USEPA selected Environmental Restoration (ER) and TRS to apply thermal conduction heating (TCH) to remediate soils impacted by chlorinated volatile organic compounds (CVOCs), primarily tetrachloroethene (PCE), at the Former Custom Cleaners Superfund Site in Memphis, Tennessee. A dry-cleaning business operated at the site for 40 to 50 years, which resulted in releases of PCE to the subsurface. EPA conducted removal actions in 2016, demolished the site buildings and excavated soils to remove the shallow contamination. Due to remaining contamination below the excavation, EPA decided to use TCH to treat the deeper CVOCs and remove the threat of contaminating the underlying aquifer, which supplies water to the City of Memphis.
The primary goal was to reduce PCE soil concentrations to less than 230 micrograms per kilogram (µg/kg). The treatment area was 4,200 square feet, with a treatment volume of 6,200 cubic yards. ER conducted baseline soil sampling and observed PCE concentrations as high as 1,900,000 µg/kg.
Subsurface construction of the TCH system began on August 22, 2022, with system operations commencing on December 16, 2022. TRS installed 45 heaters and 13 separate vapor recovery points. Further, TRS placed a 12-inch-thick cellular concrete cap over the entire treatment area to provide insulation and minimize heat losses.
Applying 1,482,000 kilowatt hours (kWh) of energy to the treatment zone over 178 days, TRS recovered 2,800 pounds of CVOCs. Confirmatory soil sampling results showed that 100 percent of the 136 soil samples had concentrations less than the remedial goal of 0.23 mg/kg.