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z <br /> 4.0 CONCLUSIONS <br /> The -roundwater samples :collected fromonitorinwell MW-1 contained <br /> 720 parts per million (ppb) methyl-tertiary-butyl ether (MTBE). 0.8 tert- <br /> amyl-methyl-ether (TAME); and 34 ppb tert-butanol (TBA). The <br /> i groundwater samples collected from monitoring well MW-2 contained <br /> 2,200 ppb TPH-G, 210 ppb benzene, 83 ppb toluene. 1. 10 ppb ethyl <br /> benzene, 170 ppb total xylenes, l .500 ppb MTBE, 5.2 ppb TAME-, and 1 3 0 <br /> ppb TBA. Groundwater samples collected from monitoring well MW-3 j <br /> contained 4.0 ppb MTBE. Groundwater samples collected from <br /> monitoring well MW-4 contained 680 ppb TPH-G, 69 ppb benzene, 36 p p b <br /> ethyl benzene, 3.4 total xylenes, 280 ppb MTBE, I3 ppb TAME. and 9 . 8 <br /> ppb TBA. Groundwater 'samples collected from monitoring well MW-5 <br /> contained 1 ,000 ppb TPH-G, 28 ppb MTBE, and 26 ppb TBA. No other <br /> hydrocarbons were detected above laboratory reporting limits in any of <br /> the groundwater samples ` collected. <br /> i Due to the limited quarterly groundwater monitoring data for the site, it <br /> is difficult to identify any clear or significant trends that may suggest <br /> contaminant levels are increasing of decreasing at this time. It is noted <br /> that all contaminant concentrations in monitoring well MW-2 decreased <br /> since the last sampling was performed at the site, but because only three <br /> sampling rounds have been performed, this is also inconclusive as to an <br /> overall contaminant concentration trend. The MTBE concentrations in <br /> monitoring well MW-I has increased during each sampling. The <br /> remaining groundwater analytical data from the remaining wells at the <br /> site did not show any clear trends. <br /> 5.0 RECOMMENDATIONS <br /> ASE recommends the subject site remain on a quarterly sampling <br /> schedule. Since the San Joaquin County PHS-EHD requested that <br /> monitoring wells at this site be sampled at the same time as the other sites <br /> on the same intersection, ' the next scheduled sampling is scheduled for <br /> May 2001. <br /> I <br /> 1 <br /> A workplan to conduct additional activities was recently prepared. ASE <br /> 1 <br /> anticipates implementing work outlined in the workplan during the next <br /> quarter. 1 <br /> I <br /> Singh's Unical Service Station Quarterly Report - April 2001 Sampling <br /> -3- k <br />