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EIIC�yt® <br /> Mr James L Barton <br />' July 12, 2004 <br /> Page 4 <br /> Waste <br /> Non-hazardous purge water generated during second quarter 2004 groundwater monitoring and <br /> sampling activities is temporarily stored on-site pending transport to Evergreen Oil Company in <br /> Newark, California <br />' Discussion <br /> Analytical results from wells MW-2, MW-3, and MW-12 indicate that the air sparge system <br /> appears to be effective as evidenced by the decreasing TPHg and benzene concentrations <br />' TPHg concentrations in well MW-11 decreased overall, however, benzene concentrations have <br /> increased Hydrocarbon concentrations in these wells have decreased overall since the <br /> beginning of remediation in October 1999 <br /> The concentrations from the soil vapor samples taken on April 29, 2004 fluctuated while the soil <br /> vapor extraction system has been stopped TPHg and benzene concentrations in wells VEW-1 <br />' and VEW-13A have increased since last quarter however, concentrations in VEW-3 have <br /> decreased <br /> The groundwater gradients appear to remain similar to previous quarters Seasonal <br /> groundwater elevation fluctuations of about 6 feet are evident in the historical groundwater <br /> elevation data The groundwater elevations for the second quarter 2004 monitoring event are <br />' similar to those found during the same season to previous events <br /> MtBE was detected in groundwater sample collected from monitoring well MW-25S at a <br /> concentration of 0 81 micrograms per liter (pg/L), during the second quarter 2004 groundwater <br />' monitoring and sampling event MtBE was not detected at or above the laboratory reporting <br /> limit in the remaining monitoring wells <br />' Benzene concentrations have risen in the outlying wells MW-7, MW-9, and MW-27 since first <br /> quarter 2004 TPHg concentrations in these wells appear to be fluctuating <br />' Recommendations <br /> During second quarter 2004, ENSR performed a mayor service on the air compressor ENSR <br />' hopes that by performing the necessary maintenance, the system will be able to run more <br /> effectively ENSR recommends that the soil vapor extraction system be restarted, pulsed <br /> operation of the AS system continues, and that further groundwater sampling be performed to <br /> confirm the system's effectiveness <br /> Future Work <br /> Consistent with the CAO, and in response to the RWQCB letter dated June 18, 2004, ENSR will <br /> install three new monitoring wells during the third quarter 2004 These wells are required <br /> because of rising concentrations in three outlying wells (MW-7, MW-9, and MW-27) The <br />' J 1Projects10694015098-293\Finai Reportsl2nd Qtr 04-QMR RSR12nd Qtr04 QMR doc <br />