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Work Plan Frontier Transportation July 23, 2001 5.0) SOIL EXCAVATION 1 The extent of area to be excavated will encompass borings 13-2, B-6, and monitoring well MW-3 (See Figure 4 for Extent of Excavation) . The pit will be excavated to approximately 30- -� feet by 25-feet by 10 feet deep only, the depth to groundwater. The SJCPHS-EHD recommended excavation below groundwater; however, this may compromise the integrity of the nearby shop structure. If concentrations are detected over 50 ppm with a photoionization (PID), then soil will be considered impacted. Petroleum impacted soil will be stockpiled on-site on visqueen and covered with visqueen for proper disposal under manifest or on-site treatment, depending on the soil analysis concentrations . An additional work plan will be provided to the SJCPHS-EHD describing in detail the method in which the soil will be treated on-site or disposed under manifest. Upon completion of excavation, a total of four soil samples will be collected from the J north, south, east, and west pit bottom at approximately 10 ' bg (See Figure 4). In addition, a total of ten soil samples will be collected from the stockpiled soil . Soil samples will be collected i in 2-inch by 6-inch brass tubes, scaled with Teflon tape and capped for transport in an ice chest with ice under chain of custody to a certified California Department of Health Services laboratory. Soil samples will be analyzed for TPH-gas, BTEX and MTBE, using EPA methods 8015 modified and 8020. Should MTBE be identified, then MTBE concentrations will be quantified using EPA method 8260. 6.0) GROUNDWATER WELL INSTALLATION A hollow stem auger drill rig will be used to provide the soil borings for well installation. Drillers will hold a California State C-57 contractor's license. Typical auger size for the well installation described below is 104nch outside diameter and 6-inch inside diameter (See Figure 4 for well location) . —I Each well will basically consist of a central section composed of riser and screen. The riser and screen will be constructed of four-inch inside diameter, schedule 40 polyvinyl chloride I (PVC) pipe. The proposed well will consist of slotted PVC extend from approximately 30 ' bg to 40 ' bg and it will contain three rows of 0.010-inch slots. The annular space around the screen -- will be filled with sand from 25 ' bg to 40 ' bg to from a filter pack. This will be overlain with a 5' seal of bentonite pellets, then grouted to near ground surface with a 5% bentonite mixture with cement and water. The replacement well for MW-3 will be slotted from 5 ' bg to 20 'bg and will also contain three rows of 0.0104nch slots. The filter pack will extend from 5 ' bg to 20 ' bg. This will be overlain with a 3 ' seal of bentonite pellets, then grouted to near ground surface with a 5% bentonite mixture with cement and water (See Figure 5, Well Construction Diagram) . Ends of the screen and riser sections will be constructed with flush joining threaded fittings to ensure leak-proof unions. 3 ILl