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Preacquisition Environmental Site Assessment March 17, 1992 Anheuser-Busch, Arch Road, Stockton, Cal'rfomia 2 2.1 Topography/Surface Drainage The site elevation lies between approximately 30 and 35 feet above mean sea level. The local topography gently slopes to the east at 0.002 ft/ft. The nearest body of surface water is North Little Johns Creek, approximately 1,500 feet north of the site (Figure 1). Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps show that the site and surrounding land is zoned AO, which are areas where 100-year shallow flooding depths are between 1 and 3 feet. A copy of the current FEMA Flood Insurance Rate Map was not available at the time of submittal of this report. The stormwater drainage system for Arch Road Business Park directs overflow to a stormwater retention basin at the northwest corner of Gold River Lane and Arkansas Place. Water that accumulated in the retention basin is pumped into North Little Johns Creek, an intermittent stream. 2.2 Geology/Hydrogeology Arch Road Business Park is located in the San Joaquin Valley of California. The San Joaquin Valley is part of the Central Valley, which is a large, asymmetric, northwest-trending trough that has been filled with up to 6 vertical miles of sediment. Overall groundwater movement in the Central Valley is from the foothills toward the valley axis and then toward the delta. Secondary structures in the valley, such as subsurface features and faults, also influence the occurrence and movement of groundwater (Page, 1986). San Joaquin County Flood Control and Water Conservation District maps (Spring 1991) indicate that local groundwater flow is to.the north-northeast and that the depth to groundwater is between 70 and 80 feet below grade. The site vicinity is not located in an aquifer recharge area (Environmental Impact Report 75-5). The uppermost geologic units in the subject area to consist of Holocene flood-plain deposits of clay, silt, and sand (Page, 1986, Geologic Map of the San Joaquin Valley, California). These unconsolidated flood-plain deposits are estimated to be up to 160 feet thick, and tend to impede vertical movement of water and restrict yields to wells. _— — !'GROUNDWATER __.,TECHNOLOGY, INC.