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<br /> complex. These excavations are hydraulically connected with pea gravel backfill material encountered
<br /> in the northeast corner of the former UST pit.
<br /> Soil samples collected from the capillary fringe of the former and new UST excavations at depths of 11
<br /> to 12 feet bgs contained petroleum hydrocarbons at concentrations of up to 130 ppm of TPHg, 50 ppm
<br /> of MtBE, 290 ppm of ethanol, and 51 ppm of tertiary butyl alcohol (TBA). Ali of the soil samples were
<br /> non-detect for benzene and the oxygenate compounds. Soil samples collected from beneath the
<br /> former product lines at depths of 3 to 4 feet bgs were non-detect for TPHg, benzene, MtBE, or the six
<br /> oxygenate compounds. A set of first generation product lines were discovered during construction
<br /> activities and removed. Soil samples were collected from beneath these product lines at depths of 2.5
<br /> to 4 feet bgs. Concentrations of TPHg (50 ppm), MtBE (0.17 ppm), and ethanol (64 ppm) were
<br /> reported in these samples. The area surrounding these samples was overexcavated and four sidewall
<br /> soil samples and one bottom sample were collected at depths ranging from 6 to 11.5 feet bgs. These
<br /> samples contained TPHg concentrations up to 950 ppm, but were non-detect for all other analytes.
<br /> Groundwater was encountered in the excavations at a depth of approximately 11 to 12 feet bgs. Two
<br /> grab groundwater samples were collected from the former UST excavation and analyzed for TPHg,
<br /> BTEX, MtBE, and six oxygenate compounds. Grab groundwater samples SW and CW, collected from
<br /> beneath the former south and center USTs, contained 8,400 and 60,000 ppb of TPHg, 310 and 1,500
<br /> ppb of benzene, 100,000 and 130,000 ppb of MtBE, and 460 and 870 ppb of tert-amyl methyl ether
<br /> (TAME), respectively (Gettler-Ryan Inc., UST and Product Line Replacement Report, dated April 23,
<br /> 1999).
<br /> Approximately 61,000 gallons of groundwater were removed from the former and present UST pits
<br /> during the 1998 construction activities, and transported by Waste Management Industrial Services
<br /> (WMIS)of Benicia, California, to the Tosco Refinery in Rodeo, California,for disposal.
<br /> Prior to backfilling and compacting of the former gasoline UST complex excavation, one conductor
<br /> casing was placed near the northwest corner of the former UST excavation. The casing was installed
<br /> to facilitate the removal of groundwater from within the former UST cavity. The conductor casing
<br /> consisted of 11.5 feet of 6-inch diameter polyvinyl chloride (PVC) and 10 horizontal feet of 6-inch PVC
<br /> in an "L" configuration extending eastward from the vertical section. The bottom 10 feet of the vertical
<br /> casing and the horizontal casing consisted of 0.02-inch machine slotted well screen. The location of
<br /> the conductor casing is shown on Figure 2.
<br /> Between February 26 and March 26, 1999, approximately 41,760 gallons of groundwater were
<br /> removed from the former UST backfill utilizing the conductor casing. Groundwater removal and
<br /> transportation was performed by WMIS. The water was transported to the Tosco Refinery for
<br /> treatment and disposal. A total of approximately 102,760 gallons of groundwater were removed from
<br /> the former and present UST pits and transported to the Tosca Refinery between January 1999 and
<br /> March 26, 1999.
<br /> Starting in January 2000, Tosco contracted Onyx Industrial Services, Inc. (Onyx) of Benicia, California
<br /> to purge approximately 5,000 gallons of groundwater from conductor casing CC-WS on a weekly basis.
<br /> The purged groundwater is transported to the Tosco Refinery in Rodeo, California for disposal. As of
<br /> July 29, 2002, Onyx has removed a total of 570,320 gallons of groundwater from the site.
<br /> In February 2002, GR advanced five offsite geoprobe soil borings (B-1 through B-5) downgradient of
<br /> the subject site. Soil and groundwater samples were collected at each of the geoprobe locations and
<br /> analyzed for TPHg (by EPA Method 8015 modified), and benzene, toluene, ethylbenzene, and
<br /> xylenes (BTEX)and MtBE by EPA Method 8021. In addition, all soil and groundwater samples were
<br /> analyzed for Ethanol, TBA, MtBE, di-isopropyl ether (DIPE), ethyl tert-butyl ether (ETBE), 1,2-
<br /> dichloroethane 1,2 DCA), TAME, and ethylene dibromide (EDB) by EPA Method 8260B. None of
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