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. ,• • <br /> 2101 Webster Street <br /> 12th Floor <br /> CA S4612 <br /> (510) 663-4100 • FAX (510) 663-4141 GEOMATRIX <br /> June 29, 2000 <br /> Project 4002.000 <br /> Mr. Robert Mihalovich <br /> Chevron Environmental Management Company <br /> P.O. Box 6012 <br /> San Ramon, California 94583 <br /> Subject: Grab Groundwater Sampling Work Plan <br /> Former Lyoth Loading Station <br /> 26501 Banta Road <br /> Tracy, California <br /> Dear Mr. Mihalovich: <br /> Geomatrix Consultants, Inc. (Geomatrix) has prepared this work plan on behalf of Chevron <br /> Environmental Management Company(CEMC) for work to be conducted at the former Lyoth <br /> Loading Station (the site; Figure 1). The proposed scope of work involves advancing one <br /> boring downgradient of existing monitoring well MW-7 for the collection of one grab <br /> groundwater sample as requested by California Regional Water Quality Control Board, <br /> Central Valley Region(RWQCB) in its March 14, 2000 letter to CEMC and as described in <br /> CEMC's April 17, 2000 response letter to the RWQCB. <br /> Previous groundwater samples from monitoring well MW-7 have been analyzed for total <br /> petroleum hydrocarbons quantified as diesel (TPHd) both with and without passing the <br /> sample extract through a silica gel column. The silica gel preparation procedure removes <br /> polar biodegradation byproducts from the sample extract, leaving only the non-polar <br /> petroleum constituents for quantification in the analysis. Groundwater samples collected <br /> from monitoring well MW-7 since 1997 indicate that TPHd is not detected in groundwater <br /> when sample extracts are passed through silica gel. However, material quantified as "TPHd" <br /> has been detected in samples from MW-7 that were analyzed without a silica gel preparation <br /> procedure. These detections are likely attributable to biodegradation byproducts of crude oil <br /> and/or biodegradation byproducts of naturally-occurring substances. The RWQCB has <br /> requested that a groundwater sample be collected downgradient of MW-7 and analyzed for <br /> TPHd without performing a silica gel preparation procedure. The proposed scope of work is <br /> described below. <br /> Geomatrix will contract with Precision Sampling, Inc. to advance one soil boring at the <br /> locations shown on Figure 2. Geomatrix will contract with a private utility locator to identify <br /> potential underground utilities at the proposed boring location and will notify Underground <br /> Service Alert (USA). The boring will be advanced to a depth of approximately 15 feet below <br /> ground surface (bgs) using a hydraulically driven, direct push core barrel and drive sampler. <br /> Soil recovered from the continuous core will be examined and logged in accordance with the <br /> Geomatrix Consultants, Inc. <br /> Engineers, Geologists, and Environmental Scientists <br />