

Urban Land Use. In: Fundamentals of Urban Runoff Management: Technical and

Institutional Issues. Terrene Institute, Washington, DC. 

Horner, R. R., J Geurdy, and M. J. Kortenhoff. 1990. Improving the Cost Effectiveness of

Highway Construction Site Erosion and Pollution Control. Washington State

Transportation Center and the Federal Highway Administration. Seattle, WA, 79pp. 

Islam, Taphorn and Utrata-Halcomb, 1998. Current Performance of Sediment Basins &

Sediment Yield Measurement of Construction Sites in Unincorporated Hamilton County,

Ohio. Prepared for Hamilton County Soil and Water Conservation District. 

Jarrett, A. 1996. Sediment Basin Evaluation and Design Improvements. Pennsylvania State

University. Prepared for Orange County Board of Commissioners, 11pp. 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 5-4

Kundell, J. and T. Rasmussen. 1995. Recommendations of the Georgia Board of Regent’s

Scientific Panel on Evaluating the Erosion Measurement Standard Defined by the

Georgia Erosion and Sedimentation Act. In Proceedings of the 1995 Georgia Water

Resources Conference. Athens, Georgia.

Leopold, L. 1968. Hydrology for Urban Land Use Planning – A Guidebook on the Hydrologic

Effects of Urban Land Use. U.S. Geological Survey. Circular No. 554. 

Leopold, L. 1973. "River Change with Time: An Example." Geological Society of America

Bulletin. 84: 1845-1860.

Leopold, L. 1994. A View of the River. Harvard University Press, Cambridge, MA.

Lim, S. and V. Olivieri. 1982. Sources of Microorganisms in Urban Runoff. Johns Hopkins

School of Public Health and Hygiene. Jones Falls Urban Runoff Project. Baltimore, MD

140 pp.

Livingston, E. “Florida’s Evolving Stormwater/Watershed Management Program” In Effects of

Watershed development and Management on Aquatic Systems. L. Roesner (ed.)

Engineering Foundation Conference. Proceedings. 1996. Snowbird, UT. (August 4-

9):567-590. 

MacCoy, D. and R. Black. 1998. Organic Compounds and Trace Elements in Freshwater

Streambed Sediment and Fish from the Puget Sound Basin. U.S. Geological Survey. 

USGS Fact Sheet 105-98. 

McCutcheon, S. C., Martin, J. L. and Barnwell, T. O., Jr., Water Quality, Chapter 11, Handbook

of Hydrology, David Maidment, Ed., McGraw-Hill, New York, 1993. 

Mackiernan, G., M. Leffler and T. Malone. 1996. Scientific Consensus and Public Policy:

Dissolved Oxygen in the Chesapeake Bay. Watershed ‘96 Conference Proceedings.

Baltimore, Maryland.

MacRae, C. and J. Marsalek. 1992. The Role of Stormwater in Sustainable Urban Development.

Proceedings Canadian Hydrology Sympposium: 1992-Hydrology and its Contribution to

Sustainable Development, June 1992. Winnipeg, Canada. 

MacRae and DeAndrea, 1999. Assessing the Impact of Urbanization on Channel Morphology. 2nd

Internaitonal Conference on Natural Channel Systems. Niagra Falls, OT.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 5-5

Masterson, J. and R. Bannerman 1994. Impacts of Stormwater Runoff on Urban Streams in

Milwaukee County, Wisconsin. National Symposium on Water Quality. American

Water Resources Association.

May, C. R. Horner, J. Karr, B. Mar, and E. Welch. 1997. Effects of Urbanization on Small

Streams In the Puget Sound Lowland Ecoregion. Article No. 18 in The Practice of

Watershed Protection. 2000. Center for Watershed Protection, Ellicott City, MD. 

http://www.stormwatercenter.net

Maxted, J. R., E. L. Dickey, and G. M. Mitchell. 1994. Habitat Quality of Delaware Nontidal

Streams. Delaware Department of Natural Resources, Division of Water Resources

Report.

Mederios, C., R. LeBlanc, and R. A. Coler. 1983. An In situ Assessment of the Acute toxicity of

Urban Runoff to Benthic Macroinvertebrates. Environmental Toxicity and Chemistry

(2):119-126.

