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01 <br /> { <br /> l PRE-TAMC REPLACEMENT Site Assessment Nora; Plan <br /> 420 NEST KETTLEHAN LANE,L00[, CA. <br /> Aegis Project No. 89-013 <br /> Page 9 <br /> w 2.9.1 Mehrten Formation <br /> The Miocene/Pliocene Mehrten Formation is composed of andesitic sand <br /> and sandstone units derived from Sierran andesitic flows and <br /> agglomerates interbedded with conglomerate tufaceous siltstone and <br /> claystone horizons. Beneath the center of the San Joaquin Valley the <br /> upper surface Of the Mehrten Formation is 800 to 1000 feet below the <br /> surface. The formation outcrops along the eastern margins of the . <br /> valley, dips toward the west and is nearly flat lying near the center <br /> of the valley. The unit thickens to 'approximately 600 feet at its <br /> western margin (DWR 1967) . <br /> 2,9.2 Laauna Formation <br /> The Pleistacene Laguna Formation unconformably overlays the Mehrten <br /> Formation. The Laguna Formation consists of heterogeneous fluvial <br /> - continental sediments of non-volcanic sands and <br /> within the Formation is the Arroyo Seco gravels. Included <br /> v <br /> the Mokelumne River consisting of weathered sandaand lcementedoutgravels l <br /> ' The Laguna Formation outcrops along the eastern margins of thevalley' <br /> dips toward the west and is nearly flat lying beneath the center of <br /> the valley. The unit thickens in a westerly direction to a <br /> i� approximately 1000 feet beneath the Lodi area DWR 196 <br /> ,, 2.9.E Victor Formation/Recent A:r� 1um <br /> T_;e Victor Formation/Recent Alluvium occurs near the center of the <br /> valley and is generally coarser grained than the underlying Laguna <br /> Formation.. The formation consists of <br /> heterogeneous deposits of sand <br /> and gravels with discontinuous lenses of silt and clay. .The Formation . <br /> dips gently and thickens to the west. At rn margin the <br /> itis western,..� Formation is approximately 100 feet thick {DWR este , <br /> 1-9-4 Structure <br /> San Joaquin County lies near the northwest trending axis of a`regional <br /> 6' syncline with a gently di - <br /> g Y Aping east. lank and a fairly-nteehly dipping <br /> west flank. Evidence has been . <br /> i- found o g <br /> f extensive nsive <br /> Of the basement rocks andene foldmarine ing and faulting <br /> no evidence of faulting orpfolding sincthe cont <br /> inentalmsedsnentsroflthe <br /> valley except along the western €lank. (DWR 1967) <br /> i.. <br /> 2.20 Fie io al Fi dro solo <br /> fihree-dater=bearing formations have been identified beneath the <br /> subject area including the Mehrten Formation., <br /> the Victor Formation. Ground water occuthe Laguna Formation and <br /> rs in the Mehrten Formation <br /> 1}1 <br /> Li: <br />