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13 December 1999 AGE-NC Project No. 98-0433 ' Page 6 of 13 sand from 9 to 30 feet bsg. Bentonite chips were used to make a one-foot transition seal above the sandpack. The remaining annular space was backfilled:to within six inches of surface grade with portland cement. A traffic-rated well box (8-inch diameter) was installed,over each well, in accordance with San Joaquin County regulations. Monitoring well design specifications are depicted ' in Appendix B. A summary of monitoring well screen depth intervals are presented in Table 6.. Following well installation, the wells were developed in order to increase water flow into the well and to minimize the amount of fine-grained sediment drawn into the well during pumping or.bailing. 3.6. GROUND WATER MONITORING ACTIVITIES On 25 August 1999, ground water monitoring activities were performed at the site. Ground water . 1 monitoring activities included the measurement of ground water levels and collection of ground water samples for eight site-related monitoring wells (MW-1 through MW-8). The water level in each monitoring well was measured relative to the tops of the well casings using a Solinst water level meter. After water levels were measured, a two-stage-submersible pump was used to purge each well. Six gallons(a minimum of three well volumes)of water were removed from wells MW-1 through MW=8. Temperature, pH and conductivity of the purged water were measured at two-gallon intervals using an ICM water analyzer during purging, and the values had generally . stabilized by the end of the purging process (Appendix Q. Purged water was stored on-site in 55- gallon, Department of Transportation (DOT) or United Nations (UN)-approved drums. 3.7. COLLECTION OF GROUND WATER SAMPLES Prior to collection of ground water samples, the depth to ground water was measured in each purged well to ensure that a minimum of 80% of the well volume had recharged. Water samples were collected from each well using a new disposable plastic bailer. Each water sample was transferred ' into three chilled 40-m1 volatile organic analysis (VOA) vials containing 0.5 ml hydrochloric acid (18%) as a sample preservative. After collection; the samples were labeled and placed in a chilled container for transportation under chain-of-custody to MAI, a DHS-certified analytical laboratory. Each sample was analyzed for: i • TPH-g and TPH-d by EPA Method 8015 Modified for each molecular range of hydrocarbons; • BTEX by EPA Method 8020; and • Oxygenated compounds; DIPS, ETBE, MTBE, TAME and TBA by EPA Method 8260 Advanced GcoEnvironmental,Inc.