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' same amcu.^.t of water ~~ then spread over an area 5 to 7 <br />times its present size, the flow rate will decrease by at <br />1 3 tin mh , •„ b..t <br />ens, es. a same vo~ume of warmer w:... be presen, ,. <br />the pit area will act as a retentior. area slowinc_ the <br />associated flow rates. <br />Dcwnstreaa; erosion. scouring and related impa~ts will <br />net occur, as stream flows of the high water channels will <br />be reduced before they leave the pit site. Eastern and <br />ncrthern bank erosion^. vrill also be reduced as a result cf <br />lower flew rates and lowering the flood channels elevations. <br />The outflow of the flood waters will travel over 10C feet cf <br />undisturbed material before discharging Into the Imhoff <br />prcpert•• ir. the same location it now does. <br />Siltation is not a significant prcblem this porticn <br />of the River as the silt content of this baryis <br />~asignificart. A screer. test of the gravel bar content was <br />performed in Aucust, 1~~1. with the following results: <br />Screen Size WeiGht Percent <br />greater than 6" 25.4 <br />6" to 1" 33.0 <br />1" to 5'S" 3 <br />. ~ q <br />5; E" to 1;16" 23.4 <br />less tha^. 1;16" 9.1a <br />Less thaII i0~ Of the material passes `. hrO::Ch a 1:16° SCree::. <br />thus an _nsig:^if,ca: t amo:.n t cf silt-sized material ;1/16 ,,.,., <br />- 200 mess sieve; is present on this site. T::e farce <br />percentage of 6" an3 larger materials contained ~. this bar <br />results very stable banks. This is a'_so why the berms <br />previously constructed on the west bank of the River have <br />withstood mercus flood events. <br />Tc help preJ•ent any permanent river course change, Peel: <br />will leave a berm 10 feet wide and 2 to 5 feet hick unmined <br />ad;acer.t to the eastern edge of the River. This berm will <br />be sloped 3 to 1 towards the pit. See Exhibit E-1 Mir.irc <br />nl ~ thi c ti, t,:.. <br />an for loca.ion an3 ckness o. t..e berms. T....~ berm <br />wall be maintained durinc each year of mining. Peck will <br />reconstruct any berm area which might be destroyed during <br />the previous season's flood prior to mining. With over 250 <br />of the gravel material being over 6" size. the berm will <br />withstand the normal high water staces of the River without <br />substantial erosion. This berm is not designed to prevent <br />flcoding from a 50 year or a 100 year event. Berm design to <br />accomplish this would require much larger and heavier <br />reinforce,:,ents which would be very detrimental to the <br />surrcundirg properties. The Peck Miring Plan intends to <br />allow the River tc flow unimpeded dur~ng flood stage. The <br />cnly purpose of this berm is tc prevent any permanent .fiver <br />ccurse chance. The Peck Mining Plan further intends to keep <br />the River in its present location during and after mining. <br />FLOODI:dG <br />Each year during the spring runoff season portions of <br />the permit area are ir:sndated by spring runoff flood waters <br />from the Uncompahgre River. The amount and extent of <br />n <br />