At 38,000 acres, Redstone Arsenal (RSA) in north-central Alabama represents one of the largest and most successful cleanup programs in the Army. Approximately 40,000 people work there--about 90 percent of them are civilian or contract employees. The installation is partially bordered by the Tennessee River; and some of its land is forest, wetlands, and flood plains. Two things make groundwater cleanup a challenge at RSA: tight clay soil and the underlying geology's complex fractures.