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4 • 43 Groundwater Analytical Results The grab groundwater samples were analyzed by Pnority Environmental Labs in Milpitas, California, and monitoring well groundwater was analyzed by CKY Incorporated Environmental Services in Pleasanton, California, for TPHG and BTEX by EPA SW-846 Methods 8020/8015 Concentrations of TPHG and BTEX were detected in both grab groundwater samples and in the sample from MW-1 Results of all groundwater sample analyses are summarized in Table 2 The laboratory reports and chain-of-custody documents are included in Appendix D 5.0 DISCUSSION Based on the soil analytical results, it appears that concentrations of TPHG and BTEX are present at a depth of approximately 9 feet bgs in the silty clay unit This depth corresponds to the bottom of the former tanks and excavation limit The concentrations appear to be located in the capillary fringe zone approximately 0 5 to 1 foot above static groundwater Ievels Petroleum hydrocarbon staining was observed along with CGI readings in boreholes B-3, B-4 and B-5 at a depths of approximately 9 0, 9 0 and 10 feet bgs, respectively, although chemical analysis of these samples were below detection limits Analysis of the grab groundwater and monitoring wells samples indicate that petroleum hydrocarbons are present in groundwater directly beneath the former excay ation and extends in a northerly direction (with groundwater flow) towards 10th Street Concentrations of petroleum hydrocarbons are also present south (upgradient), east, and vest (laterally) of the tank complex, however, based on monitoring well groundwater sample results, the concentrations appear to be limited within a 20 to 25 foot distance from the former excay ation on site 6.0 CONCLUSIONS AND RECOMMENDATIONS Subsurface drilling and sampling revealed soil and groundwater contamination in the vicinity of the former tank excavation Groundwater contamination was observed in borehole grab water samples and in the monitoring wells The groundwater problem appears relatively limited to the site, although a groundwater sample from Borehole B-3 in the street revealed some downgradient movement off site Otherwise the plume appears to have spread slowly due to the relatiyrely flat gradient Wright recommends that a quarterly monitoring program be started to monitor plume moy ement Since the extent of the plume has not been defined, a shallow groundwater survey is recommended to collect grab water samples on the north side of 10th Street Wright also recommends that soil in the vicinity of the former tank be excavated to remove contaminated soil so that it does not continue to contaminate the groundwater It is estimated to that there is approximately 130 cubic yards of gasoline impacted soil (Figure 4) at the M and M site 70 LIMITATIONS This report was prepared in accordance with the PHSIEHD guidelines This assessment was conducted solely for the purpose of evaluating environmental conditions of the soil and groundwater with respect to petioleum hydrocarbons at the site No soil engineering or geotechnical references are implied or should be inferred Evaluation of the hydrogeologic conditions at the site for the purpose of this investigation is made from a limited number of observation points Subsurface conditions may ,ary away from the mailable data collection points Additional work, including further assessment, can reduce the inherent uncertainties • associated with this type of assessment This report was prepared solely for M & M Automotive , and any reliance on this report by a third party shall be at such party's sole risk Wright Environmental Services, Inc is not responsible for laboratory anal}tical errors