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ENSR, Inc Work Plan to Evaluate Potential SVEIISAS System Enhancements and <br /> Additional Well Installation within the Deeper Aquifer Units Former Unocal Station <br /> No 5098 5400 and 5606 Pacific Avenue, Stockton, California November 2, 2004 <br /> Environmental Audit Inc (EAI) Supplemental Investigation Report Problem <br /> Assessment Report, and Work Plan Montgomery Ward Auto Service Center and <br /> Former Unocal Site, 5400 and 5606 Pacific Avenue, Stockton, California October <br /> 12, 2000 <br /> Fetter, C W Applied H dro eolo 4"' Edition Prentice Hall, 2000 <br /> Ricker, P E , Joe A Method for Evaluating Groundwater Contaminant Plume <br /> Stabili Presented at the American Water Resources Association Annual Spring <br /> Specialty Conference on Water Quality Monitoring and Modeling San Antonio, <br /> Texas April 30 to May 2, 2001 <br /> USACOE In Situ Air Sparging Subsurface Performance Checklist June 7, 1999 <br /> 4 Data Collection Requirements <br /> a Describe objectives for the ISAS system The ob)ective of the ISAS system is <br /> to reduce concentrations of dissolved petroleum hydrocarbons beneath the site <br /> to levels deemed acceptable by the Regional Water Quality Control Board <br /> (RWQCB) <br /> b What is the estimated future operation or remediation time? What is the <br /> basis for this estimate?. The ISAS system is scheduled to be operated for at <br /> least eight quarters or until there is a general decrease in concentration trends <br /> for targeted areas The basis for the estimate came from the decreasing trends <br /> in wells MW-9R, MW-10, MW-12, MW-14, MW-16, MW-17, MW-18D, MW-24S, <br /> MW-24D, and MW-25D If additional sparge wells are installed in the vicinity <br /> MW-3 and MW-11 the ISAS system will be operated until deceasing trends are <br /> achieved in the target areas near the new ISAS wells <br /> c Obtain Representative Operating Data as Follows <br /> i Air Distribution Air flow and pressure data has been collected for every <br /> sparge well for this site The ISAS system is rated to distribute 95 cubic <br /> feet per minute (cfm) at 120 pounds per square inch (psi) ENSR has <br /> monitored the individual air sparge wells quarterly since operations <br /> began in May of 2004 ENSR observed pressure and flow in almost <br /> every air sparge well Frequency of data collection for individual air <br /> sparge wells should be at least once per quarter ENSR has installed <br /> individual monitoring points for measuring pressure and air flow rate and <br /> is currently developing a plan to measure these parameters on a regular <br /> basis <br />