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r N.10� Site Delineation and RAP Addendum Proposal April 16,2006 Farmer Canteen Facility—1500 Shaw Rd Page 3 AS-SVE SYSTEM OPERATIONS Operations of the AS-SVE Skid have continued with weekly operations and monitoring (O&M) activities for the AS-SVE remediation system. SVE System Operations The following table summarizes the current operating parameters of the SVE system: Vacuum Levels Total Well Row HC Concentrations HC Concentrations SVE (in w.cLr - -{scfm) t❑ 111 -- "'Y�-----.._ Wells Min j Max Min Max Min Max Min i Max All 50 57 98 142 39.4 48.5 9.10* 11.2* Note(*): Based on laboratory results. PID readings varied from 7.1 to 62 ppmv(minus outliers) Hydrocarbon Vapor Monitoring Influent and effluent vapor concentrations from the GAC Vessels were measured weekly using a photo- ionization detector (PED) meter. During one O&M visit each month, influent and effluent vapor samples were collected in Tedlar bags and express-delivered to Pace Analytical Services, Inc. in Minneapolis, Minnesota for analysis of TPH, BTEX, and MTBE concentrations using EPA Air Toxics Method TO-3. Based upon the overall system flow rates,the hydrocarbon (TPHNOC) recovery rates during the previous quarter of monitoring varied from 0.72 to 0.97 lbs/day (0.030 lbs/hr to 0.041 lbs/hr). Through the end of December 2007, cumulative hydrocarbon vapor recovery was in excess of approximately 6,280 pounds (^-1,003 gallons). Additional Water Level Monitoring Hydrocarbon recovery rates at the site have been demonstrated to vary with significant changes in groundwater elevations. During times when the water table has been more shallow (high elevations associated with rainy periods), hydrocarbon vapor concentrations have increased, due to a reduction of the focal area for the SVE vacuum. Due to diminishing agricultural activities in the area, there were concerns that water levels may possibly rise too high for proper operation of the SVE System. To monitor this situation, the gauging of two representative wells(MW-3D and MW-1 3)was added to the O&M activities in August 2007. Following the end of the rainy season, the fourth quarter was marked by a steady decrease in site water levels. The average site-wide water level dropped in excess of 5.6 feet from the beginning to the end of the quarter. A declining trend in hydrocarbon emission concentrations mirrored the groundwater elevations. Air Sparging Operations Air sparging (AS) operations through the fourth quarter 2007 have been equivalent to other operation periods for the SVE system. Delivery pressures for the various AS sections and wells have varied from approximately 9.0 to 13.0 pounds per square inch gauge (psig). Air flow to the AS wells has varied from approximately 2 to 5 scfm per well.