Cleanup Project BulletinCleanup Project Bulletin
East Multnomah County
Area Groundwater
Project Overview
The East Multnomah County (EMC) Groundwater Contamination Area covers a three 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 300-400 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, some of 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 Portland metropolitan area. Well field use is projected to increase in the future due to growth. 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. On February 14, 1997, DEQ issued a consent order to Boeing and Cascade specifiying the requirements, deliverables and schedule for implementing the final remedy selected by DEQ.
Remedy Implementation Progress
Twenty one extraction wells, four treatment systems, associated utility lines, and discharge lines from the treatment systems to the Columbia Slough have been constructed.
The extraction wells and treatment systems were sequentially put into operation since September 1997. All 21 extraction wells have been operating since August 1998. The remedy is removing and treating approximately 1300 gallons of contaminated groundwater per minute, consistent with the requirements specified in the DEQ ROD.
In December 1998, Boeing and Cascade submitted a report with preliminary analyses on the current remedy performance and recommendations for performance criteria modifications. In January 1999, DEQ approved the recommendation to eliminate vertical gradient control criteria within the area of groundwater extraction within the SGA. An annual remedy performance evaluation report is due in July 1999.
TCE concentrations in the TSA have declined considerably since 1994 (approximately 40 percent). These declines are contributed to effective interim cleanup actions taken at both Boeing and Cascade facilities since the discovery of groundwater contamination, and the expedited implementation of the TSA remedy.
The City of Portland operated the wellfield from December 29, 1998 to January 5, 1999 for emergency supply. No remedy performance deficiencies were identified.
DEQ met with U.S. Environmental Protection Agency (EPA) officials on March 31, 1999 to provide an overview of remedy implementation and preliminary performance.