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C\TATC <br /> A S S O C I A T E S I N C <br /> Groundwater samples were collected on July 28, 1998 from wells MW2, MW3, and MW6. No <br /> groundwater sample was collected from MW4 due to the presence of free product. Prior to <br /> sample collection, each sampled well was purged of a minimum of three well casing volumes of <br /> water. Purged water was contained in labeled 55-gallon drums (DOT H), and stored on site. <br /> Groundwater samples were collected after physical parameters (pH, temperature, and <br /> conductivity) were monitored and had stabilized. Dedicated disposable bailers with bottom- <br /> emptying devices were used to collect samples from the wells. All field activities were performed <br /> in accordance with the Field Methods included in Attachment 1. Field purge logs are presented in <br /> Attachment 2. <br /> LABORATORY ANALYSES <br /> Collected groundwater samples were analyzed for total petroleum hydrocarbons as diesel (TPHd) <br /> by Sequoia Analytical, a State-certified laboratory, utilizing EPA method 8015. The analysis of <br /> groundwater samples for benzene, toluene, ethylbenzene, and xylenes has been discontinued in <br /> accordance with verbal approval by San Joaquin County Public Health Services/Environmental <br /> Health Division on March 26, 1997. Analytical results are summarized in Table 3. Laboratory <br /> data sheets and chain-of-custody documentation are included in Attachment 3. <br /> Laboratory results indicate that TPHd was detected in groundwater samples collected from wells <br /> MM2, MW3, and MW6 at concentrations of 100 parts per billion (ppb), 830 ppb, and 68 ppb, <br /> respectively, but was reported by the laboratory as an unidentified hydrocarbon. <br /> WORK IN PROGRESS <br /> A free product skimmer has been installed in well MW4 and is being monitored. If free product is <br /> encountered in the skimmer, it will be removed from the skimmer and stored on site. The next <br /> groundwater monitoring episode is sch duled-t"e-Derformed in October 1998 and will include <br /> sample collection from monitoring well MW3, MW4, and MW6 <br /> w:1943691quwt1y\3gmr1998.doc 2 <br />