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1 C,eological7-echnics Inc. Page 2 Sinclair Trucking Feasibility Study Project No. 1030.3 June 25,2003 recommendations were approved by Ms Lori Duncan, SJC PHS/EHD, in a letter dated July 22, 2002. ' On September 30, 2002, GTI prepared and submitted the Yd Quarter 2002 Groundwater Monitoring Report recommending the site be considered for closure. The request was denied by Ms Duncan in a letter dated March 3, 2003. A meeting was scheduled between Mr. and Mrs. Sinclair, Ms Duncan and Eric Price of GTI for March 27, 2003 to discuss the direction of the project and remediation alternatives. ' The Sinclair's were enthusiastic about active remediation at the site. Investigating the extent of contaminated soil via GeoProbe and the excavation of the heavily contaminated soil was the alternative agreed upon by all parties as being the best approach. After the meeting Ms. Duncan requested that a feasibility study be submitted discussing remedial ' alternatives. This report addresses this request and discusses the pros and cons of various remedial alternatives. 2.0 REMEDIAL ALTERNATIVES ' 2.1 Air Sparging/Soil Vapor Extraction Air Sparging Air sparging is the process of injecting air into the aquifer to volatilize contaminants from the groundwater. These contaminants are captured in the vadose zone and removed with the use of a vapor extraction recovery system. The addition of air into the aquifer also aids in increasing the rate of natural degradation. ' Air sparging presents a couple of concerns at the site: • Shallow depth to groundwater. Since the vadose zone at the site is approximately 9 to ' 12 feet thick, there is very little unsaturated soil zone where the vertically migrating vapors could be captured. There would be a high possibility that short-circuiting of the vapors could occur, petroleum vapor could be pushed under buildings or into utility trenches, or uncontrolled emissions to the atmosphere of petroleum hydrocarbon vapors ' could occur. • Low permeability of materials. The vadose zone soil is predominately clays and silts, which do not conduct airflow very well through the subsurface. ' . Capture and control of sparged vapors requires an expensive inventory of equipment, including extraction wells and effluent treatment by thermal oxidizers or units of granular activated carbon. Vapor Extraction Vapor extraction is the process of drawing a vacuum on the vadose zone to produce an air flow through the subsurface, which removes volatile compounds from the soil and soil pore spaces through subsurface convective air flow,-evaporation and concentration gradient ----- diffusion. Typically, the extracted air is treated using then-nal destruction (a thermal oxidizer or internal combustion engine) or granular activated carbon. 1