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S E C ® R Second Quarter 2004, Groundwater Monitoring Report July 30, 2004 • page 3 ARCO's laboratory analytical results, chain-of-custody documents, and field data sheets are provided as Attachment C REMEDIAL RESULTS SUMMARY (CHEVRON) Operation of the soil vapor extraction (SVE) and air sparge (AS) systems were initiated at the site in April 1997 The SVE system has been disabled and the AS continues to operate A brief description and performance evaluation of the remedial system between March 05, 2004 and June 11, 2004 are presented below The inactive SVE system is comprised of ten SVE wells (VW-1 and GM-1 through GM-9), underground mechanical piping, a 5-horsepower (hp) positive displacement blower, and 100-cubic feet per minute (cfm) catalytic oxidizer (Figure 2) During 2Q04, the SVE system did not operate due to high groundwater levels The SVE system has not operated since February 1998 On June 22, 2004, depth to water in the monitoring wells at the site ranged from 10 03 to 12 24 feet below ground surface (bgs) The screened intervals in the SVE wells range from 10 to 17 feet bgs, therefore water levels are currently too high for effective operation of the SVE system The AS system is comprised of nine AS wells (GM-1 and GM-9), underground mechanical piping, and a 1 5-hp rotary vane air compressor During 2Q04, the AS system was operational for 100% of the reporting period at an average flow rate of 14 4 standard cubic feet per minute (scfm) and an average injection pressure of 5 5 pounds per square inch gauge (pslg) Routine operation and maintenance visits were conducted on April 2, May 3, and June 11, 2004 CHEVRON's historical SVE data and recent AS system operational data is presented in detail as Attachment D REMEDIAL RESULTS SUMMARY (ARCO) Cumulative FP Recovered to Date 642 lbs Cumulative TPHg Removed by GWE 3,980 lbs Total Groundwater Extracted 32,000,000 gal TPHg Removed by SVE this quarter None Cumulative TPHg Removed by SVE 4,897 lbs MtBE Removed this Quarter None Cumulative MtBE Removed 4 5 lbs Approximate Depth to Groundwater 8 63—9 48 ft ARCO's historical SVE data and recent AS system operational data is presented to detail as Attachment E STATEMENT OF LIMITATIONS This report presents our understanding of existing conditions at the subject site The conclusions contained herein are based on the analytical results, and professional judgment in accordance with current standards of professional practice, no other warranty is expressed or implied SECOR I IChevron1942751Penodic MonitoringlQ M R1200412Q04 doc