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f <br />' Report of Findings <br /> 401 Frontier Transportation <br />' August 26, 2003 <br /> Page 2 <br />' through MW-7) to assess the extent of subsurface contamination beneath the site Soil samples <br /> were collected every five feet Laboratory analysis of soil samples identified no detectable <br /> concentrations of TPH-g, BTEX, or MTBE Groundwater samples were subsequently collected <br /> and results are <br />' <br /> In January 2000, BEII advanced two borings (B-5 and B-6), installed four additional <br /> groundwater monitoring wells (MW-8 through MW-11), and collected nine soil vapor samples V) h <br /> for a soil vapor survey as part of an additional site assessment Soil sample analysis identified no'W <br /> detectable concentrations of petroleum hydrocarbons with the exception of boring B-6 0, <br /> Maximum contaminant levels in B-6 were identified 100 mg/kg as TPH-g, 2,343 µg/kg as V n"'' •b 3 BTEX, and 10,600 µg/kg as MTBE at 10' bg Maximum soil vapor concentrations were ra <br /> identified at sample point V5 at 4'bg Groundwater samples were subsequently collected from <br /> all monitoring wells Results of soil and groundwater samples are v �� <br /> �L <br /> In May 2002, BEII installed two additional groundwater monitoring wells (MW-12 and <br /> j 1z-o3 <br /> MW-13) screened from 30' bg to 40' bg Soil sample results identified maximum TPH-g, BTEX, <br /> and MTBE concentrations of 700 mg/kg,'l 15,000 µg/kg,-­and 25,000 µg/kg in soil collected from <br /> MW-13 at 10'bg'Soil concentrations attenuate by 99% at 15'bg No detectable TPH-g, BTEX, <br /> 10 and MTBE were identified in MW-12 Also, monitoring well MW-3 was abandoned prior to <br /> excavation and removal of 325 tons of impacted soil and replaced by MW-3R — <br />' 3.0) SITE GEOLOGY/HYDROGEOLOGY <br />' The site is located on the boundary of the Sacramento Valley and the San Joaquin Valley <br /> within the west-central portion of the Great Valley Geomorphic province of California The <br /> Great Valley has been filled with a sequence of older to younger alluvium of Pliocene to <br />' Holocene age which overlay sedimentary rocks of Cretaceous to Tertiary age These sedimentary <br /> units, in turn, overlay a crystalline basement of Paleozoic and Mesozoic metamorphic and <br /> igneous rocks The shallow subsurface geology in the site vicinity is a heterogeneous mix of <br /> gravel, sand, silt, and clay(Reference, Site Characterization Report, Twining Laboratories, <br /> October 16, 1996) <br /> BEII encountered predominantly heterogeneous sands with clay from 0' to 40' bg during <br /> well advancement of MW-14 (See Appendix A for boring log) <br /> S.V 13` <br /> First subsurface water was encountered at depths from 1x'to;Z bg during tank removal <br /> and monitoring well installation at this site in 1995 and 1996ce then, shallow subsurface <br /> water has been encountered beneath the site between 6' an( Dg The most recent data <br /> collected in June of 2003 identified the flow of groundwater in a generally western direction / <br /> r <br />