AUDIENCE: Legislators/governmental officials/environmental organizations/industry/general public

BACKGROUND: Ground water is a vast resource that underlies the earth's surface. Nearly half of the U.S. population uses ground water for their drinking water source, including virtually all rural residents. In addition, ground water provides much of the water used for irrigation and for industry. On average, about 40 percent of the annual streamflow in the United States is comprised of ground water seepage, although in some areas more than three fourths of the average streamflow, including virtually all fair weathe flow, comes from ground water discharge to streambeds.

Ground water occurrence, including its vulnerability to contamination and its value and use as a resource, varies from place to place. In most cases, ground water needs little or no treatment prior to use. However, in many instances natural ground water quality is unsuitable without treatment. The vulnerability of ground water to contamination depends on the hydrogeologic conditions, including the extent and location of the recharge area, the depth of ground water, the soil and rock composition overlying the aquifer, the recharge rate, and the specific properties of the chemical contaminants.

Ground water contamination has been documented in every state of the United States. It is recognized that a wide variety of human activities may adversely impact the resource. Once ground water is contaminated it is often very difficult and expensive to clean up.

ISSUE: What is the appropriate response when ground water contamination is detected?

POSITION: It is the position of the National Ground Water Association (NGWA) that where ground water contamination is present, different standards for cleanup versus protection may be appropriate depending on site specific circumstances. Factors such as the potential for ground water use, the importance of the resource for local water supply and the availability of alternatives, the technical feasibility of cleanup, risk analysis, and cost should influence the determination of an appropriate cleanup level. In some places, ground water contamination will have little or no significant impact on human health or the environment. In other cases, the contamination will have to be accepted and managed because the situation is economically or technically irreversible. Our policies and programs should be sufficiently flexible and practical to operate in recognition of these different situations, providing adequate effective protection for human health and the environment.

CONTACT: Chris Reimer, NGWA, 800/ 551-7379

REFERENCE: U.S. Geological Survey, National Water Summary 1986, p. 3.