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i { r I work will be conducted b an analytical laboratory y y abo atory certified'by the State of California to conduct the required analyses. 2.2 Soil Borings At the Tank 1 and 2 location, two soil borings will be installed in positions straddling the former remedial excavation area as shown on Figure 2. Each boring will be drilled to a maximum depth of 60 feet or the current groundwater level. Soil "samples will be collected at 5-foot intervals from each boring starting at 10 bgs. All samples will be screened using a s photoionization detector (PID) or flame ionization detector (FID) and two samples from each boring will be submitted for chemical analyses at WESTON,s Analytical laboratory in Stockton, California. Additional sampling procedural details are provided in Section 3.2.1. At the completion of the soil sampling, each boring will be grouted from the bottom to the surface through the augers. All soil samples will be analyzed for TPH-D and BTEX. ;i At Tank 3 and Tank 4 locations, one boring will be placed adjacent to where the extractable hydrocarbons were originally identified. Soil samples willjibe taken at approximately 8 and 16 feet below grade and analyzed for both TPH-G and TPH-D. Both analyses appear prudent as only gasoline fuels were stored in the tanks but former analyses°'taken at the time of the tank removal suggested the presence of diesel type components in the'soils. The boring will be extended to the saturation zone and a one-time sample of groundwater will be taken with a Hydropunch tool. The samples obtained will bel analyzed for BTEX, TPH-G and TPH-D. While there is no history of the presence of B'IIEX chemicals in the soils at Tank 3 and Tank 4, the parameter is included to tie into the investigation work being completed at the Tank 1 and 2 location. 2.3 Monitor Well Location and Installation Three monitor wells will be installed in the locations shown on Figure 2. The locations of these monitor wells are based on a groundwater flow direction 'interpreted from the SJFCD map, "Lines of Equal Elevation of Water in Wells, Spring 1993.",1 One well is located upgradient and two wells are located downgradient of the excavation area. The monitor wells will be constructed by hollow stem auger drilling techniques with a 2-inch diameter PVC casing and a 20 foot screened section. It is estimated that the total depth of each well will be approximately 65 to 70 feet. The screen will be located to set the top of screen at least 3 feet above the saturated zone. A sand pack will b�!;emplaced throughout the screened interval and will extend at least 2 feet above the top of the screen. A bentonite seal will be placed above the sand and the annular space will be grouted above the seal to the surface with Ca five percent bentonite/cement grout. Each monitor well will be completed in a flush mount christie box equipped with a Iocking cap. After construction, each well will be developed by bailing, surging, and swabbing until the water is relatively free of sediments. The well head top of casing will be surveyed for elevation to facilitate groundwater gradient calculations. Soil cuttings and development water generated by the well construction will be containerized in labeled, 55-gallon steel drums with lids and left onsite pending evaluation of analytical results. 11 MX%RVrSMCMVCD.%VK 5 03114M