- - ------- - -- ~.

United States Robert S. Kerr Environmental Center for Environmental

Environmental Protection Research Laboratory Research Information

Agency Ada OK 74820 Cincinnati OH 45268

Technology Transfer EPA/625/6-87/016

EPA Handbook 06- 2 2-06

Ground Water
;..®.. ~__,. ~, .-_ . . . _ . . . . _ _ . . _ p.2

EPA/625/6-87/01 6

March 1987

Handbook

Ground Water

U .S . Environmental Protection Agency

Office of Research and Development

Center for Environmental Research Informatio n

Cincinnati, OH 45268

Robert S. Kerr Environmental Research Laboratory

Ada, Oklahoma 74820
p. 3

Figure 1-2 Plume of leachate migrating from a sanita ry iandfili on a sandy aquifer using contours of chloride

Concentration ( from Freeze and Cherry, 1979).

760

Landfill . . .. : : ; . ., ;•, 230

740 225

720 6 220 m

- -, - ~ -I--

° 10

D 0 -

> ~ 0~ t

. c 215 o

.8

m s

/O 20o 210 I

O

680 Sand 25 ~ ° `t?d5 E

, Chloride concentration, mg/ I

~ n Standpipe tip 2(10

0 100 200 (meters) ° Piezometer ti p

640 ' .•• Multi-level sampling point

0 200 400 600 (feet)

I 1 .1 1 T Water table

Horizontal Scale ~ Clay

-~ Flow direction

Figure 1-3 Vertical movement of contaminants along an

old, abandoned, or improperly constructed

well (from 1 ,3.4 Recharge from Surface Water Deutsch, 1961). Normally, ground water moves toward or

"discharges" to surface water bodies (see discussion,

Abandoned Well Chapter 4). Occasionally, however, the hydrauli c

To Municipal gradient is such that surface water has a higher

Disposal Pond (Corroded Casing) supply potential than ground water (such as during flood

stages), causing a reversal in flow . Contaminanis in

Water Tabie

UP Per Aquifer . . . . ; . , - .%'. •. . • •: . . : , . the surface water can then enter the ground-water

Piezometric Surface System.

Contaminated Water Reversal of flow can also be caused by pumping

(Figure 1-4). Lowering the ground-water level to a

level near a surface water body can induce 'eanaQe

Aquiciude - through the stream or lake bed. Contamination of a

glacial sand and gravel aquifer by organic compounds

- _ = - - - -- - - - __7 present in an adjacent river in such a manner has

been documented (Schwarzenbach et al., 1983).

LowerAquifer . : . .': .' ' . . 1 .4 Sources of Ground-Wate r

Contaminated Water Contamination

. . . . . . . . . . .• . .• . . . . . . . . . . .• . . . . . . : . . : . . . : . . : : . : : A wide variety of ground-water contamination

sources have been identified . As previously

mentioned, contaminant releases to ground water can

occur by design, by accident, or by neglect . The

Office of Technology Assessment (OTA, 1984)

grouped 33 types of ground-water contamination

sources into six major categories (Table 1-2) based

on the general nature of the contaminating activity . A

number of these sources are depicted in Figure 1-5 .

Category 1 includes sources that are intentionally

designed to discharge substances. Subsurface

percolation systems, such as septic tanks and cess

pools, injection wells, and land application of

wastewater or sludges fall within this category . Such

4
p. 4

Figure 1-4 Contaminated water induced to flow from a

surface water to g number of sources in this category are considered round water by pumping

(from Miller, 1980).

°waste" sources (e .g ., landfills, dumps,

impoundments, etc .), many others are "non-waste"

related sources . Storage tanks, stockpiles, and a

variety of containers with residues of commercial

products have been found to contribute contaminants

inal water Table - ~- to ground water.

Contaminated Orig --'-

Surface Water PU Category III consists of sources designed to retain

---- ---mpin9 Water Level substances during transport or transmission . Such

sources primarily consist of pipelines and material

transport or transfer operations . Contaminant releases

,Aquifer generally occur by accident or neglect; for example,

as a result of pipeline breakage or a traffic accident .

