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' 14 August 2000 . AGE-NC Project No 95-0128 ' Page 4 of 10 ' After depth to ground water measurements, a minimum of 3 standing water casing volumes of water was purged from each well to be sampled using a PVC submersible two-stage pump Approximately 10 gallons of water were removed from monitoring wells MW8 through MW-10 and MW-1 I and ' MW-12A, 18 gallons of water were removed from wells MW-11B and MW-12B Temperature, pH and conductivity of purged ground water were measured at 2-gallon and 3-gallon intervals, as appropriate for each well, using a Hydac water analyzer The field data and field sheets are included ' In Appendix B Purged water was temporarily stored on-site in 55-gallon DOT-approved H-17 storage drums pending proper 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 2 6 GROUND WATER SAMPLE COLLECTION A water sample was collected from each well using a new, clean, disposable plastic bailer Immediately upon retrieval, samples were transferred into three 40-m1 EPA-approved VOA vials containing 0 5 ml 18% hydrochloric acid as a sample preservative and into one-liter amber bottles without the preservative The samples were logged on a chain-of-custody form, stored in a chilled container and transported under chain-of-custody to McCampbell Analytical Inc (MAI), a California Department of Health Services(DHS)-certified laboratory The ground water samples were analyzed in accordance with • EPA Method 8015M modified for total petroleum hydrocarbons quantified as gasoline (TPH-g), • EPA Method 8015M for total petroleum hydrocarbons quantified as diesel (TPH-d), • EPA Method 8020 for volatile aromatic compounds benzene, toluene, ethylbenzene and ' total xylenes (BTEX) and methyl-tertiary butyl ether (MTBE), and • EPA Method 8260M modified for oxygenated fuel additives di-isopropyl ether(DIPE), ethyl tertiary butyl ether (ETBE), MTBE, tertiary butyl alcohol (TBA) and tertiary amyl methyl ether (TAME) 27 SURVEYING The casing elevation of each well installed in June 2000 for the Arco Mini-Mart investigation was surveyed relative to City of Stockton Bench Mark#344 On 18 July 2000, a California state-licensed survey engineer from Baumbach &Piazza, Inc surveyed a reference point on the top of each ground fwater monitoring well at the site to the nearest 0 01-foot relative to the City of Stockton Bench i Advaieced GeoEnvironmenta[Inc