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1 3-7 <br />The second and third flow systems, as presented above, are similar to <br />to <br />those discussed in D'Appolonia (1981b) report on seepage. Continued <br />readings of piezometers and observed seepage conditions provide no <br />additional evidence to modify these conditions. The condition in the <br />core of the dam further supports this assessment. <br />The high permeability and open work gravels in the dam foundation may be <br />the result of natural deposits, but could also have been aggravated by <br />transport of fines to downstream areas. Several seep locations have <br />flowed freely for some time. Small amounts of soil could have been <br />Flow through foundation materials is primarily horizontal with some <br />vertical flow. Upstream and perhaps immediately downstream of the <br />cutoff, the flow is downward through the pond bottom and/or the alluvial <br />soils into the bedrock. Downstream of the dam toe, the flow is upward <br />from the bedrock through the alluvial soils. As 'long as the upward <br />pressure is less than the weight of the alluvial soils, the upward flow <br />(1 <br />ww <br />does not cause quick conditions in the soil, but can cause seepage and <br />wetness at the surface. The general wetness downstream of the dam is <br />caused by this mechanism. Where the soil can no longer resist this <br />pressure, a quick condition or boil may result as was noted in December <br />1982. Relief of the pressure or increasing the downward soil weight can <br />prevent this situation from occurring. <br />Seepage <br />occurring through the foundation apparently does not seek the <br />blanket drain beneath the downstream shell of the dam since no flow has <br />been observed exiting from the drain. This may be the result of <br />isolation of the drain from the foundation seepage paths by a low <br />permeability zone in the alluvium, or it may be caused by the foundation <br />materials having a higher permeability than the drain. The low head <br />loss in the foundation from the area downstream of the cutoff to the toe <br />area indicates that high permeability in the foundation may be the <br />principal cause of this condition. <br />The high permeability and open work gravels in the dam foundation may be <br />the result of natural deposits, but could also have been aggravated by <br />transport of fines to downstream areas. Several seep locations have <br />flowed freely for some time. Small amounts of soil could have been <br />