Screen Again, most substances which would be subject to

release from sources within this category are not

wastes but raw materials or products to be used for

some beneficial purpose.

Category IV includes those sources discharging systems are primarily designed to use the natural substances as a consequence of other planned

capacity of the soil materials to degrade wastewaters . activities. This category contains a number of

Injected wastewaters are often placed in unusable agriculturally related sources such as irrigation return

zones to be assimilated with poor quality ground flows, feedlot operations, and pesticide and fertilizer water of natural origin . Septic tanks and cess pools applications. A number of sources related to urban

have been estimated to discharge the largest volume activities such as highway desalting, urban runoff, and

of wastewater into the ground and are the most atmospheric deposition are included . Surface and

frequently reported source of ground-water underground mine-related drainage also fall within contamination (Miller, 1980). this category.

Injection wells are another major potential source of Category V comprises sources providing conduits or contamination. Although injection wells can be inducing discharge through altered flow patterns . For constructed and operated properly, contamination of the most part, such sources are unintentional

ground water can occur in several ways (EPA, 1979) : ground-water contamination sources and include

o Faulty well construction (e.g., drilling and casing) water, oil, and gas production wells, monitorin;; - :~i!s,

exploration holes, and construction excavations . The

o The forcing upward of pressurized fluids into potential to contaminate ground water from production

nearby wells and aquifers, and faults and wells stems from poor installation and operation

fractures of confining beds -methods, and incorrect plugging or abandonment

o The migration of fluids into hydrologically procedures. Such practices create opportunitief for

connected usable aquifers cross-contamination by vertical m,y : attun of

contaminants.

o Faulty well closing .

Finally, Category VI includes naturally occurring

The depths and operating procedures used in waste sources whose discharge is created or made worse

injection generally make monitoring and leak by human activity. Ground-water/surface water prevention very difficult to validate . interactions, described in the previous section, and

Land application is a popular, inexpensive alternative salt-water intrusion or upconing (ground-water

for wastewater and sludge treatment . The U.S. EPA movement upward as a result of pumpage) provide

(1983) estimated that 40 to 50 percent of the the basis for this category . Withdrawals significantly in

municipal sludge generated every year is applied to excess of recharge can affect ground-water quality .

the land. Salt water intrusion in coastal areas and brine-water

upconing from deeper formations in inland areas can Category 11 includes sources that are designed to occur when pumpage exceeds the aquifer's natural

store, treat, or dispose of substances but are not recharge rate .

designed to release contaminants to the subsurface .

Landfills, open dumps, local residential disposal, Contaminant releases are also referred to as

surface impoundments, waste tailings and piles, originating from point or nonpoint sources . Point

materials stockpiles, graveyards, aboveground and sources are those which release contaminants from a

underground storage tanks, containers, open burning discrete geographic location . Examples include

sites, and radioactive disposal sites all fall into this leaking underground storage tanks, septic systems,

broad category . It is important to note here that while and injection wells . Nonpoint contamination situations

5
p. 5

Table 1-2 Sources of Ground-Water Contamination (from OTA, 1984) .

Category I-Sources designed to discharge substances Open burning and detonation sites

Subsurface percolation (e .g ., septic tanks and cesspools) Radioactive disposal sites

Injection Wells

Hazardous waste Category III-Sources designed to retain substances during

Non-hazardous waste (e.g ., brine disposal and drainage) transport or transmissio n

Non-waste (e .g ., enhanced recovery, artificial recharge, solution Pipelines

mining, and in-situ mining) Hazardous waste

Land application Non-hazardous waste

Wastewater (e.g., spray irrigation) Non-waste

Wastewater byproducts (e.g ., sludge) Materials transport and transfer operations

