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Ms. Lori Duncan S E C ® R <br /> May 6, 2005 <br /> Page 3 <br /> QUARTERLY RESULTS SUMMARY(CHEVRON &ARCO) <br /> Groundwater flow across both sites was to the north-northeast at an approximate hydraulic <br /> gradient ranging from 0.003 to 0.004 foot per foot (ft/ft). Groundwater gradient has typically <br /> been to the north across both sites. A groundwater elevation contour map of the two sites <br /> is presented as Figure 2. Groundwater concentrations for both sites are summarized for <br /> TPHg, benzene, and MtBE in Figure 3. CHEVRON's and ARCO's groundwater elevation <br /> and analytical data are summarized in Tables 1 and 2, respectively. CHEVRON's and <br /> ARCO's groundwater analytical data for oxygenated compounds is presented in Tables 3 <br /> and 4, respectively. Historical groundwater gradient data is presented in Table 5. Field and <br /> laboratory procedures are presented in Attachment A. CHEVRON's and ARCO's <br /> laboratory analytical results, chain-of-custody documents, and field data sheets are <br /> provided as Attachment B and Attachment C, respectively. <br /> On March 7, 2005, depth to water in the monitoring wells at the site ranged from 5.04 to <br /> 9.47 feet below ground surface (bgs). The screened intervals in the soil vapor extraction <br /> (SVE) wells range from 10 to 17 feet bgs, therefore water levels are currently too high for <br /> effective operation of the SVE system. <br /> REMEDIAL RESULTS SUMMARY(CHEVRON) <br /> Operation of the SVE and AS systems were initiated at the site in April 1997. The SVE <br /> system has been disabled and the AS continues to operate. A brief description and <br /> performance evaluation of the remedial system between January 7, 2005 and March 25, <br /> 2005 are presented below. <br /> The inactive SVE system is comprised of ten SVE wells (VW-1 and GM-1 through GM-9), <br /> Underground mechanical piping, a 5-horsepower (hp) positive displacement blower, and <br /> 100-cubic feet per minute (cfm) catalytic oxidizer (Figure 2). The SVE system has not <br /> operated since February 1998. <br /> The AS system is comprised of nine AS wells (GM-1 and GM-9), underground mechanical <br /> piping, and a 1.5-hp rotary vane air compressor. During 1Q05, the AS system was <br /> operational for 80% of the reporting period at an average flow rate of 14.6 standard cubic <br /> feet per minute (scfm) and an average injection pressure of 5.5 pounds per square inch <br /> gauge (psig). <br /> CHEVRON's AS system operational data is presented in detail as Attachment D. <br /> • <br /> I:IChevron1942751Per1odic MonitodnglQ M R1200511 005.doc <br />