Long Summary of Camp Pendleton Case Study
The Camp Pendleton Case Study focuses on the In-Situ Thermal Remediation (ISTR) of a former fuel storage site located at Marine Corps Base (MCB) Camp Pendleton in Oceanside, California. The treatment zone spanned an area of 4,800 square feet to a depth of 35 feet below ground surface (bgs), covering areas that included vehicle maintenance and repair facilities, a vehicle painting shop, a wash rack, and a fuel storage station. The site’s lithology consisted of heterogeneous silts, clays, sands, and gravel lenses, which added complexity to the remediation process due to the varied subsurface composition(Camp_Pendleton).
Contaminants and Remediation Objectives:
The primary contaminants included PCE (tetrachloroethylene), TCE (trichloroethylene), vinyl chloride, BTEX compounds (benzene, toluene, ethylbenzene, and xylene), and naphthalene. The goal was to achieve significant mass removal of these contaminants from both soil and groundwater, with a target temperature of 100°C across the entire subsurface treatment zone(Camp_Pendleton).
Remediation Technology and Approach:
Thermal Conductive Heating (TCH) was employed using 80 heater wells to uniformly heat the subsurface from the surface down to approximately 40 feet bgs. The wells were powered by natural gas, which facilitated the heating of both soil and groundwater in the target zone.
Multiple-Phase Extraction (MPE) Wells: A total of 33 MPE wells were positioned within the thermal treatment zone to serve as the primary extraction points for mobilized contaminants. These wells were complemented by shallow horizontal vacuum extraction points installed in gravel just below the insulating cover to maintain pneumatic control of the uppermost heated zone.
Monitoring Systems: Four temperature and pressure monitoring points were strategically placed throughout the site to track the progress of subsurface heating and ensure that the desired temperature was maintained uniformly. The MPE system was operated for 20 days prior to heating to establish hydraulic and pneumatic control before active heating commenced(Camp_Pendleton).
Remediation Results:
Duration of Heating: The heating phase lasted for 113 days, during which the target temperature of 100°C was reached one week ahead of schedule. This allowed for efficient mobilization and volatilization of the contaminants.
Mass Removal Achieved: Over 52,000 pounds of chlorinated and petroleum contaminants were removed from the treatment zone during active heating.
Reduction Rates: Average reductions of over 99% were achieved for all target contaminants, including PCE, TCE, vinyl chloride, BTEX compounds, and naphthalene. These results highlight the effectiveness of the ISTR method in significantly reducing contamination levels in both soil and groundwater(Camp_Pendleton).
Conclusion:
The Camp Pendleton project demonstrates the efficacy of in-situ thermal remediation for complex subsurface contamination involving mixed chlorinated solvents and hydrocarbons. The use of TCH heater wells, MPE systems, and effective monitoring resulted in the comprehensive cleanup of the contaminated zone. The project met its remediation targets efficiently, achieving over 99% mass reduction across all contaminants, with more than 52,000 pounds of pollutants extracted from the soil and groundwater. The success of this project underscores the value of thermal remediation technologies for large-scale, mixed contaminant sites, particularly in challenging geological environments with diverse subsurface compositions.
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