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1- 3330 Data Drive Delta : :.�z,;l;� i •t -!4 K iL,i_ Suite 100 r 3 f Rancho Cordova, CA 95674 Environmental �_, �;�•� � �+ 7 916r638-20$5 Consultants,Inc. r- ��' 2 FAX:916/638-8385 June 28, 1994 Ms. Marla Guensler Exxon Company, U.S.A. Post Office Box 4032 Concord, California 94524-2032 Subject: Quarterly Ground Water Monitoring Report, Second Quarter 1994 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 quarterly ground water monitoring and sampling conducted on May 31, 1994. The location of the site is shown in Figure 1 and site features are illustrated in 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 Ground water table elevations were measured in each of the four existing monitoring wells at the site on May 31, 1994. Depths to ground water in the monitoring wells ranged from 11.10 to 11.41 feet below the tops of the well casings. Ground water table measurements are presented in Table 1. A water table contour map constructed from the ground water table elevations recorded on May 31, 1994, 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 0.002. Subjective Analysis No liquid-phase petroleum hydrocarbons or hydrocarbon sheens were present in the wells during the May 1994 site visit. Analytical Results Ground water samples collected from monitoring wells MW-3, MW-4, MW-5, and MW-6, on May 31, 1994, were submitted to a California-certified laboratory for analysis of benzene, toluene, ethylbenzene, total xylenes, and total petroleum hydrocarbons as gasoline. Analytical test 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 concentration of benzene in the ground water sample collected from monitoring well MW-5 was 4.0 parts per billion. Delta Delivers Solutions