S e n s i t i v e

E n v i ronments 

and the Siting 

of Hazardous Wa s t e

Management 

F a c i l i t i e s

Environmental Protection May 1997

A g e n c y

Solid Waste and Emergency Response (5305W)

This publication discusses sensitive types of enviro n m e n t s

that pose special challenges to the siting, expansion, 

and operation of RCRA hazardous waste management

facilities. Locating hazardous waste management facilities

in certain areas – because of their soils, terrain, gro u n dw a t e r, or weather conditions – may pose significant risks 

of releases and possible exposures to humans and the

e n v i ronment. The environmentally sensitive locations

a d d ressed in this book are :

Floodplains Unstable Te r r a i n

Wetlands Un f a vorable We a t h e r

Groundwater C o n d i t i o n s

E a rthquake Zo n e s Incompatible Land 

Karst So i l s Us e

In addition to these technical siting factors, there are social

concerns that affect the appropriateness of a hazard o u s

waste facility’s location. These social concerns and re l a t e d

e valuation factors will be addressed in a future EPA

guidance document. 

I n t r o d u c t i o n
What Are Environmentally Sensitive

Locations and 

Why Are They a Concern?

Se n s i t i ve environments are locations that, because of their

physical conditions, may be disturbed or perm a n e n t l y

damaged by hazardous waste contamination. Wetlands, for

example, are especially sensitive to chemical contamination.

Se n s i t i ve environments are also locations that are physically

unstable and may change so greatly that they can cause the

release of a hazardous waste or complicate its cleanup. 

I n c o m p a t i b l e

Land Use

K a r s t

F l

Unstable Terrain

U n f a v o r a b l e

W e a t h e r

C o n d i t i o n s

E a r t h q u a k e

Z o n e s

Locating hazardous waste facilities in the sensitive environments shown in this

figure increases the risk of contamination.

A q u i f e r
For example, floodwaters spilling into floodplains may damage waste

management stru c t u res such as tanks or berms (walls of earth), causing

the release of hazardous waste to the environment. This bro c h u re

p rovides additional information on wetlands and floodplains and

discusses other environments that are sensitive, particularly in re l a t i o n

to hazardous waste management facilities.

Soil, gro u n d w a t e r, and weather conditions are important technical

factors in determining how environmentally sensitive a location is.

K n owing about environmentally sensitive areas helps ensure that a

h a z a rdous waste management facility is sited at a location that is safe

for our health and our environment. For example, facilities constru c t e d

on unstable ground or in floodplains are at greater risk for landslides or

floods, re s p e c t i ve l y, which could cause accidental hazardous waste

releases. T h e re f o re, when selecting a

location for a hazardous waste facility,

such safety concerns must be considered.

Other nontechnical factors to consider in

locating a hazardous waste management

facility are the people living and work i n g

a round the facility, that is, the number of

people, their ages, and their health. Also,

hospitals and schools should be considered

because they may be difficult to eva c u a t e

in the event of a hazardous waste spill.

This is why many states re q u i re

h a z a rdous waste management facilities to

locate a safe distance from densely

populated areas, hospitals, schools, or

prisons. These issues will be discussed in

f u rther detail in an upcoming

companion bro c h u re on social factors. 

W e t l a n d s

o o d p l a i n s
Companies that plan to construct and operate hazardous waste

management facilities should avoid siting their facilities in

e n v i ronmentally sensitive areas. If a company does decide to locate a

facility in a sensitive area, its owner should design the facility to

m i n i m i ze risks to people and the environment. By law, an ow n e r’s

a p p roach to locating a safe hazardous waste management facility must
The distribution of three of the types of sensitive

locations–wetlands, land use (population), and 

major areas of karst–demonstrates the need to site

hazardous wastes carefully.

include consideration of the physical site, the facility’s design, and its

operating conditions. The facility’s design includes such factors as

whether it is designed to protect surrounding soils and gro u n d w a t e r s .

