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t r PM 141EISS ASSOCIATES Consulting in Geology F Geohydrology 2938 McClure Strcct, Oakland. CA 91609 415.465-1100 3 May 1989 � � Sohn Randall Chevron USA SEP 2I �$8� 2410 Camino Ramon San Damon, CA 94583 EN1/IR0NMENTAL HEALTH Re: Chevron Scrvicc Station #96465 PERMIr/SEWCES 5608 North Pershing Avenue Stockton,California WA Job #4-305-01 Dear Mr. Randall: Weiss Associates (WA) collectcd ground water samples from five monitoring wells on 23 March 1989 as part of the quarterly ground water monitoring program at Chevron Service Station #96465 in Stockton, California(Figure 1). Monitoring wells MW-2, MW-6, and MW-7 (Figure 2) contained benzene above the California Department of Health Services (DHS) recommended action level for drinking water. GROUND WATER SAMPLING Robert Kitay,WA geologist,collected ground water samples from five monitoring wells on 23 March 1989. Monitoring wells MW-I and MW-3 were not sampled because they contained insufficient water for sample collection. Prior to sampling,each well was purged of at least four wclI-casing volunics of water,approximately 2 to 32 gallons per well,using steam-cleaned PVC and Teflon bailers. Each ground water sample was collected with a steam-cleaned Teflon bailer and decanted into a 40 mi glass volatile organic analysis vial (VOA) with a Teflon septum,presurved with sodium bisulfate,and refrigerated for transport to Superior Analytical Laboratory, Inc. of San Francisco, California. To reduce the possibility of sample contaiw-nation during transport or storage,each sample was sealed within a plastic guard bottle containing granular activated carbon. This sampling methodology and sample handling protocol is consistent with generally accepted ground water sampling procedures. The water sample collection and chain of custody records are included +s Attachments A and B, respectively. A bailer blank and a travel blank were shipped with the ground water samples. The bailer blank was prepared )y pouring distilled water into a steam-cleaned Teflon sampling bailer prior to sample colli :tion. The water was then decanted from the bailer into a 40 ml VOA preserved,refrigerated and transported to the laboratory with the ground water samples. A travel blank of certified organic-fret boiled distilled water, supplied by the laboratory, accompanied the samples to p-ovide assurance that contamination was, t introduced during sample bottle transport or sample storage. . . A Oirrsion ut.4plu.Ji.r -