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�+ Work Plan far Refined Plume Definition and Management ofFloating Product-7500 W 11th St., Tracy, CA, Page 55 stockpile will be quartered and a total of four samples will be taken, one from each quarter. The samples will be recovered by driving a clean, 2-in. diameter by 4-in. long, brass sampling tube into the bottom of a pit dug into the stockpile at each of the four designated .. sampling locations until the tube is completely filled with soil. Following sample recovery, each sample tube will be cleaned externally, its ends covered .�.. with a Teflon sheet and closed with tightly-fitted plastic caps. The caps will be secured with adhesiveless tape. Each sample tube will be labeled for identification, entered into chain-of- custody control and packed on chemical ice for transport to STL's laboratory in Pleasanton, California. At the laboratory, the samples will be composited and the composite sample will be analyzed -- for the same suite of analytes listed in Section 9.4.1.3.1 above. If the stockpiled soil is shown to be free of analytes of concern at concentrations above regulatory limits, that soil will be spread on the 7500 West Eleventh Street property and incorporated into the landscaping. If '— not, it will be loaded onto trucks and transported for disposal as a special waste at the Forward Landfill. 9.4.1.7 Restoration of Site Depending upon the quantities of clean excavated soil available, after the permeable crushed L rock has been placed in it, the remaining open volume of the cut-off trench will be backfilled, either by clean excavated soil that has been stockpiled on site, or by Caltrans Class II road base To prepare the rock backfill prior to completion of the trench backfilling, the excavator will be used to level its surface and it will then be thoroughly compacted using a pad-footed, vibratory compactor. As is shown on Figure 12, when the crushed rock backfill has been thoroughly compacted, a sheet of permeable geotextile will be laid over it so that fine soils in the final backfill will not migrate into it and reduce its permeability. The front loader will then be used to place clean or treated soil over the rock in the cut-off trench and to spread it in uniform, 6- to 8-in. high layers, each of which will be thoroughly compacted using the vibratory compactor. Note: Given the proposed location of the cut-off trench, it is expected that compaction of the backfill in the trench in the workman like manner described above will be sufficient. However, if requested by the SICDPW, a compaction curve for the final backfill material according to .procedure D1557-00 published by the American Society for Testing and Materials (ASTM) (American Society for Testing and Materials 2000b) will be generated to identify its maximum dry density and its optimum moisture content for use as backfill, Then, to ensure that a minimum relative density of 90% (or such other relative density as might be .� specified by the SJCDPW), a nuclear density gauge will be used to measure the relative density of the compacted backfill according to the procedure specified by sic