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u i Work Plan ' ) Frontier Transportation ' May 31 , 2001 5.0) SOIL VAPOR SURVEY Soil vapor probes will be advanced to 4 ' bg with a direct push hydraulic rig. A hollow casing with a retractable tip will be advanced to 4 ' bg using the direct push hydraulic rig. At 4 ' bg, the tip will be retracted and the casing will be lifted approximately 6-inches leaving a six- inch interval in the soil for vapor collection. An air pump will be connected to the casing and soil vapors will be withdrawn and collected in a I -liter Tedlar bag or glass syringe. A mobile laboratory will be used for on-site field analysis to make real time field decisions, where they will be analyzed for TPH-g and BTEX using EPA methods 8015 modified and 8020. -� 6.0) TRENCH EXCAVATION Upon completion of the soil vapor survey, two exploratory trenches will be excavated near the former UST location. The trenches will be excavated 5-feet deep by 3 -feet wide by 20- feet long using a backhoe to observe the presence of subsurface soil staining in the area. Soil will be field screened with a PID. If concentrations are detected over 50 ppm, then soil will be I_ 1 considered impacted. Petroleum impacted soil will be stockpiled on-site on visqueen and J covered with visqueen for disposal or on-site treatment, depending on the soil concentrations. I i - 7.0) GROUNDWATER WELL INSTALLATION A hollow stem auger drill rig will be used to provide the soil borings for well installation. LDrillers will hold a California State C-57 contractor's license. Typical auger size for the well L installation described below is 8-inch outside diameter and 4 '/a-inch inside diameter. Each well will basically consist of a central section composed of riser and screen. The riser and screen will be constructed of two-inch inside diameter, schedule 40 polyvinyl chloride _ (PVC) pipe. Slotted PVC will extend from approximately 5 ' bg to 20 ' bg and it will contain l l three rows of 0.010-inch slots. Ends of the screen and riser sections will be constructed with flush joining threaded fittings to ensure leak-proof unions. FThe annular space around the screen will be filled with sand 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. The bentonite and annular seals are necessary to Lprevent the annulus from serving as a vertical conduit for potential contaminants. A lockable flush-mount protective casing will be set over the well top and surrounded by a surface seal of concrete. A filter pack of sand will be placed around the screen to retain the finer grained fractions of formation material and to create a zone of high permeability that allows free entry of water in the well . The pack will consist of clean quartz sand (Monterey #3) . Following placement of the 3 [ I