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S E C 0 R <br /> �._e' l <br /> J <br /> Services, Inc. (Onyx) beginning in January 2000. Between January 2000 and February <br /> 2003, approximately 754,820 gallons of groundwater were removed from beneath the site. <br /> In February 2002, GRI supervised the drilling of five off-site geoprobe soil borings (B-1 <br /> through B-5) downgradient of the subject site. Soil and groundwater samples were <br /> collected at each of the geoprobe locations, and analyzed for TPHg (by Environmental i <br /> Protection Agency [EPA] Method 8015 modified), and benzene, toluene, ethylbenzene, J <br /> and xylenes (BTEX) and MtBE by EPA Method 8021. In addition, soil and groundwater <br /> samples were analyzed for ethanol, TBA, MtBE, di-isopropyl ether (DIPE), ethyl tertiary <br /> butyl ether (EtBE), 1,2-dichloroethane (1,2-DCA), TAME, and ethylene dibromide (EDB) <br /> by EPA Method 8260B. Petroleum hydrocarbon and fuel oxygenate constituents were <br /> not detected in soil. Four groundwater samples (B-1, B-2, B-4, and B-5) contained MtBE <br /> at concentrations ranging from 3.0 to 10,000 ppb. <br /> On May 28 and 29, 2002, GRI oversaw the installation of five off-site groundwater <br /> monitoring wells (MW-13 through MW-17) to depths ranging from approximately 20 to 21 <br /> feet bgs. Petroleum hydrocarbon constituents were not detected in soil, with the <br /> exception of one soil sample (MW-16-S9.5) that contained MtBE at a concentration of <br /> 0.040 ppm. MtBE was the only constituent detected in groundwater samples from the <br /> newly installed monitoring wells; concentrations ranged from 28 to 3,900 ppb. <br /> In December 2002, GRI supervised the installation of four off-site groundwater <br /> ==: monitoring wells (MW-18 through MW-21) completed at a depth of 20 feet bgs, and 15 <br /> }==j ozone sparge (OS) points (SP-1 through SP-15) completed at depths between 30 feet f <br /> and 37 feet bgs. With the exception of MtBE (0.0067 ppm) in a 10-foot soil sample from <br /> boring MW-19, petroleum hydrocarbons and fuel oxygenates were not detected in soil <br /> samples. Groundwater samples from well MW-19 contained TPHg and MtBE at 60 ppb <br /> and 200 ppb, respectively. An OS system was also brought on-line on December 20, <br /> 2002 and was initially configured to cycle through each OS point 16 times a day for 5 to <br /> 15 minute periods. <br /> SENSITIVE RECEPTORS <br /> i <br /> J <br /> A sensitive receptor survey and a '/2-mile radius water well survey were performed by <br /> Alisto in 1999. No basements or subways were found within a 300-foot radius of the <br /> subject site. An off-site subsurface utility survey indicated the presence of a sanitary <br /> sewer trench adjacent to the subject site that may influence the transport of petroleum <br /> hydrocarbons in groundwater. A search of California Department of Water Resources <br /> (DWR) and Banks Information Solutions files indicated that seven water wells had been <br /> installed within a %2-mile radius of the subject site; however, the wells could not be located r <br /> based upon the information provided by DWR. Additional water supply wells were not <br /> identified during field reconnaissance of the area (Alisto, 1999). f <br /> MONITORING AND SAMPLING <br /> The current monitoring well network consists of N wells (MW-1 through MW-6, MW-8 <br /> through MW-21, and CC-WS) that are monitored and sampled quarterly. Groundwater <br /> r` samples from each well are analyzed for the presence of gasoline range organics <br /> .1 <br /> a <br /> I:IConocoPhillips\Retall Sites1111951QSR&QRPS 2005/11195 QSR&QRPS 1Q05.doc <br />