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First Semiannual 2012 Groundwater Monitoring Report <br /> Former Texaco Service Station <br /> Chevron Site ID 309075 <br /> June 21, 2012 <br /> r <br /> 3.3 Waste Disposal <br /> Purge water and equipment decontamination water generated during the sampling event was <br /> transported by Clean Harbors Environmental Services to Evergreen Oil located in Newark, <br /> California. <br /> 4.0 MONITORING AND SAMPLING DATA <br /> r <br /> 4.1 Groundwater Monitoring Data Analysis <br /> CURRENT MONITORING DATA <br /> Chevron wells monitored and sampled: MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, <br /> and MW-6D <br /> Monitoring and sampling dates: April 13, 2012 <br /> r <br /> Were SPH observed this event? No <br /> DTW range (ft below TOC): 48.68—49.95 <br /> Average change in groundwater elevation 2.28 feet decrease <br /> since last event (ft): <br /> Groundwater flow direction and gradient Northeast at an approximate horizontal <br /> foot per foot [ft/ft]): hydraulic gradient 0.002 ft/ft <br /> V <br /> 4.2 Groundwater Sample Analysis <br /> V <br /> Subsequent to collection, samples were packed on ice, cooled to approximately 4 degrees <br /> Celsius (°C) and shipped under appropriate chain-of-custody protocols for analysis to Lancaster <br /> Laboratories, Inc. (Lancaster) of Lancaster, Pennsylvania, a California Department of Public <br /> r Health certified analytical laboratory. The groundwater samples were screened for the following <br /> analytes per the parameters listed: <br /> • Total petroleum hydrocarbons as motor oil (TPH-MO) [C16-C36] by United States <br /> Environmental Protection Agency (USEPA) Method 80158 modified <br /> • TPH-MO [C16-C36] with silica gel cleanup (SGC [10-gram column]) by USEPA Method <br /> 8015B <br /> ,r • Total petroleum hydrocarbons as diesel range organics (TPH-DRO) [C10-C26], total <br /> petroleum hydrocarbons as gasoline range organics (TPH-GRO) [C6-C12] by USEPA <br /> Method 8015B <br /> • TPH-DRO [C10-C26] with SGC (10-gram column) by USEPA Method 8015B modified <br /> • Benzene, toluene, ethylbenzene and total xylenes (BTEX) by USEPA Method 8260E <br /> g:\aproject\env\chevron\309075\6 del lverables\pedodic monitoring\2012\tsa12\text\309075 1sa12 gmr fin 06212012.doc 3 <br /> r [� <br />