ARCHIVED REPORTS XR0010164 - Laserfiche WebLink

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Approximately 900 cubic yards (about 24,300 cubic feet) of soil was removed Excavated soil was loaded onto dump trucks as the work proceeded due to the limited site area The soil was characterized with composite samples collected on December 12, 2003 for landfill acceptance (see Appendix B for Kiff Analytical and GeoAnalytical Laboratories, Inc , Modesto reports) The excavated soil was disposed at Forward Landfill in Manteca, California (see Appendix C) The excavations were backfilled with a self compacting fill to approximately 5 ft BG, then completed backfill to surface grade with removed clean overburden soil and the surface was repaved where pavement was removed, and finish graded with crushed rock in the remaining areas Groundwater monitoring wells MW-3 and MW-9 had to be abandoned under approved SJC EHD permits, as they were located within the excavation area These wells are scheduled to be replaced under approved SJC EHD permits upon completion of the excavation work 3 2 Temporary Dewatering Points, Water Treatment and Disposal Three temporary dewatering points were installed to dewater portions of the excavation (see Figure 1 and Appendix D) These wells were approved by the SJC EHD for the work and were used to dewater the excavations and send the water to a surface holding tank The points (two 12-inches in diameter) were constructed of corrugated and perforated plastic pipe, the 6" diameter pipe was constructed of perforated PVC pipe The two 12" pipes perforations were supplemented with hand-drilled holes, and the pipe was placed in the excavation backfill The maximum dewatering point depths were 12 to 14 feet These wells are designed for temporary dewatering use in this excavation cleanup work Points EW-1 and EW-3 (both 12-inch diameter) remain, and EW-2 (6- inch diameter) was removed when that portion of excavation was completed. The dewatering points were pumped to keep the water levels low during the excavation and soil sampling work and pumped for an average of 5 5 hours per day The contaminated water was sent to a holding tank and then treated with activated carbon in one 2000-pound canister Originally two canisters were moved on-site, however one canister was sufficient to treat the water Water samples of the inflow and outflow was collected to ascertain the contaminant load and to check for the proper disposal limits at the outfall per City requirements A poly tank was used to hold the initial 6,000 gallons of water pumped through the carbon canister Once the chemical data was received and approved by the City of Tracy, the water was sent to a 20,000 gallon Baker tank and continuously treated and discharged at the sewer outfall The treated water was disposed to the City of Tracy Sanitary sewer under approved permit (effective date December 23, 2003) Three bi-weekly "treated water" samples were drawn and sent to a state certified laboratory for analysis as an ongoing check/confirmation for clean discharge water Results were provided to the City of Tracy, Sewer Division Approximately 239,250 gallons of water was removed and • treated for disposal during excavation Page 5 of 13