ARCHIVED REPORTS_XR0012741 - Laserfiche WebLink

Home Browse Search

M. 1, €r r\ r CHAPTER 3 HYDROGEOLOGY This section presents the hydrogeology based on Brown and Caldwell ConsuItant's investigation of the site. - Regional Geology ` Lodi is underlain by three major geological units. In descending stratigraphic order they are; (1) unconsolidated alluvial sediments, (2) consolidated nonmarine and marine sedimentary i rocks,and(3)metamorphic and igneous basement rocks. The regional geology was determined from the Department of Water Resources Bulletin 118-6 and the State Geological Map, Sacramento Quadrangle. Alluvial deposits of Quaternary-age immediately underlie Lodi. These formations, which may be up to 500 feet in thickness, are made up of layers of sand, silt, and clay, with --_ interfingered ancient stream channel deposits of sand and gravel. Permeability is variable except in the ancient buried stream channels where it is generally high. These unconsolidated deposits contain fresh water. j Underlying these formations are Late Eocene through Pliocene-Pleistocene-age,alluvial,and lacustrine deposits up to 1,620 feet in thickness. With the exception of the Eocene-age formations,these formations are generally freshwater-bearing. Underlying the nonmarine sequence are consolidated marine racks of Cretaceous and Early Tertiary-age. These rocks generally do not contain fresh water. Beneath the marine rocks are metamorphic and igneous basement rocks. These rocks y' contain small localized quantities of saline water. Regional Groundwater Flow The Quaternary-age and Plio-Pieistocene-age sedimentary deposits supply groundwater for the Lodi area. Recharge to the regional groundwater systam occurs by deep percolation of rainfall and appLed irrigation water, by percolation of the Mokelumne River,and by subsurface from the east.--Re Regional 8t groundwatcrmovemeni is generally..thought ro be to the:west and z {