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---mm - ME F _ t kw Page 6 February 6, 1990 Job No.21.-71-6 i Mokelump River,which is located about 13/4:Hiles to the north, and a number of percolation basins and the South Main Canal,which are looted about 13/4 miles to the west. In the Lodi area,the large production water wells are screened within the alluvial deposits,the Victor Formation, and the Laguna Formation. The overall permeability of these units is considered fairly high (CDWR, 1967). Sand and gravel deposits have the highest transmissivities and are the main water-bearing units;the silt and clay layers generally have lower transmissivities. Ground waEpr in this area is generally unconfined or semi-confined (CDWR, 1967). The elevation of ground water is shown to be at approximately mean sea Ievel (MSL) near the site, according -- to the Regional Ground-Water Map(Fire 4). This map was prepared by the California Department of Water — Resources for water levels measured during the sPrirg of 1980- Earlier potentiometric maps for 1950 and 1964 shod'the ground-water elevation in the site vicinity to be IU feet MSL and 0 feel MSL,respectively. These three California Department oy Water Resources maps show the regional ground-water gradient ec the site is directed to the south, towards the City of Stockton where the ground water is subjected to extensive pumping and withdrawal (CDWR, 1967). `" INSTAI.LATTON OF RECOVERY WELL RW-I PHASE I Recovery well R-1 was drilled on November 17, 1989 by West Hazmat Drilling Corporation at the location shown on Figure 2. The well was completed to a depth of 8o feet using 6-inch diameterschedule 40 PVC casing and r. -inch slot. The well log is presented in Appendix A. The well instaUa;ion TTMCO High Flow Screen"'with 0.02 and seal was witnessed by Ms. Eleanor Ratliff of the San Joaquin County Public Health Services. Soil samples were collected during dritling by continuous coring. Soil samples were visually classified by a Du Pont Environmental Services Registered Geologist using the Unified Sail Classification System (USCS,ASTM D-2487-85)- Soil samples from above the water table were collected at 5-foot intervals and field tested for volatile organic vapors using an OVM. The results of the field organic vapor measurements are included on the well fog ti (Appendix A). Based on the field organic vapor measurements, soil samples were selecied for laboratory analysis, the results of which are summarized in Table A. The soils encountered during the drilling of recovery well RW-1 consisted of interbedded units of At,sand,sandy silt,clayey silt,and silty clay. Free ground water was encountered at approximately 62 feet below grade during drilling. Recovery well RW-1 was developed on November 29, 1989 by Kvilhaug Wel!Drilling and Pump Company. The well was surged and pumped for extended periods of time until the purged water was relatively clear and free of turbidity. All purge water was contained on-site in a Baker Tank which was also used to store the discharge water produced dur;ng the aquifer test performed on well RW-I. Du Pont.Environmental Services �,