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Environmental Audit Inc (EAI) Supplemental Investigation Report Problem Assessment <br /> Report, and Work Plan Montgomery Ward Auto Service Center and Former Unocal Site, <br /> 5400 and 5606 Pacific Avenue, Stockton, California October 12, 2000 <br /> EPA 6001R-961041 Diagnostic Evaulation of In-situ SVE Based System Performance <br /> EPA 5421R-971007 Analysis of Selected Enhancements for Soil Vapor Extraction <br /> Fetter, C W Applied Hydrogeology (4th Edition} Prentice Hall, 2000 <br /> Ricker, P E , Joe A Method for Evaluating Groundwater Contaminant Plume Stability <br /> Presented at the American Water Resources Association Annual Spnng Specialty <br /> Conference on Water Quality Monitoring and Modeling San Antonio, Texas April 30 to <br /> May 2, 2001 <br /> USACOE Vapor Extraction Subsurface Performance_Checklist June 7, 1999 <br /> 4 Data Collection Requirements <br /> a Describe objectives for the SVE system To collect an appropriate amount of <br /> soil vapor samples to enable ENSR Corporation (ENSR) to evaluate the <br /> effectiveness of the SVE systems ability to reduce volatile organic compounds <br /> (VOCs) in targeted areas ENSR collects soil vapor samples from 14 SVE wells <br /> on a quarterly basis Samples are collected in Summa canisters and analyzed for <br /> total petroleum hydrocarbons as gasoline, benzene, toluene, ethyl benzene, <br /> xylenes and MTBE using TO-3 series methods <br /> b What is the estimated future operation period or time for remediation time? <br /> What is the basis for this estimate? The SVE system was scheduled to be <br /> operated between approximately September 2004 and September 2005 (1-yr of <br /> continuous operation) The basis for the estimate came from the anticipated time <br /> it would take for the SVE system to produce a general decrease in concentration <br /> trends for targeted areas The SVE system ceased to operate on November <br /> 30, 2004 as a result of a failure of the thermal oxidizer ENSR submitted a <br /> SVE system permit modification request to the San Joaquin Valley Air <br /> Pollution Control District (SJVAPCD) in December 2004 The permit request <br /> has not been approved as of 1131105 ENSR anticipates that the SVE system <br /> will be operated for approximately nine months once the permit modification <br /> is approved and the SVE system is restarted <br /> c Operating Data — Collect the following SVE system data for the most recent <br /> year of operation Any additional historical datd wlll be helpful IdcntI y <br /> any missing data The Regional Water Quality Control Board (RWQCB) <br /> approved the shut down of the SVE system in October 2003 The RQWCB <br /> approved the restart of the SVE system in September 2004 The SVE system <br /> ceased to operate on November 30, 2004 as a result of a failure in the outside <br /> wall in the thermal oxidizer A comprehensive system monitoring plan needs to <br /> be developed to identify data collection parameters, key sampling locations on <br /> the system, and optimization of sampling frequency <br />