In Situ Thermal Treatment
This demonstration used a Radio Frequency heating system and Soil Vapor Extraction System (SVE) to remediate 1,1,1-trichloroehtane (TCA) dense non-aqueous phase liquid (DNAPL) contaminated groundwater at the site. The Radio Frequency heating system used electromagnetic energy to reduce TCA DNAPL contamination in groundwater. Details regarding the demonstration are provided below:
- The Radio Frequency heating system was comprised of nine boreholes that were 30.5 meters deep and 20 centimeters in diameter, a 27 megahertz four channel, 20-kilowatt Radio Frequency generator, four antennae, fiber optic thermometry, applicators, and transmission lines.
- The SVE system was comprised of 26 vacuum extraction points, 12 shallow overburden extraction wells, and 14 deep overburden and shallow bedrock extraction wells.
- In December 2003, the Radio Frequency heating system and SVE system were activated.
- The maximum radio frequency power input was 19 kilowatts with a maximum groundwater temperature of 52 degrees Celsius.
U.S. Environmental Protection Agency
Alicia Kabir/John W. McTigue
Environmental Resources Management (ERM)
399 Boylston Street, 6th Floor
Boston, Massachusetts 02116
Ray Kasevich/Jeb Rong
JR Technologies, LLC
46 East Street
Mount Washington, Massachusetts 01258
Historical use of TCA DNAPL at an active manufacturing facility has resulted in elevated groundwater contaminant concentrations in a source area that encompasses 232 square meters. Residual contamination was also identified in bedrock fractures at the site.
Type/Quantity of Media Treated:
Purpose/Significance of Application:
This report evaluated the use of Radio Frequency Heating in fractured bedrock in conjunction with a SVE system to reduce TCA DNAPL concentrations in groundwater at the site.
Regulatory Requirements/Cleanup Goals:
Fiber optic thermometry was used to monitor groundwater temperatures throughout the course of the treatment. Groundwater temperature was increased from 21 degrees Celsius to 52 degrees Celsius over 36 months. The total volume of groundwater treated was 8,400 cubic meters. TCA concentrations were reduced by 97% by May 2010.
The typical Radio Frequency heating remediation cost is $100-$150 per cubic yard. This does not include costs associated with the SVE system, drilling, subsurface investigations, or groundwater monitoring.
Site investigation results indicated that residual DNAPL and elevated dissolved phase concentrations were present in the source area. This contamination is attributable to the historic use of TCA at the active manufacturing facility onsite.
Radio Frequency heating was selected as the treatment technology after several studies and tests were conducted to evaluate which technology was best suited to treat residual contamination in the bedrock fracture network. Several advantages of using Radio Frequency Heating were presented. These advantages were the ability to focus the thermal energy on the impacted groundwater in the bedrock fractures, the ability to heat a volume of area independent of the poor fracture interconnectivity, and the sites hydrogeological characteristics were favorable.
The Radio Frequency heating system was comprised of nine, 30.5 meter deep boreholes. Antennae were placed in four wells in a square array and were connected to a Radio Frequency generator via transmission lines. Fiber optic thermometry was used to monitor groundwater temperature throughout the use of the Radio Frequency heating system. This system was operated for 36 months at a maximum output of 19 kilowatts.
An SVE system consisting of 26 extraction points and a sub-slab depressurization system of 12 shallow overburden extraction wells was installed to treat volatile organic compound vapors in the source area. This system also incorporated 14 deep overburden and shallow bedrock extraction wells located in the source area. Over the course of its operation, 144 pounds of volatile organic compound contaminated material was captured.
The use of Radio Frequency heating to treat TCA contamination at the site was considered a success. TCA concentrations were reduced by 97% by May 2010. Over the course of the treatment, groundwater temperature was increased from 21 degrees Celsius to 52 degrees Celsius. This increased temperature accelerated the dissolution rate of TCA, increased the biodegradation rate, and improved conditions for abiotic transformation.