Technology:
In-Situ Thermal Desorption (ISTD)
- Two demonstrations were conducted - a thermal well and a thermal blanket - using the MU-125 (125 cfm capacity) unit
- 12 thermal/vapor extraction wells, installed to a depth of 14 ft bgs and screened from 6 inches to 14 ft, used to treat deeper soil
- Two thermal blankets used to treat shallow soils
- Emissions control system included a flameless thermal oxidation unit, a heat exchanger, and GAC augmented with pelletized calcium hydroxide
- Heating was conducted for a period of 35 days (over 3 months) to reach the target temperature of 600F at four central monitoring locations
- Process flow rates ranged from 38 to 82 scfm
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Cleanup Authority:
California EPA
U.S. Navy Contacts:
Mr. Ken Spielman
EFA West, NAVFAC
Code 182
900 Commodore Drive
San Bruno, CA 94066
Telephone: 650-244-2539
Fax: 650-244-2553
Email: khspielman@efawest.navfac.navy.mil
Mr. Chris Lonie
EFD Pacific
Env Restoration 258 Makalapa Dr
Pearl Harbor 96860-3134
Telephone: 808-474-5962
Email: LonieCM@efdpac.navfac.navy.mil | Regulatory Contact:
Not identified |
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Contaminants:
PCBs
- PCB levels were measured as high as 2,200 mg/kg, with an average of 220 mg/kg during a RI |
Waste Source:
Contaminated wash water discharged to soil |
Type/Quantity of Media Treated:
Soil
- Aquifer material - siltstone/fine-grained sandstone
- Groundwater depth - approximately 9 feet to 15 feet bgs
- Moisture content - approximately 20%
- Porosity - approximately 30% |
Purpose/Significance of Application:
Field demonstration of in situ thermal desorption to treat PCBs in shallow and deep contaminated soils |
Regulatory Requirements/Cleanup Goals:
- The primary performance objective for the demonstration was to treat PCBs in soil to a concentration of less than 2 mg/kg
- Off-gas limits included an HCL emission rate limit of 4.0 lbs/hr |
Results:
All post-treatment samples had no-detectable total PCB concentrations at a quantitation limit of 10 ug/kg, thus meeting the performance objective of <2 mg/kg
- On average, the thermal wells reduced total PCBs from 53,540 ug/kg to <10 ug/kg, to 12 ft depth
- On average, the thermal blankets reduced total PCBs from 20,607 ug/kg to <10 ug/kg, to 1 ft depth
- The HCl emission rate limit of 4.0 lbs/hr was not exceeded during the demonstrations
- CO emissions were below 10 ppmV with a mean concentration of approximately 2 ppmV
- Total hydrocarbon emissions ranged from 0 to 8 ppmV with a median discharge rate of less than 0.002 lb/hr as CH4
- Excess oxygen was >= 12%, except during the change over to the thermal blanket |
Cost Factors:
- Actual construction and operating costs for this project are not available
- Depending on site-specific factors, the vendor has established an overall cost range of approximately $100 to $250 dollars per ton |
Description:
The Former Mare Island Naval Shipyard includes an electrical workshop, known as Building 866, which was used from 1955 to 1994. From 1955 to 1978, transformers washed in the workshop contained polychlorinated biphenyl (PCB) oils, which were drained and washed into a 30-gallon sump through floor grates and drains. The liquid waste and sludge that accumulated in the sump were pumped to a 3,000 gallon grease trap near the western corner of the building. The test site was located in the area of the former grease trap and adjacent paved areas located at the northwest corner of Building 866. Levels of PCBs as high as 2,200 mg/kg were identified at the site during the remedial investigation (RI). A demonstration of In-Situ Thermal Desorption (ISTD) using thermal blankets and thermal wells was conducted in this area by the U.S. Navy and the Bay Area Defense Conversion Action Team (BADCAT) Environmental Technology Project (ETP).
ISTD is a combination of thermal desorption and vacuum extraction, and is conducted in-situ. Two demonstrations were conducted (thermal well and thermal blanket) and were found to be effective in treating PCB impacted soils, achieving the performance objective of 2 mg/kg. The demonstrations added to the level of experience of system operators, while suggesting minor modifications in well heater materials, control, and monitoring which will aid in more even soil heating and extend heater life and efficiency. The unusual heater failures experienced on this project were attributable to the use of 316 stainless steel heater strips (rather than 310 stainless steel), and the initially high operating temperature of heaters. |
