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Response to Exhibit C. Comment 7 <br />The area west of the Phase I pit will be inundated <br />during a 100-year flood event. The floodplain study shows that <br />the majority of flood waters will be carried by the main <br />(existing) river channel and a normally dry channel to the west. <br />The volume of water sheet-flowing between the channels is <br />estimated to be no more than 400 cfs. Assuming that all of this <br />water spills into the mined out pit along a 50-foot wide stretch <br />of embankment, the flow velocity would be 12.5 feet per second <br />down the side of the pit. This could erode the west bank of the <br />pit. To prevent this from happening, the sheet flow should be <br />contained so that it continues to flow northerly until it is past <br />the limits of the mined out pit. <br />The riprap to be placed along portions of the east and <br />west banks must have a median size of 2 feet. The material <br />shall meet all requirements of Section 506 and Table 506-2 of the <br />State of Colorado, Division of Highways, Standard Specifications <br />for Road and Bridge Construction, 1991. <br />Page 7 <br />