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1 <br /> <br /> <br />-a- <br />6. The riprap-lined channel that leads to the South Pit is to built on <br />slopes exceeding 30X. Flow velocities may exceed 18 ft/sec. In order <br />to assure that the channel will be stable, the designs should address <br />riprap gradation and the need for a filter blanket. <br />7. Many ditches were designed assuming vegetative conditions. However, <br />initially there will be no vegetation and excessive flow velocities may <br />scour the channel and prohibit vegetation establishment. The amendment <br />should address the problem of channel scouring during unvegetated <br />conditions. The magnitude of the problem and mitigation should be <br />discussed. <br />B. The South Pit lake will utilize a V-notch weir spillway. This pit may <br />receive floating debris such as fallen timber. The amendment should <br />address the need to install a trash rack that will leave the spillway <br />functional. <br />9. Sediment loads and erosion control practices for the dumps and reclaimed <br />pit area were not addressed in enough detail. The amendment should <br />quantify erosion rates off of dumps and reclaimed areas. This could be <br />done by picking a worst-case slope and slope length. The amendment <br />should specify what erosion control measures are necessary to minimize <br />rill and gulley formation and insure vegetative growth. <br />10. Drainage designs should specify how runoff from the dump terraces (i.e <br />Tie Camp, Indian Creek) will be safely routed to the base of the pile <br />without causing undue erosion of the shoulders of the pile. <br />/cd <br />cc: Ed Bischoff <br />Ooc. 0258E <br />