ARCHIVED REPORTS XR0004093 - Laserfiche WebLink

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Findings From Water Sample Analysis All wells are non-detect for MTBE**. Extraction well EW-1 shows TPHg(1.6ppm), Ethyl- Benzene(169ppb), and Xylene(215ppb). Monitoring well GMX-1 shows TPHg(6.5ppm), Benzene(ND<6ppb), Toluene(90ppb), Ethyl-Benzene(521ppb), and Xylene(1030ppb). MW-2 shows TPHg(.89ppm),Benzene(.5ppb),Toluene(.6ppb),Ethyl-Benzene(27ppb),and Xylene(26ppb). The values for MW-2 are a significant decrease from the previous monitoring event because water has risen above the screen. In the previous sampling event a grab sample was taken from the cup of the casing which is confined and separate from the groundwater. MW-3, and MW-4 continue to have a clean history. The proposed clean up levels from the approved "Final Remedial Plan" and the maximum remaining concentrations are as follows: Compound Concentration Goals Maximum Remaining Concentrations Benzene 5ug/L Less than 6.0 ug/L* MTBE lug/L Less than 10 ug/L** TPHg 2,000ug/L 6,500ug/L *Note that GMX-1 was non-detect for Benzene,but had an elevated reporting limit of 6ug/L. ** Also note that GMX-1 was non-detect for MTBE, but had an elevated a reporting limit of 10ug/L. The direction of flow is South East with a gradient of s=0.0013. Mass Remaining in Water From the Second Quarter, 2005 sampling a TPHg concentration contour map was made and is attached. The mass of TPHg remaining was calculated to be 1.38Kg(0.35ga1). • Mass Remaining in Soil The mass remaining in the soil is calculated for the soil samples of MW-2, MW-3, and MW-4. Only MW-2 showed results for contaminated soil. The estimated mass of TPHg is 4.7Kg or approximately 1.7ga1. Conclusions Pump and treat has reduced the mass of contamination in the plume. The estimated mass of TPHg before pump and treat was 27.2Kg and the estimated mass remaining from the current sampling event is 1.38Kg, which is a 95% reduction. Recommendations Foothill Engineering continues to recommend that the San Joaquin County Public Health Services, Environmental Health Department issue a letter stating no further action is required for this site. Please contact Mike Vlach a pRo !oN 84 if any questions arise concerning this report. Respectfully submitted, Q�Q��. OBE,9 L,CO y m Foothill Eng' en g 57707 s * EXP.12-31-05 1 Vlach P.E. 6> CIV11 ichae , OFCA��F Attachments:Site Map,Concen ontours,Mass in Soil Calculation,Groundwater sample Analysis Recap, Del-Tech Field Report, Laboratory Reports cc: Diana Maragos, Attorney for Sun West Liquors, W. T. Mitchell Group 3