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W--,- .14 September-1.998 AGE-NC Project No. 98-0440 Page'2 of 9 r. concentration of 1-,200 arts per billion re orted'as micro ams per kilogram' bin a soil�sam le' p p { p ! P pp ) P collected from the east portion of the UST removal excavation.,The'laboratory,detected totals:. ' etroleum h di'acarbons` ` uaritified as asoline,' TPH- at concentrations Fran in as high as ` p Y q g {- g) g g g 1,700;000 ppb.�The laboratory detected BTEX at concentrations ranging.as high as 370,000 ppb; greatest benzene concentration was 12,000 Ppb. The highest. and BTEX concentrations were . • `detected in the samples collected from the east portion of the UST removal excavation: y , 2.J REGIONAL GEOLOGIC SETTING' According•to Geologic Map of California (1966, California Department of Conservation Division of Mines and Geology),'the site area is within the Great Valley. Geomorphic.Province (GVGP) of t :' California,a Iarge;elongate, northvves't trending structural trough.'The GVGP is subdivided into two major divisions designated the'Sacramento and S.an Joaquin.Valleys, which have been filled to the present elevation with thick sequences'of sedirtient ranging'in age from.Jurassic to present day, creating a nearly flat-lying alluvial plain extending,from the Tehachapi Mountains in the south to the Klamath Mountains in the north. 'The'.western=and eastern boundaries of this province'are icomprised,of the California Coast Range and the Sierra Nevada, respectively. Based on .General Soil Map (1992, United States Department of Agriculture Soil Conservation Service) obtained from the-San Joaquin.County Soil Survey, the'site area i,s shown,as being within',; the Capay-Stomar-Zacharias(CSZ)soil association.The CSZ soils are located on i.nterfan basins and on alluvial fans and stream'terraces in,the southwestern partof'San Joaquin' County. The,.soils genemlly..consist of moderate.to well'drained, fmne'textured soils.The CSZisoils generally formed , in.alluvium derived from sediinen'tary and mixed rock sources. I GROUND WATER DEPTH AND'GRADIENT ;. ,I Based on information from the Lines,OfEqual Elevation.Of-Water In' Wells : Unconined•Aquifer Spring 1993;' published by the California Department of Water Resources,the;estimated ground water elevation 'at..the site is,approximately 50 feet above sea level. Based 'on',an approximate ' , �•. elevation of 35',feet'above sea level; the depth to,ground water at the`site is as's'un ed,to,be 15 feet below surface,grade.(bsg).The regional'ground wate'r'•flovi direction near the site'area is generally toward the north,'although flow directmons may vary;to cally..and,,seasona y Advanced GroEnvironiaental,Inc. ,