Menzie-Cura and Associates. 1995. Measurements and Loadings of Polycyclic Aromatic

Hydrocarbons (PAH) in Stormwater, Combined Sewer Overflows, Rivers, and Publically

Owned Treatment Works (POTWs) Discharging into Massachusets Bay. 

Morisawa, Marie and Ernest LaFlure. 1979. Hydraulic Geometry, Stream Equalization and

Urbanization. In the Proceedings of the Tenth Annual Geomorphology Symposia Series

entitled “Adjustments of the Fluvial System” held at Binghamton, New York September

21-22, 1979. Kendall/Hunt Publishing Company, Dubuque, IA.

NOAA. 1992. 1990 Shellfish Register If Classified Estuarine Waters: Data Supplement. National

Oceanic and Atmospheric Agency, National Ocean Service, Rockville, MD.

New Mexico Surface Water Quality Bureau, 1999. Six Mile, Cieneguilla and Moreno Creeks -

Draft Fecal Coliform TMDL Document. 

Novotny, V. and G. Chesters. 1981. Handbook of Nonpoint Pollution: Sources and

Management. Van Nostrand Reinhold Company NY.555 pp.

Orth, R. and K. Moore. 1983. Chesapeake Bay: An Unprecedented Decline in Submerged

Aquatic Vegetation. Science 22:51-52. 

Pasternack, G. 1998. Physical Dynamics of Tidal Freshwater Delta Evolution. PhD Dissertation.

Johns Hopkins University, Baltimore, Maryland. 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 5-6

Pitt, R. 1998. Epidemiology and Stormwater Managment. In Stormwater Quality Management.

CRC /Lewis publishers. New York, NY.

Pitt, R. and J. Voorhees. 1989. Source Load and Management Model – An Urban Nonpoint

Source Water Quality Model: Wisconsin Department of Natural Resources, v. I-III,

PUBL-WR

Richey, J.S. 1982. Effects of Urbanization on a Lowland Stream in Urban Washington. PhD

Dissertation. University of Washington.

Samadpour, M. and N. Checkowitz. 1998. Little Soos Creek microbial source tracking.

Washington Water RESOURCE, Spring, 1998. University of Washington Urban Water

Resources Center.

Sauer V. et al. 1983. Flood Characteristics of Urban Watersheds in the United States. US

Geological Survey Water Supply Paper 2207.

Schiff, K. 1996. Review of Existing Stormwater Monitoring Programs for Estimating

Bight-Wide Mass Emissions from Urban Runoff. SCCWRP Annual Report 1996. 

Schueler, T.R. 1987. Controlling Urban Runoff: A Practical Manual for Planning and Designing

Urban Best Management Practices. Publication No. 87703. Metropolitan Washington

Council of Governments. Washington, DC. 272 pp. http://www.mwcog.org

Schueler, T.R. 1994. The Importance of Imperviousness. Article No. 1 in The Practice of

Watershed Protection. 2000. Center for Watershed Protection, Ellicott City, MD. 

http://www.stormwatercenter.net

Schueler, T.R. 1999. Microbes and Urban Watersheds. Article No. 31 in The Practice of

Watershed Protection. 2000. Center for Watershed Protection, Ellicott City, MD. 

http://www.stormwatercenter.net

Schueler, T. R. and J. Lugbill, 1990. "Performance of Current Sediment Control Measures at

Maryland Construction Sites." Publication No. 89705. Metropolitan Washington

Council of Governments, Washington, DC. 89 pp. http://www.mwcog.org

Schueler, T.R. and D. Shepp. 1993. "The Quantity of Trapped Sediments in Pool Water Within

Oil Grit Separators in Suburban Maryland." Metropolitan Washington Council of

Governments, Washington, DC.

Scott, J., C. Steward and Q. Stober. 1986. Effects of Urban Development on Fish Population

Dynamics in Kelsey Creek, Washington. Transactions of the American Fisheries Society.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 5-7

Short, F.T. and S. Wyllie-Echeverria. 1996. A Review of Natural and Human-induced

Disturbance of Seagrasses. Environmental Conservation 23(1):17-27. 

SMBRP. 1996. An Epidemiological Study of Possible Adverse Health Effects of Swimming in

Santa Monica Bay. R. Haile, J. Alamillo, K. Barrett, R. Cressey, J. Dermond, C. Ervin, A.

