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�y . Delta 3164 Gold Camp Drive Suite 200 ilk Cordova,CA 95670 Environmental 916/638-2085 Consultants,Inc. FAX: 916/638-8385 February 29, 1996 00"CENED Fit T Ms. Marla Guensler APR 15 'S�s Exxon Company, U.S.A. 2300 Clayton Road, Suite 490 ENVIRONMENTAL HEALTH Concord, California 94520 PERMIT/SERVICES Subject: Quarterly Ground Water Monitoring Report, First Quarter 1996 Exxon Service Station No. 7-3330 3128 West Benjamin Holt Drive Stockton, California Af w Delta Project No. D093-810 Dear Ms. Guensler: Delta Environmental Consultants, Inc. (Delta) has been authorized by Exxon Company, U.S.A. (Exxon)to conduct quarterly ground water monitoring at Exxon Service Station No. 7-3330, located at 3128 West Benjamin Holt Drive, Stockton, California. This letter report presents the . results of quarterly ground water monitoring and sampling conducted on January 26, 1996. The location of the site is shown on Figure 1 and site features are illustrated on Figure 2. All work conducted at the site by Delta was performed in accordance with the field methods and procedures described in Enclosure A. Ground Water Table Elevations, Flow Direction, and Hydraulic Gradient Depth to ground water was measured in monitoring wells MW-3 through MW-6 on January 26, 1996. Measured depths to ground water ranged from 9.68 (MW-6) to 9.87 (MW-3) feet below the tops of the well casings. Cumulative ground water table measurements are presented in Table 1. A water table contour map constructed from the ground water table measurements recorded on January 26, 1996, is included as Figure 3. The water table contours illustrated in Figure 3 indicate that ground water flowed toward the northeast with a hydraulic gradient of Iess than 0.01, which is consistent with the historical ground water flow direction. Sub jrective_Analysis No liquid-phase petroleum hydrocarbons or hydrocarbon sheens were present in the wells during the 3anua 2 site visit. Ground Water_Sampiima_and Analytical Results Ground water samples were collected from monitoring wells MW-3 through MW-6 and were submitted to Sequoia Analytical (a California-certified laboratory) for analysis of benzene, toluene, ethylbenzene, total xylenes, and methyl tertiary butyl ether (MTBE), using EPA Method 8020, and total petroleum hydrocarbons as gasoline using EPA Method 8015 Modified. Cumulative analytical results are summarized in Table 2. Ground water samples collected from monitoring wells MW-3, MW-4, and MW-6 did not contain detectable concentrations of petroleum hydrocarbons. The ground water sample collected from monitoring well MW-5 reported MTBE at a concentration of 12 micrograms per liter (µg/L). All other analytes were below the laboratory's limits of detection. Providing a Competitive Edge