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r I � 3164 Gold Camp Drive Delta Suite 200 Rancho Cordova.CA 95670 �nvironmentai 9161638-2085 Consultants,Inc. FAX: 9161638-8365 October 16, 1995 Ms. Marla Guensler Exxon Company, U.S.A. 2300 Clayton Road, Suite 490 Concord, California 94520 Subject: Quarterly Ground 'Water Monitoring Report, Third Quarter 1995 Exxon Retail Station No. 7-3330 3128 West Benjamin Holt Drive Stockton, California 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 Retail Station No. 7-3330, located at 3128 West Benjamin Holt Drive, Stockton, California. This letter report presents the results of overpurging and sampling of MW-5 on July 27, 1995, and the results of quarterly ground water monitoring and sampling conducted on August 31 and September 11, 1995. 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 well MW-5 (10.57 feet below the top of casing) on July 27, 1995, prior to overpurging. Depth to ground water was measured in three of the four monitoring wells (MW-4 through MWS at the site on August 31, 1995. Depth to ground water could not be measured in monitoring well MW-3 on August 31, 1995, because the well had been paved over. All four monitoring wells were measured on September 18, 1995, after the pavement had been cleared from monitoring well MW-3. On September 18, 1995, depths to ground water in the monitoring wells ranged from 11.41 (MW-6) to 11.80 (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 September 18, 1995, 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 approximately 0.001, which is consistent with the historical ground water flow direction. Subjective Analysis �I No liquid-phase petroleum hydrocarbons or hydrocarbon sheens were present in the wells during the August 31 or September 18, 1995, site visits. Providing a Competitive Edge