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CIIARWATER <br /> C R O U P E N C <br /> remediation because influent hydrocarbon concentrations will be too high <br /> However, GAC may be used to treat extracted vapor after influent hydrocarbon <br />' concentrations drop below approximately 1,000 ppm <br /> 7.3 Evaluation of Groundwater Remediation Alternatives <br /> The feasibility of several groundwater remediation options have been evaluated for <br /> their particular effectiveness and limitations as they apply to this specific site The <br /> edge of the soluble plume and SPH appear to be within less than ten feet of the <br /> domestic well (Figure 6) Although TPHg and BTEX have not been detected in <br /> samples collected from the domestic well in concentrations exceeding the method <br /> detection limit, the ongoing threat to the well by the plume makes groundwater <br /> remediation necessary For this reason, monitoring of soluble plume for natural <br /> attenuation will not be considered as a remedial alternative The groundwater <br /> remediation alternatives considered include water extraction and treatment, and air <br /> sparging <br /> 7 3 1 Groundwater Extraction and Treatment <br /> Groundwater extraction has been a widely used technology to control the migration <br /> of groundwater contamination or recover SPH Various types of pumps can be <br /> employed to bring groundwater to the surface for treatment before discharge <br /> typically to either sanitary or storm sewers, surface bodies of water, or infiltration <br /> galleries Although the benefits of groundwater extraction and treatment have <br /> become suspect by many environmental professionals in the last several years, <br /> groundwater extraction can stili has the potential to reverse local groundwater <br /> gradient and thus capture the plume of groundwater contamination The capacity <br />' of this technology to mitigate further migration of SPH toward the domestic well <br /> makes this an appealing remedial alternative Clearwater recommends using <br /> groundwater extraction as a primary tool to mitigate plume migration and capture <br /> and recover SPH <br /> Results of aquifer testing indicate that this alternative is feasible for the site An <br /> additional groundwater recovery well located near well MW-1 will be needed to <br /> capture the entire soluble plume Of the numerous types of pumps available for <br /> groundwater extraction (e g electric submersible, pneumatic with controls, and <br /> controllerless total fluids pneumatic), Clearwater recommends using controllerless, <br /> top-filling, total fluids, pneumatic pumps at this site These pumps are simple to <br /> operate and do not require above ground controls or valves to regulate flow They <br /> pump as fast as they fill (maximum flow <15 gpm), and thus flow is controlled by <br /> depth of placement in the well The only above ground equipment needed is a <br /> pressurized air source, which is typically an electric air compressor These pumps <br /> are well suited for this site because maximum flow from RW-1 will not exceed 7 <br /> gpm, and they have the capability to pump SPH as it enters the well, which will <br /> likely occur at some point during groundwater extraction <br /> D-107,PAR/RAP 19 February 21, 1996 <br />