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Beacon #3641 page 2 <br /> 1210 E. Hammer Lane, Stockton <br /> In evaluating the SCM, EHD concluded that the investigative phase for this site is <br /> not complete. EHD noted that MW-12 and MW-13 ground water contamination <br /> data indicates that the ground water contamination detected in soil boring B-5 is <br /> not present after two sampling events at 130 feet below ground surface (`bgs). <br /> Although the placement of these wells was outside the `core' area as defined by <br /> laboratory data included in the SCM, the ground water data collected so far from <br /> MW-12 and MW-13 indicates that the contamination noted in B-5 at 130' bgs has <br /> not migrated laterally. EHD concurs with your consultant's conclusion that the <br /> ground water plume is vertically delineated. <br /> Although the petroleum plume may be vertically delineated in the core area to <br /> the maximum depth investigated, there is a data gap in the interval from 75' bgs <br /> (MW-5) to the next deeper wells (MW-12 & 13) at -130'-135' bgs. The <br /> contamination detected at 100' bgs in B-5 has not been adequately investigated. ,f <br /> In order to investigate the elevated ground water contamination in MW-5 and <br /> confirm if there is elevated ground water contamination at -100QLbg <br /> documented from B-5, EHD will require a well o be placed near the B-5 location <br /> in the sand zone at approximately 95'-100' bgs. This well is to be sampled <br /> quarterly for all constituents for at least one year. If it can be shown that a <br /> change in the sampling and analytical suite can be justified, EHD will evaluate a <br /> request at the end of the year's period. <br /> A work plan for the monitoring well installation should be submitted to EHD <br /> immediately. <br /> Please continue to address your reports and correspondence to Michael Infurna <br /> and you may contact him at (209) 468-3454 should you wish to call. <br /> Donna Heran, RENS, Director <br /> Enviro mental Health Department • <br /> Michael J. Infurna Jr., Senior REHS Margare Lagorio, R S <br /> LOP 1 Site Mitigation Unit IV Supervisor <br /> C, CVRWQCB - James Barton, Sacramento. <br /> c: SWRCB-CUF - Mark Owens, Sacramento. <br /> c: Horizon - R. Smith, 4970 Windplay Dr. #C5, EI Dorado Hills, 95762 <br />