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<br />• 15 SEDCAD+ design information shop+~s the 10-year storm event passing through the <br />,/ emergency spillway for pond 4-1. Please review and correct. <br />6r Response -Emergency spillway for Pond 4-1 has been redesigned and new Sedcad printouts are <br />attached. Figure Ex. 15-14 has been revised to show correct information <br />IVY 16 For pond 4-1, figure EX. 15-14 indicates an elevation of 6701.5 feet for the lowest set of <br />holes but the SEDCAD+ run reflects 6700.5 as the lowest set of holes. Please review and correct. <br />Or ¢5r Response -Figure Ex. 15-14 has been revised to show the correct information. <br />17 For pond 8-l, figure EX. ] 5-14 indicates an elevation of 6685 feet for the lowest set of holes <br />Ivy ~ but the SEDCAD+ run reflects 6686 as the lowest set of holes. Please review and correct. <br />ti ~r <br />Q~' Response -Pond 8-1 has been redesigned to take some of the flow to 8-2. New Sedcad <br />printouts are attached. Figure Ex 15-14 has been revised to show correct information. <br />]8 Concrete ditch lining is proposed for ditch WS-6 in EX.15-15, Ditch Summary. Rule <br />05.3(3) only allows concrete when approved by the Division to prevent seepage or provide <br />stability. The Division would not approve of the use of concrete for this ditch or + <br />any other ditch on the site unless extremely unusual circumstances aze explained. <br />Please propose the use of riprap or another armoring alternative. <br />•~~ Response -The design is for concrete rubble, not concrete. <br />D <br />a~ <br />~~1` <br />l9. An un-named ditch diverts upland flows below life-of--mine pond 018 to the south above fill <br />4-3 before tenrtinating in a small arroyo. Please provide designs or identify which designs apply <br />to this ditch. The map should also be revised to identify this ditch by name. Is a culvert required <br />under the existing road for this diverted flow. Please provide information as necessary. <br />Response -Design information is attached. The ditch has been identified as "unnamed ditch" on <br />the Surface Water Management Plan, and a culvert has been designed as shown on Map 2.05.3-3 <br />and in Exhibit 14. ~ , ~.! ~c 127~c~ C G <br />.~.w ~~ <br />\_o <br />20 Please provide an explanation as to why some ditches associated with fills are designed using <br />a 100-yeaz storm event while others use a 10-year storm event in the design. <br />Response - 100-yeaz ditches will remain to divert water to natural drainages after operations <br />close. 10-year ditches are temporary, and will be removed or abandoned after mining operations <br />end. <br />21. Drainage ditches handling flow from fill 8-1 were designed using a ]00-yeaz storm event but <br />rainage ditches handling flow from above the fill were designed using a 10-yeaz storm event. <br />r~ <br />f/ <br />