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v <br /> ATC <br /> r ASSOCIATES I N C . <br /> Groundwater samples were collected on January 14, 1999 from wells MWl, MW2, MW3, MW5, <br /> and MW6. No groundwater sample was collected from MW4 due to the presence of free <br /> product. Prior to sample collection, each sampled well was purged of a minimum of three well <br /> casing volumes of water. Purged water was contained in labeled 55-gallon drums (DOT H), and <br /> 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 /> On September 18, 1998 the skimmer was temporarily removed due to a faulty seal. The skimmer <br /> was reinstalled on October 23, 1998. On December 10, 1998, the skimmer was temporarily <br /> removed due to a faulty seal. The seal was replaced and the skimmer was reinstalled on January <br /> 14, 1999. <br /> LABORATORY ANALYSES <br /> Collected groundwater samples were analyzed for total petroleum hydrocarbons as diesel (TPHd) <br /> = f 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 /> MW2, MW3, MW5, and MW6 at of concentrations of 61 parts per billion (ppb), 1,100 ppb, 52 <br /> ppb, and 57 ppb, but was reported by the laboratory as an unidentified hydrocarbon. The sample <br /> collected from well NMI was nondetect. <br /> WORK IN PROGRESS <br /> A free product skimmer was 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 scheduled to be performed in April 1998 and will include <br /> sample collection from monitoring wells MW3 and MW6. <br /> w:1943691quargy\1 gmr1999.doc 2 <br /> I <br />