Hazardous waste Hazardous waste

Non-hazardous waste Non-hazardous waste

Non-waste

Category II-Sources designed to store, treat, and/or dispose of

substances; discharge through unplanned release Category IV-Sources discharging substances as consequence

of other planned activitie s

Landfills Irrigation practices (e.g ., return flow) Industrial hazardous waste Pesticide application

s

Industrial non-hazardous waste Fertilizer applications

Municipal sanitary Animal feeding operations

Open dumps, including illegal dumping (waste) De-icing salts applications

Residential (or local) disposal (waste) Urban ruhnoff

Surface impoundments Percolation of atmospheric pollutants

Hazardous waste Mining and mine drainage

Non-hazardous waste Surface mine-related

Waste tailings Underground mine-related Waste piles

Hazardous waste Category V-Sources providing conduit or inducing discharge Non-hazardous waste

Materials stockpiles (non-waste) Production wells through altered flow pattern s

Graveyards Oil (and gas) wells

Animal burial Geothermal and heat recovery wells Aboveground storage tanks Water supply well

s

Hazardous waste Other wells (non-waste) Non-hazardous waste Monitoring wells

Underground storage tanks Construction excavation Non-waste Exploration wells

Hazardous waste

Non-hazardous waste Category VI-Naturally occurring sources whose discharge is Non-waste

Containers , created and/or exacerbated by human activity

. Groundwater-surface water interactions

Hazardous waste Natural leaching

Non-hazardous waste Salt-water intrusion/brackish water upconing (or intrusion and

Non-waste other poor-quality natural water)

6
F p . 6

Figure 1-5 Sources of ground-water contamination ( from Geraghty and Miller, 1985).

C`' r -,'~_ ~ ,~c ^, '~ ir~ f_~r-- • ~ 1 _

y_ d-,.

~t(F--~~>~ r^ ~~,1 Precipitation r Evapotranspiration

, _ `_-•-•~- ~-• L r'~---

~.a._ --~ ~_ S

t'1~11 ~ ~\\ \ * i ~ ►. 1 11~~ ; ~ \, \~ . \ \~\ \ } Disposal or • I

Injection Well 1 ~1ti ~ Pumping Well Landfill, Dump a'• Pumping Well f

Land Spreading ~ Septic Tank/ or Refuse Pile Lagoon, Pit pm

or Irrigation or Basin r g Cesspool Sewe

-i-' ~-------

i f Stream

Water Table i--- ------- i

Percolation , P

. _

_ rcolation ag

e

-Discharge i -I ~

i + + Leakage

Water Table Aquifer

Confining Zone

Artesian Aquifer (Fresh) Leakage

Confining Zona

Discharge

or Injection Artesian Aquifer (Saline)

Intentional Unintentional Ground-Water

Input Input Movement

are more extensive in area and diffuse in nature . It is movement is governed by the hydraulic principles

therefore difficult to trace contaminants from nonpoint discussed in Chapter 4 .

sources back to their origin. Agricultural activities (i .e

., For example, Darcy's Law states that the flow rate application of pesticides and fertilizers), urban runoff, through any porous medium is proportional to the

and atmospheric deposition are potential nonpoint head loss and inversely proportional to the length of contaminant sources

. the flow path:

1 .5 Movement of Contaminants In Q= -K x A x h1/L (1 -1 )

Ground Water

where:

1 .5.1 Contaminant Migration Q ground-water flow rate, in gal/d

In broad terms, three processes govern the migration A cross-sectional area of flow, in ft2

of chemical constituents in ground water : (1 )

advection, movement caused by the flow of ground ht =head loss, in feet, measured between two

water ; (2) dispersion, movement caused by the points L ft apart

irregular mixing of waters during advection ; and (3)

retardation, principally chemical mechanisms which K hydraulic conductivity, a measure of the

occur during advection. ability of the porous medium to transmit

water, in gal/d/ft 2

1 .5.1 .1 Advection Equation 1-1 can be rearranged in the following

Ground water n its natural state is constantly in . manner to produce the "bulk," or what is called

motion (advection), although in most cases it is Darcian, velocity : moving very slowly (Todd, 1980) . Ground-water

7