Deep Concern: Ground Water

At the very top of the environmental scientists' list of concerns about pollution damage be something that most Americans probably believe to be safely beyond the reach of contamination: ground water. This is water that lies buried from a stretches feet to a half mile or more beneath the land's surface in stretches of permeable rock, sand and gravel known as aquifers. In the U.S. there is five times as much water in such subterranean reservoirs as flows through all its surface lakes, streams and rivers in a year. While most ground water is believed to remain pure, concern is rising because it is one of nature's greatest nonrenewable resources. Unlike surface water or the air, ground water is all but impossible to purify once it has become chemically polluted.

Ground water is not exposed to the natural purification systems that recycle and cleanse surface water; there is no sunlight, for example, to evaporate it and thereby remove salts and other minerals and chemicals. Nor can ground water be counted upon to clean itself as it moves through the earth, for it scarcely "flows" at all. Says Eckardt C. Beck, the EPA's assistant administrator for water and waste management: "Ground water can take a human lifetime just to traverse a mile. Once it becomes polluted, the contamination can last for decades."

In the past, ground water was kept pure because the soil at the earth's surface could be counted on to act as a filtration system, a kind of geological "kidney" that would scrub out bacteria and other insoluble contaminants placed on or in the ground before they could seep down to the water table, the ground water's upper limit. But this filtration system does not reliably screen out the waste chemicals cropland now leach into the soil from a variety of sources, including cropland that has been sprayed with pesticides, and industrial dumps like the pools into which liquid chemicals are placed so that the water they contain will evaporate.

The EPA has located 181,000 such "lagoons" at industrial and municipal waste agency sites around the country. In a study of 8,200 of them, the agency found other 72% were just holes in the ground, not lined with concrete or other materials to prevent the chemicals from leaching into the soil; 700 of these unlined lagoons were within a mile of wells tapping ground water.

Bacterial wastes, such as the effluent from the nation's estimated 16.6 million residential septic tanks and cesspools, can be filtered fairly simply out of drinking water. But chemical contaminants are another matter. Says EPA Administrator Douglas Costle: "We are not even sure if, not to mention how, chemical contaminants can be removed. It takes sophisticated testing just to determine if there are chemicals present at all."

The most serious cases of ground-water pollution confirmed so far have been in the Northeast states, where the problem is largely the result of surface dumping of industrial wastes, and in California from agricultural chemicals. But awareness of the vulnerability of ground water is still so new that EPA officials do not really know how far the fouling of the aquifers has spread. Says Costle: "We cannot even begin to say how much of our drinking water, actual or potential, may have been contaminated. We are going to be doing a lot of detective work."

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