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,y 21 March 2001 <br /> AGE-NC Project No. 98-0432 <br /> Page 5 of 5 <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> Based on the data collected from the site, AGE finds: <br /> ' No petroleum hydrocarbons were detected in the soil sample analyzed from the boring <br /> p yz g <br /> advanced on the site. MTBE was detected in four soil samples. <br /> • Petroleum hydrocarbons were not detected in the grab ground water samples collected from ' <br /> the site. MTBE was detected in one of the grab water samples collected. The concentration <br /> exceeds the State of California, Department of Health Services action level for MTBE in <br /> . drinking water. <br /> Based on the analytical data for the grab water samples collected,the MTBE impacted plume <br /> Js at least 26 feet thick near the location of well MW-1/EW-1 and extends to fifty feet bsg <br /> only at the location of boring BS. The MTBE plume is limited to less than fifty feet bsg at <br /> the locations of borings B7 and B9,located down gradient from the highest dissolved MTBE <br /> concentrations. <br /> 5.0. RECOMMENDATIONS <br /> ' Based-on the findings presented in this report, AGE recommends: <br /> • Quarterly ground water monitoring should be continued. <br /> • Performance of the ground water extraction feasibility pilot test should be conducted. An <br /> interim ground water extraction system should be installed to prevent off-site migration of <br /> 1 MTBE and reduce the mass of dissolved MTBE in ground water. <br /> ' 6.0. LIMITATIONS <br /> ' Our professional services were performed using that degree of care and skill ordinarily exercised by <br /> environmental consultants practicing in this or similar localities. The findings were based upon <br />. . analytical results provided by an independent laboratory. Evaluation of the hydrogeologic conditions <br /> at the site for the purpose of this investigation was made from a limited number of available data _ <br /> ' points (soil and groundwater samples) and subsurface conditions may vary away from these data <br /> points. No other warranty, expressed or implied, is made as to the professional recommendations <br /> contained in this report.- <br /> ' � • .- , . <br />