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' Consequently, the locations of the injection wells are estimated, based on historical data, slug test data, and information gathered during the visual site inspection A computer model of the bioremediation system (including groundwater flow patterns, and the growth of the biofilm) may be performed to maximize flow and minimize the ' potential of hydrocarbon migration The results of the model should reveal the optimum spacing for the injection wells Analytical, as well as hydrogeologic data, ' indicate that MW-01 and HP-5 are located near the edge of the petroleum hydrocarbon plume With an anticipated radius of influence of 30 feet, the downgradient location of MW-01 is optimal as an injection point MW-01, which is ' a 2-inch diameter PVC-cased well, will be converted into an injection well Groundwater was encountered at a depth of 12 feet bgs in this well The analytical results presented in the ASA/RO Report indicate that elevated levels of total petroleum hydrocarbons as gasoline (TPH-g) and benzene, toluene, ethylbenzene, and total xylenes (BTEX) were detected in HP-5 HP-5 is upgradient of the zone of contamination and downgradient of the former USTs Waste Science proposes to place an injection well (MW-11) approximately 10 feet upgradient of HP-5 This placement should allow all the impacted groundwater to be affected by the injection well. MThe third injection well (MW-10) will be placed between HP-6 and HP-7, approximately 10 feet west of MW-08 The location of the third injection well is ' outside the plume boundaries, but within the capture zone Both newly installed injection wells (MW-10 and MW-11) will be drilled to a depth of 25 feet bgs and completed in accordance with the SJCPHS standards as 2-inch diameter PVC wells The wells will be screened from 5 feet to 25 feet with 0 02-inch factory slotted screen It is anticipated that the low levels of TPH-g and BTEX detected in MW-09 will be captured by the combined radii of influence of injection wells MW-01 and MW-10 Upon concurrence of this RAP, well construction details will be provided as part of the well pernnt application process The extraction and injection wells will be connected via a 2-inch PVC pipe to a 1,000 gallon mixing tank, thereby, creating a "closed loop" system An injection and sample monitoring port, an in-line mixer, and an air pump will be placed in-line between the extraction well (MW-08) and the tank The purpose of the in-line mixer ' and the air pump is to provide optimum oxygenation to accelerate the growth of naturally occurring bacteria and increase enzymatic activity ETEC's enzymatic complex will be introduced into the extracted water stream as it travels to the mixing 9488 East Bay Municipal Utility Dtstnet 40429601 rap 9 Remedial Action Plan i I 1