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V Environmental Assessment Report Advanced Environmental Concepts, Inc. underground gasoline USTs. The locations of B-9, B-10, and B-1 6H appear to be within the former tank emplacement location,hence the identification of gasoline constituents in the shallow subsurface. The identification of gasoline at depths of 10 to 14 feet represent the lateral migration of the hydrocarbons on the capillary fringe creating a"smear zone" of gasoline contamination. V 6.2 Pesticides in Soil Soil samples were collected adjacent to the weed oil AST and the Ag-chemical storage building and analyzed for organochlorine and organophosphate pesticides, and phenoxy acid herbicides. The analytical results recorded concentrations below detectable limits for all constituents analyzed. V 6.3 Hydrocarbons in Groundwater Reconnaissance groundwater samples indicate the presence of TPH-g concentrations above 1,000 ppb and detectable concentrations of BTEX in borings 8-9, B-10, and B-11. Minor concentrations of benzene,toluene,xylenes and ethylbenzene of were detected in borings B-4, B-7, and B-8.All other constituents were either below detectable limits or were not analyzed. The gasoline plume appears to have migrated to the northeast and the zone of significantly impacted groundwater occupies a spatial area of approximately 60'x 40'. 7.0 CONCLUSIONS On the basis of our investigation,AEC presents the following conclusions: a) There appears to have been two separate UST emplacements. It is the opinion of AEC that area-1 contained two gasoline USTs, on the east side of the warehouse-storage building. The estimated capacities of the USTs are 500 gallons and 2,000 gallons. The area-2 tank emplacement is adjacent to the south wall of the oil drum storage Quonset structure. It appears that there was only one UST, having an estimated volume of 1,000 to 2,000 gallons and formerly contained diesel fuel. b) The soil profile at the subject site generally consists of interbedded clay and clayey silt to 10 feet BGL then is underlain by a fine-to-coarse grained water bearing sand having an approximate thickness of 3 feet. C) The analytical results indicate elevated levels of TPH-g and BTXE to a total depth of 10 feet ,r in B-9,B-10,B-11,B-16H,and B-17H and non-detectable concentrations at 15 feet BGL. The perimeter borings exhibit non-detectable TPH-gBTXE concentrations_ Groundwater is impacted with gasoline in the vicinity of borings B-9, B-10, B-11, B-1 6H, and B-1 7H and appears to have migrated to the northeast. The domestic well exhibited TPH-g/BTXE concentrations below detectable limits. d) The vertical extent of the gasoline and diesel migration appears to extend to an estimated depth of 14 feet BGL.The lateral extent of the elevated concentrations of gasoline in area 1 is 70'x 45'x 14' and has an approximate soil volume of 1,633 cubic yards of impacted soil. The lateral extent of the diesel plume in area 2 is about 10'x 10'x 12' and the approximate soil volume of the plume is 44 cubic yards. rr Project: AEC 96C-1703 8 • ENVIRONMENTAL CONCEPTS WITH DESIGN IN MIND• �"� 4400 ASHE ROAD,*206 BAKERSFIELD.CA 93313 8051831-1646 FAX 8051831.1771