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r r January 27, 1992 Former Texaco Station, Manteca, California �i Subjective Analyse014 s Samples of ground water were taken from the monitoring wells for subjective analysis. No floating product or product sheen was noted in sary pies from the monitoring wells. Results of the subjective analyses are presented in Table 1 After performing subjective analyses, the technician purged the three monitoring wells before collecting samples. Disposal of the purged water remains your responsibility. After pt rging each well, the technician collected ground-water samples for laboratory analysis. Laboratory Analyses The samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg) using modified Environmental Protection Agency ( PA) Method 8015, total petroleum hydrocarbons as diesel (TPHd) using modified E11A Method 8015, and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) using EPA Method 602. Laboratory analyses were performed at RESNA Environmental Laboratories in Fremont, California (Hazardous Waste Testing Laboratory No. 1211). The results of these and previous analyses are summarized in Table 3. Copies of the laboratory analysis reports are attached to this f report. Laboratory analyses did not detect concentrations f TPHg, TPHd, benzene, ethylbenzene, or total xylene isomers, with the exception of the sample collected from well MW-3 where a TPHg concentration of 200 parts per billion (ppb) was detected. Toluene was detected in the samples from the three wells at concentrations ranging from 0.8 ppb to 5.7 ppb. CONCLUSIONS AND RECOMMENDATIONS Dissolved hydrocarbons have been either not det ctable or below their respective MCL's since March 1990. Therefore, because dissolved hydrocarbons have remained below the California Department of Health Services Maximum Contaminant Levels established for Drinking Water for nearly two years, we recommerid discontinuing quarterly monitoring of ground water and abandoning the three monitorir g wells at the site. We further recommend that signed copies of this letter report be forwarded to Ms. Linda Turkatte of the San Joaquin County Public Health Services Department, P.O. Box 2009, Stockton, California 9520L and Mr. Jim Maughan of the California Regional Water Quality Control Board, Central Valley Region, 3443 Rout er Road, Sacramento, California 95827- 3098. M 1231ghro 3$053-4 3 n