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1 <br /> Ellet® <br /> 1 <br /> • Mr James L Barton <br /> 1 December 2, 2004 <br /> Page 5 <br /> 1 event were as follows (TPHg/benzene in micrograms per liter (pg/L)) MW-11 (11,00014,400), <br /> MW-3 (23,00014,000), MW-2 (2,8001300) The average concentration of benzene has decreased <br /> from 1,249 pg/L In the fourth quarter of 1998 to 747 pg/L in the fourth quarter of 2004 (40 percent <br /> 1 reduction) TPHg has decreased from an average concentration of 7,700 pg/L in the fourth <br /> quarter of 1998 to 3,702 pg/L in the current quarter (52 percent reduction) Historical contaminant <br /> concentration data is presented and discussed in greater detail in the Comparative Analysis <br /> section of this report <br /> 1 System Description <br />' The remediation system consists of an Air Sparge 1 Soil Vapor Extraction (AS/SVE) system <br /> The AS system is comprised of an air compressor with a maximum positive displacement of <br /> 95 standard cubic feet per minute (scfm) at 125 pounds per square inch (psi) and Is manifold to <br />' sixteen sparge wells The system injects air into the subsurface saturated zone at rates <br /> between approximately enabling a phase transfer of hydrocarbons from a dissolved phase to a <br /> vapor phase The air is then vented through the unsaturated (vadose) zone <br />' The sparge wells are manifolded to the system by Schedule 40 polyvinyl chloride (PVC) pipe <br /> The flow rate for each sparge well can be manually adjusted to optimize the system <br /> l <br /> Additionally, each sparge well Is equipped with ports that allow for the monitoring of air flow <br /> ie rates and pressure <br /> The SVE extracts vapors utilizing a positive displacement vacuum blower rated at 400-scfm, off <br /> gasses are treated via a thermal oxidizer that utilizes a 1,000,000 British Thermal Units (BTU) <br /> burner The SVE system operates at a vacuum of approximately 80 inches of water ("H20) <br /> Vacuum Is applied through fourteen soil vapor extraction wells that are screened In the vadose <br /> I zone soil The system is operated under San Joaquin Valley Air Pollution Control District <br /> (SJVAPCD) authority to construct (ATC) number N-5879-1-0 <br /> The SVE wells are manifolded to the system by Schedule 40 PVC piping The flow rate for <br /> each extraction well can be manually adjusted and each extraction well is equipped with ports <br /> that allow for the monitoring of air flow rates and or pressure Figure 3 shows the current <br />' remedial system layout <br /> Comll2arative Analysis <br /> This analysis is being conducted as part of a remedial system evaluation (RSE) to evaluate the <br /> performance of the remedial system and to analyze potential system enhancements or <br /> modifications and the feasibility of accelerating site closure EAI's Corrective Action Plan for <br /> Montgomery Wards Auto Service Center dated July 6, 1998 had estimated that remediation <br /> would require approximately two years for completion The remedial system was installed and <br /> became fully operational in the fourth quarter of 1999 The SVE system was temporarily shut <br /> down in late 2003 due to "a general downward concentration trend for all wells" The air sparge <br /> unit underwent a complete overhaul in June 2004 The SVE system was restarted in <br /> September 2004 due to Increasing concentration trends The SVE and AS systems have been <br /> 1kDcsacramentolprojects\Projects10694015098 293TinaRReports15098 RSE Results Report doc <br />