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Mr Jeff Wong Page 3 of 4 4.0 SUMMARY AND CONCLUSIONS The measured free product in well MW1 ranged from 0 02 to 0 22 feet during the reporting period Approximately 16 gallons of product/water mixture was removed from well MW 1 during the reporting period The total volume of product/water mixture removed from the well since August 16, 2001 is 59 5 gallons Although the thickness of free product was reduced from 123 feet on September 1, 2001 to just a sheen on February 11, 2002 through a program of periodic bailing, product thickness has rebounded to 0 22 feet on June 12, 2002 A chart showing product thickness in well MW 1 over time is presented on Figure 5 Between March 2002 and June 2002, groundwater levels fell an average of 0 52 feet in the shallow aquifer, and 1 14 feet in well MW9(B) Groundwater flow was in a northeasterly direction at a gradient of approximately 11 feet per mile The destruction of the old water supply well apparently eliminated a groundwater depression previously measured in well MW4 Since the last sampling round in March 2002, MTBE concentrations decreased in wells MW5 and MW6, but increased in wells MW2, MW3, and MW4 Benzene concentrations decreased in well MW6, but increased in wells MW2, MW3, and MW4 Time versus concentration plots of constituents of concern(TPHg, benzene, MTBE) in site wells are included in Attachment C • Except to south and west of well MW2, the lateral extent of gasoline constituents in groundwater beneath the site has essentially been defined except for MTBE, which has not been defined north of well MW6 Based upon the absence of contaminants in well MW9B, dissolved contamination in the upper water-beanng zone does not appear to extend into deeper zones north of the source area Based upon the presence of MTBE exceeding 1,000 ppb in the old water supply well, however, it is possible that deeper zones east of the source area have been impacted 5.0 RECOMMENDATIONS Based upon the results of subsurface investigations conducted to date, Ground Zero makes the following recommendations • Install additional groundwater monitoring wells to further define the lateral extent of groundwater contamination EHD agreed with this recommendation in a letter dated April 3, 2002 and has requested a workplan The workplan to complete the work will be submitted under separate cover • Evaluate the feasibility and cost-effectiveness of interim remediation and to control migration of the contaminant plume The aforementioned workplan will also address these issues The next monitoring and sampling event is scheduled for August 2002 EHD will be notified at least 48 hours prior to conducting fieldwork G\DatalGROUNDZEITULBBURG\Reports\QMR\2QM2002 doc