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r , <br /> 1 <br /> N <br /> i <br /> 1 1 <br /> . 05 September 2000 <br /> AGE-NC Project No 99-0555 <br />' Page 2 of 5 <br />' beneath the eastern end of the center UST location Volatile aromatics - benzene, toluene, ethyl <br /> benzene and xylenes (BTEX) were detected at concentrations as high as 170 mg/kg from the same <br /> sample location I , <br />' Approximately 150 cubic yards of soil were excavated during removal of the USTs The excavated <br /> soil,was stockpiled on site <br /> 2 3 REGIONAL GEOLOGIC CONDITIONS <br /> I ' 1 <br /> The site is situated within the Great Valley Geomorphic Province of California, a large, elongate <br /> northwest tending, asymmetric structural trough The Great Valley Province has been filled with <br />' thick sequences of sediment ranging in age from Jurassic to Recent, creating a nearly flat lying <br /> alluvial plain, which extends,from the Tehachapi Mountains in the south to the Klamath Mountains <br />' in the north The western and eastern boundaries of this province are comprised of the California <br /> Coast Range and the Sierra Nevada., respectively Rocks composing the basement complex of the <br /> province have not been completely defined but are believed to be of metamorphic and igneous <br />' ongin The Great Valley Province has been subdivided into two major divisions identified as the <br /> Sacramento and San Joaquin Valleys <br />' The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the <br /> principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground <br /> Water Basin (Basin 5-22) This basin is drained primarily by the San Joaquin River <br /> 24 SITE HYDROGEOLOGIC CONDITIONS <br />' The closest surface water features to the site are San.'Joaquin River and Walker Slough located <br /> approximately 4,500 feet southwest of the site Water from the site drains into the San Joaquin River <br />' Deep Water Channel which is primarily used for commercial and recreational boating Based upon <br /> well information obtained from nearby sites, ground water flow direction is northeasterly and is <br /> currently estimated to occur at a depth of approximately 20 feet below surface grade (bsg) <br /> I , <br /> 3.0. PROCEDURES <br /> 4 <br /> All field procedures were overseen by an AGE representative under the supervision of a California <br />' Registered Geologist Procedures for soil excavation,soil sampling, and equipment decontamination <br /> • are outlined below <br /> 4 ' I <br />