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REQUEST FOR SITE CLOSURE REPORT -2- Former Beacon Statton #610 . 3300 Waterloo Road, Stockton, Califorma AMV Project No 19042 04 2.0 INITIAL INVESTIGATION RESULTS 2.1 Initial Distribution of Petroleum Constituents in Soil Nine soil borings were advanced at the site between March 1987 and March 1993 Applied GeoSystems (AGS) of Fremont, California, advanced six soil bonngs at the site in March and April 1987. Soil boring locations are illustrated on Figure 2 Soil samples were collected from .r each boring, and one soil sample from each boring collected at depths ranging from 35 to 40 feet ,p -3 below grade was submitted for laboratory analysis of the petroleum hydrocarbon constituents benzene, toluene, ethylbenzene, total xylenes (BTEX), total volatile hydrocarbons (TVH) (which is approximately equivalent to total petroleum hydrocarbons as gasoline (TPHg)), and total extractable hydrocarbons (TEH) Results of the investigation were presented in AGS's "Subsurface Environmental Investigation" report, dated May 11 1987. Benzene was not detected above the laboratory method detection limit in any sample submitted for analysts Three additional soil borings were advanced to approximately 90 feet below grade at the site by SSB Environmental Consultants, Inc (SSB), in March 1993 Soil samples were collected from • each boring at 5 -foot intervals during drilling, and six soil samples from each boring were submitted for laboratory analysis of TPHg and BTEX Detectable concentrations of petroleum hydrocarbon constituents were not present in the soil samples submitted for analysis Analytical results of soil and ground water samples from previous subsurface investigations performed by other consulting firms are presented in Appendix B �_tk �. 1,LA,4,) lv3_� - 2 AeewJ«'6: In October 1993, the existing USTs were removed and replaced Soil samples were collected from beneath the product lines and UST locations as required during UST removal Results of the UST removal were documented in AMV's "Tank Closure Report" dated November 22, 1993 Ten soil samples were collected from directly beneath the former tank locations at depths ranging from 13 to 21 feet below grade and from beneath the product distribution lines on October 14, 1994 Soil samples were submitted to a state -certified laboratory for analysis of BTEX, TPHg, total petroleum hydrocarbons as diesel (TPHd), ethylene dibromide (EDB), and total lead None of the soil samples collected on this date contained detectable concentrations of benzene Only two soil samples contained detectable amounts of TPHg greater than 1 milligram per kilogram (mg/kg) at 2 8 and 9 1 mg/kg, and two soil samples collected on this date contained TPHd above the method detection limit at 1 8 (20 5 feet below grade) and 56 mg/kg (21 feet below grade) Overexcavation of the southwest extent of the UST excavation was performed on October 18, 1994 Twelve additional soil samples were collected from the sidewalls and bottom of the excavation to determine the horizontal and vertical extent of petroleum hydrocarbon constituents in soil beneath the site Soil sample locations are illustrated on Figure 5. Concentrations of TPHg in soil samples collected on October 18, 1993, ranged • from less than 1.0 to 2,400 mg/kg in a sample collected from the southwest sidewall at 16 feet rpa 14 m, BQ011 S22