The Umatilla Army Depot (also known as the Umatilla Chemical Depot) is a 19,728-acre facility formerly used for the storage, maintenance, and demilitarization (deactivation and/or disposal) of conventional munitions and weapons of various types, including the storage of chemical weapons. The Depot opened in 1941. From the 1950s to 1965, approximately 85 million gallons of explosives-contaminated wastewater was discharged into two unlined lagoons. Soil and groundwater beneath the lagoons were contaminated. Explosives residues and lead were found in surface and subsurface soils at other locations throughout the Depot, from past disposal practices. In one 1,750-acre area, unexploded ordnance (bombs, mines, grenades, etc.) was on the surface and in subsurface soil. No contaminants migrated off the Depot property. In July 1987, EPA placed the site on the National Priorities List. In October 1989, a Federal Facilities Agreement was signed by EPA, DEQ and the Army. The agreement required the Army to investigate and clean up the site in accordance with CERCLA and with DEQ's Environmental Cleanup Rules. Eight operable units (study areas) were designated. Units 1 and 2 consisted of the soil and groundwater, respectively, beneath the Explosive Washout Lagoons. Unit 3 was the Explosives Washout Plant. Unit 4 was the soil around the former small arms Deactivation Furnace. Units 5 and 6 consisted of one active and several inactive landfills, respectively. Unit 7 was the 1,750-acre Ammunition Demolition Activity (ADA) Area. Unit 8 was a catch-all unit consisting of 32 distinct sites where hazardous substances may have been disposed of or released. In 2004, under a Hazardous Waste Permit, the Depot began destruction of the chemical stockpile.
Additional information on the environmental cleanup is available at the
USEPA Region 10 Umatilla Depot Site.
Additional information on the Chemical Demilitarization can be found at the
Oregon DEQ Chemical Demilitarization Program Site.