Seattle, WA - Rapid PCE remediation for Brownfield redevelopment - Case Study


Courtesy of TRS Group, Inc.

Brownfield Redevelopment in South Lake Union Area of Seattle

Project Summary

TRS Group, Inc. (TRS) designed, installed and operated an electrical resistance heating (ERH) source area remediation project at a former commercial laundry and dry cleaning facility in the rapidly growing area of South Lake Union in Seattle, WA, The scope of the remediation was to treat tetrachloroethene (PCE) as dense non-aqueous phase liquid (DNAPL) underlying, and adjacent to, the area of the site where underground storage tanks (USTs) were located. The site is being purchased by a
biotech real estate investment trust (REIT) for future development.

The consultant evaluated soil vapor extraction, chemical oxidation, excavation and disposal, enhanced reductive dechlorination (ERD) and ERH for site remediation. The final cleanup strategy included using ERH in the source area to reduce PCE in soil to concentrations below the hazardous waste threshold allowing the owner to dispose of the cleaned soil from the excavation for a future underground parking garage. The ERH remediation reduced PCE concentrations in soil and groundwater by approximately 98% which saved the owner approximately $10M in landfill disposal fees.

The PCE concentrations in groundwater during the ERH remediation were reduced low enough that the client is considering the use of ERD as a groundwater polish, The project required execution on a very fast schedule with portions of install and characterization occurring simultaneously. System install commenced April 2013 and operations were completed December 2013.

TRS contracted with Frontier Environmental Management to operate the ERH system until either the remedial objective (1,000 pg/L PCE in groundwater), or the design energy of 6,640,000 kilowatt hour (kWh) had been applied to the treatment volume, whichever occurred first.

The overall ERH treatment volume of the site was determined using the 1,000 pg/L PCE contour in groundwater. The site was sub-divided into two treatment regions. The overall treatment area was approximately 37,500 sq, ft, and within that treatment region, a 'hot spot' was defined as an area of approximately 7,500 sq, ft. The hot spot was centered on and somewhat hydrologically down gradient of the former UST locations. The hot spot was treated from a depth of 4 to 40 feet below grade surface (ft bgs). The remainder of the treatment area was treated from a depth of 10 to 40 ft bgs.


The Site currently is an unoccupied city block, located at 700 Dexter Avenue North, in Seattle, Washington. The site was formerly occupied by a commercial laundry facility, a parking garage, and an automotive repair facility. The total area of the site was approximately 44,000 square feet. All structures were demolished prior to installation and operation of the ERH remediation system. This resulted in an approximately 50 foot high wall from the treatment area ground surface up to the level of Dexter Avenue North, The eastern and western sides of the site sloped down to the east from the elevation of Dexter Avenue North to the street level at 8th Street. The outer building structural walls bordering Dexter Avenue North, Roy Street and Valley Street were left in place and supported with steel shoring beams; this was done to ensure that the streets did not collapse into the void left by removal of the buildings.

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