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s _=is w. } WEGE surveyed each well (top of casing) with a transit using the southwest Corner of the current tank pau (see Figure 3A) as the danm. Survey readings were recalculated to adapt elevations to the USGS topographic map (USGS E•ist Stockton Quad., Figure 2). Based upon ground water elevation measurements obtained thoughout the evaluation of this site, the overall local flow direction is to the east-northeast at a relatively flat slope (see Figures 4A- 4G). Measurements obtained an May 25, 1990 (Figure 4G) show a flaw direction to th9 north and northeast with a flat slope of 0.3% (0.56'/163') and a moderate ridge trending from monitor well MW-4 toward monitor well MW-2. 2.2 GROUND WATER QUARTERLY SAMPLING AND PROCEDURES E Quarterly ground water samples were collected on 4/12/89, 8/24/89, 1/12/90, and 5/25/90 by a WEGE geologist and "chain of custody" hand delivered on ice to a state certified testing lab (McLaren Analytical or Chemtech Analytical Laboratories) for chemical analyses. These samples were analyzed for TPH, BTEX, and Ethylene Dibromide (EDB) concentrations using EPA Methods 8015, 602, and modified 601, respectively. Complete chemical results are presented in Table 1 of this report. Before ground water sampling or "purging" commenced, a resistivity" meter was lowered into each well and depth to ground water, measurements were recorded. Next, a specially designed bailer was lowered into the ground water to determine if gasoline product was floating on top. If product was observed, product thickness was measured and ground water elevations were recalculated to compensate for the weight of the gasoline. Monitor'; we11s that MCq Wpta ned gasoline product here not sampled or:"purged" (MW-' ah In order to "purge" each well, a dedicated disposable nylon 1 1/2" x 3' bailer was repeatedly lowered down into the ground water. Temperature, pH, and conductivity was measured for each bailer volume recovered. Bailing continued for each well until pH, conductivity, and temperature parameters stabilized (approximately 5 gallons), and then the ground water sample was obtained (see Appendix C). The "purged" water was contained in the ConVault tank along with the purged water stored previously in labeled 55 gallon drums that had been transferred to the ConVault tank earlier that day. A sample of this "purged" water was then obtained for analysis at a state certified lab. The lab results showed the contaminate to be below detectable limits (Table 1 and Appendix B). After "purging", a representative ground water sample was obtained from each monitor well using the dedicated disposable nylon bailer. The samples were stored in labeled one liter "Boston Rounds" and 40 milliliter VOA vials. They were then placed in an insulated cooler with ice and "chain-of-custody" hand delivered to Chemtech Analytical Laboratories (DHS c(.rtified #359) for chemical analyses. 8