Combined Remedies for DNAPL Remediation
TRS Group, Inc. (TRS) teamed with KEMRON and AMEC, under KEMRON's U.S. Army Corps of Engineers (USAGE) Environmental Remediation Services Multiple Award Task Order Contract (MATOC), to perform electrical resistance heating (ERH) for the remediation of volatile organic compounds (VOCs) in the vadose zone soil and shallow groundwater at Operable Unit 1 (Well 12A) of the Commencement Bay - South Tacoma Channel Superfund site in Tacoma, Washington. The
remediation was conducted in cooperation with USEPA, USACE and WA Department of Ecology,
The intent for this project was to design and implement In Situ Thermal Remediation (ISTR) within the designated ISTR treatment zone beneath and in the vicinity of the former Time Oil Building. The specific ISTR treatment goals were:
- A 90% reduction in average soil concentrations, based on all samples collected in the vadose and saturated zones.
- No soil sample shall have a concentration that exceeds 10 mg/kg.
- No more than 50% of the soil samples shall exceed the average soil concentration.
The Well 12A site has been undergoing remediation since 1983 to address releases of chlorinated volatile organic compounds and petroleum hydrocarbons from historical operations at the site, including: paint and lacquer thinner manufacturing, oil
recycling and reprocessing, and canning of oil. Previous remedial actions included:
- Air stripping treatment at municipal supply well 12A (1983-present)
- Shallow soil excavation (1986,1991-1992, 2011-2012)
- Groundwater extraction and treatment (1988-present)
- Soil vapor extraction (1993-1997)
USEPA completed a focused feasibility study in 2009 to analyze potential remedial alternatives to address ongoing contamination at the Well 12A site (CDM Smith, 2009), The 2009 Record of Decision Amendment =2 provided an amended remedy and additional remedial action objectives. The selected amended multi-component remedy includes continued operation of the groundwater extraction and treatment system (GETS), continued wellhead treatment at Well 12A, excavation and disposal of filter cake and shallow contaminated soil east of the former Time Oil Building, in situ thermal remediation (ISTR), enhanced anaerobic bioremediation (EAB), institutional controls, and long-term plume monitoring with a contingency for monitored natural attenuation, shown on Figure 1 below. The right panel depicts a cross-section of the site,