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i <br /> This option requires definition of the horizontal and vertical extent of hydrocarbons in <br /> groundwater via regular sampling of monitoring wells It must include a complete <br /> evaluation of the beneficial uses of the impacted water-bearing zone, as well as the <br /> background (regional) quality of the groundwater <br /> After a complete assessment of the extent of groundwater contamination, the <br /> beneficial uses of the water-bearing zone, and background water quality, an in-depth <br /> assessment of the potential threat to the public health must be undertaken In some <br /> cases this must be presented in the form of a formal health risk assessment prepared <br /> by a certified industrial hygienist In addition to the issues outlined above, the <br /> potential for migration of the groundwater plume must be evaluated When all of <br /> these parameters have been defined, and no significant threat to the public health has <br /> been demonstrated, a long-term groundwater monitoring program may be negotiated <br /> with the concerned regulatory agencies <br /> 2.2 Ex-Situ Groundwater Remediation Alternatives (Pu mr)-and-Treat) <br /> Ex-situroundwater remediation alternatives include the design, installation, and <br /> g 9 <br /> operation of a suitable number of groundwater recovery wells located so as to enable <br /> the capture of the contaminant plume Following extraction, contaminated <br /> groundwater is treated by an appropriate water-treatment technology to achieve target <br /> cleanup levels, with treated water being discharged by either re-injection, discharge <br /> to sanitary sewer, storm sewers, and/or land surface This treatment alternative is <br /> also referred to as "pump-and-treat" and experience has demonstrated this technology <br /> alone is not an effective groundwater treatment alternative Therefore, groundwater <br /> extraction and treatment systems are usually installed for the purpose of hydraulic <br /> control, to halt migration of a contaminated plume, and are usually used in <br /> combination with in-situ technologies to effectively remediate contaminated <br /> groundwater <br /> The selection of an ex-situ groundwater remediation alternative depends on adequate <br /> design of the extraction system (recovery wells) Depending on the site, a suitable <br /> water treatment system must be designed to be compatible with the flow rate <br /> delivered from the extraction system as well as the contaminant type Before <br /> embarking on design of an extraction and treatment system, the feasibility of <br /> discharge of treated water to various receptors, National Pollutant Discharge <br /> Elimination System (NPDES) permits, etc , must be considered. <br /> All of the aforementioned design parameters, cleanup objectives, and compatible in- <br /> situ treatment technologies must be evaluated to develop the most feasible, cost- <br /> effective cleanup system for a specific site <br />' 2 2 1 Air Stripping <br /> Air stripping involves the removal of organic compounds by increasing the surface area <br /> of the processed groundwater and volatilizing organic compounds by mixing the water <br /> with blowing air The most common air-stripping design is counter-current, packed- <br />` tower aeration Other techniques include vacuum stripping, aspiration stripping, steam <br />