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.