ARCHIVED REPORTS_XR0011319 - Laserfiche WebLink

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Wm. J. Hunter & Associates CONCLUSIONS: 1. The vertical limits of soil& groundwater contamination have been well delineated. 2. Soil contamination exists beneath the southeast comer of the office& shop building, and possibly to the north along the driveway on the east side of the building. 3. The highest levels of groundwater contaminants have been measured in MW-1, which is located closest to, and downgradient from, the removed UST's. 4. The water table has fluctuated from an average depth of 6.39'bgl to 9.12'bgl, and has always been below the tops of the well screens, which are at 5' below grade. 5. MW-1 has consistently measured the highest levels of contaminants in the groundwater. 6. MW-1 &MW-2 have never revealed MTBE since sampling began in December, 1995. 7. The levels of BTEX& TPHg in MW-3 show a decrease with time, suggesting that bio- remediation is occurring, since there is no evidence that the plume is migrating down- gradient. 8. MTBE was detected in MW-3 from the February, 1999 sampling event, but was not confirmed. It was not detected in the latest sample, indicatinp,that the 2/99 reading was incorrect. RECOMMENDATIONS: Based upon the evidence obtained to date, we continue to believe that additional investi- gative work is not required, and recommend the installation of ORC material in MW-1 to �~ reduce contamination to minimum levels. Air-sparging/soil vapor extraction is not feaible because of the shallow water table, and additional soil cannot be excavated due to the proximity of the building, an electrical transformer, and a large California Water Service water Line which traverses the site in the middle of the driveway on the east side of the building.. We do not believe that additional monitoring is justified without a plan to mitigate the remaining contamination. We requested a response to this recommendation in the previous report, but have yet to receive a reply. The owners are anxious to proceed with whatever additional work is required by the County EHD in order to obtain site closure. We would a reci to your prompt review and response to this report. W W J. n er&Associates ^44e �� cc: alley Wholesale Drug Co. - M k List, RWQCB a V:,,' �. �,s ITER OF c ,`.00H' i