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I , d Addendum to Interim Corrective Action Plan Frontier Transportation, Inc. April 14, 2006 Page 9 Each well will basically consist of a central section composed of riser and screen. J The riser and screen will be constructed of two-inch inside diameter, schedule 40 polyvinyl chloride (PVC) pipe. The proposed shallow wells will consist of slotted PVC extend from approximately 20' bgs to- 5 ' bgs and it will contain three rows of 0 .010-inch - - slots. The annular space around the sreen will be filled with an appropriate grain size of sand from 20 ' bgs to 4.5 ' bgs to form a filter pack. This will be overlain with a P seal of bentonite pellets, then grouted to near ground surface with a 5% bentonite mixture with cement and water. Ends of the screen and riser sections will be constructed with flush- joining threaded fittings to ensure leak-proof unions. 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 sand (#2/16). The bentonite and annular seals are necessary to prevent the annulus from serving as a vertical conduit for -� potential contaminants. Following placement of the annular seal, a large-diameter flush- mount protective casing will be installed around the wellheads. The casing will be firmly seated in concrete and supplied with lockable covers for security. l The locations of the new wells are not near the source area and are in close proximity to a previously logged and sampled well. Therefore, soil samples are not 4o anticipated to provide any new data. Should the San Joaquin Environmental Health -J Department request that soil samples be taken the previously employed sampling protocol will be followed as detailed below: • A total of four soil samples would be collected from each of the four shallow wells. • Soil samples will be collected at 5 ' intervals • All samples will be collected in a split spoon sampler lined with 2-inch by 6-inch brass tubes. • The bottom brass tube will be immediately sealed with Teflon tape, capped, and packaged in a cooler with ice. • The second brass tube will be field screened using a PID to detect volatile organic compounds and used to classify soil sediments, I_ • All soil samples that detect petroleum hydrocarbon vapors using a PID or visual i inspection will be submitted to a California certified laboratory for analysis. _; • All soil samples submitted to the laboratory will be analyzed for TPH-g, BTEX, and MTBE and oxygenates using EPA methods 8015 modified and 8260. LJ � 9