The Lake City Area 17B Site, located in Independence, Missouri, was the focus of an in-situ thermal remediation project carried out by GEO Environmental Remediation Company in 2023. The site, historically part of an Army Ammunition Plant, had been used for the disposal of petroleum hydrocarbons and chlorinated solvents. The contaminated area spanned approximately 15,072 square feet and included silty clay, paleochannel sand, and bedrock lithology extending to an average depth of 51.3 feet below ground surface (bgs)(Lake City, MO).
The contaminants present at the site included a range of chlorinated solvents such as PCE (Tetrachloroethylene), TCE (Trichloroethylene), DCE (Dichloroethylene), as well as BTEX (Benzene, Toluene, Ethylbenzene, Xylenes) and TPH (Total Petroleum Hydrocarbons). These contaminants existed in the form of both dense non-aqueous phase liquids (DNAPLs) and light non-aqueous phase liquids (LNAPLs)(Lake City, MO).
The primary remedial objective of the project was to significantly reduce the mass of NAPL and VOCs present in the target treatment zone (TTZ), as well as to evaluate the efficiency of removing semi-volatile organic compounds (SVOCs) co-located within the zone. GEO Environmental employed In-Situ Thermal Conduction Heating (TCH) technology to achieve these goals(Lake City, MO).
The treatment system was composed of 127 TCH heater wells powered by natural gas, 71 co-located multiphase extraction (MPE) and soil vapor extraction (SVE) wells, 32 shallow SVE wells, and 55 horizontal SVE wells. The wells were strategically placed to optimize the removal of NAPL, liquid, and steam from the subsurface. 20 temperature and pressure monitoring points were used to monitor the progression of subsurface heating throughout the treatment process(Lake City, MO).
Treatment Details and Technology:
Active Heating: Active heating was conducted for 243 days, reaching a target temperature of 100°C in the subsurface. The goal was to reach and maintain temperatures of 85°C or above across the saturated zone to effectively volatilize the contaminants.
Treatment Area: The treatment area covered 15,072 square feet with a treatment depth from 0 to 51.3 feet bgs, amounting to a total treatment volume of 28,624 cubic yards.
Temperature Evolution: The average temperature in the TTZ ranged between 87.5°C and 100°C for a period of 62 days prior to shutting down the system. The multiphase extraction (MPE) system operated for 20 days without heating to establish hydraulic and pneumatic controls prior to full-scale thermal activation(Lake City, MO).
Results:
The project resulted in the successful removal of over 43,626 pounds of chlorinated solvents and petroleum-based contaminants from the treatment zone.
A greater than 95% mass removal rate was achieved, highlighting the effectiveness of the thermal remediation approach in reducing both chlorinated solvents and hydrocarbon concentrations in the soil and groundwater(Lake City, MO).
Treatment System Features:
Three-Stage Vapor Treatment: The treatment system included a three-stage vapor treatment process involving cooling-condensation, C3 Technology, and VGAC absorption. These components were integrated to ensure efficient condensation, capture, and removal of contaminants from the vapor stream before being released.
Thermal Conduction Heating (TCH): The use of thermal conduction heating wells was key to reaching the high temperatures necessary for volatilizing and extracting the VOCs and other contaminants present in the treatment zone.
The Lake City project serves as a significant example of the capabilities of in-situ thermal remediation for treating complex contamination scenarios. The implementation of GEO's GTRTM well systems and comprehensive monitoring allowed for effective removal of a diverse range of contaminants, leading to the substantial cleanup of a formerly contaminated industrial site. The outcome also highlighted the benefits of targeted thermal treatment to expedite remediation, reduce environmental impact, and meet regulatory cleanup objectives within a relatively short timeframe.
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