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S E C 0 R Ms. Lori Duncan May 12, 2006 Page 3 The documentation of these well installations and development will be included in a Site Conceptual Model following installation of the remaining Chevron wells (MW-5R, MW-7R, and MW-91R), scheduled for the second quarter 2006. On March 20, 2006, depth to groundwater in the monitoring wells ranged from 4.69 to 8.28 feet below ground surface (bgs). Groundwater flow across the site was to the north- northeast at a hydraulic gradient of 0.003 foot per foot (ft/ft). A groundwater elevation contour map of the two sites is presented as Figure 2. Groundwater concentrations for both sites are summarized for TPHg, benzene, and MtBE as Figure 3. Chevron's and ARCO's groundwater elevation and analytical data are summarized in Tables 1 and 2, respectively. Chevron's and ARCO's groundwater analytical data for oxygenated compounds are presented in Tables 3 and 4, respectively. Historical groundwater gradient data are presented in Table 5. Field and laboratory procedures are provided in Attachment A. The laboratory analytical report and chain-of-custody documents are provided in Attachment B, and field data sheets are provided in Attachment C. REMEDIAL RESULTS SUMMARY (CHEVRON) Operation of the SVE and AS systems was initiated at the site in April 1997. The SVE system has been disabled and the AS system was shut down in April 2005 and removed in May 2005 as a result of the service station teardown and rebuild. The inactive SVE system was 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 4). The SVE system has not operated since February 1998. The SVE wells were destroyed and the remediation equipment was removed from the site in May 2005. The inactive AS system was comprised of nine AS wells (GM-1 and GM-9), underground mechanical piping, and a 1.5-hp rotary vane air compressor. The AS wells were destroyed and the remediation equipment was removed from the site in May 2005. REMEDIAL RESULTS SUMMARY (ARCO) Cumulative Free Product Recovered to 642 pounds (lbs) Date: Cumulative TPHg Removed by 3,980 lbs Groundwater Extraction: Total Groundwater Extracted: 32,000,000 gallons 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 Measured Depth to Groundwater: 4.69—8.28 feet 1AChevron1942751REP0RTSIQ M R1200611Q06.doc