Underground Storage Tanks Investigations
Boating Facility, Clackamas, Oregon


The site is located along the Willamette River. A release of gasoline occurred at the site in 1988 as a result of a failure in the product piping associated with a former 10,000-gallon underground storage tank (UST) system located on the northern portion of the site. Following characterization of the contaminant plumes, a remediation system was installed to extract groundwater containing elevated concentrations of petroleum hydrocarbon constituents including free liquid product. Treatment was performed by passing extracted fluids through a coalescing plate oil-water separator, a tray-aeration air stripper, and three (3) carbon canisters. The treated groundwater was discharged into the adjacent Willamette River under the Department of Environmental Quality (DEQ) National Pollutant Discharge Elimination System (NPDES) 1500A Permit. Remediation efforts were expanded to the shoreline of the Willamette River after consultation with the DEQ, Oregon Division of State Lands, US Army Corps of Engineers, and the City of Portland. Expanded remedial efforts included installation of a dual-phase extraction (DPE) system replacing the submersible pumps previously installed in recovery wells and installation of an air-sparging system including installation of 19 air-sparging wells in the beach area.

Following remedial action, final compliance was evaluated by determining the risk posed by residual soil and groundwater contamination. Risk to both human health and ecological receptors were evaluated through completion of a conceptual site model (CSM) and identification of applicable exposure pathways. Cleanup levels included risk-based concentrations (RBCs) established in the DEQ document “Risk-Based Decision Making (RBDM) for the Remediation of Petroleum-Contaminated Sites," as well as Level II Screening Levels Values (SLVs), dated December 2001. SLVs were used for the groundwater surface water connection with the Willamette River.