Operating conditions may include how many hours each day an

incinerator may burn waste and how well a technology destroys or

t reats waste. 
F l o o d p l a i n s

Floodplains are lands that are subject to periodic flooding.

T h ey are usually lowlands along rivers, streams, lakes, and

oceans. Often, they occur where annual water flow is low or

n o n existent, but they may also occur due to large amounts 

of melting snow or rainfall that run off the land.

Facts About Floodplains

Floodplains act as natural storage areas, slowing down ru s h i n g

floodwaters and reducing dow n s t ream flooding. Floodplains also help

maintain the quality of rivers and streams by filtering eroded soils (also

k n own as sediments) and nutrients such as nitrogen and phosphoru s .

What is a 100-Year Floodplain?

A 100-year floodplain is any land area that

is subject to a 1 percent or greater chance

of flooding in any given year from any

s o u rc e .

The Problem with Locating 

a Facility in a Floodplain 

In d u s t ry considers floodplains as va l u a b l e

locations for development because they 

a re often flat and near water and

t r a n s p o rtation routes. Howe ve r, EPA has

recently seen the damage that flooding can

cause at hazardous waste management

facilities (for example, the 100-year and

5 0 0 - year floods that have occurred along

To Learn Where

Floodplains are

Located . . .

Floodplain maps can be

obtained at no cost from the

Federal Emergency Management Agency’s Flood

Map Distribution Center,

6930 (A-F) San Tomas

Road, Baltimore, MD 21227-

6227 or from the U.S. Army

Corps of Engineers, the Soil

Conservation Service, the

National Oceanic and Atmospheric Administration, the 

US Geological Survey, the

Bureau of Land Management, the Bureau of Reclamation, the Tennessee Valley Authority, and State and

local flood control agencies.

Your county or city planning

office should also have

floodplain maps. Know your

local zoning laws!
the Mississippi River). In some cases, floodwaters have floated

h a z a rdous waste storage tanks off their foundations and floodwaters

h a ve flowed into waste ponds, carrying their hazardous contents

d ow n s t ream. 

The speed of flood waters is also a concern because high flow rates can

e rode wastepiles, berms, landfills, or other types of waste management

s t ru c t u re s .

Facility Siting Recommendations

Facilities should avoid building in floodplains. Existing re g u l a t i o n s

re q u i re hazardous waste management stru c t u res built in a 100-ye a r

floodplain to be built above the 100-year flood level or built to

withstand the flooding event. See Title 40 of the Code of Fe d e r a l

Regulations, Section 264.18 (40 CFR 264.18). 

Floodplains are typically lands along waterways that may flood.

Facilities can be declared exempt from this regulation if they prove

(1) that they can remove all waste before the flood or (2) no harm

will come to human health or the environment when the flood

occurs. Regulations also allow facilities to locate in 100-year

floodplains if owners can prove that the facility can withstand a

washout in the event of a flood (40 CFR 270.14(b)(11)(iv)). In

addition, all facilities should have detailed, up-to-date emergency

response plans that can be put into action before and during floods.

Check your state and local regulations; they may have more

stringent requirements that also have to be met.
W e t l a n d s

Wetlands are areas that are waterlogged for an ex t e n d e d

period of time and include a variety of fish and wildlife

habitats. Swamps, marshes, bayous, bogs, and Arctic tundra

a re wetlands. Wetlands are highly sensitive areas that are

among the most pro d u c t i ve ecosystems in the world. 

In t e resting Facts about Wetlands 

■ On e - t h i rd of all bird species appear in wetlands, which serve as 

vital migratory resting, staging, and nesting areas for waterf owl

and other species.

■ 96 percent of all fish species caught by commercial fishers depend

upon wetlands for part of their life-cyc l e .

■ Wetlands control shoreline erosion, which protects other 

ecosystems from storms, improves water quality, supplies water, 

and regulates climates.

The Problem with Locating 

a Facility In or Near Wetlands

C o n s t ruction or expansion of hazardous waste management facilities

d i rectly in and near wetlands can destroy fish and/or wildlife habitats.

