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' Gealogiea!1'ec6ueics W, Page 6 Sinclair Trucking Feasibility Study Addendum Project No. 1030.3 April 26,2004 Even at low groundwater levels dewatering would be required. Water containment and disposal will be added costs to this remediation method. If we assume that the 60 x 60 ' excavation had only 2 feet of water to be removed this would be equivalent to 7,200 cubic feet or 53,856 gallons of water being produced. It is likely water would continue to fill the pit during excavation and the depth of two feet would be exceeded. ' The septic tank would have to be removed or shored prior to excavation_ The leach lines would have to be removed to get the heavily contaminated soil south of the former tank pit. A sanitation permit from the San Joaquin County Environmental Health Department (SJCEHD) would be required prior to work on the wastewater disposal system. The new septic system would need to be engineered and an inspection of the septic tank and leach line field would be required before backfilling trenches and system. The trees would have ' to be cut down and removed prior to excavation. The following is an estimate of costs associated with excavation: Descrli tion Estimated Costs Project Planning & Coordination $ 5,000 Septic System (Removal, engineering, permitting, installation) 10,000 Excavation of 1,500 yd' (Labor, Equipment,Disposal, Clean Backfill) 147,000 —43500 Water Storage and Disposal (assuming 50,000 gallons produced) 46,000 Soil Analyses for disposal (four(4) composite samples) 500 Project Management & Supervision 5,000 Data Evaluation & Reporting 4,000 ' The source of the contamination will be removed requiring minimal monitoring to insure the remediation has been effective. Very little laboratory data will be generated during this type of remediation, reducing the reporting costs. ' 2.4 Associated Factors ' As discussed previously, the issue with removal and replacement of the septic tank and leach line system is addressed in the excavation option. The propane tank and gas lines will have to be moved regardless of the remedial method chosen. Therefore, these costs are not evaluated at this time. We have presented the County guidelines for septic system ' installation established in October 2003. Other cost factors not included in this feasibility study are the costs for vapor and ' groundwater extraction. This site has too many limitations to make this option viable. These limitation include: fine grained soils over most of the site, shallow groundwater that make vapor extraction difficult, uncapped site that makes vapor extraction impractical since ' short circuiting of vapors from surface is a significant factor, and the lack of disposal options for the treated groundwater that would be pumped by dual phase extraction. - - 1 1