Glasser, N. Harawa, P. Harmon, J. Harper, C. McGee, R. Millikan, M. Nides, J. White.

Monterey Park, CA.

Sonzogni, W., C. Chesters, D. R. Coote, D. N. Jeffs, J. C. Konrad, R.C. Ushy, and J. B.

Robinson. 1980. Pollution from Land Runoff. Environmental Science and Technology.

Vol 14(2):148-153.

Spence, B., G. Lomnicky, R. Hughes, and R. Novitzki. 1996. An Ecosystem Approach to

Salmonid Conservation. TR-401-96-6057. ManTech Environmental Research Services

Corporation, Corvallis, OR. (Available on the NMFS-NWR website:

http://www.nwr.noaa.gov) 

Spinello, A. G., and D. L. Simmons. 1992. “Base Flow of 10 South-Shore Streams, Long Island,

New York, 1976-85, and the Effects of Urbanization on Base Flow and Flow Duration.”

USGS. Water Resour. Invest. Report 90-4205. 

Stern, D. 1996. Initial Investigation of the Sources and Sinks of Cryptosporidium and Giardia

Within the Watersheds of the New York City Water Supply System. In Proceedings of a

Symposium on New York City Water Supply Studies. Eds. McDonnel et al. TPS-96-2

184pp. American Water Resources Association. Herndon, VA.

Steuer, Jeffrey, William Selbig, Nancy Hornewer, and Jeffrey Prey. 1997. Sources of

Contamination in an Urban Basin in Marquette, Michigan and an Analysis of

Concentrations, Loads, and Data Quality. U.S. Geological Survey, Water-Resources

Investigations Report 97-4242.

Stevenson, J., L. Staver and K. Staver. 1993. Water Quality Associated with Submersed Aquatic

Vegetation along an Estuarine Gradient. Estuaries 16(2): 346-361.

Sturm, Terry W. and Ronald E. Kirby, Jr. 1991. Sediment Reduction in Urban Stormwater Runoff

from Construction Sites. Georgia Institute of Technology. Atlanta, GA, 104 pp. 

Trimble, S. 1997. Contribution of Stream Channel Erosion to Sediment Yield from an

Urbanizing Watershed. Science. 278: 1442-1444.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 5-8

USDA. 2002. Technical Release No. 20: Computer Program for Project Formulation Hydrology

(TR-20). Technical Release No. 55: Urban Hydrology for Small Watersheds (TR-55). 

U.S. Department of Agriculture. Natural Resources Conservation Service, National

Water and Climate Center. Portland, OR.

http://www.wcc.nrcs.usda.gov/water/quality/hydro/

USDA, 2000. 1997 National Resources Inventory. (Revised December 2000). U.S. Department

of Agriculture. Natural Resources Conservation Service. Washington, DC. 

http://www.nrcs.usda.gov/technical/NRI/

USEPA. 2002. Economic Analysis of Proposed Effluent Limitation Guidelines and New Source

Performance Standards for the Construction and Development Category; May 2002. EPA

821-R-02-008. http://www.epa.gov/waterscience/guide/construction/

USEPA. 2002a. Development Document for Proposed Effluent Limitation Guidelines and New

Source Performance Standards for the Construction and Development Category; May

2002. EPA 821-R-02-007. http://www.epa.gov/waterscience/guide/construction/

USEPA. 1999. Economic Analysis of the Final Phase II Storm Water Rule. U.S. Environmental

Protection Agency. Washington, DC.

USEPA. 1998a. "The Quality of Our Nation’s Water: 1996 Report to Congress." EPA-841-S97-001. U.S. Environmental Protection Agency, Office of Water, Washington, DC. 

http://www.epa.gov/305b/

USEPA. 1998b. EPA Beach Watch web site. http://www.epa.gov/waterscience/beaches . U.S.

Environmental Protection Agency, Office of Water, Washington, DC.

USEPA. 1996. Safe Drinking Water Act Amendments of 1996: General guide to provisions. PB810-S-96-001. U.S. Environmental Protection Agency, Office of Water, Washington,

DC. 

USEPA. 1993. Urban Runoff Pollution Prevention and Control Planning. EPA-625-R-93-004.

U.S. Environmental Protection Agency, Office of Research and Development,

Washington, DC.