In addition, the high amounts of unstable soils and water in we t l a n d s

make them poor areas for land-based hazardous waste stru c t u res such

as landfills. 

Any hazardous wastes spilled on wetlands can spread faster through the

g roundwater and surface water. Such contamination may harm

c o m m e rcial and re c reational fisheries and shellfish harvesting. Eating

finfish and shellfish that have accumulated toxic substances can be
d a n g e rous to human health. Ha z a rdous waste releases into wetlands can

also reduce the variety and re p roduction of species living in we t l a n d s .

One of the most serious consequences of a hazardous waste spill or 

leak in a wetland can occur in the process of restoring the we t l a n d .

Re m oving the contaminated sediments can be ve ry costly and may even

d e s t roy the wetland. Because wetlands are typically found at the

headwaters of rivers, lakes, and streams, re m oval of contaminated

bottom sediments in wetlands could unintentionally release contaminants dow n s t ream to unsuspecting human, fish, and wildlife

p o p u l a t i o n s .

Facility Siting Recommendations

Ha z a rdous waste management facilities should not be located in

wetlands. This strategy of no construction in wetlands supports the

E PA’s goal of no net loss of this important re s o u rce. Facilities planning

to locate near wetlands should also take special pro t e c t i ve steps. 

They should (1) investigate how the soil and groundwater would be

affected by spilled hazardous wastes, and 

(2) design the facility to pre vent spills. Highlights 

of We t l a n d s

Protection Laws

Section 404 of the Clean

Water Act (CWA) requires

permits from the Army Corps

of Engineers for activities

involving the discharge of

dredged or fill materials into

"waters of the United States,"

which include wetlands.

Other laws that provide some

protection to wetlands are:

the Wild and Scenic Rivers

Act, the Fish and Wildlife

Coordination Act, the Endangered Species Act, and the

Coastal Zone Management

Act. In addition, some States

are now enacting wetlands

protection laws.

S w a m p

M a r s h

B o g

Wetlands are often assigned to

three categories. Swamps are

dominated by trees, marshes by

grasses, and bogs by mosses.
Groundwater

Groundwater is a collection of water beneath the eart h’s

s u rface that is fed either by rainfall percolating through soil

and rock or by surface water. Hi g h - value groundwater is 

(1) the sole source of drinking water available, or (2) the

water feeding into a sensitive environment such as a we t l a n d .

Hyd ro g e o l o gy is the study of the interaction between groundwater and

its source (soil, surface water) along with its movement. A site’s

h yd rogeology is considered complex when scientists cannot accurately

c h a r a c t e r i ze, monitor, or predict groundwater movement. 

Interesting Facts About Groundwater

■ O ver half the U.S. population 

uses groundwater as its main 

drinking water sourc e .

■ 95 percent of rural households

rely on groundwater for their 

drinking water.

■ Groundwater is the only 

s o u rce of drinking water 

for people in some are a s .

■ 34 of the 100 largest U.S. 

cities rely on groundwater for 

drinking and commercial 

p u r p o s e s .
The Problem with Locating a Facility 

Near High-Value Groundwater

In certain parts of the country, contaminants can move quickly into

the gro u n d w a t e r. It can be ve ry difficult and expensive, if not

impossible, to clean up this contamination. The underground soil and

rock in certain areas make it difficult for scientists to find out the

d i rection of groundwater flow, which further complicates cleanup.

Most of the time, groundwater cannot be cleaned for a reasonable cost

and within a reasonable time frame. Re m oving contamination fro m

g roundwater may take hundreds of years. 

Facility Siting Recommendations

Ex p e rts believe that hazardous waste management facilities should 

not be located over high-value groundwater or areas where the

u n d e r g round conditions are complex and not understood. If a facility

plans to locate in one of these areas, EPA re q u i res several studies as part

of the groundwater investigation, such as (1) determining the

complexity and importance of the groundwater for drinking supplies,

(2) determining the direction of groundwater flow, (3) assessing the

ability of the groundwater to be replenished, and (4) determining 

h ow other waters (e.g., rivers and wetlands) are connected to the

g ro u n d w a t e r.

