ARCHIVED REPORTS_QUARTERLY MONITORING AND REMEDIATION REPORT - FIRST QUARTER 2007

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24 April 2007 AGE-NC Project No. 04-1207 Page 2 of 9 is historically uncontaminated. The site and surrounding area are illustrated on Figure 1.A plan of the site,including monitoring and vapor extraction well locations, is illustrated on Figure 2. Site background information detailing previous assessment activities conducted at the site is provided in Appendix A. 2.0. PROCEDURES Field work was performed in accordance with guidelines issued by the Central Valley Regional Water Quality Control Board(CV RWQCB)for the investigation ofunderground storage tank(UST) sites and by the San Joaquin County Environmental Health Department(EHD)for the sampling of ground water monitoring wells. Ground water monitoring and sampling procedures are outlined in the AGE-prepared Monitoring Well Installation Work Plan,dated 08 March 2005; SVE and ground water extraction system installation, operation, and monitoring procedures are detailed in Interim Remedial Action Work Plan, dated 06 October 2006. 2.1. WELL MONITORING AND EVACUATION On 18 January 2007, the depths to ground water in monitoring wells MW-1 through MW-5 were measured relative to the tops of the well casings (well heads) to the nearest 0.01-foot utilizing a Solinst water level meter. Ground water elevation in each well was calculated by subtracting the measured depth to ground water from the surveyed casing elevation(Table 1). After water levels were measured,approximately 6 to 8.25 gallons of water(a minimum of three casing water volumes per well)were purged from wells MW-1 through MW-5 using a Waterra inertia pump and dedicated tubing. Ground water temperature,pH,and conductivity were measured for stabilization at regular intervals during purging using an Oakton water analyzer; field sheets and data are included in Appendix B. Purged water was stored on-site in properly labeled, Department of Transportation (DOT)-approved 55-gallon drums pending proper disposal. 2.2. COLLECTION AND ANALYSIS OF GROUND WATER SAMPLES Ground water samples were collected from each well using the Waterra inertia pump and dedicated tubing after allowing the wells to achieve a minimum 80%recovery of the pre-purge water volume. Each water sample was transferred into three laboratory-supplied,40-milliliter(ml)volatile organic analysis (VOA) vials without a sample preservative. After collection, the samples were properly labeled, placed in a chilled container, and transported under chain of custody to Cal Tech Environmental Laboratories (CTEL), a State of California Department of Health Services (DHS)- Advanced GeoEnvironmental,Inc.