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LFR Inc. <br /> proposes to sample these 10 wells prior to system shutdown to assess current baseline <br /> groundwater concentrations within the former source area. The wells will be purged <br /> and sampled using three-volume purge groundwater sampling techniques, and samples <br /> will be analyzed for Hazardous Substances using EPA Method 8260B. <br /> After sampling of the groundwater monitoring wells from within the sparge area has <br /> been completed, the operation of the sparging system will be halted for approximately <br /> 45 days. <br /> After approximately 45 days, and before reactivation of the sparging system, the <br /> groundwater monitoring wells will be re-sampled to assess whether concentrations have <br /> changed or rebounded during the 45-day shutdown. <br /> 2.3 System Restart <br /> As noted above, upon completion of the 45-day shutdown period and before restarting <br /> the SVETS and the sparging system, soil-gas and groundwater sampling will be <br /> performed. After sampling is completed, the SVETS and sparging system will be <br /> reactivated to normal operating conditions. <br /> Initially the SVETS will be reactivated and the SVETS influent will be monitored with <br /> a PID to assess whether influent concentrations have changed or rebounded compared <br /> to pre-shutdown conditions. In addition, the following two samples will be collected <br /> from the SVE influent using Summa canisters: <br /> • Sample#1 will be collected approximately 10 minutes after system restart(after all <br /> stagnant air within the conveyance lines has been purged), and <br /> • Sample #2 will be collected approximately 60 minutes after system restart. <br /> After the SVETS is fully operational, the ozone sparging system will be reactivated <br /> while the samples are analyzed and the data assessed. <br /> 3.0 DATA ASSESSMENT <br /> 3.1 Soil Gas <br /> The soil-gas baseline and 45-day rebound test data will be compared to determine if <br /> significant rebound is occurring. <br /> The soil-gas concentration data from the 10 wells will initially be compared to <br /> California Human Health Screening Levels (CHHSL; California Environmental <br /> Protection Agency 2005). If the soil-gas concentrations are at or below the CHHSL, <br /> then a recommendation to permanently terminate the SVETS operation will be made. If <br /> Pap 6 pie iosure-PhRIV_IRA-AugM06750.dw:deh <br />