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W�j • 25 January 2005 AGE-NC Project No 99-0559 Page 3 of 10 2 2 COLLECTION AND ANALYSIS OF GROUND WATER SAMPLES Prior to ground water sampling,the ground water level In each well was measured to ensure that the well achieved a minimum of 80 percent recharge Following depth measurement, ground water samples were collected from well chambers well chambers 5B, SC, 5D, 5E, 6B, 6C, 6E, 7B and 7E utilizing 3/8-inch diameter polyethylene tubing The sample collected from chamber 7D was collected In the same manor but without purging the chamber prior to sampling The ground water samples were transferred Into three 40-milliliter(ml)EPA-approved volatile organic analysis(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 properly labeled, placed In a chilled container and transported under chain of custody protocol to Cal Tech Environmental Laboratories (CTEL), a California Department of Health Services-certified laboratory, for analysis The ground water samples were analyzed for the following • Total petroleum hydrocarbons quantified as gasoline (TPH-g) in accordance with EPA Method 8015 Modified, and • Benzene, toluene, ethylbenzene and xylene (BTEX) and the fuel additives tertiary butanol (TBA), dl-isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETBE), tertiary-amyl methyl ether (TAME), methyl tertiary-butyl ether (MTBE), 1,2-dlbromoethane (EDB) and 1,2-dlchloroethane (1,2-DCA) In accordance with EPA Method 8260B 2 3 GROUND WATER ELEVATION AND GRADIENT The elevation of ground water In each monitoring well at the time of the monitoring event was calculated by subtracting the depth to ground water from the surveyed casing elevation, current and historical ground water elevation results are provided in Table 1 Each ground water elevation Is grouped according to the HU on the assumption that the elevation will reflect hydrostatic conditions within the designated HUs HU1 and HU2 The depth to ground water In monitoring wells MW-1 through MW-3 was affected by the presence of free petroleum product and the level of ground water In well MW-4 was below the casing, these wells were considered dry The depth to ground water measured In wells MW-5A through MW-7A ranged between 63 91 and 64 09 feet below the top of casing (btoc) The ground water elevation was calculated between 38 56 feet(MW-6) and 39 49 feet(MW-5)below mean sea level(MSL),the ground water elevation decreased an average of 0 8 feet since the September 2004 monitoring event In the multi-level wells The top of the ground water table remained within the Advanced 4,e0Lnv1r0nmcnt21,Inc