USGS. 2000. National Hydrography Dataset. U.S. Geological Survey. Washington, DC. 

http://nhd.usgs.gov

Walling, D. and J Woodward. 1995. “Tracing Sources of Suspended Sediment in River Basins:

A Case Study of the River Culm, Devon, UK” Marine and Freshwater Research. 46: 324-

226. 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 5-9

Waschbusch et al. 2000. "Sources of Phosphorus in Stormwater and Street Dirt from Two Urban

Residential Basins in Madison, Wisconsin, 1994-1995." In: National Conference on

Tools for Urban Water Resource Management and Protection. US EPA February 2000:

pp. 15-55.

Woodward-Clyde Consultants. 1992. Source Identification and Control Report. Prepared for the

Santa Clara Valley Nonpoint Source Control Program. Oakland, California.

York J. H. and W. J. Herb. 1978. Effects of Urbanization and Streamflow Sediment Transport in

Rock Creek and Anacostia River Basins. Montgomery County, MD, 1972-1974. U.S.

Geological Survey Professional Paper No. 1003. 72 pp. 
Appendix A

Evaluating Pollutant Loadings from Construction Activities

that Potentially Impact the Environment 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 A-1

Appendix A Evaluating Pollutant Loadings from Construction Activities

that Potentially Impact the Environment 

This appendix details aspects of the methodologies described in Section 3 to pollutant discharges

that result from construction activities under two options. Specifically, it expands on the

discussion presented in Section 3, providing additional information on the assumptions used by

EPA in its assessment.

Estimates of Affected Area

The Phase II NPDES storm water rule economic analysis (USEPA, 1999) presented information

on the size and nature of construction activities under the Phase I and II storm water programs. 

In addition, the Phase II economic analysis (EA) detailed an extensive analysis of pollutant

loadings for a range of site sizes, soil types, land slopes, and locations. EPA’s current evaluation

uses the results presented in the Phase II report to update its overall estimate of national

construction site loadings. EPA expects that new regulation of the construction and development

(C&D) category will augment the existing state and Phase I NPDES storm water programs. In

addition, new regulations will shape future development of construction programs expected

under the Phase II NPDES storm water program.

EPA identified the array of potentially affected construction sites in the nation. EPA’s assessment

of construction site loadings is based on regulation of approximately 2.17 million acres per year.

This regulated acreage estimate was calculated based on estimated national development rates

from the 1997 National Resources Inventory (USDA, 2000), less the estimated acreage either

occupied by sites less than 1 acre in size (not regulated) or sites which receive Phase II “R”

waivers. “R” waivers are those applied for and granted under the construction general permit for

sites with very low erosivity. The Phase II EA estimated the total acreage granted “R” waivers to

be approximately 33 thousand acres (approximately 1.8 percent of the total constructed acreage).

Based on its assessment of probable construction site size distribution, EPA estimates that

another 1.7 percent of the annual constructed acreage will be on sites less than 1 acre. In

addition, under Option 1, EPA is considering removing sites smaller than 5 acres. EPA estimates

that approximately 18 percent of construction occurs on sites less than 5 acres in area.

EPA’s Analysis of State Programs

Table A-1 presents the results of EPA’s analysis of state construction programs. EPA focused on

the states with the largest annual construction footprint to estimate the level of current control

(i.e., not all state regulations were reviewed). As a result, the absence of a “Yes” value in Table

A-1 may indicate that a construction program was not evaluated by EPA. Overall, the results in

Table A-1 were converted into a ecoregion “score” or the percent of developed acreage that
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 A-2

would gain greater management under EPA’s options. Table A-2 indicates the resulting

percentage of construction acreage affected by the potential effluent guidelines in each ecoregion. 

