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• 2.05.3(4)(a)(ii) <br />(ii) Detailed Design Plan <br />The configuration of the mine site will change significantly during <br />the reclamation process. Culverts and ditches which were designed <br />to facilitate mining activities around the site are no longer <br />required. Roads and benches which previously served as drainage <br />breaks will be obliterated. An open drainage channel is designed <br />to cross the site from north to south to convey drainage from <br />undisturbed areas above the site to undisturbed areas below the <br />site. <br />The objective of the post reclamation drainage design was to min- <br />imize or eliminate all ditches and culverts if possible. Since the <br />run-off characteristics of the soil on site change after <br />reclamation, it is feasible to revise the drainage system yet not <br />have to revise the size of the sediment pond or its spillway. <br />A new drawing titled Post Reclamation Drainage System Map, Map No. <br />2.05.3(4)-2(a), has been prepared to show the current plan for <br />drainage and sedimentation control after the earthwork portion of <br />reclamation has been completed and the area has been seeded and <br />mulched. This drawing shows the location and typical sections of <br />the main drainage channel, upper diversion ditch, lower catch ditch <br />and the culvert which crosses under the main drainage channel. The <br />• drainage areas shown on this map are the same areas which were used <br />for the original design calculations during 1980, see Figure <br />2.05.3(4)(a)-1. These areas were checked and found to be accurate. <br />Table 2.05.3(4)(d)-1 summarizes the acreages which contribute run- <br />off to the sedimentation pond. A total of 43.437 acres will drain <br />to the existing pond. Tables 2.05.3(4) (d)-2 & 3 show the same <br />acreages but are split into the areas east and west of the main <br />drainage channel. Table 2.05.3(4)(d)-4 shows the peak flow <br />calculations for the two ditches, one culvert and the pond <br />spillway. The lower catch ditch controls the run-off contributed <br />by the No. 1 east area. The culvert must pass the flow from both <br />the No. 1 6 No. 2 east areas. Table 2.05.3(4)(d)-5 shows the <br />calculations performed to determine the required sedimentation pond <br />capacity. <br />Tables 2.05.3(4)(d)-9 though 12 present the design of the upper <br />diversion ditch for the refuse pile. This diversion ditch is <br />designed to safely divert the surface runoff from a 100-year 24- <br />hour precipitation event away from the refuse pile. <br /> <br />-98- Revised January 14, 1994 <br />