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29 January 1999 AGE-NC Project No. 98-0536 Page 2 of 5 ethyl benzene, xylenes, tertiary amyl methyl ether (TAME) and tertiary butyl alcohol (TBA) were also detected in soil samples collected. 2.3. SITE HYDROGEOLOGIC CONDITIONS The closest surface water feature to the site is Mormon Slough, located approximately 1000 feet north of the site. Water from Mormon Slough drains into the Stockton Deep Water Channel and is primarily used for commercial and recreational boating. Based upon well information obtained from San Joaquin Flood Control And Water Conservation District (Lines of Equal Elevation to Groundwater Spring 1996), ground water flow direction is southeast and is currently estimated to occur at a depth of approximately 70 feet below surface grade (bsg). Ground water occurs in a generally sandy layer extending from approximately 60 feet bsg to 85 feet bsg. The sedimentary units are relatively horizontal and continuous over the area. 2.4. REGIONAL GEOLOGIC CONDITIONS The site is situated within the Great Valley Geomorphic Province of California, a large, elongate northwest tending, asymmetric structural trough. The Great Valley Province has been filled with thick sequences of sediment ranging in age from Jurassic to Recent, creating a nearly flat lying alluvial plain, which extends from the Tehachapi Mountains in the south to the Klamath Mountains in the north. The western and eastern boundaries of this province are comprised of the California Coast Range and the Sierra Nevada, respectively. Rocks composing the basement complex of the province have not been completely defined but are believed to be of metamorphic and igneous origin. The Great Valley Province has been subdivided into two major divisions identified as the Sacramento and San Joaquin Valleys. The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin (Basin 5-22). This basin is drained primarily by the San Joaquin River. 3.0. SCOPE OF WORK Based on the laboratory analysis of soil samples collected during UST removal, hydrocarbon- impacted soil is present at the site in the former UST and dispenser area. Prior to backfilling of hte excavation, AGE proposes to excavate approximately 100 cubic yards (135 tons) of impacted soil from the floor and sidewalls of the present excavation. Upon removal of the impacted soil, soil samples will be collected from the floor and sidewall of the excavation. After completion of the .advanced GeoEnvironmental.Inc.