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I 18 February 2003 ' AGE-NC Project No 96-0229 Page 4 of 9 relative to the City of Stockton Bench Mark Datum BM # 15 The surveying report (Baumbach & Piazza Job No 9797) is presented in Appendix C 2 2 QUARTERLY GROUND WATER MONITORING PROCEDURES On 25 November 2002, depth to ground water was measured in each well from the top of the well casing to the nearest 0 01-foot utilizing a Solinst water level meter The ground water elevation in each well was calculated by subtracting the measured depth to ground water from the surveyed casing elevation.(Table 2) Ground water elevations were plotted and contoured on a scaled site map (Figure 7) After water levels were measured, approximately 4 to l 1 gallons of ground water (a minimum of three casing-water volumes per well) were evacuated(purged) from wells MW-1 through MW-12 utilizing disposable bailers, approximately 6 gallons of water were purged from MW-1 before the well was purged"dry" Temperature,pH and conductivity were measured for stabilization at regular purge-volume intervals from each well using an Oakton water analyzer Field data and logs are � . included with Appendix. D Purged ground water was containerized in 55-gallon drums and was stored on-site in an area lacking general public access 2 2 1 Ground Water Sampling Following well purging, the ground water level from each well was allowed to achieve a minimum of 80 percent recharge prior to sample collection Ground water samples were collected from the purged wells utilizing new,disposable polyethylene bailers,and transferred to 40-m1 EPA-approved VOA vials containing 0 5 ml 18% hydrochloric acid as a sample preservative Care was taken to ensure that visible air bubbles were not present in the vials after filling and capping Ground water sample containers were labeled with the well designation, date, time, and sampler's initials 2 2 2 Laboratory Analysis Of Ground Water Samples Each ground water sample was logged on a chain-of-custody form,placed in a chilled container and transported to a California DHS-certified laboratory for analysis for TPH-g by EPA Method 5030/8015M, • BTEX and MTBE by EPA Method 8020, and • EDB, 1,2-DCA, TBA, DIPS, ETBE, TAME and MTBE by EPA Method 8260 Modified Advanced CeoEnvironmental,Inc I