As expected, new BMPs required under the options (e.g., certification of sediment basins) were

not found in existing state regulations, and overall, existing state requirements require optionlevel BMPs for approximately 30-35 percent of the acreage developed annually.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 A-3

Table A-1. Assessment of State Construction Control Programs

State/Territory

Minimum of 3600

Cubic Feet per Acre

Storage Requirement

for Larger Sites

14-Day or

More 

Inspection

Frequency

14- Day

Cover

Required

States with Less than

20 Inches of

Precipitation Per

Year

Alabama

Alaska Yes Yes Yes

Arizona Yes Yes Yes Yes

Arkansas 

California Yes Yes Yes

Colorado Yes

Connecticut Yes Yes Yes

Delaware Yes Yes Yes

District of

Columbia

Florida 

Georgia 

Hawaii 

Idaho Yes

Illinois Yes

Indiana 

Iowa Yes Yes Yes

Kansas 

Kentucky 

Louisiana 

Maine 

Maryland 

Massachusetts Yes Yes Yes

Michigan 

Minnesota 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

State/Territory

Minimum of 3600

Cubic Feet per Acre

Storage Requirement

for Larger Sites

14-Day or

More 

Inspection

Frequency

14- Day

Cover

Required

States with Less than

20 Inches of

Precipitation Per

Year

June 2002 A-4

Mississippi 

Missouri 

Montana Yes Yes

Nebraska 

Nevada Yes

New Hampshire Yes Yes Yes

New Jersey 

New Mexico Yes Yes Yes Yes

New York 

North Carolina 

North Dakota Yes

Ohio Yes Yes

Oklahoma Yes

Oregon 

Pennsylvania Yes Yes Yes

Rhode Island 

South Carolina Yes Yes Yes

South Dakota Yes Yes Yes Yes

Tennessee Yes Yes Yes

Texas Yes Yes Yes

Utah Yes Yes Yes Yes

Vermont 

Virginia Yes Yes Yes

Washington 

West Virginia Yes Yes

Wisconsin
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

State/Territory

Minimum of 3600

Cubic Feet per Acre

Storage Requirement

for Larger Sites

14-Day or

More 

Inspection

Frequency

14- Day

Cover

Required

States with Less than

20 Inches of

Precipitation Per

Year

June 2002 A-5

Wyoming Yes Yes
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 A-6

Table A-2. Percentage of Acreage Developed Without Option Equivalent Requirements

Ecoregion

3600 Cubic Feet per

Acre Storage in

Sedimentation

Basins for Larger

Sites 

(Criterion 1)

Certification of

Sediment Basins

(Criterion 2)

14-Day or more

frequent

inspection

(Criterion 3)

14- Day Cover For

Wet-States, or

none required for

dry states

(Criterion 4)

Overall

Weighted

Percentage of

Acres Without

Coverage

ER 1 28.96% 0.00% 28.25% 30.72% 24.7%

ER 2 39.16% 0.00% 57.61% 57.61% 47.1%

ER 3 0.00% 0.00% 10.66% 10.66% 8.0%

ER 4 77.06% 0.00% 77.06% 77.06% 65.5%

ER 5 65.74% 0.00% 65.74% 65.74% 55.9%

ER 6 100.00% 0.00% 100.00% 100.00% 85.0%

ER 7 100.00% 0.00% 100.00% 100.00% 85.0%

ER 8 64.45% 0.00% 68.16% 64.45% 56.6%

ER 9 50.16% 0.00% 55.30% 42.80% 43.4%

ER 10 74.51% 0.00% 81.79% 81.79% 68.8%

ER 11 71.53% 0.00% 71.70% 71.70% 60.9%

ER 12 51.80% 0.00% 65.17% 65.17% 54.1%

ER 13 89.38% 0.00% 32.32% 89.38% 47.4%

ER 14 67.34% 0.00% 53.83% 71.01% 51.4%

ER 15 62.15% 0.00% 100.00% 100.00% 81.2%

ER 16 5.65% 0.00% 100.00% 100.00% 75.6%

ER 17 100.00% 0.00% 100.00% 100.00% 85.0%

ER 18 100.00% 0.00% 100.00% 100.00% 85.0%

ER 19 100.00% 0.00% 100.00% 100.00% 85.0%

National

Average

Weighted by

Land

Developed

64% 0% 70% 69% 58.9%
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 A-7

Information in Table A-2 was converted into an overall national “score,” to discount estimated

TSS loadings reductions by accounting for acres covered by equivalent programs. To combine

the four analyzed criteria, EPA assumed that the individual contributions to reductions were 10,

15, 50, 25 percent, respectively. For example, sedimentation basins based on 3,600 cubic feet

contribute 10 percent of the estimated reduction between baseline and option loadings. On a

national basis, EPA estimated that approximately 41 percent of land is served by equivalent

programs, and would not be affected by Option 1 or 2 requirements.
Appendix B

Inventorying of Streams Potentially Impacted By

Construction Activities
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 B-1

Appendix B Inventorying of Streams Potentially Impacted By

Construction Activities

Overview

This appendix describes EPA’s effort to inventory and assess environmental impacts of

construction activities. Specifically, the appendix describes, in detail, the analytical steps

performed to inventory the nation’s stream system and provides general background information

on the rationale used to develop the inventory approach. Delineation of impacted stream

environments forms the basis for assessing the future benefits of regulatory controls on

construction and activities. 