Facility owners should also take extra steps to make sure that no leaks

or spills will occur from stru c t u res that hold hazardous wastes. 

They should use conserva t i ve assumptions when engineering waste

management stru c t u res such as adding more spill containment systems

a round stru c t u res. Also, the number of monitoring wells used to detect

spills in these environments may need to be increased and samples

taken more fre q u e n t l y.
Earthquake Zones 

Ea rthquake zones are areas affected by eart h q u a k e s .

Ea rthquakes are a significant threat to public safety and

we l f a re over many parts of the United States, particularly 

the West Coast, Alaska, parts of the Rocky Mountains, the

Mississippi Va l l ey, and selected areas along the Ea s t e rn

Se a b o a rd. 

The Problem with Locating a Facility 

in an Earthquake Zone

E PA is concerned about earthquakes affecting hazardous waste

management facilities because they can damage stru c t u res that hold

wastes and result in accidental releases to gro u n d w a t e r, surface water,

soil, and air. Damage can result from movement of large pieces of

g round or, more commonly, ground shaking. Because stru c t u res that

hold hazardous waste (e.g., landfills, ponds, or lagoons) are often made

of soil and rock, they can be damaged by earthquake activity.

St ru c t u res above the ground, such as tanks and incinerators can also 

be damaged, toppled, or destroye d .

When is an Earthquake Zone a Siting Concern?

The magnitude or amount of ground shaking at a site is a good

m e a s u re for determining if a site is appropriate for a hazardous waste

management facility. To help determine the level of risk from shaking,

scientists have mapped out seismic impact zones. These zones measure

the amount that the ground could potentially shake during an

e a rthquake. The risk is based on the area's geology and past eart h q u a k e

a c t i v i t y. Maps of seismic impact zones are available to the public

t h rough the U.S. Geological Su rvey (USGS) and state and local

g ove r n m e n t s .
Facility Siting Recommendations

E PA currently has regulations designed to pre vent damage to hazard o u s

waste management facilities in areas with earthquake activity. In Title 40

of the Code of Fe d e ral Re g u l a t i o n s, Section 264.18(a) bans facilities fro m

siting new hazardous waste management units within 200 feet of a

Holocene fault (that is, faults that have been active within the last 10,000

years). These faults are located in certain areas of the western United St a t e s.

And 40 CFR 270.14(b)(11)(ii) also re q u i res owners and operators of

h a z a rdous waste management facilities to investigate Holocene faults that

a re within 3,000 feet of a facility.

In addition to the re g u l a t o ry re q u i rements, earthquake expert s

recommend a number of safety features for facilities in areas where

e a rthquake activity can cause ground shaking or ground ru p t u re :

■ Design stru c t u res at hazardous waste management facilities to re s i st

g round motion or shaking and withstand the maximum hori zo n t a l

a c c e l e r a t i o n – the highest acceleration value expected at the eart h’s

s u rface in that particular area. It has been found that the horizo n t a l

d i rection of shaking is much more damaging to stru c t u res than the

ve rtical dire c t i o n .

■ Build stru c t u re containment systems to pre vent spills in case of a failure .

■ Pay special attention to site factors such as soil moisture and slope

s t a b i l i t y, which may enhance ground shaking and lead to structural failure. 

The side-to-side motion of the ground during earthquakes causes the most

damage to structures. 
Karst Terrain

Karst terrain consists of rock – such as limestone, dolomite, or

gypsum – that slowly dissolves when water passes through it.

The dissolving rock leaves underground voids, tunnels, and

c a ves. Sometimes these underground spaces can grow so large

that their "ceilings" will collapse, forming large sinkholes. 

The Problem with Locating a Facility in Karst Terrain

Facilities located in karst areas may have an increased chance of

h a z a rdous waste spills because sinkholes can form suddenly. These 

spills can contaminate the groundwater and make it difficult to clean

up since the hyd rogeology is complex in these areas. Engineers do not

h a ve good methods to protect hazardous waste management facilities

against sinkhole collapse. 

