EPA ID# OR6213820917
EPA Region 10
Umatilla County

2nd Congressional District

Other Names: Umatilla Chemical Depot
Last Update: September, 2007

Hide details for Site DescriptionSite Description

The Umatilla Army Depot (Lagoons) site occupies about 20,000 acres in Hermiston, Oregon and has operated as a storage depot for conventional munitions and chemical warfare agents since 1941. Areas of the site were contaminated with explosives and metals as a result of past demilitarization and disposal operations. Between the 1950s and 1965, about 85 million gallons of wastewater from explosive washout operations were discharged into two unlined lagoons. The lagoons cover about half an acre. The groundwater contaminant plume is estimated to cover 350 acres, and access to the site is restricted. There are about 100 people living on post, and approximately 900 people live within three miles of the site. The nearest drinking water well is located about 6,500 feet from the disposal area. Commercial agriculture is conducted within the vicinity of the depot, and crops are irrigated with area groundwater.

Site Responsibility: This site is being addressed through state and federal actions under a CERCLA federal facilities agreement.

NPL Listing HistoryDates
Proposed Date:10/15/1984
Removed Date:
Withdrawal Date:
Final Date:07/22/1987
Deleted Date:

Hide details for Threats and ContaminantsThreats and Contaminants

Media Affected: Groundwater, Soil & Sludges
On-site groundwater and soil are contaminated with explosives including trinitrotoluene (TNT) and cyclonite (RDX). Soil contains heavy metals such as lead and barium. Potential health threats include accidental ingestion of and direct contact with contaminated groundwater and soil.

Hide details for Cleanup ProgressCleanup Progress

The site is being addressed through seven long-term cleanup actions addressing the cleanup of the following work areas: Work Area 1-Deactivation Furnace; Work Area 2-Washout Lagoons Soils; Work Area 3-Active and Inactive Landfills; Work Area 4-Washout Lagoons Groundwater; Work Area 5-Explosives Washout Plant; Work Area 6-Ammunition Demolition Activity; and Work Area 7-Miscellaneous Areas.

The Army completed a site-wide Remedial Investigation and Feasibility Study (RI/FS), to determine the nature and extent of contamination, at the site in 1992. By the Fall of 1994, remedies were selected for all seven specified work areas. Information on each is provided below.

Work Area 1-Deactivation Furnace: The remedy was selected in December 1992, which included on-site solidification/stabilization of 6,000 tons of lead-contaminated soil. Treatment residues were placed in the on-site Active Landfill. Construction activities were completed by the Army in 1996.

Work Area 2-Washout Lagoons Soils: The remedy was selected in September 1992. It included on-site bioremediation (composting) of 15,000 tons of explosives-contaminated soils. Treatment residues will be backfilled on-site. The Army completed construction activities in the Fall of 1996.

Work Area 3-Active and Inactive Landfills: After completing investigations at both the active and inactive landfills, it was determined that they pose no risks to public health or the environment. No further action was selected in August 1993.

Work Area 4-Washout Lagoons Groundwater: The remedy was selected in September 1994. It included a groundwater pump and treat system that uses granular activated carbon (GAC) to reduce the level of contamination in a 350-acre explosives-contaminated groundwater plume. The Army finished building and began operating the 1500-gallon per minute system in early 1997. Explosives-laden GAC is treated by off-site thermal regeneration. The system reinjects clean groundwater at the site, and its operation is estimated to be necessary for 27 years. Work is currently being done to optimize the system, and continues to operate.

Work Area 5-Explosives Washout Plant: The washout plant posed a hazard due to potentially reactive quantities of explosives that remained in the process equipment, and residue of explosives within the building. Under those existing conditions, the building was unstable. The remedy, selected in July 1994, included steam cleaning, treating by flash flaming, and demolishing the building. These activities were completed by the Army in 1996.

Work Area 6-Ammunition Demolition Activity Area: The remedy, selected in July 1994, included excavation, solidification/stabilization, and on-site landfill disposal of 30,000 tons of soil contaminated with metals and explosives, off-site removal of unexploded ordnance (UXO), and implementation of institutional controls to prevent public access to the area. In early 1997, surface clearance of UXO was completed and treatment of soils was completed in 2002. Work to map subsurface UXO and refined cost estimates for clearance of subsurface UXO have also been completed. Subsurface clearance of UXO remains to be completed.

Work Area 7-Miscellaneous Areas: The remedy selected in July 1994 addressed several remaining areas where soils were contaminated with metals. The remedy included, excavation, solidification/stabilization, and on-site landfill disposal of 400 tons of metals-contaminated soil. These construction activities were completed by the Army in 1996.

Site 39: Contains small quantities of unexploded ordnance. A Record of Decision for final cleanup of this area was completed in June 2005, Remedial Action is scheduled to begin in 2008.

Periodic (Five-Year) Reviews of site conditions and the protectiveness of the remedial actions were completed in 1999 and 2004. The next Periodic (Five-Year) Review is scheduled to be completed in 2009.

Hide details for Regional ContactsRegional Contacts

PHONE NUMBER:503-326-3689
Information pertaining to this site is housed at the following location(s):
Hermiston Public Library (Administrative Record)
235 East Gladys
Hermiston, OR 97838

Umatilla Chemical Depot (Administrative Record)
BRAC Environmental Coordinator
1 Umatilla Army Depot
Hermiston, OR 97838