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4 ~....~ "w.»~ a - .~ i ... ` - `.t Preliminary Sediment Transport Study for Challenger Pit No. 1 Introduction Thies report has been prepared for the Challeng Partnership to address concerns voiced by the Mined tion Division with regard to mining along the River and the downstream effects that the proposed of a lake would hove on the river. The Challenge has proposed the creation of a lake approximately through which the river would be routed (See Figure in a letter dated Mey 23, 1985 asked for evidence th would not impact the upstream and downstream po river. The particular phenomenon that is the cause of th sometimes referred to ae "sediment affinity". It la demonstrated by the construction of large dame which allow the sediment being carried by the river into the reservoir. Water that is released down reservoir is clear and has an "affinity" for pi sediment downstream of the channel, which in caa along the Colorado River has caused scouring of the for a distance of up to 20 miles downstream. The cause of this attraction to sediment can explained by the water quality of the river. Thar elements in water that can form an electromechanical themselves and sediment. Thies allows the stream flc terry some sediment. Streams such ea the Colorado hea a high salt content, can transport a high volume Sodium is en element with unpaired electrons that electro-mechanical bond mentioned. Thies attract cohesive soils that have a high silt end clay conten Transport of sediment in coheaionleas soils (san works on a different principle. There ere two me in sediment transport o£ coheaionleaa soils. First load which consists of sediment that is pushed, ro and anltates from one position, if the veloc riverbed is large enough. Second, there is auap which is lifted and carried by the tractive forces The slope of the river channel is an Smportant fact the volume of sediment discharge. Also, a well g which has fewer voids ten have an effect on the charge. Generally, if discharge, channel width, size are held constant, the elope of the rive {actor in determining channel degradation. ~.1.1 ~ ~f ._.- ~' z $ ~9~J + -- - ~~- r Grovel Pit end Reclama- Big Thompson construction Partnership DO feet long ). The MLRD t the mining tiona of the a concern is dramatically cross rivers o settle out trenm of the king up more a documented fiver channel be partially are certain bond between to lift and River, which of sediment. can form the on occurs in and gravel) ode involved there is bed led, or 7umpa ty along the nded sediment f the water. r and affects ceded alluvium sediment dis- end particle is the mayor