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elevation contours estimated using the depth-to-water measurements collected on December 31, 1997 indicated that groundwater flow at the site was generally consistent with the estimated flow on September 18, 1997 On March 27, 1998, Condor personnel were on site to conduct quarterly groundwater momtoring Laboratory analyses of groundwater samples collected from the site monitor wells indicated that BTEX, TPH-G and the selected gasoline oxygenates/additives were not detected at or above the laboratory reported detection limits in the sample collected from MW-1 Ethanol, tertiary-butanol, DIPE, ETBE, and TAME were not detected at or above the laboratory reported detection limits in any of the groundwater samples Detection limits for the analysis of the samples collected from MW-2 and MW-3 were raised, however, due to relatively high concentrations of MTBE in the samples collected from those wells (as described below) Benzene and TPH-G were not detected at or above raised detection limits and low concentrations of TEX constituents were detected in the sample collected from MW-2 MTBE was detected at 110,000 µg/1 m the MW-2 sample BTEX and TPH-G I were not detected at or above the laboratory reported detection limits m the sample collected from MW-3 MTBE was detected at 1,900 µg/l in the MW-3 sample TPH-G and BTEX constituents were detected in the sample collected from MW-4 MTBE was not detected at or above the laboratory reported detection limit in the MW-4 sample No floating product, sheen, or petroleum hydrocarbon odor was noted in the monitor wells Laboratory analytical results of the groundwater samples for the first quarter, 1998, monitoring event were generally consistent with historical quarterly groundwater analytical data MTBE concentrations in samples from MW-2, however, increased by more than two orders of magnitude during the three sampling events conducted at the site Groundwater elevation measurements collected at the site monitor wells on March 27, 1998, indicated that the average depth from the ground surface to groundwater was approximately 5 feet The average depth to water at the site increased by approximately 1 foot between December 31, 1997 and March 27, 1998 Groundwater elevation contours estimated using the depth-to-water measurements collected on March 27, 1998, indicated that groundwater gradient at the site was generally consistent with the estimated gradient on September 18, 1997, and ' December 31, 1997 In a telephone conversation on March 23, 1998, Mr Ronald Rowe of the San Joaquin County Public Health Services/Environmental Health Department (PHS/EHD) indicated that based on his review of the report dated ' December 11, 1997 (referenced above), he was requesting that quarterly groundwater monitoring continue at the site Furthermore, he requested that a work plan be prepared for conducting quarterly surface water sampling and additional investigation of the gasoline oxygenate/additive plume to the east of monitor well MW-2 Condor ' subsequently prepared the Work Plan Additional Soil and Groundwater Investigation / Surface Water Sampling, dated May 27, 1998 In a faxed note dated June 1, 1998, Mr Rowe approved the work plan with the stipulation that a work plan addendum be prepared describing installation of additional borings to those proposed ' in the work plan and grab sampling of the Herman & Helen's Manna drinking water source Condor subsequently prepared the Work Plan Addendum, dated July 9, 1998 In a fax dated July 27, 1998, Mr Ron Rowe approved the work plan addendum adding that both the facility pre-treated drinking water and the post- treatment water should be sampled and analyzed by appropriate methods On June 26, 1998, a Condor representative was on site to conduct quarterly groundwater monitoring Laboratory ' analyses of groundwater samples collected from the site monitor wells indicated that BTEX, TPH-G and the selected gasoline oxygenates/additives were not detected at or above the laboratory reported detection limits in the sample collected from MW-1 Ethanol, tertiary-butanol, DIPE, and ETBE were not detected at or above the ' laboratory reported detection limits in any of the groundwater samples TAME was detected in the samples collected from MW-2 and MW-3 MTBE was detected in the samples collected from MW-2, MW-3, and MW-4 BTEX and TPH-G were not detected at or above raised laboratory detection limits in the samples collected from MW-2 and MW-3 Relatively low concentrations of benzene, ethyl benzene, total xylenes, and TPH-G were detected in the sample collected from MW-4 Toluene was not detected at or above a raised laboratory detection