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. which are carried into the valley and deposited as asequences of <br /> clay, silt, sand, and gravel formations, predominantly <br /> ursconaolidated. The valley is continually subsiding, allowing the <br /> deposited sediments to build-up and become thicker, with little <br /> affect upon the surface elevations. The final result is a thick <br /> sequence of interbedded sediment* (gravels, sands, edits, and <br /> clays) along with the associated folds and faults. <br /> Clay layers are found throughout the sedimentary section. These <br /> clay layers will tend to slow the downward migration and recharge <br /> of ground water to the underlying formations. The re!-barge of <br /> ground water will be accomplished by downdip flog from the outcrop <br /> areas to the east along the foothills of the Sierra Nevadr, <br /> Mountains, by slog leakage from the overlying clay layers, and <br /> by more rapid movement vertically beyond the limits of the clay <br /> layers. <br /> Ground hater Occurance in The Stockton Area <br /> Ground water production in this region is predominantly from the <br /> sands and gravels associated with the Laguna and Mehrten <br /> formations Which are non-marine (continental) sediment deposits of <br /> Alio-pleistocone age. Underlaying the Kehrten formation: is the <br /> Valley Springs formation which are non-marine (continental) <br /> sediments that unconformally overlie the undifferfntiated marine <br /> Markley-Nortonville formation. <br /> Ground water recharge to the above mentioned formations and to the <br /> younger formations, surface to near surface deposits situated <br /> above them (the Quaternary age Alluvium fan and basin deposits and <br /> the Pleistocene victor formation) , is predominantly vertical <br /> leakage and lateral movement downdip along the less permeable <br /> layers. The Mehrten formation can be found outcropping to the east <br /> of Stockton in the foothills of the Sierra Nevada Mountain Ranges. <br /> Ground water recharge of this formation is predominantly from the <br /> exposures in the foothills with some vertical laakage from the <br /> overlying formations. The Laguna formation, which overlays the <br /> Mehrten formation does not outcrop in the fcott.ilis of this <br /> designated area, but outcrops further north and east of Lodi. <br /> Ground water recharge for the Laguna formaticn is also <br /> predominantly from its exposures in the foothills and seepage from <br /> the Mokelumne and Calaveras Rivers. The overlaying Victor <br /> Formation and Alluvium deposits are recharged from surface <br /> exposures, leakage from the Mokelumne and Calaveras Rivers, and <br /> vertical leakage from the surface Basin and Interfan soil layers <br /> in the area. <br /> The direction of free ground water movement in this region is to <br /> the west and towards south Stockton from the foothills of the <br /> Sierra Nevada Mountain Ranges, and towards the east from the <br /> Sacramento - Ban Joaquin Delta. At present, intrusion of more <br /> saline waters from the Delta are imparing the quality of the <br /> ground water in the Stockton area. <br /> • 10 <br />