4 GROUND-WATER POLLUTION

䊳 15.4 GROUND-WATER POLLUTION

sonous fluids soaked the playground, seeped into base-

Love Canal

ments of nearby homes, and saturated gardens and lawns.

STUDY

Children who attended the school and adults who lived Love Canal in Niagara Falls, New York, was excavated

nearby developed epilepsy, liver malfunctions, skin sores, to provide water to an industrial park that was never

rectal bleeding, and severe headaches. In the years that built. After it lay abandoned for several years, the Hooker

followed, an abnormal number of pregnant women suf- Chemical Company purchased part of the old canal early

fered miscarriages, and large numbers of babies were in the 1940s. During the following years, the company

born with birth defects.

disposed of approximately 19,000 tons of chemical The Love Canal incident is not unique. In December wastes by loading them into 55-gallon steel drums and

1979, the U.S. Congress passed the Comprehensive dumping the drums in the canal. In 1953, the company

Environmental Response, Compensation, and Liability covered one of the sites with dirt and sold the land to the

Act (CERCLA), commonly known as the Superfund. Board of Education of Niagara Falls for $1. The city then

This law provides an emergency fund to clean up chem- built a school and playground on the site.

ical hazards and imposes fines for maintaining a dump During the following decades, the buried drums

site that pollutes the environment. After the Superfund rusted through and the chemical wastes seeped into the

was established, the Environmental Protection Agency ground water. In the spring of 1977, heavy rains raised

(EPA) identified 20,766 hazardous waste sites in the the water table to the surface, and the area around Love

United States. By 1989, the General Accounting Office Canal became a muddy swamp. But it was no ordinary

estimated that there were 400,000 hazardous waste sites. swamp; the leaking drums had contaminated the ground

Many are small, involving a few rusting drums in a back- water with toxic and carcinogenic compounds. The poi-

lot, but others contaminate large aquifers.

268 CHAPTER 15

G RO U N D WAT E R

More than 50 percent of the people in the United In contrast, non-point source pollution is generated States drink ground water. The EPA has established max-

over a broad area. Fertilizers and pesticides spread over imum tolerance levels for a variety of chemicals that

fields fall into this latter category. may be present in water drawn from wells. Recent

Once a pollutant enters an aquifer, the natural flow of studies show that 45 percent of municipal ground-water

ground water disperses it as a growing plume of contami- supplies in the United States are contaminated with

nation. Because ground water flows slowly, usually at a synthetic organic chemicals. According to the Association

few centimeters per day, the plume also spreads slowly. of Ground Water Scientists and Engineers, approximately

Some contaminants, such as gasoline and diesel fuel,

10 million Americans drink water that does not meet are lighter than water and float on top of the water table EPA standards.

as they spread (Fig. 15–14a). Others are water soluble Wells in 38 states contain pesticide levels high

and mix with ground water. Mixing dilutes many conta- enough to threaten human health. Every major aquifer in

minants, diminishing their toxic effects. However, New Jersey is contaminated. In Florida, where 92 per-

because ground water moves so slowly, dilution occurs cent of the population drinks ground water, more than

slowly. Still other contaminants are nonsoluble and 1000 wells have been closed because of contamination,

denser than water. These chemicals sink to an imperme- and over 90 percent of the remaining wells have de-

able layer and then flow slowly downslope (Fig. 15–14b). tectable levels of industrial or agricultural chemicals. It

Many contaminants persist in a polluted aquifer for is common to read about cities and towns in the United

much longer times than they do in a stream or lake. The States where a certain type of cancer or other disease af-

rapid flow of water through streams and lakes replen- flicts a much greater percentage of the population than

ishes their water quickly, but ground water flushes much the national average. In many cases, contaminated drink-

more slowly. In addition, oxygen, which decomposes ing water is suspected to be the cause of the disease.

many contaminants, is less abundant in ground water than in surface water.

AQUIFER CONTAMINATION There are many sources of ground-water pollution (Fig.

TREATING A CONTAMINATED AQUIFER 15–13). Point source pollution arises from a specific

The treatment, or remediation, of a contaminated aquifer site such as a septic tank, a gasoline spill, or a factory.

commonly occurs in a series of steps.

treatment plant

dusting

Poorly designed hazardous waste

Leakage from Salts from

Leakage from

Seepage

Leakage from

Agricultural

septic tank injection well

highway

lagoon or

from river

gas tank

and pesticides

dump site

Figure 15–13 Point and non-point sources pollute ground water.

Ground-Water Pollution 269

Leaking tank

Unsaturated soil

Water table

Aquifer Bedrock

Free

Gasoline components

gasoline

dissolved in ground water

Contaminant plume moves with

Ground

(a)

ground water

water flow

Unsaturated zone

Water table

Aquifer Bedrock

Trichlorethylene Contaminant plume

spreads over bedrock at base of aquifer

(b) Figure 15–14 (a) Gasoline and many other contaminants are lighter than water. As a re-

sult, they float and spread on top of the water table. Soluble components may dissolve and migrate with the ground water. (b) Other pollutants, such as trichlorethylene, are heavier than water and may sink to the base of an aquifer.