The objectives of this appendix are as follows:

• To describe a method to characterize streams by their hydrologic function based on regional

differences

• To establish the appropriate map scale for inventorying streams based on their size and

geometry (e.g., length, slope, dimensions).

Stream Characterization

Many of the impacts on streams are a function of drainage area and hydrologic regime. 

Producing a national summary of potentially impacted stream networks is challenging because

the nature and size of streams vary significantly throughout the country. For example,

watersheds that produce a minimum base flow of 1 cubic foot per second (cfs) occupy 1 square

mile in the eastern United States but require 100 square miles in the arid southwest. To account

for this variation, EPA divided the country into 19 large hydrologic regions and then further

inventoried the streams in each region separately, based on approximate stream size categories

(i.e., stream orders). Representative watersheds in each of the 19 large ecoregions in the

contiguous U.S. (see Figure B-1) were inventoried to determine the average stream density for

the stream orders that are the most likely impacted in each ecoregion. 

EPA developed the boundaries for the 19 ecoregions based on a stream density assessment that

used EPA’s Reach File 1 (RF1) stream network and the 76 ecoregions developed by Omernik

(1987). Figure B-2 shows the RF1 densities in terms of acres per stream mile for each of the 76

ecoregions. Combining the 76 ecoregions into the 19 ecoregions shown in Figure B-1 helps

simplify the analysis while still capturing a reasonable number of regions with similar stream

densities and accounts for gross changes in hydrology, land forms, soil types, and potential

natural vegetation.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 B-2

In general, the literature indicates that environmental sensitivity (e.g., geomorphologic changes,

pollutant toxicity) is greater on smaller stream orders, from the intermittent headwater streams to

small perennial streams. For most environmental impacts (except perhaps nutrient loadings), the

impacts of the construction and land development industry tend to decrease with increased

stream size, and the impacts tend to become confounded with other influences (e.g., other point

and nonpoint source pollutant loads). For this reason, the inventory focused on relatively small

watersheds (between 2 and 7 square miles) to better assess the impacts of hydrologic changes on

small streams.







 

























	

	

 











Figure B-1. Regions for Stream Inventorying
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 B-3









	






	


	

	



	





		



	

	



	
 



















	





	



 







	

	

	



	

	




	




	








	

	


	

	
















	





	






	

	













	







Region

01

02

03

04

05

06

07

08

09

10

11

12

13

14

15

16

17

18

19

Ecoregion Boundary

Figure B-2. Stream Densities for Omernik Ecoregions

(in units of acres per stream mile)

Because EPA focused on small streams, it was necessary to select a method by which to

characterize streams by size. Historically, various schemes have been created to characterize and

count streams within a drainage network, including the following:

• Stream order is determined by counting stream segments starting with the smallest stream

channels found on a selected map scale.

• Stream level is determined by counting stream segments starting from the most downstream

discharge point (ocean or estuary) on a selected map scale.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 B-4

• Streams are characterized by physical descriptions including flow frequency (perennial or

intermittent streams), size (large, medium, or small), and/or terms such as swales, creeks,

and rivers.

• Watershed size is based on the scale of the map on which the watersheds are just visible.

EPA selected the first method, stream order characterization, for use in this assessment.

Map Scale Selection

Because any network of “streams” identified at the outset of a hydrologic inventory is highly

dependent on the scale of the map used, selecting the appropriate scale is a critical step. Rills

and swales that are obvious and identifiable on a 1:2,400-scale map are completely absent on a

1:250,000-scale map. Figure B-3 shows the streams visible on the following three scales of maps

for a typical watershed (10 square miles) in northeastern Maryland: 

• U.S. Geological Survey (USGS) 1:250,000-scale map or streams found in EPA’s RF1

stream network

• USGS 1:100,000-scale map or streams found in EPA’s Reach File V. 3 (RF3) and National

Hydrography Dataset (NHD) (USGS, 2000) stream networks

• USGS 1:24,000-scale map.

