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GERAGHTY & MILLER, INC 7 <br /> W-ORK PLAN <br />' TASK 1: OPERATION AND MAINTENANCE (O&M) <br /> Periodic maintenance of the biosparging system will be performed on a monthly basis <br /> ' for 3 months to monitor system performance Dissolved-oxygen levels in monitoring wells <br /> will be recorded prior to sampling to verify the effectiveness of the air-sparging system. The <br /> ' SVE system will be started when groundwater levels recede below 15 feet bgs Depth-to-water <br /> measurements will be collected during the monthly O&M site visits. A system effectiveness <br /> report detailing SVE radius of influence, hydrocarbon mass removal, and btosparging <br /> ' effectiveness will be prepared following approximately 6 months of SVE operation The <br /> system effectiveness report will confirm the use of SVE with biosparging as the best available <br /> ' technology for the site <br /> It is anticipated that the preferred remedial approach will meet the objectives of the <br /> SJCPHS for attaining background levels of petroleum hydrocarbons in groundwater. <br /> Operation of the SVE system will continue until the SVE system is no longer effective on a <br /> mass-removal basis Technical effectiveness will be evaluated on the basis of SVE influent <br /> concentrations attaining asymptotic levels The biosparging system will continue to add <br /> oxygen to the subsurface, enhancing biological activity, until concentrations of petroleum <br /> hydrocarbons have been reduced such that natural attenuation will achieve acceptable levels of <br /> ' petroleum hydrocarbons in groundwater At that point, the biosparging system will be turned <br /> off <br /> TASK 2: GROUNDWATER MONITORING <br /> ' Quarterly groundwater monitoring will continue until concurrence by the SJCPHS that <br /> reduced monitoring is appropriate or that no further action is required at this site. <br /> ' TASK 3: ADDITIONAL VERTICAL DELINEATION <br /> ' Groundwater samples were collected from the deep-zone air-sparging wells on April 1, <br /> 1997, to determine if the deeper zone was affected by petroleum hydrocarbons (Table 2) <br /> ' Laboratory analytical results are shown in Attachment 4 The groundwater samples contained <br /> hydrocarbon concentrations similar to those found in monitoring wells screened across the <br /> groundwater surface To further mvestigate the vertical extent of contamination, an additional <br /> boring will be completed to collect soil samples next to the tank pit The proposed location is <br /> shown in Figure 6 <br /> ' Pro1 ect No RC0309.010 <br />