Technology:
- Electrical Resistive Heating - Six-Phase HeatingTM (SPH) for subsurface heating
- Soil Vapor Extraction (SVE) system for vapor recovery
- Above-ground treatment system to process vapor and liquid wastes generated by SVE
- ERH system:
- Two 500 kilowatt (kW) power control units (PCU) operating 101 electrodes.
- Electrodes installed to a depth of approximately 10 to 10.5 feet below ground surface (bgs) with a lateral spacing of approximately 14 feet.
- PCU 1 began operating on October 3, 2001 in the more contaminated “southern” portion of the Target Treatment Area (TTA).
- PCU 2 began operating in the “northern” portion of the TTA on December 13, 2001.
- From April 15 to May 15, 2002, the entire ERH system operated using 101 electrodes, twelve 8-inch diameter steel piles, six Geoprobe electrodes, and 310 ¾-inch diameter ground rods.
- To optimize performance, both PCUs cycled with 50 minutes of operation followed by 10 minutes of shut-down, to allow “re-wetting” of the electrodes and prevent the drying of soils close to the electrodes.
- The average weekly power input during the nine-month ERH operation was approximately 278 kilowatts (kW), with a maximum power input of 520 kW that occurred during the week immediately following the start-up of PCU-2. The ERH system was shut down on July 8, 2002.
- A condenser (to remove water vapor), a cooling tower (to cool condensate), and granular activated carbon (GAC) adsorption units (to treat dry vapor prior to atmospheric release).
- Following completion of the ERH in July 2002, TTA monitoring continued until March 2004.
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Cleanup Authority:
Resource Conservation and Recovery Act (RCRA) - Corrective Action
Contacts:
EPA Region 4
Mr. Dann Spariosu
EPA Region 4
61 Forsyth Street, S.W.
Atlanta, GA 30303-8960
Phone: (404) 562-8552
Email: spariosu.dann@epa.gov
State Regulator
Mr. David Scaturo
South Carolina Department of Health and Environmental Control
Bureau of Land and Waste Management
2600 Bull Street
Columbia, SC 29201
Phone: (803) 896-4185
Email: scaturdm@dhec.sc.gov
Owner’s Contractor
Mr. Dean Williamson
CH2M Hill
Phone: (352) 335-7991
Email: dean.williamson@ch2m.com |
Contaminants:
Chlorinated Solvents – PCE Dense Non-Aqueous Phase Liquid (DNAPL), TCE, cis-1,2-DCE, 1,1-DCE, VC
Initial maximum contaminant concentrations:
- Total volatile organic compounds (VOCs) – 18,000 µg/L
- PCE – 8,090 µg/L |
Waste Source:
Use, storage, disposal, and accidental release of chlorinated solvents at a former dry cleaning facility |
Type/Quantity of Media Treated:
Groundwater and DNAPL
Approximately 4,300 cubic yards of media were treated. This volume is based on a 7-foot deep (saturated zone: 4 feet bgs to 11 feet bgs treatment zone) over a 16,525 square feet (ft2) TTA. |
Purpose/Significance of Application:
Use of ERH to remediate chlorinated solvents and PCE DNAPL in groundwater |
Regulatory Requirements/Cleanup Goals:
The objective of the ERH treatment was to reduce the amount of chlorinated volatile organic compounds (CVOC) DNAPL present in the aquifer, thereby reducing its potential to act as a continuing source for dissolved-phase contamination. A quantifiable cleanup objective was not established during this remediation action. |
Results:
- In general, ERH resulted in a decrease in the area of the plume and a decrease in the number of high concentration zones.
- In March 2004 (22 months after ERH shutdown), PCE was detected in a monitoring well at a concentration of 283 µg/L. This suggested a 95 percent reduction in concentration compared to the pre-treatment baseline.
- Total volatile organic compounds concentration decreased by 83 percent.
- Total CVOCs and PCE mass recovered during ERH system operation was calculated at 247 and 234 lbs respectively. |
Cost Factors:
The total cost for the full-scale application was approximately $1,250,000. Costs were divided into the following categories:
- Capital costs - $ 373,000, including $ 71,000 for mobilization/demobilization
- Operational costs - $ 473,000
- Retrofit (electrode installation and well replacement) - $ 60,000
- Monitoring (laboratory analytical services) - $ 50,000
- Project oversight - $ 215,000 |
Description:
Charleston Naval Complex area of concern (AOC) 607 consisted of a former dry cleaning facility. PCE was one of the primary chemicals that was used, stored, disposed of, and accidentally released at the site.
A RCRA Facility Investigation conducted in 1996 and 1997 detected dissolved-phase chlorinated solvents in the saturated zone including PCE, TCE, cis-1,2-DCE, 1,1-DCE and VC. In addition, PCE in the form of DNAPL appeared to have migrated into the shallow saturated zone. Initial maximum contaminant concentrations included 18,000 µg/L of total VOCs and 8,090 µg/L of PCE. The site was remediated under the RCRA Corrective Action Program. Operation of the ERH system was initiated in October 2001 and continued until July 2002. Approximately 4,300 cubic yards of media were treated. This volume is based on a 7-foot deep (saturated zone: 4 feet bgs to 11 feet bgs treatment zone) over a 16,525 square feet (ft2) TTA.
The objective of the ERH treatment was to reduce the amount of DNAPL present in the aquifer, thereby reducing its potential to act as a continuing source for dissolved-phase contamination. A quantifiable cleanup objective was not established during this remediation action.
In general, ERH resulted in a decrease in the area of the plume and a decrease in the number of high concentration zones. PCE concentrations reduced by about 95 percent in concentration compared to the pre-treatment baseline. Total VOCs decreased by 83 percent. Total CVOCs and PCE mass recovered during ERH system operation was calculated at 247 and 234 lbs respectively.
The total cost for the full-scale application was approximately $1,250,000. Costs were divided into the following categories:
- Capital costs - $ 373,000, including $ 71,000 for mobilization/demobilization
- Operational costs - $ 473,000
- Retrofit (electrode installation and well replacement) - $ 60,000
- Monitoring (laboratory analytical services) - $ 50,000
- Project oversight - $ 215,000
One of the main issues that arose during the ERH treatment at AOC 607 was that the treatment took longer than anticipated, mainly due to slower heating of the groundwater in deeper portions of the saturated zone. The ERH system was enhanced by using additional electrodes to achieve adequate heating. |
