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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 all collected groundwater samples at <br /> concentrations ranging from 150 parts per billion (ppb) (MW6) to 540 ppb (MW3), but was <br /> reported by the laboratory as an unidentified hydrocarbon. <br /> WORK IN PROGRESS <br /> The next groundwater monitoring episode is scheduled to be performed in January 1998 and will <br /> include sample collection from monitoring wells MW through MW6. <br /> Please contact our Modesto office at 209 579-2221 if you have any questions or comments. <br /> Very truly yours, <br /> Smith Technology Corporation(ATC Associates) <br /> DAI- t4l- <br /> AJJ— <br /> Drew Van Allen 90FESSlQ�y <br /> Staff Scientist �0 J NNE 9lcy <br /> H MSEY �= <br /> Jeanne Homsey, P.E. N0.CC474I0 <br /> CA Registered Engineer No. C4 74 10 .*. Exp. -17_-(9_R <br /> Attachments q� CIVI <br /> OF CAL1 <br /> PC: Mr. Jim Escobar, City of Stockton <br /> Ms. Elizabeth Thayer, RWQCB <br /> w:N3691quartlyAgmr1997.doc 2 <br /> • <br /> SMTH <br />