Windrow Composting of Explosives Contaminated Soil at Umatilla Army Depot Activity Hermiston, Oregon

Site Name:

Umatilla Army Depot


Hermiston, Oregon

Period of

May 1992 to November 1992


Field Demonstration


Roy F. Weston, Inc.

Composting - Excavated soil screened and mixed with soil amendments - Nonaerated and aerated windrows composted for 40 days - Treated soil mixed with top soil and revegetated, redeposited in excavated area, or landfilled - Windrows contained contaminated soil (30%), cow manure (21%), alfalfa (18%), sawdust (18%), potatoes (10%), and hen manure (3%) - Mixed 3 to 7 times per week, temperature 15 to 60xC, oxygen up to 21%, moisture 30 to 40%, pH 5 to 9

Cleanup Authority:

SIC Code:
9711 (National Security)
Point of Contact:
Remedial Project Manager Umatilla Army Depot Activity Hermiston, OR

Explosives - Primary soil contaminants include 2,4,6-trinitrotoluene (TNT); hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX); and octahydro-1,3,5,7- tetranitro-1,3,5,7-tetrazocine (HMX) - Contaminant levels >100 ppm limited to soils in the first 2 to 4 feet below the surface of the lagoons

Waste Source:
Surface Impoundment/Lagoon

Type/Quantity of Media Treated:
Soil - 244 cubic yards (8 windrows, 28 cubic yards each) - Predominantly Quincy fine sand and Quincy loamy fine sand

Purpose/Significance of Application:
Field demonstration of windrow composting to biodegrade explosives- contaminated soils.

Regulatory Requirements/Cleanup Goals:
- Concentrations of explosives in soil to be below 30 ppm; target compounds were TNT and RDX - Top 5 feet of soil below the lagoons to be excavated, treated, and returned to the excavated area

- Windrow composting performance after 40-day treatment generally reduced the levels of target explosives to below the cleanup goals - TNT reduced from 1,600 to 4 ppm (aerated and nonaerated) - RDX reduced from 1,000 to 7 ppm (aerated) and 2 ppm (nonaerated) - HMX reduced from 200 to 47 ppm (aerated) and 5 ppm (nonaerated)

Cost Factors:
- No costs were available for the field demonstration

Projected cost for full-scale windrow composting:
- Capital cost for treatment activities - $1,840,000 (including equipment, buildings, structures, mechanical/piping, and electrical) - Five-year operating cost - $2,000,000 (including power, amendments, fuel, labor, and maintenance) - Full-scale costs assume 20,000 tons of soil, 5-year project duration, nonaerated windrows, mixed daily, 30% soil loading, 30-day treatment periods, and compliance with RCRA Waste Pile Facility Standards

From approximately 1955 to 1965, the Umatilla Army Depot Activity (UMDA) operated a munitions washout facility in Hermiston, Oregon, where hot water and steam were used to remove explosives from munitions bodies. About 85 million gallons of heavily-contaminated wash water were discharged to two settling lagoons at the site. The underlying soils and groundwater were determined to be contaminated with explosive compounds, primarily TNT, RDX, and HMX, and the site was placed on the NPL in 1987.

Windrow composting was used in a field demonstration at UMDA from May to November 1992 to treat 244 cubic yards of contaminated soil. Nonaerated and aerated windrows were treated for 40 days, using several soil amendments, and tested for residual contamination. TNT was reduced from 1600 to 4 ppm (aerated and nonaerated), RDX reduced from 1000 to 7 ppm (nonaerated) and 2 ppm (aerated), and HMX reduced from 200 to 47 ppm (aerated) and 5 ppm (nonaerated) in the 40 day treatment period. With the exception of HMX (aerated), these levels were below the targeted soil cleanup levels of 30 ppm.

Costs were not available for the field demonstration. The costs for a full-scale application of windrow composting at Umatilla were estimated assuming treatment of 20,000 tons of soil, 5-year project duration, nonaerated windrows, mixed daily, 30% soil loading, 30-day treatment periods, and RCRA Waste Pile facility standards. The capital cost for the full-scale application was estimated as $2,118,000, and the annual operating cost as $527,000.