Encyclopedia of Environmental Science and Engineering, Volume I and II

446 GROUNDWATER RESOURCES

containing 5,000 mg/l dissolved solids but low concentrations

of sodium, magnesium, and sulfate are desirable. The quality

required for irrigation water depends on the soil, composition,

climate, type of crops, amount of groundwater used, etc.

Groundwater is primarily used as a water source for

public and private drinking-water supply, industrial-process

and cooling water, and agricultural supply. The acceptability

of a groundwater source for use depends on the standards

for quality for that use. The Drinking Water Standards for

major chemicals are regulated by the U.S. Environmental

Protection Agency (EPA) (2004). These standards are shown

in Table 2.

REMEDIATION CONSIDERATION

Pollution Control and Remediation Policy

This section briefly describes the major federal environmen-

tal laws that control and regulate groundwater quality. In

the United States, the protection of groundwater is accom-

plished through a set of statutes passed at different times.

The goal of these laws is to protect the public health and

regulate sources of contaminations.

The first and probably most important modern envi-

ronmental law was enacted in January of 1970, namely the

National Environmental Policy Act (NEPA) of 1969. NEPA

is a milestone in man’s understanding regarding his own

survival and the survival of the total ecology that has sup-

ported all life of earth. This act dictated that decision makers

approach industrial development by balancing the environ-

mental, economic, and technological factors to protect and

enhance public health and welfare. Following NEPA, many

important statutes were enacted to restrict the improper han-

dling of hazardous wastes. Currently, there are more than 30

laws concerning environmental issues, among which 2 deal

directly with water.

The Clean Water Act (CWA) of 1972, although it does

not deal directly with groundwater, is the cornerstone of

surface-water-quality protection. It established the basic

structure for regulating pollutant discharges into the water

system as well as regulatory tools to sharply reduce those

pollutant discharges. These tools are employed to achieve

the broader goal of restoring and maintaining the chemical,

physical, and biological integrity of the water system.

The Safe Drinking Water Act of 1974 was established

to protect the quality of drinking water in the United States.

It focuses on all waters actually or potentially designed for

drinking use, including both surface water and groundwater

sources. Since their enactment, these statutes have played a

very important role in preventing the creation of new contami-

nated sites. However, they have had no effect on the hazardous-

waste sites already in existence. If a healthy environment is to

be established, these long-term dangers cannot be ignored.

The cleanup action started with the enactment of the

Comprehensive Environmental Response, Compensation,

and Liability Act of 1980 (CERCLA, or Superfund), which

is a remedial program for cleaning up the nation’s worst

hazardous-waste sites created by past industrial disposal

practices. CERCLA established a hazardous-substance

Superfund as well as regulations controlling inactive

hazardous-waste sites. Extensive liability has been brought

to owners and waste generators alike. As a consequence,

the public is more concerned than ever about groundwater

contamination. The implementation of Superfund is chal-

lenging, both technically and economically.

Remediation

Groundwater cleanup is very expensive and extremely dif-

ficult, if not impossible. An important and necessary step is

removal of contaminants from the vadose (unsaturated) zone,

which in most cases serves as a source of contamination.

TABLE 2

Drinking-Water Standards

Standards

Chemicals MCLG (mg/l) MCL (mg/l)

Organics

Aldicarb 0.001 0.003

Benzene 0 0.0002

Benzo[a]pyrene (PAH) 0 0.0002

Bromodichloromethane 0 0.08

Carbon tetrachloride 0 0.005

Chlordane 0 0.002

Chloroform (THM) 0.07 0.08

Di (2-ethylhexyl) phthalate 0 0.006

Dichloroethane (1,2-) 0 0.005

Dichloroethylene (1,1-) 0.007 0.007

Dichloroethylene (cis-1,2-) 0.07 0.07

Dichloromethane 0 0.005

Dichloropropane (1,2-) 0 0.005

Endrin 0.002 0.002

Heptachor 0 0.0004

Lindane 0.0002 0.0002

Monochlorobenzene 0.1 0.1

Polychlorinated biphenyls (PCBs) 0 0.0005

2,3,7,8-TCDD (Dioxin) 0 3E-08

Tetrachloroethylene 0 0.005

Trichloroethane (1,1,2-) 0.003 0.005

Xylenes 10 10

Inorganics

Arsenic 0 0.01

Cadmium 0.005 0.005

Mercury (inorganic) 0.002 0.002

Nitrate (as N) 1 1

MCLG—maximum contaminant-level goal, a nonenforceable health goal

that is set at a level at which no known or anticipated adverse effect on the

health of persons occurs and that allows an adequate margin of safety.

MCL—maximum contaminant level, the highest level of a contaminant that

is allowed in drinking water. MCLs are set as close to the MCLG as feasible

using the best available analytical and treatment technologies and taking

cost into consideration. MCLs are enforceable standards.

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