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Groundwater Elevation Data • Depth to groundwater was obtained from the existing groundwater monitor wells at the site using a water level indicator graduated to 0 01 foot The depth to groundwater measurement was converted to a groundwater elevation for each well and used to construct a groundwater elevation contour map (Figure 2), and calculate the local groundwater flow direction and hydraulic gradient Groundwater at the site was measured at depths between 66 80 to 80 35 feet below ground surface (bgs) The groundwater potentiometric surface elevation averaged approximately 29 24 feet bgs during this momtonng event The groundwater elevation has decreased approximately 0 51 feet since the last sampling event in July 1999 The groundwater flow direction during this reporting period is toward the south/southwest with a hydraulic gradient of approximately 0 03 ft /ft A summary of data regarding groundwater levels measured through November 24, 1999 is presented in Table 1 Copies of field observations documenting work performed at the site is presented in Attachment I Groundwater Analytical Results The distribution of groundwater sample analytical results obtained from monitor wells at the site on November 24, 1999, is presented on Figure 2 and summarized in Table 2 TPHg and BTEX were present at detectable concentrations in eight of the ten samples submitted for analysis Chemical analytical results indicate the highest concentrations of TPHg and benzene are in the vicinity of monitor wells MW-1, MW-3 and MW-4 TPHg concentrations in groundwater samples ranged from 6,320 micrograms per liter (ug/L) in monitor well MW-1, to less than detectable levels in samples collected from monitor wells MW-8 and MW-10 Benzene concentrations ranged from below the laboratory method detection hmit in monitor wells MW-1, MW-8 and MW-10, to 193 ug/L in MW-4 MTBE concentrations in groundwater samples ranged from below the laboratory method detection limit in monitor wells MWA, MW-3 and MW-7 through MW-10, to 17 5 ug/L in a sample collected from monitor well MW-4 Attachment II contains photocopies of the laboratory analytical reports and the chain-of-custody form Purge Water Purge water generated during groundwater purging is currently contained on-site in Department of Transportation rated 55-gallon drums and will be removed to a disposal/recycling facility SITE REMEDIATION Soil Remediation System Construction A corrective action plan, including the installation and operation of an air sparging and soil vapor extraction and treatment system, has been approved by San Joaquin County Public Health Services The soil vapor extraction system (VES) consists of seven soil vapor extraction (SVE) wells (W-1, W-3 through W-8), two groundwater monitor wells (MW-1 and MW-3) and four air sparge wells (AS-1 through AS-4) with catalytic oxidation treatment at the site Construction of the remediation system was completed at the site in December 1999 A Site Plan depicting the locations of the remediation wells, subsurface piping, and remediation equipment compound is included as Figure 3 Initial start-up air discharge compliance testing was completed on December 13, 1999 Initial • D Alin OLML kerordQ4 99 2 SFCOR February 077 41737 003 25 2000