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. Ms Margaret Lagroto August 11,2004 Subsurface Assessment Report Protect No 2033-15600-01 Joe's Truck Plaza, 15600 South Harlan Road,Lathrop,CA Page 9 SUMMARY The following summarizes the findings of the investigation • Borings CPT-1 through CPT-8 were advanced to depths of approximately 80 to 100 feet bgs Soil and depth-discrete water samples were collected from each of these borings • Boring MW-7 was advanced to a depth of approximately 19 feet bgs using 10-inch diameter hollow stem augers The boring was converted to a 4-inch diameter groundwater monitoring well (MW-7) • The CPT borings encountered primarily fine-grained material (predominantly silty clay, clayey silt, and clay, with minor amounts of silt, sandy silt, and material classified by CPT as "stiff fine grained") to the total depth explored Three laterally extensive sand strata (identified as Sand A, Sand B, and Sand C) were encountered within this fine-grained unit, along with several thin, laterally restricted sand bodies Sands A, B, and C do not appear to be stratigraphically connected • Sand A is encountered at approximately 5 to 8 feet bgs, and is approximately 3 to 10 feet thick Sand B is encountered at depths between 25 and 35 feet bgs, and is approximately 7 to 18 feet thick Sand C is encountered at depths between 50 and 65 feet bgs This stratum is approximately 15 to greater than 25 feet thick • Based on PPDT's conducted during the investigation at depths between 22 5 and 915 feet bgs, the calculated water table (phreatic surface) ranged from 7 73 to 15 64 feet bgs (Table 3) Depth to water in well MW-7 was measured at 8 89 feet bgs • The lateral and vertical extent of impact to soil and groundwater beneath the site appears to be adequately characterized SCM UPDATE Based on data gathered during this investigation, the stratigraphzc and lrthologic conditions beneath the site appear to be adequately characterized Three laterally continuous sandy strata, separated by strata of silt and clay, were encountered to depths up to 100 feet bgs The three mayor sand strata identified during this investigation do not appear to be stratigraphically connected Further characterization of the subsurface lithologic and stratigraphic conditions does not appear warranted The vertical extent of MTBE impact in soil was adequately characterized by this �i investigation, and extends to a maximum depth of approximately 25 feet bgs to the P Voe's Truck P1aza\RcportslCPT report 08-2004 doc