A karst sinkhole in east-central Missouri.
Facility Siting Recommendations

Ha z a rdous waste management facilities should avoid locating in

“a c t i ve” karst areas. Ap p roximately 5 percent of the United States 

has “a c t i ve” karst, including Missouri, Ke n t u c k y, Florida, In d i a n a ,

A rkansas, and Pu e rto Rico. Companies planning to locate facilities 

in karst areas should demonstrate that they can (1) engineer a waste

management stru c t u re that protects against sinkhole formation 

(e.g., additional foundation support) and, in turn, hazardous waste

spills, and (2) monitor and clean up groundwater contamination if it

occurs. It is important that companies conduct site characterization

studies in which they map sinkholes and underground cave r n s ,

determine ground stability, and measure the speed and direction of

g roundwater flow.

Sinkhole

Losing Stream

Cave

Deeply Weathered

Bedrock

Limestone and

Dolomite

Sandstone

Spring

Karst soils are poor foundations for any structure.
Unstable Terrain

Unstable terrain is any area where movement of the land

s u rface can damage stru c t u res and buildings. Un s t a b l e

terrain is divided into two kinds of land movement: 

(1) the movement of rock and soil on steep slopes by gravity

(e.g., landslides), and (2) rock and soil sinking, swelling, 

or heaving.

The Problem with Locating a Facility 

on Unstable Terrain

E PA is concerned that movement of unstable soils can damage

h a z a rdous waste facilities and lead to spills and leaks. Mass move m e n t

of rock and soil onto a hazardous waste facility can crush or destroy

buildings, puncture and bury drums of hazardous waste, and bre a k

a p a rt earthen stru c t u res containing liquid wastes. Poor foundation

conditions can:

■ Cause buildings to shift and crack

■ Di s rupt landfill gas and leachate collection

■ Rip landfill liner systems.

Damages such as these may cause hazardous waste spills that can be

difficult to clean up.
Facility Siting Recommendations

Unstable terrain is found throughout the United States. T h e re f o re ,

companies seeking locations should check for past mining activities,

flood control, or groundwater withdrawal, which could cause the

g round to sink. Natural conditions, such as high water content in soil

and fre ezing temperatures that cause soil to heave or swell, should also

be identified along with slumping soils caused by steep slopes that have

high soil moisture, poor drainage, or weak soils.

It is possible to build a safe facility on unstable terrain; howe ve r,

c o n s t ruction and operating costs would increase considerably.

Although most of the risks to facilities in unstable terrains can be

a d d ressed by good design and engineering, EPA recommends that

facilities perform geotechnical analyses of soil and geologic pro p e rt i e s

to determine the extent of unstable conditions. This information will

help a facility decide if its unit should be located in another area 

or if additional design and engineering measures are needed.

Building on unstable soils can lead to serious environmental consequences.
Unfavorable Weather Conditions

Ce rtain areas of the United States have atmospheric

conditions that increase the chance of breathing air

contaminants. Some parts of the country may have long

periods with little or no air movement (such as Los An g e l e s’

smog inversions). In these areas, air contaminants are not

easily dispersed. In mountainous areas, air contaminants can

also become trapped for a long time. This situation occurs

because mountains can affect regional wind patterns by

acting as barriers that reduce air flow.

The Problem with Locating a Facility in an Area 

with Unfavorable Weather Conditions

Ha z a rdous waste management facilities increase the chance of exposing

people and the environment to air contaminants in areas where

stagnant weather conditions exist. Young and elderly people, along

with people suffering with re s p i r a t o ry ailments, are more susceptible to

extended exposures to air contaminants. In addition, eating food

p roduced in areas with air pollutants (e.g., meat, milk, and grains)

becomes a concern because these pollutants may be taken up by plant

or animal respiration or by contaminated rainfall. Ha z a rdous waste

facilities that burn or incinerate waste (i.e., combustion facility,

incinerator) may cause unacceptable contamination and, in turn,

e n v i ronmental exposures in these stagnant areas. 

