SITE INFORMATION AND CORRESPONDENCE_1987-1992

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L� LEEDSHILL•HENKENHOFF. INC. CHAPTER 2 BACKGROUND DATA 2.1 Introduction Prior to initiating the field work portion of this investigation, LH con- ducted a search for information pertaining to groundwater conditions at the Lincoln Village Center (LVC) site and adjacent areas. Specifically, infor- mation regarding wells located within a mile of LVC, previous site investi - gations, previous hydrogeological studies near LVC, local water quality, general groundwater direction and elevations, and previous site mitigation measures were gathered. Data was collected from San Joaquin County Flood Control and Water Conservation District, California Department of Health Services (DOHS, Stockton) , City of Stockton (City) , San Joaquin County Public Works (SJCPW), California Water Service (CWS) , the Central Valley Regional Water Quality Control Board (RWQCB) , and the Environmental Health Division of the San Joaquin Local Health District (Environmental Health) . 1 2.2 Historic Groundwater Direction ' The general direction of groundwater flow around Stockton is governed by the ' quantity and location of existing groundwater pumpage. Lincoln Village Center is generally located within one of several pumping depressions lo- cated around Stockton. A review of groundwater contour maps prepared by the San Joaquin County Flood Control and Water Conservation District, entitled, "Lines of Equal Elevation of Water in Wells" show the groundwater gradient under LVC to be essentially flat (no slope) from 1980 to 1985. From 1985 to ' 1987 the groundwater gradient apparently shifts slightly to a northerly direction, as indicated on the contour maps. Figure 2.1 presents San Joaquin County's Spring 1987 "Lines of Equal Elevation of Water in Wells," ' as measured in wells tapping both the unconfined and semi-confined aquifer. ' 2-1 1