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r26485 THORNTON ROAD <br /> • WKA No 2556 02 <br />' August 18, 1994 <br /> Page 5 <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Based on the above analytical data and observations made at the time of our field work, soil <br /> contamination exists beneath the site in the general area of the "estimated extent of <br /> contamination" shown on Plate 2 The soil contamination appears to extend from approxiinately <br /> five feet below surface grade to the soillground water interface <br /> Based on these findings, it appears that the remaining soil contamination may be a result of <br /> petroleum hydrocarbons spreading laterally along the surface of the ground water As a result, <br /> we recommend that the remaining soil contamination be addressed at the same time as the ground <br /> water contamination. <br /> Additional laboratory analysis of water samples obtained from the three on-site wells indicates <br /> that ground water contamination extends easterly to monitoring well MW2 and northerly to <br /> MW3 The water samples obtained westerly from the former USTs in monitoring well MW1, <br /> revealed no detectable concentrations of TPH as gasoline or BTEX. <br /> Based on our findings, we recommend additional ground water evaluation to establish a "zero <br /> line" of contamination Hydropunch sampling may be a cost-effective method of delineating the <br /> extent of ground water contamination prior to installation of additional wells In addition, the <br /> existing wells should be surveyed to the nearest benchmark so that ground water flow direction <br /> and gradient can be evaluated When the extent of ground water contamination has been <br /> Idelineated, a Final Remedial Plan should be prepared for review by the regulatory agencies. We <br /> additionally recommend that San Joaquin County Public Health Services Department be provided <br /> Iwith a copy of our findings and recommendations <br /> WALLACE KUHL <br /> Recycled paper S AssoCIATES INC. <br />