Closure of an Unlined Evaporation Pond: a Case History

Abstract

In 1985, the Fort Worth District, Corps of Engineers, successfully permitted and executed the closure of an unlined evaporation pond at the Longhorn Army Ammunition Plant in east Texas. The pond, constructed in 1963 at the site of an active explosive waste-burning ground area, had been used to store explosive wastes resulting from the washout of rocket motor casings and solvent residues from operations involving pyrotechnic material preparation and mixing. Because operation of the unlined evaporation pond appeared to be primarily responsible for locally contaminating the ground water, the Army ceased operation of the pond in 1984 and began formal closure activities for the unit as a Resource Conservation and Recovery Act (RCRA) interim status surface impoundment. Under Phase I of the closure contract, a total of 1,877,113 gal of wastewater was removed and shipped via tank truck to a permitted disposal well some 80 mi from the site. The Phase II contract consisted of removal and transporting of contaminated sludges and soils to a permitted hazardous waste disposal site, backfilling the pond, installing a filter drain system, and turfing. A total of 8,116 yd 3 of material was excavated and shipped from the site.