Pilot-Scale Demonstration of In-Situ Chemical Oxidation Involving Chlorinated Volatile Organic Compounds - Design and Deployment Guidelines (Parris Island, SC, U.S. Marine Corp Recruit Depot, Site 45 Pilot Study)
Citation:
Huling, S., B. Pivetz, K. Jewell, AND S. Ko. Pilot-Scale Demonstration of In-Situ Chemical Oxidation Involving Chlorinated Volatile Organic Compounds - Design and Deployment Guidelines (Parris Island, SC, U.S. Marine Corp Recruit Depot, Site 45 Pilot Study). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-16/383, 2017.
Impact/Purpose:
A pilot-scale in situ chemical oxidation (ISCO) demonstration, involving subsurface injections of sodium permanganate, was performed at the U.S. Marine Corps Recruit Depot, site 45, Parris Island, SC. The ground water was originally contaminated with perchloroethylene (PCE), a chlorinated solvent used in dry cleaner operations. High resolution site characterization involved multiple iterations of soil core sampling and analysis. The results from this study are intended to provide details and guidelines that can be used by EPA and Department of Defense remedial project managers regarding ISCO remediation at other sites.
Description:
A pilot-scale in situ chemical oxidation (ISCO) demonstration, involving subsurface injections of sodium permanganate (NaMnO4), was performed at the US Marine Corp Recruit Depot (MCRD), site 45 (Parris Island (PI), SC). The ground water was originally contaminated with perchloroethylene (PCE) (also known as tetrachloroethylene), a chlorinated solvent used in dry cleaner operations. High resolution site characterization involved multiple iterations of soil core sampling and analysis. Nested micro-wells and conventional wells were also used to sample and analyze ground water for PCE and decomposition products (i.e., trichloroethyelene (TCE), dichloroethylene (c-DCE, t-DCE), and vinyl chloride (VC)), collectively referred to as chlorinated volatile organic compounds (CVOC). This characterization methodology was used to develop and refine the conceptual site model and the ISCO design, not only by identifying CVOC contamination but also by eliminating uncontaminated portions of the aquifer from further ISCO consideration. Direct-push injection was selected as the main method of NaMnO4 delivery due to its flexibility and low initial capital cost. Site impediments to ISCO activities in the source area involved subsurface utilities, including a high pressure water main, a high voltage power line, a communication line, and sanitary and stormwater sewer lines. Utility markings were used in conjunction with careful planning and judicious selection of injection locations. A portable, low cost injection system was designed, constructed, and deployed at the site. The oxidant delivery design and deployment methods were used to achieve aggressive, effective, and efficient oxidant delivery and oxidation of CVOCs. Specifically, this included numerous injection locations, a narrow radius of influence of the injected oxidant, short vertical screen injection intervals, low injection pressure, outside-in oxidant injection, and a total porosity oxidant volume design. Three oxidant injection events were carried out, where the oxidant loading was more aggressive and the areal footprints were progressively larger. In this process, the oxidant was delivered into the targeted zones, hydraulic control of the injected oxidant was maintained, the oxidant persisted in zones where heavy oxidant loading was delivered, and significant CVOC destruction was achieved. Ground water and aquifer material sampling and analysis involved an array of parameters, including CVOC, iron, chloride, oxidation reduction potential (ORP), methane, metals, dissolved oxygen, total organic carbon, oxidant demand, molecular biological tools, and compound-specific isotopic analysis. Monitoring these parameters provided insight into the impact of ISCO and ISCO treatment performance, but limited insight was provided by some parameters. Significant reductions in post-oxidation CVOC concentrations in ground water and soil, and a 92% and 76% reduction in total CVOC mass flux in shallow and deep micro-wells, respectively, occurred as a result from the three oxidant injections. CVOC rebound was determined in 3 of the 38 wells. At one depth interval in the source area, elevated post-oxidation CVOC concentrations were measured in the soil, indicating the presence of PCE dense non-aqueous phase liquids. This result suggests that rebound will continue and that subsequent ISCO activities are needed, on a limited scale, in the source area to address CVOC rebound. Specific details and guidelines are provided regarding continued monitoring and recommended ISCO activities. The results of this study are intended to provide details and guidelines that can be used by EPA and Department of Defense remedial project managers regarding ISCO remediation at other sites.