Cleanup of Petroleum Contaminated Soil - Whitcomb Unit, Umatilla National Wildlife Refuge

Excavated Soil Photo EA Engineering In 1998 the Fish and Wildlife Service conducted an Environmental Compliance audit for the Whitcomb Unit of the Umatilla National Wildlife Refuge and identified a potential release of petroleum from two above ground storage tanks. A refuge cleanup proposal was submitted to address the problem. In April 1999, the two above ground storage tanks (AST's) and associated piping were removed and approximately 300 tons of petroleum-impacted soil was excavated. Analytical laboratory results indicated the presence of additional petroleum-impacted soil on the southeast and southwest sidewalls of the excavation. Two groundwater-monitoring wells (MW-1 and MW-2) were installed and sampled to evaluate groundwater conditions beneath the site. In addition, seven test pits were excavated and sampled to evaluate the extent of the petroleum-impacted soil around the former AST area. After reviewing EA Engineering, Science and Technology, Inc's (EA) report describing these previously mentioned activities, the Washington State Department of Ecology (Ecology) added the Whitcomb Island site to the State's List of Suspected and Confirmed Contaminated Sites. On July 21 and 22, 2000, Environmental West Exploration, Inc. installed three additional 2-inch diameter groundwater monitoring wells (MW) and one 4-inch diameter soil vapor extraction well. Petroleum-impacted soils were previously identified to a depth of 20 feet in the vicinity of MW-1.

Test Pit Photo EA Engineering Petroleum hydrocarbon concentrations above Washington-state cleanup levels were found in groundwater samples from MW-1, MW-3, MW-4, and MW-5. No petroleum hydrocarbon compounds were detected in MW-2 groundwater or in the residential well. The soil vapor extraction test showed that the gravels from 10 to 25 feet have a relatively high effective porosity. A significant amount of the subsurface petroleum hydrocarbons could be recovered by vapor extraction, and effective remediation required spacing of vapor extraction wells on 20 foot centers and utilizing a temporary or portable SVE equipment. MW-4 and MW-5 were connected to a vapor extraction system in order to remediate the lower sand across the water table. A portable SVE, consisting of a blower fan, a water knock-out drum, and two 55-gallon Carbon drums for off-gas treatment was installed and put into operation in May 2001. The system continues to operate with monthly Operations and Maintenance (O&M) visits. Influent gasoline concentrations have dropped 50 percent after one month of operation and these levels will continue to be monitored. The system operates from 7 am to 7 pm, Monday through Friday to create a pulsing effect and optimize performance. We expect to complete this project and obtain a Clean Order from the State of Washington by June 2002.

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