ARCHIVED REPORTS XR0006465 - Laserfiche WebLink

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i Joaquin Delta. At present, encroachment of saline waters from the Delta is impairing the quality of the ground water in the Stockton area. WEGE surveyed each well (top of casing) with a transit using the southwest corner of the current tank pad (see Figure 3A) as the datum. Survey readings were recalculated to correct elevations to the USGS topographic map (USGS East 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- 4H) . Measurements obtained on November 27 , 1990, (Figure 4H) , show a flow direction to the north and northeast, with a channel flowing from monitor well MW1 east towards MW2 and then heading southeast towards MW3 and MWS. 2. 2 GROUND WATER QUARTERLY SAMPLING AND PROCEDURES Ground water samples have been collected on 4/04/89, 8/24/89 , • 1/12/90, 5/25/90 and 11/27/90 . These samples were collected by a WEGE geologist and "Chain of Custody" hand delivered on ice to a state certified testing laboratory (McLaren Analytical or Chemtech Analytical Laboratories) for chemical analyses. These samples were analyzed for TPH, and BTEX concentrations using EPA Methods 8015 and 602 respectively. Since diesel has never shown up in the sample results, the samples obtained on 11/27/90 were analyzed using EPA methods 5030 and 602 for Total Fuel Hydrocarbons and BTEX, see Appendix A. Complete chemical results are presented in Table 1 of this report. Before water "purging" or sampling commenced, a ground water interface probe (resistivity meter) was lowered into each well and depth to water measurements were recorded. Next, a specially designed bailer was lowered into the water to determine if gasoline product was floating on the water. If product was observed, product thickness was measured and ground water elevations were recalculated to compensate for the weight of gasoline. Monitor wells that contained gasoline product were then "purged" until depletion of the floating product was observed. Approximately a quart of gasoline was recovered by this method from MW1 on 11/27/90. The recovered product was stored with the ground water produced from "purging" the monitor wells for sampling, on site in a 55 gallon hazardous material drum. In order to "purge" each well, a dedicated disposable PVC 1 1/2" x 31 bailer was repeatedly lowered down the well and into the water . 3