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S E C O R <br /> Ms.Victoria McCartney <br /> July 28, 2005 <br /> Page 2 <br /> UNDERGROUND UTILITY LOCATING <br /> Underground Service Alert (USA) will be notified at least 48 hours prior to commencing field <br /> activities to identify any public utility alignments that may be in conflict with the proposed <br /> monitoring wells and soil vapor probes. In conjunction with the USA, a private utility <br /> locating company will be utilized for clearing proposed monitoring well locations for <br /> underground utilities. <br /> MONITORING WELL INSTALLATION <br /> Two boreholes for monitoring wells will be advanced using a hollow-stem auger to a depth <br /> of approximately 40 feet below ground surface (bgs). An attending geologist will log <br /> cuttings and sample in accordance with American Society for Testing and Materials (ASTM) <br /> D-2488 — Standard Practice for Description and Identification of Soils (Visual-Manual <br /> Procedure). Soil samples will be logged at five-foot intervals. Upon completion of drilling, a _ <br /> 2-inch diameter groundwater monitoring well, screened from approximately 25 to 40 feet <br /> bgs, will be installed in the boring. `( - <br /> Soil Analysis <br /> � W@30 <br /> Selected. soil samples will be submitted under chain-of-custody documentation to a <br /> California State certified laboratory and analyzed for total petroleum hydrocarbons as .S <br /> gasoline (TPHg) and methanol by EPA Method 8015, benzene, toluene, ethylbenzene, total <br /> xylenes (BTEX), methyl tertiary butyl ether(MtBE), tertiary butyl alcohol (TBA), di-isopropyl <br /> ether (DIPE), ethyl tertiary butyl ether (EtBE), tertiary amyl methyl ether (TAME), 1,2-/ <br /> dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB) by EPA Method 8260. <br /> Monitoring Well Development and Sampling <br /> Commencing at least 72 hours after installation, the monitoring wells will be developed by <br /> surging the well over the length of the screen interval then purging approximately 10 casing <br /> volumes of water. Following development, groundwater samples will be collected from <br /> each well and sent under chain-of-custody documentation to a California State-certified <br /> laboratory and analyzed for the presence of TPHg and methanol by EPA Method 8015, <br /> BTEX, MtBE, TBA, DIPE, EtBE, TAME, 1,2-DCA, and EDB by EPA 8260. <br /> O <br /> I:\Chevron\91452\REPORTS\2005\Addendum to work plan 11-24-04 dated 7-28-05.doc <br />