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amec�9 <br /> These advantages and disadvantages were considered for this feasibility analysis. <br /> If managed correctly, it may be possible to continuously remove CDCs from captured <br /> groundwater and re-inject the treated water to provide additional hydraulic control, aquifer <br /> flushing and hydraulic containment. Several options are available for aboveground treatment <br /> of VOCs including granular activated carbon, air stripping, biological treatment, and advanced <br /> oxidation processes using ultraviolet light and/or hydrogen peroxide and ozone. There may be <br /> certain constituents in groundwater near the WWTP that are not COCs but nonetheless may <br /> be considered to be groundwater contaminants. These include total dissolved solids (TDS), <br /> arsenic, nitrate and trace organic compounds related to the discharge of industrial and <br /> municipal wastewater (derivatives of personal care products, pharmaceuticals and other trace <br /> exotic chemicals). The treatment options described may not treat these compounds and <br /> therefore re-injection of these may occur under a groundwater recirculation scenario, which <br /> could cause a more widespread distribution of non-COC contaminants and exacerbate <br /> groundwater quality problems. <br /> 3.0 TECHNOLOGY EVALUATION <br /> 3.1 TREATMENT AREA AND PRELIMINARY DESIGN <br /> In the WWTP area, the highest COC concentrations have been reported for groundwater <br /> samples from monitoring wells in the Intermediate Aquifer M-1 7C1, M-20C1, M-30C1 and M- <br /> 31 Cl; Figure B.3-1). This area of elevated COC concentrations in groundwater (greater than <br /> 100 µg/L) in the intermediate aquifer is estimated to be approximately 120 acres in size, based <br /> on the locations of these monitoring wells, not including the area directly beneath the WWTF, <br /> which is assumed to be underlain by clean groundwater (Figure B.3-1). <br /> A proposed alignment of pump and treat wells that would adequately contain groundwater with <br /> elevated VOC concentrations near the WWTF is depicted in Figure B.3-1. The preliminary <br /> design for the P&T system includes alternating pairs of injection wells and extraction wells <br /> spaced at 300 foot offsets. Each well pair includes a well screened in the upper and <br /> intermediate aquifer zones. Groundwater would be extracted from the extraction wells, treated <br /> at a central aboveground treatment system, and re-injected through a series of injection wells, <br /> each located next to an extraction well. The preliminary design injection and extraction flow <br /> rates for this well configuration are 50 gallons per minute (gpm) for a total system flow rate of <br /> 2.88 million gallons per day (MGD). The annual volume of water treated using these design <br /> flow rates would exceed 1 billion gallons. <br /> 3.2 EFFECTIVENESS <br /> A groundwater recirculation system installed in the area depicted in Figure B.3-1 could <br /> theoretically be designed to adequately contain groundwater impacts near the WWTF, but the <br /> AMEC Geomatrix, Inc. <br /> \\oad-fs1\doc_safe\9000s\9837.006\4000 REGULATORYTS Assessment_Apx B_012711\Attachment B.3\Attach B-3.docx 133-2 <br />