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Analyses of sod 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 /> 23 SITE CHARACTERIZATION <br /> 1 Soil and ground water investigations were performed by Kleinfelder, Inc , <br /> in March 1990 and by ERM in March 1991 Kleinfelder conducted a soil <br /> gas survey, installed three shallow soil borings, and installed three <br /> monitoring wells (MW-1 through MW-3) ERM subsequently installed <br />' two additional monitoring wells at the site (MW-4 and MW-5) <br /> The extent of hydrocarbon release to soil was estimated based on the <br />' results of investigations at Former Tank Site #1, and was summarized in <br /> the Preliminanj Assessment Report for Former Storage Tanks Located at 1325, <br /> .1541, & 1515 West Weber Avenue - Stockton, California (ERM, May 1993, <br />' hereinafter "PAR") The lateral and vertical extent TPH and benzene, <br /> toluene, ethylene, and xylene (BTEX) in soil at Former Tank Site #1 was <br /> limited to a localized area in the vicinity of the former UST, in a zone <br />' between approximately 6 and 11 feet bgs Based on data obtained during <br /> the investigation, the volume of soils containing TPH as gasoline in excess <br /> of the 100 milligrams per kilogram (mg/kg) cleanup goal for TPH at <br /> Former Tank Site #1 was estimated to be approximately 200 to 300 cubic <br /> yards 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 /> 2.4 EXCAVATION <br />' Soil excavation activities were conducted in October 1993 by ERM and <br /> Sunriver Engineering & Construction, Inc , of Brentwood, California A <br /> state-certified mobile laboratory, Transglobal Environmental <br />' Geochemistry (TEG) of Sacramento, California, was used to perform on- <br /> site analysis of soil samples for the chemical analysis Excavation and <br /> confirmation sampling activities were summarized in a letter report <br />' submitted to PHS/EHD on 2 March 1994 <br /> Soil excavation activities at Former Tank Site #1 were initiated on <br /> 15 October 1993 The excavation extended to a depth of approximately <br /> 9 feet with areal dimensions of 25 feet in Iength 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 Ground <br /> water seepage was encountered at excavation depths below 7 feet Soil <br /> excavation proceeded until mobile laboratory analytical results indicated <br />' ERM 9 CATELLUS/2996 10-10/13/99 <br />