The three map scales, respectively, permit successively finer viewing of stream sizes: (1) large

perennial streams, (2) medium perennial to intermittent streams, and (3) larger swales and

intermittent streams. Although not shown in Figure B-3, an even finer detail stream

network—one based on 1:2,400-scale maps (a scale commonly used by local governments) that

includes the smallest swales—can be visualized by increasing the number of 1:24,000-scale

streams threefold (i.e., delineation of watersheds as small as 2 acres). Figure B-3 illustrates the

importance of map scale selection:

• Inventorying stream networks based on 1:24,000-scale will include many more streams than

a 1:250,000-scale inventory;

• The stream order assigned to any stream will be different based on the map scale; and

• Direct evaluation using only EPA’s RF1 and RF3 hydrologic stream coverages would

grossly undercount the number of streams potentially impacted.
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 B-5

0.9 0 0.9 1.8 2.7 Miles

S

N

W E

Swale = 1:24,0 00

EPA R F3 = 1:100,000

Stream Network Scale

EPA R F1 = 1:250,000

Figure B-3. Stream Networks for 1:250,000-, 1:100,000-, and 1:24,000-Scale Maps

Note: The 1:24,000-stream network shown contains more streams than the USGS identified on its 7.5-minute

quadrangle maps using typical blue or dashed blue lines. This figure includes all swales that can be drawn

based on contour lines given on the 1:24,000 map, resulting in an enhancement that shows two to three times

more “streams” than are shown on the original map (down to watersheds approximately 10 acres in size). 

Interpretation of contour lines defines a stream network based on land forms as the contours are

present because streams/swales have created them. This contour-based enhancement defines a

“stream” based on topography, regardless of whether or not the stream is actually drawn on the

map.

Because using an increased detail of stream network (smaller map scale) requires increased effort

levels, EPA developed a method that was both practical and depicted the appropriate stream level

for this assessment. The amount of stream data available is extensive; the national coverage for

RF1 contains 100 megabytes of data, while RF3 contains 7,400 megabytes. All of RF1 (data on

just the largest rivers in the nation) can reside and be analyzed on a single microcomputer. 

However, the RF3 network and the similar, newer NHD are so large they can be analyzed in a
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 B-6

microcomputer environment only when divided into 20 separate parts. Therefore, EPA assumed

that a national dataset containing all streams and swales identifiable from 1:2,400-scale maps

would be unworkable within the current limits of any microcomputer. 

To maintain a relatively small map scale, EPA performed an inventory of streams and swales

identifiable based on 1:24,000-scale maps (where swales are added manually) by first sampling

representative watersheds or areas. (An actual inventory of individual swales and streams on a

1:24,000-scale for specific acreage developed in any given state in any given year is beyond

current computational capabilities and the limits of available data, requiring some type of

approximation or sampling technique). EPA used digital elevation maps (DEMs), which allowed

EPA to process contour data, enhancing the original stream network to provide data on the larger

intermittent streams (typically streams draining less than 30 acres). Because EPA’s assessment

of the construction industry indicates that a medium-sized construction start is approximately 20

acres, this approach is refined enough to inventory the number and size of streams potentially

impacted by construction and land development activities. The number and length of streams in a

larger area were then estimated by using the stream density found in the sampled watershed/area. 
Appendix C

Impacts of Construction Activities on Hydrology
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

1 The Soil Conservation Service (SCS) is the former name of the Natural Resources Conservation

Service (NRCS).

June 2002 C-1

Appendix C Impacts of Construction Activities on Hydrology

Overview

This appendix describes hydrologic changes that result from construction and post-development

activities, and focuses primarily on changes in runoff rates and soil infiltration. The general

hydrologic changes caused by these industries have environmental and economic impacts.

The objectives of this appendix are:

• To demonstrate the variation in runoff rate for a 10-acre site as it changes from a forested

condition into a construction condition.

• To describe the environmental benefits of current BMPs primarily designed to limit

discharge from construction sites.

Methodology

A simple hydrologic model was developed to depict the hydrologic changes that result from

construction and land development activities on a (10-acre) site. The size of 10-acres was chosen

because it represents the typical size for a construction site. In addition, the hydrologic changes

are believed to be similar to changes that result on larger sites such as 100-acre sites and 1000-

acre sites.

