Cleanup Project Bulletin
East Multnomah County
Area Groundwater
Project Overview
The East Multnomah County (EMC) Groundwater Contamination Area covers a three (3) square mile area within the cities of Gresham and Fairview, Oregon. The area extends from NE Halsey Boulevard to the Columbia River, and from NE 178th Avenue to NE 223rd Avenue.
Three aquifers within the project area are contaminated with trichloroethene (TCE), an industrial solvent. The groundwater contamination covers a 400 acre area centrally located within the project area. The contamination was caused by land disposal of used solvents at the Cascade Corporation and Boeing of Portland facilities during the 1960s. At the time, it was thought that the solvents would completely volatilize; instead, the solvents seeped into the groundwater.
Eight of the City of Portland’s South Shore wellfield supply wells are located within the project area and downgradient of the area of contamination. The wellfield serves as a backup source of drinking water for the city. A number of other domestic and municipal water supply wells are also located within the project area. None of Portland’s wells have been impacted to date.
In May 1993, EPA proposed to place EMC on the National Priorities List (NPL). This would designate EMC as a federal "Superfund" site. In September 1995, DEQ requested that EPA defer listing of the site.
In December 1996, DEQ issued a remedial action record of decision (ROD) for the area-wide contamination in the deeper Troutdale Sandstone Aquifer (TSA). The TSA groundwater cleanup includes the installation of up to 23 groundwater extraction wells and treatment using air stripping technology. The cleanup is projected to cost Boeing and Cascade $10 to $12 million and take up to 20 years to complete. DEQ issued a consent order to Boeing and Cascade on February 14, 1997 which specifies the requirements, deliverables and schedule for implementing the final remedy selected by DEQ.
Remedy Implementation Progress
As of June 1, 1998, a total of 18 extraction wells have been drilled and tested. Three treatment systems, water and electrical lines from the treatment systems to the extraction wells, and discharge lines from the treatment systems to the Columbia Slough have been constructed. Extraction wells and treatment systems have been sequentially been put into operation since September 1997. Currently, 15 extraction wells are removing contaminated groundwater from the aquifer at a rate of 800 gallons per minute. During June 1998, three additional extraction wells will be put into operation, increasing groundwater extraction rates to approximately 1050 gallons per minute. Two additional wells are projected to be completed in early July 1998, bringing the total extraction rate from the TSA to 1200 gallons per minute.
One extraction well was installed in the deep Sand and Gravel Aquifer (SGA) to remediate localized area of groundwater contamination identified in December 1996. The well has been drilled and tested, and will be in operation by July 1, 1998. Extraction rates from the well will be in the range of 100-150 gallons per minute bringing the total groundwater extraction rate up to the 1320 gallon per minute minimum extraction rate required in the DEQ ROD.