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<br />~nl""'" <br />U., ' . <br />Uvl.i <br /> <br />1'- <br /> <br />10 <br /> <br />colJbles and pebbles, ~oth for the pervious portion of tile embankme!lt <br /> <br />and the aggregate for concrete. The presence of fine sand and silt <br /> <br />in this material may be a cause for concern if it is not free-draining. <br /> <br />Coarse material is not available in the iImnediate vicinity of <br /> <br />the d.am site. The use of tl'.ore re::o.ote SOUI:ces of coarse aggregate ,.,ill <br /> <br />depend upon transportation costs and the physical characteristics of <br /> <br />t~e rock, specifically, how they would blend with the pervious materials. <br /> <br />Riprap will have to be shipped in from ~cky Mountain sources <br /> <br />where hard and durable granite is available. <br /> <br />ITEMS TO CONSIDER <br /> <br />1. A three-dimensional mace! should be made to determine the <br /> <br />beneficial effects of a cutot'f '...all acting simultaneously with pre9sure <br /> <br />relief wells. Good computer simulation modeling capability exists for <br /> <br />such studies at several places. <br /> <br />2. A model for stu~ying ~~e local transient effects of inflow <br /> <br />during flood stages would be most helpful in detennining maximum <br /> <br />gradients and the duration of peak gradient conditions. <br /> <br />3. The Pierre Shale varies enormously in physical characteris~ics <br /> <br />from place to place at the d~ site. It has a notorious reputation for <br /> <br />swelling under certain conditions and Slaking when expos~d to air and <br /> <br />water. Field tests at several localities, including pits or trenches, <br /> <br />would provide more data on which to base the design ot various <br /> <br />strUctures. <br /> <br />4. A continuo'U3 seismic profile along th~ d&!\ axi3 defining the <br />