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20 March 2000 <br /> AGE-NC Project No 96-0232 <br /> Page 2 of 5 <br /> MW-6B and MW-7 utilizing a two-stage submersible pump, ground water pumping was initiated <br /> at the top of the water column and the pump was slowly lowered to total depth to purge ground water <br /> within the entire well casing Approximately 4 gallons of ground water were removed from well <br /> MW-613 before being pumped "dry" Temperature, pH and conductivity were measured for <br /> stabilization at regular purge-volume intervals from each well using a Hydac water analyzer Field <br /> data and logs are included with Appendix A Purged ground water was containenzed in 55-gallon <br /> drums and was stored on-site in an area lacking general public access <br /> 22 GROUND WATER SAMPLING <br /> Following well purging, ground water levels in monitoring wells MW-1, MW-2, MW-4, MW-5, <br /> MW-6A,MW-6B and MW-7 achieved a minimum of 80 percent recharge prior to sample collection <br /> Ground water samples were collected from the purged wells utilizing new, disposable polyethylene <br /> bailers and transferred into nonpreserved one-liter amber bottles and 40-m1 EPA-approved VOA <br /> vials containing 0 5 ml 18%hydrochloric acid as a preservative Care was taken to ensure that visible <br /> air bubbles were not present in the vials after filling and capping Ground water sample containers <br /> were labeled with the well designation, date, time, and sampler's initials <br /> 23 LABORATORY ANALYSIS OF GROUND WATER SAMPLES <br /> Each ground water sample was logged on a chain-of-custody form, placed in a chilled container and <br /> transported to a California Department of Health Services (DHS)-certified laboratory for analysis <br /> for <br /> • Total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d, <br /> respectively) by EPA Method 8015M, <br /> • Volatile aromatic compounds (benzene, toluene, ethyl benzene and xylene BTEX) with <br /> methyl-tertiary butyl ether (MTBE) by EPA Method 8020, and <br /> • Ethylene dibromide (1,2-dibromoethane), 1,2-Dichloroethane (1,2-DCA), Tertiary butanol <br /> (TBA), di-isopropyl ether (DIPE), ethyl tert butyl ether (ETBE), tert amyl methyl ether <br /> (TAME) and MTBE by EPA Method 8260M <br /> 30. FINDINGS <br /> Ground water elevation, flow direction and gradient were determined from field data collected on <br /> 25 February 2000, the contaminant impact to ground water was assessed from the laboratory data <br /> Ads anced GeoEn%ironmental,Inc <br />