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Mr Jeff Wong <br /> Page 4 of 5 <br /> removed from the well since August 16, 2001 <br /> The newly installed water supply well was placed into service and the old water sypply well was <br /> sampled and abandoned during the reporting period Groundwater samples collected from the old well <br /> at depths of 90 and 200 feet contained MTBE at levels exceeding 1,000 ppb <br /> Between November 2001 and March 2002, groundwater levels rose an average of 1 25 feet in the <br /> shallow aquifer, and 129 feet in the deep aquifer Groundwater flow was in a northeasterly direction <br /> with a relatively flat gradient The destruction of the old water supply well apparently eliminated a <br /> groundwater depression previously measured in well MW4 <br /> Since the last sampling round in November 2001, MTBE concentrations decreased in wells MW2, <br /> MW3, MW5, and MW6, but increase in well MW4 Benzene concentrations decreased in wells MW2 <br /> and MW3, but increased m wells MW4 and MW6 Tune versus concentration plots of constituents of <br /> concern(TPHg, benzene, MTBE)in site wells are included in Attachment E <br /> Except to south and west of well MW2, the lateral extent of benzene and TPHg contamination in <br /> groundwater beneath the site has essentially been defined The lateral extent of MTBE contamination <br /> beneath the site has been defined in all directions except north of well MW6 Based upon the absence <br /> of contaminants in well MW9B, dissolved contamination in the upper water-bearing zone does not <br /> appear to extend into deeper zones north of the source area Based upon the presence of MTBE <br /> exceeding 1,000 ppb in the old water supply well, however, it is possible that deeper zones east of the <br /> source area have been impacted <br /> 5.0 RECOMMENDATIONS <br /> Based upon the results of subsurface investigations conducted to date, Ground Zero makes the <br /> following recommendations <br /> • Install additional groundwater monitoring wells to further define the lateral extent of groundwater <br /> contamination EHD agreed with this recommendation in a letter dated April 3, 2002 and has <br /> requested a workplan by May 15, 2002 <br /> • Continue to bail product from well MW as needed and evaluate the need for additional interum <br /> remediation EHD has requested a report by June 1, 2002 that will evaluate feasibility and cost- <br /> effectiveness of at least two remediation alternatives to control migration of the contaminant <br /> plume <br /> G1Data1GROUNDZS1TULEBURG\Reports\QMR11QM2002 doc <br />