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.
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.