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Administrative Draft Environmental Impact Report Gill Medical Center Project below, water years are designated by the year in which they end. For example, the 2015 water year began on October 1, 2014 and ended on September 30, 2015. The average annual rainfall from 1926 to 2017 is 15.00 inches. The wettest year on record was 1983, with 30.34 inches of rain. The driest year on record was 1977, with 6.46 inches of rain. 4.12.1.2 Surface Water The Project site is located at the northern end of the San Joaquin Valley and east of the Sacramento-San Joaquin Delta. The closest waterways and sloughs associated with the Delta are approximately five miles to the west. Bear Creek is approximately three-quarters of a mile to the south while the Mokelumne River is approximately six miles north, running along the north side of the City of Lodi.The Woodbridge Irrigation District canal is located along the north side of the Project site. There are no municipal storm sewers in the Project vicinity. Due to the very flat surface topography, stormwater runoff moves by sheet flow toward surrounding roadways, where it is typically conveyed in shallow ditches to the nearest canal or creek. Figure 4.12-1 shows the FEMA floodplain map for the Project vicinity. The site is located within an area with a 0.2 percent annual chance flood hazard (i.e., a 500-year flood hazard zone) that also has the potential of inundation with an average depth of less than one foot during a 1-percent annual chance flood event (i.e., a 100-year flood).The site is not within a regulatory floodway. 4.12.1.3 Groundwater The Project site is located within the Eastern San Joaquin Subbasin within the larger San Joaquin Valley Groundwater Basin. The Eastern San Joaquin Subbasin is designated as basin number 5-022.01 by the DWR (2006). The subbasin area is shown on Figure 4.12-2. The basin encompasses most of San Joaquin County east of the San Joaquin River and Sacramento-San Joaquin Delta, with an area of approximately 1,195 square miles (ESLGA 2019), or approximately 765,000 acres. The Eastern San Joaquin Subbasin consists of one principal aquifer that provides water for domestic, irrigation, and municipal water supply. The principal aquifer is composed of three water production zones: Shallow Zone that consists of the alluvial sands and gravels of the Modesto, Riverbank, and Upper Turlock Lake formations; Intermediate Zone that consists of the Lower Turlock Lake and Laguna formations; and Deep Zone that consists of the consolidated sands and gravels of the Mehrten Formation. In the Project area, the base of the Shallow Zone is approximately 300 feet below ground surface (ft bgs) while the base of the Deep Zone is at least 1,000 ft bgs (ESJGA 2019). Aquifer transmissivities range from 90,000 gallons per day per foot (gpd/ft) in the Shallow Zone to 59,500 gpd/ft in the Intermediate Zone, to 250,000 gpd/ft in the Deep Zone. Hydrology and Water Quality 4.12-2 October 2021