Technology:
In situ conductive heating
- Three free-standing trailers - a control trailer containing instrumentation, an electrical substation providing power for the system (1 to 1.5 MW), and an off gas vapor treatment trailer containing a flameless thermal oxidizer
- Heater/vacuum wells (4.5 inches in diameter with sand packed liners in 6 inch augured holes) were operated at 1,400 - 1,600°F; heat was injected into the subsurface with soil gas extracted using a vacuum
- Two areas treated - Area GP-31 (150 ft by 50 ft to a depth of 18 ft); Area GP-28 (30 ft by 20 ft to a depth of 11 ft); Area GP-31-130 heater/vacuum wells installed on 7.5 foot triangular spacing to a depth of 19 feet,with 25 of these wells drilled through the concrete loading dock; Area GP-28 - 18 heater/vacuum wells installed on 7.5 foot triangular spacing to depths of 12 feet, with approximately 1 well per 50 square feet of surface area treated
- Surface area between wells was covered by an impermeable silicone rubber sheet to prevent fugitive emissions; thermally insulated mat was used to minimize surface heat loss; 5 ft deep dewatering trench was installed
- Maximum soil temperature in the treatment area at a depth of 13 ft - 212°F to 500°F
- During operation, recharge of water in the wet till region prevented temperatures in this area from rising above 212°F; however, all temperatures in the area were at least as high as the boiling of water
- Off-gases were treated with an 1800 scfm flameless thermal oxidizer with an operating temperature range of 1800 - 1900°F
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Cleanup Authority:
State voluntary cleanup program
Contacts:
Technology System Vendor
Ralph Baker, Ph.D.
CEO and Technology Manager
TerraTherm, Inc.
356 Broad St.
Fitchburg, MA 01420
E-mail: rbaker@terratherm.com | State Regulator
Mary Beth Tuohy
Assistant Commissioner
Indiana Department of Environmental Management
Office of Environmental Response
P.O. Box 6015
Indianapolis, IN 46206 |
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Contaminants:
Chlorinated Solvents
- Trichloroethene (TCE) - up to 79 mg/kg; tetrachloroethene (PCE)- up to 3,500 mg/kg; 1,1-dichloroethene (DCE) - up to 0.65 mg/kg
- The high concentration of PCE suggested the presence of DNAPL |
Waste Source:
Leaks and spills from manufacturing operations |
Type/Quantity of Media Treated:
Source zone (unsaturated)
- Estimated area treated was 5,000 cubic yards or 6,500 tons of soil |
Purpose/Significance of Application:
Use of in situ conductive heating to treat VOCs, including DNAPL, in an unsaturated source zone |
Regulatory Requirements/Cleanup Goals:
- The soil cleanup goals were 8 mg/kg for PCE, 25 mg/kg for TCE, and 0.080 mg/kg for 1,1-DCE
- Cleanup goals were based on the Indiana Department of Environmental Management (IDEM) Tier II Clean-Up Goals for Industrial Land Use |
Results:
- Results of confirmatory sampling showed that concentrations of PCE and TCE in both areas were reduced to below the cleanup goals; no data were provided for DCE
- Prior to discontinuing heating, 50 soil samples were collected from the coldest locations (centroids) furthest from each heater well and analyzed for VOCs; based on these results, along with data from temperature profiles and HCl monitoring, heating was discontinued in December 1997
- Confirmation sampling was conducted about six months later, after soil temperatures within the treatment area had cooled to below 100°F. |
Cost Factors:
No cost data was provided for this application. |
Description:
The 16 acre site is a chemical manufacturing facility located in the southern portion of Portland, Indiana, From 1937 to the mid-1970's, the site was used for the manufacture of hard rubber products used in automobiles and then for the manufacture of plastic exterior automobile parts and is currently being used for reworking automotive parts. Sampling showed the presence of volatile organic compounds (VOCs) in in subsurface soils in two areas at the site that had been used as loading docks. Area GP-31 was contaminated primarily with PCE and TCE; Area GP-28 was contaminated primarily with DCE. VOCs were not found above the cleanup goals in groundwater.
In situ conductive heating was used from July to December 1997 to treat the unsaturated source zone in these two areas. A total of 130 heater/vacuum wells were installed in the larger area (GP-31) and 18 in the smaller area (GP-28). These wells were used to injected heat into the subsurface (1,400 - 1,600 °F) using the vacuum to extract soil gas. Off-gases were treated with a flameless thermal oxidizer. Prior to discontinuing heating, about 50 soil samples were collected from the coldest locations (centroids) furthest from each heater well and analyzed for VOCs. The results from the soil samples, along with data from temperature profiles and HCl monitoring, were used to determine whether additional heating was required. Based on the results, heating was discontinued in December 1997. Before confirmation sampling was conducted, soil temperatures were monitored for about 6 months as the soil within the treatment area cooled to below 100°F. Results of confirmation sampling showed that PCE and TCE concentrations were below the cleanup goals. |
