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r FIELD PROCEDURES On July 12 and 20, 1990, Alton Geoscience monitored and sampled the Monitoring Wells MW-1, MW-2, MW-4 , MW-5, MW-6, MW-7, MW-8, P-1, and P-2 in accordance with the requirements and procedures of the Central Valley Regional Water Quality Control Board (CVRWQCB) and the San Joaquin County Public Health Services (SJCPHS) . Prior to purging and sampling, the depth to ground water in each well was measured from the top of casing to the nearest 0.01 foot using an electronic sounder. Ground water samples were collected using a hand bailer and observed for the presence of free product or sheen. Each well was purged of the required casing volumes or until stabilization of pH, temperature, and conductivity was achieved prior to sample collection. The water sampling field survey forms are included in Attachment A. Ground water samples for laboratory analyses were collected using a clean Teflon bailer and then decanted into appropriate containers for delivery to a state-certified laboratory following proper sample preservation and chain of custody protocol. No water sample was collected from MW-3 for laboratory analysis due to the presence of free-floating product. DISCUSSION OF RESULTS The results of the ground water monitoring and laboratory analysis of water samples are summarized in Table 1. The official laboratory reports and chain of custody records are presented in Attachment A. A ground water elevation contour map, based on the recent depth to ground water measurements, is shown in Figure 1. The ground water flow direction, as determined from this sampling event, is to the northwest, which differs slightly from the last sampling events. The gradient for this monitoring event was determined to be 0.007 foot/foot onsite and 0.04 foot/foot offsite to the north. Results of the recent ground water monitoring and analysis as well as results of previous sampling events indicate the following; o The levels of total petroleum hydrocarbon as gasoline (TPH-G) and benzene, toluene, ethylbenzene, and total xylenes (BTEX) constituents in MW-1 have remained nondetectable. o Free-floating product has been continually observed in MW-3 with approximately 0.01 foot measured in the recent sampling event.