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, , 28 February 1997 , AGE-NC Project No 95-0144 ` Page 2 of 20 y r4 Hydrocarbon-impacted soil was encountered in each excavation Due to the presence of hydrocarbons and the shallow depth to ground water, further assessment investigation was required by the PHS-EHD The former UST locations are illustrated on Figure 2 ' I k 23 REGIONAL GEOLOGICAL/HYDROGEOLOGICAL SETTING 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 s ' 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 metanldrphic 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 -24 LOCAL GROUND WATER SET PING 1 The closest surface water feature to the site is the Stockton Deep Water Channel {McLeod Lake} located approximately 400 feet southeast of the site Water from the Deep Water Channel is primarily used for commeicial and recreational boating Ground water is currently encountered at a depth of approximately 17 feet below surface grade (bsg) at the site, and has a northerly flow ' direction, away from the deep water channel Since the Deep Water Channel is up-gradient with respect to the,ground water flow direction, impacted water at the site does not pose a threat to 1 beneficial use of the Deep Water Channel Ground water occurs in a generally sandy layer extending from approximately 20 feet bsg to 36 feet bsg'The sedimentary,units are relatively horizontal and ' continuous over the site Recent depth to ground water information is summarized on Table 4 25 MUNICIPAL WELL SURVEY Drinking water near the site is supplied by the City of Stockton municipal wells California Water Service Company(Cal Water) maintains a municipal well and tank approximately 1,700 feet west j of the `site at Lindsey Street and Edison Street No other municipal wells maintained by the City of 1 , t `E