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-~ ' ~ -•' <br />~:• . . <br />-, , - <br />.. <br />February ~, 1980 ~~ "'': <br />M _ ~ ~ • ' ~) <br />iR <br />B~HBON NINE . <br />f~~ i~f . 76-6 ' .~: "' <br />RE: Sedt Control ,~; ~ ' may. . <br />.. ~: R <br />~. , <br />' : " ~~ ~` <br />T) .gain sediment pond Clarification is necessary regarding the 1rRation <br />of the storage reservoir and sediment ponds.~he design area submitted by <br />Ute Engineering does not site the dam at' i existing spot. and does not <br />appear to follow nef~2a~ coNto~7c5, PIe submit tilformation detailing <br />ah~re aZZ earthworks asp Siumad and. urea enclosed (the design area in the <br />Ute plan will not accoioii~$'~ et with an eight foot embanlanent <br />unless major excavations eri;led out). Cross=sections of major <br />embankments should be includ' nd that, of the dam across the stream channel <br />should Indicate depth to bedrand demonstYate'that the dam will not be <br />undercut by seepage. Alluvial material. not be suitable for embankments - <br />Please clarify how seepage and stabi~~~~~blems will be dealthwith. <br />Elevation/capacity information ti .a eded foe the reservoir. <br />Stream water above and below the must be mpnitored regulaily (applicant <br />to suggest a schedule), in addition to t;e discharge monit_ring on,Che ponds . <br />specified by the NPDSS permltr. St is nsosasary to.dsapnstrate that a 10-yeas <br />flood on Bubbard Creek t result in dam overtopping. Also, please <br />clarify how water will eleased from 'Che_eorid 5N 2esPo~~stto a downstream <br />call while maintaining quality. <br />Reclamation plan for the pond, includ~g restorat#os of stream channel <br />roughness and gradient, are nagfssar'y. <br />,{.. <br />An alternative would be te:'`~ a small sediment pond close t~o the slope <br />(near the soot marked "found- `to landle runoff frart the bench, and divert <br />only undisturbed Plow into the reservoir. This would obviate the necessity <br />. of striat•design controls on the reservoir. '- <br />II) The mine plan (addendum p. 60) ice' thet twq spillways will be built <br />in the ponds, but the two are stated ~ be one and the same in the Ute <br />submission (sheet 7). Please clarify. <br />III) The calculations for peak flow were ev_~~]sntly made wsrongly assuming <br />unifgrm distribution of rainfall over 24 hours, leading to underwatering <br />flows by as much as an order of magnitude. Diveraign ditches and overflow <br />weizs should be recalculated and betmi;,~saanstz~efer~~to be able to divert <br />the flows. The culvert may need to bG~eRlzed. <br />,' <br />IF) The spillwiny draining the mine shelf should be. redesigned. <br /> <br />:. ~- <br />_ . iE'~ ~. <br />