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RRAMMA Monitoring&Sampling Report Gaut Property, Stockton, CA December 22, 1992 Page 2 indicated that gasoline and gasoline constituents were detected above laboratory method detection limits in the groundwater samples collected from the site. A more detailed discussion of the previous investigation can be found in RESNA's "Interim Problem Assessment Report, Soil and Groundwater Contamination, " dated June 8, 1992. RESNA has been retained by Mr. Gaut to perform confirmation groundwater monitoring and sampling from the three on site monitoring wells. This work was requested by the San Joaquin County, Public Health Services, Environmental Health Division (PHS/EHD). GROUNDWATER MONITORING AND SAMPLING RESNA personnel performed groundwater monitoring in October and November, 1992. Sampling of the site monitoring wells was conducted on October 20, 1992. Field work consisted of measuring the depth-to-water in wells MW1, MW2, and MW3; using a water/product electronic interface probe to determine if free product existed atop the water table; purging and sampling the wells; and subjectively analyzing collected water samples for the presence of petroleum hydrocarbon constituents. Static groundwater elevations were measured in each monitoring well on October 20, 1992 and November 20, 1992. Groundwater gradient maps are presented on Figures 2 and 3, respectively. Groundwater monitoring data is summarized in Table 1. Figure 2 depicts a northeasterly groundwater gradient of 0.0012 ft/ft or approximately 6.3 feet/mile. Figure 3 depicts flow to the north-northeast at a steeper gradient of 0.0029 ft/ft or approximately 15.3 feet/mile. Both gradient maps support a general northeast gradient as determined by initial fluid level measurements. The electronic water/product interface probe did not detect the presence of free product on the water table during either monitoring event. The probe has an accuracy to the nearest 0.01 foot. Groundwater samples were collected from each site monitoring well on October 20, 1992. Samples were collected after stabilization of pH, electrical conductivity (EC), and temperature. The monitoring wells were purged and sampled according to RESNA's Quality Assurance/Quality Control Plan, on file with the PHS/EHD. Monitoring well MW1 was pumped until dry twice, a total of five gallons (approximately three well casing volumes) of water were removed. A total of 49 and 40 gallons of water were removed from wells MW2 and MW3, respectively. Purge water was contained in labeled DOT approved 55 gallon drums and QUA RTLYIQR 102992.FNL