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T Remedial Action Plan-Tosco 76 Branded Facility No. 11195 Ji m 1, 1999 Soil samples collected from the capillary fringe of the former and new UST excavations at depths of 11 to 12 feet bgs contained petroleum hydrocarbons at concentrations of up to 130 ppm of TPHg, 50 ppm of MtBE, 290 ppm of ethanol, and 51 ppm of tertiary butyl alcohol (TBA). All of the soil samples were reported as not detected benzene and the remaining oxygenate compound analytes. Soil samples collected from beneath the former product lines at depths of 3 to 4 feet bgs were reported as not detected for TPHg, benzene, MtBE, and the six oxygenate compounds. A set of first generation product lines were discovered during construction activities. Soil samples collected from beneath these product lines at depths of 2.5 to 4 feet bgs. Two of these samples were reported as not detected for all analytes except that one sample contained 0.17 ppm of MtBE and the other sample contained 64 ppm of ethanol. The third sample contained 50 ppm of TPHg and was not detected for all other analytes. A 13 feet by 13 feet by 11.5 feet deep overexcavation was dug around this sample. Four sidewall soil samples and one bottom sample were collected at depths ranging from 6 to 11.5 feet bgs. These samples contained TPHg concentrations ranging from not detected to 950 ppm. The remaining analytes were reported as not detected. Groundwater was encountered in the excavations at a depth of approximately 11 to 12 feet bgs. Two grab groundwater samples were coilected from the former UST excavation and analyzed for TPHg, BTEX, MtBE, and six oxygenate compounds. Grab groundwater samples SW and CW, collected from beneath the former south and center USTs, contained 8,400 and 60,000 ppb of TPHg, 310 and 1,500 ppb of benzene, 100,000 and 130,000 ppb of MtBE, and 460 and 870 ppb of tert-amyl methyl ether (TAME), respectively (Gettler-Ryan Inc., UST and Product Line Replacement Report, dated April 23, 1999). Groundwater sample analytical data are summarized in Table 1 Approximately 61,000 gallons of groundwater were removed from the former and present UST pits during the recent construction activities, stored on-site on portable tanks, then transported by Waste Management Industrial Services (WMIS) of Benicia, California to the Tosco Refinery in Rodeo, California fcr treatment and disposal. Groundwater sample W-ST1 was collected on February 1, 1999 and analyzed for TPHg, BTEX, and MtBE to comply with Tosco Refinery disposal requirements. The sample contained 600 ppb of TPHg, 8.0 ppb of benzene, and 12,000 ppb of MtBE (Gettler-Ryan Inc., 1999). Sample W-ST1 analytical data are summarized in Table 1. Prior to backfilling and compacting of the former gasoline UST complex excavation, one conductor casing was placed near the northwest corner of the former UST excavation. The casing was installed to facilitate the removal of groundwater from within the former UST cavity. The conductor casing consisted of 11.5 vertical feet of 6-inch diameter polyvinyl chioride (PVC) and 10 horizontal feet of 6-inch PVC in an "L" configuration extending eastward from the vertical section. The bottom 10 feet of the vertical casing and the horizontal casing consist of 0.02-inch machine slotted well screen. The location of the conductor casing is shown on Figure 2. Details of the conductor casing construction are shown on Figure 3. Between February 26 and March 26, 1999, an additional 41,760 gallons of groundwater were removed from the former UST backfill utilizing the conductor casing. Groundwater removal and 140193.07-1 3