The report provides, in a generalized, largely graphic format, a representation of ground-water vulnerability, precipitation distribution, population density, potential well yield, and aquifer sensitivity for each of the 48 conterminous states. A classification scheme is developed based on an assessment of the vulnerability of surficial and relatively shallow aquifers. Aquifer sensitivity is related to the potential for contamination. That is, aquifers that have a high degree of vulnerability and are in areas of high population density are considered to be the most sensitive. About 46 percent of the land area of the conterminous United States consists of vulnerable class I aquifers. Of this amount, 26.4 percent is Class Ia, 10.4 percent is Class Ib and Ib-v, 8.1 percent is Class Ic, and Class Id accounts for an additional 1.4 percent. The moderately vulnerable Class II aquifers cover about 1 percent of the United States, while the least vulnerable, Class III, makes up about 19 percent. The undefined systems, Class U, account for an additional 19 percent.

"EPA/600/2-91/043." Contract no. Contract Number: EPA CR-815754-01-0. "Cooperative agreement: CR-815754." This report covers a period from 4-10-89 to 4-9-91 and work was completed as of 4-9-91"--Page v. "August 1991." "Project officer, Jerry Thornhill." Includes bibliographical references.