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<br />Ty <br />12/20/79 Memo, p. 2, #1 <br />"1. In Eckman Park, temporary ditches are proposed to <br />divert runoff around the active pit. The construction <br />and operation of the ditches is unclear. How far in <br />advance of the pit would the ditches be constructed? <br />What spacing between ditches? Would the ditches be <br />located in areas still undisturbed or would they be <br />constructed in areas stripped of topsoil?" <br />See p. 816-29(a) <br />12/20/79 Memo, p. 2, #2 <br />"2. Clarify ditch sizing. According to "Design Charts <br />for Open-Channel Flow", cited as a ditch sizing reference, <br />the lower chart (Retardance-C) should be used to compute <br />channel volume (pg. 39). For example: Ditch C1- <br />Q=15cfs, slope = 38 should have a depth of 0.82 feet <br />instead of the 0.75ft as computed on the upper curve <br />(Retardance-D)." <br />Ditches were resized in accordance to the instructions <br />given in the reference. Plate I, Sedimentation <br />Ponds, Energy Mines No. 1 and 2, and Eckman Park <br />found in Exhibit 13, has been revised accordingly. <br />Ditch depths were increased from 0 to 0.3 feet. <br />Backup calculations have been added as a Supplement <br />to Appendix B of Exhibit 13 in the "Ditches" <br />section. <br />See also p. 780-151(a)-(e) <br />12/20/79 Memo, p. 2, last paragraph: <br />"The application refers to check dams, gravel dams, and <br />other types of secondary sediment control that might be <br />used within the mine plan area. Before such sediment <br />control is emplaced, design specifications, and an oper- <br />ation and maintenance plan should be submitted to the <br />Division for approval as a TR." <br />See p. 780-151(a) <br />