Investigation of hydrologic changes was performed by using two hydrologic models: TR-55 and

TR-20. These models use data developed over many years by USDA/Natural Resources

Conservation Service (NRCS), and are among the most often employed models for the

hydrologic design of hydraulic structures, such as storm drainage systems (USDA, 2002).

The 10-acre watershed was assumed to have a 50/50 mix of soils in the type B and C hydrologic

soil classification, with an average ground slope of 7 percent. Time of concentration was derived

based on standard TR-55 worksheets that analyze sheet flow, shallow concentrated flow, and

pipe flow. For the analysis, the 2-year 24-hour SCS1

 type II rainfall event, totaling 3.2 inches of

rainfall, was used to conservatively estimate the runoff hydrographs. 

Multiple land use conditions (Table C-1) were evaluated to help assess the hydrologic impacts

for the small 10-acre site. EPA notes that most construction sites occupying 10 acres are
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 C-2

equipped with a sedimentation pond, intended to minimize sediment discharge from the site.

Although sediment ponds are not designed specifically shave the peak runoff rate (i.e., limit the

construction site peak discharge rate to be equal to or less than the peak runoff from the forested

site), these structures inherently have some capability of peak-shaving depending on the site

conditions. In addition, sedimentation ponds can be built to increase its peak-shaving capability.

For the purposes of this assessment, EPA assumed that a sedimentation pond (Condition 3)

shaves the peak completely, as shown in Figure C-1.

Table C-1. Evaluated Hydrologic Conditions for a Typical 10-Acre Site

Land Use

Condition Description

1 Pre-development: a forested land use

2 Construction: cleared and grubbed soil surface with no vegetation and without

construction runoff BMPs (No sedimentation ponds)

3 Construction: cleared and grubbed soil surface with no vegetation with storm water

BMPs (a sedimentation pond that also shaves the peak runoff to match the predevelopment peak flow)

The results of the analysis are presented below for each of these land use conditions.

Discussion of Runoff Results for Modeled Land Use Conditions

Figure C-1 compares the predicted runoff hydrographs for Land Use Conditions 1 through 3. 

The hydrographs in the figure show the large increase in runoff volume and peak runoff rate that

occurs for construction sites with or without storm water BMPs that limit the peak runoff rates.

This increase is caused by the removal of existing vegetation and compaction of site soils with

earth moving equipment, which greatly diminishes the site’s ability to absorb rainfall and limit

discharge. In fact, NRCS data strongly suggest that a fully-constructed site (e.g., a residential

neighborhood) produces less runoff than a denuded site under construction, even though

impervious surfaces (e.g., driveways, roofs) have not yet been installed. 
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 C-3

Comparison of Various Construction Conditions for A T en Acre 

Construction Site

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

10 12 14 16 18 20

Time In Hours

Flow Discharged (cubic feet per second)

Forested

Construction Site W ithout BMPs

Construction Site W ith BMPs

Figure C-1. Runoff Hydrographs for a 10-Acre Construction Site

Although the implementation of peak-shaving BMPs minimizes some of the flooding

downstream of a construction site due to high peak flows, it does not eliminate the potential for

enhanced flooding that is caused by longer durations of high-flow discharges. Table C-2

indicates that the construction site produces high flows for a much greater duration than flows

originally released from the forested site. In fact, the 10-acre site that once produced a flow rate

equal to or greater than 3 cubic feet per second (cfs) for only 0.2 hours will produce more than 3
Environmental Assessment of Construction and Development Proposed Effluent Guidelines

June 2002 C-4

cfs for 3.2 hours when peak-shaving BMPs are employed during construction. Should a 2-year

storm occur during the construction period, the longer flow duration increases the chances that

the discharge will be combined with downstream peak flows from other developing/developed

locations to produce a flooding condition.

Table C-2. Comparison of Durations of High Flow Rates

for Different Land Use Conditions

Land Use Condition

Hours of flow equal to

or greater than: 

3 cfs 2 cfs 1 cfs

Forested 0.2 0.3 0.8

Construction site without peak shaving BMPs 0.9 1.4 3.3

Construction site with peak shaving BMPs 3.2 4 5.7

cfs = cubic feet per second