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1 26 September 2003 • AGE-NC Project No 95-0128 Page 3 of 8 I2 5 GROUND WATER MONITORING AND SAMPLING On 24, 25 and 26 February 2003, a quarterly ground water monitoring and sampling event was conducted on the monitoring well network The ground water monitoring activities at the site was coordinated to occur concurrently with the ground water monitoring activities at the Pacific Car i Wash site(4405 Pacific Avenue) 1 2 5 1 Ground Water Monitoring and Evacuation On 24 February2003 a Sohnst water level meter was used to measure the depth to ground water In P monitoring wells MW-1 through MW-16 and vapor well VW1, the ground water elevation in each well was calculated by subtracting the measured depth to ground water from the surveyed casing elevation On 25 and 26 February 2003, a minimum of 3 casing-water volumes were purged from each well to be sampled using a Waterra bailer system or disposal bailer, except for wells MW-8 and MW-9, which was purged dry after four and two and one-half gallons of water were removed,respectively Temperature, pH and conductivity of purged ground water were measured at various intervals, depending on the volume of water In each well, using an Oakton water analyzer The field data and I field sheets are included in Appendix C Purged water was discharged into the active ground water treatment system for disposal Following purging,the depth to ground water was measured to ensure that a minimum of 80% well-volume recharge had been achieved prior to sampling I 2 5 2 Ground Water Sample Collection IA water sample was collected from each monitoring well using a new disposable bailer or dedicated Waterra bailer system after allowing the wells to achieve a minimum 80%recovery of the pre-purge Iwater volume Immediately upon retrieval,the samples were transferred into three 40-milliliter(ml) EPA-approved volatile organic analysis (VOA) vials containing 0 5 ml 18% hydrochloric acid (sample preservative) and into one 1-liter amber bottle without the preservative The samples ! collected were logged on a chain-of-custody form, placed in a chilled container and transported to McCampbell Analytical Inc (MAI), a California Department of Health Services (DHS)-certified laboratory in Pacheco, for analysis The ground water samples were analyzed for • Total petroleum hydrocarbons quantified as gasoline and as diesel (TPH-g and TPH-d) by EPA Method 8015 Modified, IAdvanced GcoEnvironmentai Inc