The Army Creek Superfund site is located in New Castle County, Delaware. The 60 acre site was a, former sand and gravel pit which was operated during the 1960s by New Castle County as a landfill for municipal and industrial wastes. Contaminants leaching from the landfill were discovered in nearby private drinking water wells in 1972. In 1973, the County installed a recovery well system which effectively prevented the contaminated groundwater from migrating to nearby public water supply wells. This removed the immediate threat to human health presented by the site. However, the recovered groundwater was discharged without treatment, directly into Army Creek which forms' the lower limits of the landfill area. The landfill was placed on the National Priorities List in 1983.