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Analyses of soil and ground water samples collected from the tank <br /> excavation after removal activities indicated that gasoline and gasoline <br /> components were present in site soils <br />' Site Characterization <br /> Soil and ground water investigations were performed by Kleinfelder, <br /> Inc , in March 1990 and by ERM in March 1991 Kleinfeider conducted a <br /> soil gas survey, installed three shallow soil borings, and installed three <br /> monitoring wells (MW-1 through MW-3, Figure 3-1) ERM <br /> subsequently installed two additional monitoring wells at the site <br /> (MW-4 and MW-5, Figure 3-1) <br /> The extent of hydrocarbon release to soil was estimated based on the <br /> results of investigations at Former Tank Site #1 The lateral and <br /> vertical extent of total petroleum hydrocarbons (TPH) and benzene, <br /> ' toluene, ethylene, and xylene (BTEX) in soil at Former Tank Site #1 <br /> was limited to a localized area in the vicinity of the former UST, in a <br /> zone between approximately b and 11 feet bgs Based on data obtained <br /> ' during the investigation, the volume of soils containing TPH as <br /> gasoline in excess of the 100 mg/kg cleanup goal for TPH at Former <br /> Tank Site #1 was estimated to be approximately 200 to 300 cubic yards <br /> The extent of TPH and BTEX in ground water also appeared to be <br /> limited to a localized area in the vicinity of the former tank <br /> ' _Excavation <br /> Soil excavation activities were conducted in October 1993 by ERM and <br /> Sunriver Engineering & Construction, Inc , of Brentwood, California <br /> A state-certified mobile laboratory, Transglobal Environmental <br /> ' Geochemistry (TEG) of Sacramento, California, was used to perform <br /> on-site analysis of soil samples for the chemical analysis Excavation <br /> and confirmation sampling activities were summarized in a letter <br /> ' report submitted to PHS/EHD on March 2, 1994 <br /> Soil excavation activities at Former Tank Site #1 were initiated on <br /> October 15, 1993 The excavation extended to a depth of approximately <br /> 9 feet with areal dimensions of 25 feet in length and 20 feet in width <br /> (including side slope dimensions) For excavation near the building, <br /> ' �`• " shoring equipment was used to support the building structure <br /> Ground water seepage was encountered at excavation depths below <br /> 7 feet Soil excavation proceeded until mobile laboratory analytical <br /> results indicated that the cleanup goal (100 mg/kg for TPH) was <br /> attained at the excavation sidewalls and bottom or until building <br /> structures prevented further excavation <br /> 3-2 <br />