Steam Enhanced Soil Mixing with Real Time Data Monitoring for Remediation at MGP Sites
Jason Marberry, Project Manager, FECC, Inc.
The Technology and Objective: Steam enhanced soil mixing can be an effective method for removal of MGP-derived volatile organic compound (VOC) contaminants such as benzene, toluene, ethylbenzene, and xylene (BTEX) and naphthalene, as well as reducing the relative concentrations of SVOCs prior to solidification. VOCs and the lower boiling point SVOCs are often primary risk drivers for MGP remediation sites. This technology includes injecting and mixing steam into the soil column, volatilizing a wide range of organic compounds, bringing them to the surface via air, and condensing and/or capturing them with granulated activated carbon. Furthermore, this technology uses real time data monitoring used to make decisions during site operations as well as focusing remediation efforts on hotspots, as needed. The steam enhanced removal of VOCs and SVOCs prior to stabilization reduces both long term risk and overall cement dosing requirements, while at the same time documenting the mass of removal of contaminants. Overviews of the technology applied at two sites (LNAPL and DNAPL) will be presented..
Site Background / Objective: A brief case studyof perchloroethene (PCE) was released into the subsurface at the site, located in Jacksonville, Florida, during dry cleaning activities over a period of approximately twenty years. Suspected source areas included a former UST, which may have contained spent solvents; a floor drain; the former dry cleaning machine; and a former supply well that provided water for dry cleaning operations. Site assessment activities reported contamination in soil and groundwater to a depth of approximately 70 feet below ground surface (bgs). Solvent contamination in the vadose zone soils (approximately 0 to 8 feet bgs) appeared to have been either removed during the UST closure excavations or during SVE operations. Previous remedial methods for treating the contaminated groundwater were largely unsuccessful due to the likely presence of DNAPL at varying depths within the saturated soils. The objective of this remedy was to remove the remaining adsorbed, soluble, and potential DNAPL contaminant mass located in the source areas.
FECC’s Steam Enhanced Soil Mixing with Real Time Data Monitoring Technology used large diameter auger (LDA) soil mixing equipment to deliver a mixture of high-pressure steam and hot air to volatilize the majority of the contaminant mass, followed by an injection of a zero-valent iron (ZVI) slurry into the thermally-treated soil column to act as a long-term polishing agent for continued treatment of residual chlorinated solvent contamination. A vapor collection system recovered the off-gas stream at the ground surface and transported the mixture through activated carbon beds for onsite treatment. Real-time data monitoring enabled the remedial process to effectively delineate the areal extent of the source area and to quantitatively assess the treatment effectiveness. FECC treated 17 LDA soil columns to a depth of approximately 65 feet over a 900 square-foot area. Approximately 361 pounds of contaminants were removed during treatment. Thermal treatment and ZVI costs were approximately $160/CY.
At a second site, FECC a similar process to mitigate petroleum contamination. FECC’s treatment was shown to be effective when working from the perimeter of the contamination toward the source area. Considerations were built into the system to handle high concentrations of contamination and to address the risk of encountering LEL concentrations in the vapor stream.
Jason Marberry is a Project Manager with FECC, Inc. based in Orlando, Florida. Jason has Bachelor of Science degree in Rangeland Ecology and Management from Texas A&M University and over 12 years of environmental consulting/remediation experience. He was an environmental consultant for 10 years and has spent the last two years with FECC managing large remediation projects including FECC’s large diameter auger steam enhanced soil mixing technology as well as traditional remediation projects. FECC’s large diameter auger steam-enhanced soil mixing technology allows FECC to volatilize contaminants in-situ and extract them in a vapor stream while providing concentration data in real time. His experience as both a consultant and as a contractor helps FECC work well with a wide variety of clients and subcontractors.