Laserfiche WebLink
<br />7- ( ~ <br />,.} <br />2.05.3 (4) (a) 3'yy`~ / Y/ ~ <br />v '~ <br />required to store 26.1 gpm for 24 hours is 0.12 a.f. The new <br />design size of the pond is 2.38 a.f. for water storage or 0.22 <br />a.f. short. <br />G L The sediment volume was found to be 0.9 a.f. compared to <br />yy~the design of 1.38 a.f. for a three-year storage volume. Mine <br />~~Iwater is primarily settled underground; therefore, no additional <br />sediment volume is being designed for mine discharge. Rule <br />y~ 4.05.6(3)(b) does not require a three-year storage volume; <br />~P <br />therefore, the sediement volume will not be changed. The ea~ima^~ <br />d, ~ <br />_~ <br />~5~~` will be cleaned out upon reaching 608 of the available volume. ~ <br />"a^~ <br />~,y(Le,Ue.~ Map 2.05.3(4)-2a shows the proposed cut and fill to be <br />~'~ used to expand the capacity of the pond to the design size. Tfie <br />extension will leave 2h:ly slopes in the cut area and 3h:ly on the <br />fill slope. Both the cut and the fill are consistent with the <br />proposed D-seam Portal cut and fill projections. Minor changes <br />will be made in ditches 9 and 16, Map 2.05.3(4)-2, to route <br />runoff into the pond. A ditch will be established along the <br />access ramp used to extend the pond. The peak flow for this <br />ditch, 43.6 cfs, was taken from Table'2 of Figure 2.05.3(4)(a)-1 <br />of the permit application. Using a ditch four feet wide at the <br />base and having 3h:ly side slopes requires a water depth of <br />10". The velocity of the water would be 8.1 fps; therefore, <br />requiring rip-rap. A rip-rap size .of 8" or greater was calcu- <br />lated using the formula: <br />D50 = r V x S 0. 172 <br />Il 7.58 <br />D50 = rock size in feet <br />V = velocity <br />S = Slope <br />REVISED August 21, 1984 <br />96b <br />