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I <br />I <br />I <br />D <br />I <br />o Existing Foundation Conditions <br />- The foundation soils beneath the dam are <br />alluvial and consist of heterogeneous mater- <br />ials. Zones or layers of high permeability (5 <br />X 10-4 cm/sec) consisting of clean sands and <br />open work gravels layered with less permeable <br />materials occur in the alluvial soils. <br />Interconnection of the high permeability <br />layers is probable. The embankment cutoff <br />does not fully penetrate the soils in all <br />locations beneath the dam. <br />- The thickness of the foundation soils varies <br />and is thickest (36 feett) near the, center of <br />the valley. <br />- The rock beneath the alluvial soils is <br />severely weathered and fractured In the top 7 <br />to -47 feet and exhibits high permeability (5 x <br />10 cm/sec.) <br />- The rock increases in integrity with depth <br />becoming tighter (i.e., lower permeability) <br />than the overlying rock. A fault may exist in <br />the rock along the east side of the structure, <br />and the fault could penetrate the more <br />competent rock. <br />o Seepage and Flow Paths <br />- Flow is occurring from the pond through three <br />primary interconnected, systems as follows: <br />1) Horizontally through the embankment <br />shells, with a steep vertical gradient <br />through the inner section of the dam, into <br />the high permeability foundation materials <br />downstream of the embankment cutoff. <br />2) Vertically through the pond bottom and <br />embankment shells and horizontally through <br />the alluvial soils, passing beneath the <br />embankment cutoff where the cutoff does <br />not fully penetrate the foundation soils. <br />3) Vertically through the alluvial soils in <br />the pond bottom beneath the upstream shell <br />of the dam and horizontally through the <br />fractured bedrock. <br />" <br />1-4 <br />