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9 Former Countryside Market,Stockton, California Feasibility Study and Interim Remedial Action Plan May 20,2013 completed and will include evaluation of breakthrough pressure, sustained air flows, and distribution of air in the subsurface. Operation of the system will begin immediately after start,up. It is anticipated that the start-up period, including the testing/shakedown of the new remediation equipment, will continue for approximately two weeks. Thereafter, at a minimum, weekly O&M of the sIystems will be performed at the Site. These Site visits will include equipment maintenance, monitoring of wellhead vapor phase hydrocarbon concentrations (field readings), oxygen content, gas injection flows (scfm), injection pressures (psi), electricity usage, and valve positioning. The sparge system will be operated at a flow rate that will provide the greatest ROI, while not creating an excessive migration of COPCs into the vadose zone that cannot be passively treated via natural attenuation processes. The distribution of air to each sparge point will be pulsed on and off to avoid potential groundwater mounding and dispersion of impacted groundwater. In addition to general "housekeeping," system maintenance will be con ucted to clean equipment, change fluids, and lubricate valves and machinery per manufacturer specifications. Injection rates will also be adjusted (as necessary)to optimize the remedial efforts, and data collected from the groundwater monitoring events will be used to evaluate sparge system effectiveness/influence. Sparge wells exhibiting signs of high pressure and/or low flow rates will be evaluated for bio-fouling and silt build up. Bio-fouling and/or silt build up within a sparge well can plug the screen and reduce the overall ability to inject air into the subsurface. Bio-fouling and siltation eve luation may include injection pressure/flow testing, measuring the total depth of the well, and/or video logging of the screen interval. Rehabilitation of wells with bio-fouling and/or siltation issues may include well development and/or well replacement. SGI has not experienced significant bio-fouling and/or siltation at similar sites that have used a hollow-stem auger drill rig for borehole completion. 7.4 Soil Gas Monitoring It is anticipated that the potential for fugitive emissions from sparging operations at the Site is minimal due in large part to the fact that a significant attenuation zone is present above the groundwater table. However, as discussed previously, vapor well VW-1 will be installed n the former UST area for potential use as a vapor monitoring point and/or to assist in the treatment of residually impacted source area soils via bioventing or another viable remedial technology. SGI also plans to routinely collect soil gas data from existing groundwater monitoring wells located in proximity to sparge wells as a precautionary measure (assuming the respective screened intervals are not submerged) and the proposed observation wells. Additionally, results of the groundwater monitoring program will be used to further evaluate potential vapor t uild up associated with the operation of the proposed sparge system. Should the feasibility testing and/or subsequent IRAP results indicate that more rigorous soil gas monitoring is a prudent course of action, vapor probes and/or additiona vapor wells will be installed so that soil gas concentrations in the subsurface adjacent to the various residential properties can be Feaibility Study andlFeaibildy Study 8 IRAP_Text Fineltlx 7-5 The Source Group,Inc.