Over the past 15 years, evidence has accumulated that the nation's ground water resource, which supplies more than 50 percent of the population's drinking water, is threatened not only by excessive overdrafts but also by contamination caused by past and present industrial, agricultural, and commercial activities. In the United States, it is estimated that more than 300,000 sites may have contaminated soil or ground water requiring some form of remediation (see Table 1-2 in Chapter 1). The potential cost of these remedial activities may be as large as $750 billion in 1993 dollars to be spent over the next 20 to 30 years (see Chapter 1). The magnitude.
