Electrical resistive heating (ERH) Six Phase Heating followed by biosparging
-- Initial ERH system (May 2000 to May 2001) 60 electrodes, each capable of directing power to three zones.
-- Electrodes placed in hexagonal arrays of 6 electrodes each, with a seventh neutral electrode in the middle of each array.
-- 13 subsurface pressure monitoring points and 8 subsurface thermocouples
-- 95 kilowatt (kW) transformer to convert standard three phase electrical power to six separate phases; initial heating limited to the bottom interval (45-58 feet bgs) to establish a "hot floor" and prevent downward migration of contamination
-- 50 "electrode vents" added in December 2000 to treat areas where contaminated steam and hot water had been observed.
-- Expanded system (May to December 2001) added 13 electrodes, 17 electrode vents, and 3 thermocouples.
-- Soil vapor extraction (SVE) system, consisting of 53 vapor extraction wells, used to recover the steam and contaminant vapors from the unsaturated region immediately above the heated region (5 10 ft bgs).
-- Biosparging conducted intermittently from December 2002 through October 2003 to address residual concentrations and utilized the existing treatment system infrastructure.
Jennifer Sutter, Project Manager
Oregon Department of Environmental Quality
2020 SW Fourth Avenue
Portland, OR 97201 4987
Telephone: (503) 229 6148
Current Environmental Solutions
Applied Process Engineering Laboratory
350 Hills St.
Richland, WA 99352
Telephone: (509) 371 0905
-- Trichloroethene (TCE); cis 1,2 dichloroethene (DCE); and vinyl chloride (VC)
-- Dense non-aqueous phase liquid (DNAPL) suspected based on presence of contaminants in groundwater at greater than 1% of solubility
Dry well used for the disposal of laboratory wastes
Type/Quantity of Media Treated:
Source zone (saturated and unsaturated)
-- Estimated 48,000 to 65,000 cubic yards based on a treatment area of three quarters to one acre in size and a depth of 40 ft
-- Groundwater plume size estimated to be 120 ft by 80 ft
Purpose/Significance of Application:
Use of ERH, in conjunction with SVE, to treat DNAPL in a source zone. Biosparging used as a polishing step to address remaining residual contamination in groundwater.
Regulatory Requirements/Cleanup Goals:
Cleanup goals were based on Oregon maximum concentration levels (MCLs): 5 micrograms per liter (µg/L) for TCE, 70 µg/L for DCE, 2 µg/L for VC, and 5,600 µg/L for toluene.
- TCE, DCE, and VC concentrations were monitored in the Overbank layer and DCE, VC, and benzene concentrations were monitored in the Troutdale Gravel Aquifer (TGA) layer of the site
As of December 2001, maximum groundwater contaminant concentrations in the Overbank layer had been reduced from 150,000 µg/L to 100 µg/L for TCE; from 370,000 µg/L to 1,300 µg/L for DCE; and from 24,000 µg/L to 50 µg/L for VC
- Through June 2002, TCE concentrations decreased to 8.11 µg/L while DCE and VC concentrations were unchanged in the Overbank layer
- As of December 2001, the concentrations of DCE and benzene in the TGA layer had increased to 49.5 µg/L and 200 µg/L, respectively. VC concentrations decreased from 2.11 µg/L to not detected
- According to the vendor, the increase in benzene concentrations indicated a possible compromise in three well casings, which provided a conduit for contamination migration from the Overbank layer. These wells were abandoned in April 2002
- In April 2005, following both ERH and biosparging, VOC concentrations were slightly above MCLs in a few wells in the Overbank layer and in one well in the TGA layer, and in general, concentrations appeared to be declining.
- Based on this data and the determination that remaining contamination does not pose a significant risk, Oregon Department of Environmental Quality (DEQ) concluded no further action was required for this site. Groundwater monitoring continues to be conducted in accordance with the DEQ-approved long-term monitoring plan.
No cost data were provided for this application
The ICN Pharmaceuticals site, located in Portland, Oregon, was used as a clinical laboratory from 1961 to 1980. The laboratory used a variety of organic and inorganic compounds with wastes from laboratory operations disposed in a dry well, which was about 20 ft deep. In 1980, the laboratory was shut down and materials and machinery were removed. In 1993 and 1994, the laboratory building and associated structures were removed from the site. Results of groundwater investigations at the site indicated the presence of volatile organic compounds (VOCs) including TCE, DCE, VC, benzene, and toluene in the vicinity of the former dry well. TCE, DCE, and VC were detected in the groundwater at concentrations greater than 1% of their solubility, suggesting the presence of DNAPL. ERH, in conjunction with SVE, was implemented at the site to treat the DNAPL source and dissolved phase VOCs in groundwater. Biosparging was conducted to address residual contamination remaining after ERH treatment.
Cleanup goals were based on Oregon MCLs: 5 µg/L for TCE, 70 µg/L for DCE, 2 µg/L for VC, and 5,600 µg/L for toluene. As of December 2001, maximum groundwater contaminant concentrations in the Overbank layer had been reduced to 100 µg/L for TCE; 1,300 µg/L for DCE, and 50 µg/L for VC. Concentrations remained above Oregon MCLs as of June 2002. In the TGA layer, concentrations of VC were reduced, but concentrations of DCE and benzene in the TGA layer increased as a result of a possible compromise in the well casings; these wells were abandoned in April 2002. Following ERH treatment, residual concentrations remained above MCLs. Biosparging was conducted intermittently between December 2002 and October 2003 to address this remaining contamination. Results from April 2005 indicated that only a few wells remained above MCLs and concentrations were generally declining. Based on these results and the determination that remaining contamination does not pose a significant risk, Oregon DEQ concluded no further action is warranted for this site. Groundwater monitoring continues in accordance with the DEQ-approved long-term monitoring plan.