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Comfort Air, Incorporated February 7, 2008 <br /> 1607 Turnpike Road <br /> Stockton, California 95206-1960 <br /> The EHD does not concur with AGE that COC are defined both vertically and laterally in soil <br /> and groundwater at the former UST site on your property. The EHD has reached this <br /> conclusion based on the following: Samples collected during the advancement of cone <br /> penetration test (CPT) boring CPT-1 in the source area have indicated that COC were detected <br /> in the one soil sample collected at approximately 85 feet bsg, and in the two groundwater <br /> samples collected at approximately 100 and 117 feet bsg. Although groundwater samples <br /> collected quarterly from the only deep monitoring well (MW-13), screened between <br /> approximately 112 and 117 feet bsg, have been reported as "non-detect' for petroleum <br /> hydrocarbons, this well is at least twenty feet from the source area and there is no data to <br /> determine the groundwater gradient at this depth. Based on analytical results for COC reported <br /> for the soil and groundwater samples collected from CPT-1, and based on the soil lithology for <br /> CPT-1, the EHD believes a deep well, screened between approximately 112 and 1.17 feet bsg, <br /> is needed in the source area to monitor groundwater at this depth. <br /> By email on January 17, 2008, AGE requested that groundwater collected from monitoring <br /> wells MW-9A, MW-10A, MW-IOB, MW-11A, MW-12A, MW-12B, and MW-13 be sampled <br /> annually instead of quarterly based on "non-detect' results reported for groundwater samples <br /> collected since at least the first quarter of 2006. By email on January 29, 2008, the EHD <br /> approved the annual sampling for these wells with the understanding that depth-to-water will <br /> be measured in these wells each quarter for the purpose of determining the groundwater <br /> gradient. The EHD also approves the removal of methyl tertiary-butyl ether (MTBE), ethyl <br /> tertiary-butyl ether (ETBE), and tertiary-butyl alcohol (TBA) from the analytical regimen since <br /> these compounds have not been detected in any groundwater samples collected quarterly since <br /> 2004. <br /> Please submit a work plan to the EHD by June 5, 2008, that will address the petroleum <br /> hydrocarbon contamination at the former UST location and in the area west of Turnpike Road. <br /> If you have any questions, please contact Vicki McCartney, Senior Registered Environmental <br /> Health Specialist, at (209) 468-9852 or by email at vmccartney@sjcehd.com. <br /> Sincerely, <br /> Victoria L. McCartney, REHIS� Nuel C. Henderson, Jr., PG <br /> Senior Registered Environmental Health Specialist Engineering Geologist <br /> c: Ms. Ally L. Colavita, Advanced GeoEnvirormmntal, Inc., 837 Shaw Road, Stockton, <br /> California 95215 <br /> Mr. James L.L. Barton, PG, California Regional Water Quality Control Board Central <br /> Valley Region, 11020 Sun Center Drive, Suite 200,Rancho Cordova, California 95670 <br />