Facility Siting Recommendations

Facilities that burn hazardous wastes should avoid locating where

u n f a vorable weather conditions exist. Atmospheric conditions 

in this type of area should be evaluated carefully by the facility.

Facilities should evaluate the distribution and age of the population
and other vulnerability factors and the effects of land features on wind

patterns and pollutant mixing in the air. Seasonal effects on wind

patterns should also be evaluated. Special engineering and placement of

the facility at the site may be necessary to ensure acceptable dispersion

of air contaminants. The permit for the facility may also need to

restrict the operations of the facility to times when weather conditions

a re favorable. 

Regulations Controlling Air Emissions 

from Hazardous Waste Management Facilities

Both the Clean Air Act and the Re s o u rce Conservation and Re c ove ry

Act contain regulations on the control of air pollution from hazard o u s

waste facilities (40 CFR 264, Su b p a rts I, J, K, and O and 40 CFR 266,

Su b p a rt H). Combustion regulations address specific chemical

pollutants; tank, container, and waste pond regulations address vo l a t i le

organic pollutants as a class. Howe ve r, both sets of regulations target

emission reduction. They do not address the siting of emission sourc es.

An inversion can be worsened by a mountain range forcing warm desert air to

move up and over cooler ocean air flowing in the opposite direction.
Incompatible Land Use

Ce rtain pre existing land uses may not be compatible with 

the operation of a hazardous waste management facility. 

For example, densely populated areas or facilities such as

hospitals, schools, and prisons are especially vulnerable to

ha z a rdous waste ex p o s u re s .

Human Exposure to Hazardous Wastes

People may become exposed to hazardous waste contaminants 

by breathing, drinking water, eating food, eating dirt (children, 

p a rticularly), or by skin contact (with soil, air, or water).

The Problem with Locating a Facility 

Near Sensitive Populations

C e rtain people may be more sensitive to exposure to hazardous waste

than the average person. Studies have shown that children and the

elderly may be more sensitive to certain toxic substance exposure s .

L i k ewise, people who are sick can also be more vulnerable to tox i c

e x p o s u res, and their illnesses may become worse.

Facility Siting Recommendations

Ha z a rdous waste management facilities should avoid locating near

s e n s i t i ve populations or in densely populated areas. Areas near schools,

nursing homes, day care centers, or hospitals should be avoided. Ma n y

states have setback distances that prescribe the minimum distance a

h a z a rdous waste facility can be from certain types of land use. 

These minimum distances are meant to protect the public or 

the environment from potential exposure to hazardous waste.
E PA recommends NOT siting hazardous waste facilities in sensitive

locations for the following re a s o n s :

L o c a t i o n Environmental Consequences

Fl o o d p l a i n s Waste ponds may wash out.

Tanks may be moved from foundations.

We t l a n d s Fish and wildlife are thre a t e n e d .

Spills are spread to groundwater 

and surface waters faster.

Cleanup is difficult, costly, 

and sometimes more damaging. 

Land Us e Se n s i t i ve populations such as the elderly, 

c h i l d ren, and the sick are more affected 

by toxic exposures. 

Hi g h - Va l u e Contaminants are transported quickly.

Gro u n d w a t e r Cleanup is costly and difficult.

E a rthquake Zo n e s Ground fractures and shaking damage

s t ru c t u res, leading to spills.

Karst Te r r a i n Sinkholes may deve l o p, leading to

s t ru c t u re failure and spills.

Unstable Te r r a i n Soil movement can shift and damage 

s t ru c t u res causing waste re l e a s e s .

Un f a vo r a b l e Stagnant air concentrates pollutants.

Weather Conditions Mountains may block pollutant dispersion.

For Further Information . . .

For further information on sensitive environments, please contact 

the RCRA hotline at 800-424-9349 or TDD-800-553-7672. 

In the Washington, DC, area, call 703-412-9810.

This publication is also available on the Internet at

h t t p : / / w w w. e p a . g ov / e p a o s we r / h a z w a s t e .