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• <br />A diversion will be constructed above existing cAr3ima.+t Pond 008 located <br />in the NW; of Section 7, Tamship 5 North, Range 86 West. The purpose of <br />this structure is to intercept surface water runoff so as to divert the <br />flow to Sediment Pond 008. The runoff will then be treated by Pond 008 <br />prior to release through Pond 008's NPDFS discharge point. This system <br />will eliminate the need to construct a sedimentation pond near the center <br />of Section 6. The following design discusses the approved diversion ditch <br />and the redesign of Pond 008 spillways. Investigations show that Pond 008 <br />can handle the additional ~>>++P*'t load and surface water runoff with <br />modifications to the spillways. Peabody proposes to construct a <br />trapezoidal emen7ency spillway to comply with the current Q4L~RD <br />regulations. <br />SITE DFSCCRIP'i'ION <br />• Sediment Pond 008 has a 340.9-acre watershed. The pond previously treated <br />surface water from a 290.44-acre watershed that included a small diversion <br />ditch approved in TR 14. The current ditch aryl pond system was approved <br />in TR-17. The following design was based on a worst case approach. It <br />was assumed that sedimentation and surface runoff would be highest when <br />the disturbance was the highest in the watershed. According to the <br />current mirLvig plan, that situation will occur in the beginnirxJ of 1993. <br />Diversion No. 1 (Deadhead Route) <br />A trapezoidal diversion ditch will be wnstructed on the east side of the <br />deadhead route at the toe of the fill. The ditch will be designed to <br />carry the flow as a result of the 10 year-24 hour precipitation event. In <br />the event that erosion does start to oa.~ur, that section of the ditch will <br />be riprapped as per Addendiun 7-6f-C. Please refer to Exhibit 7-7 for <br />general location. <br />• <br />7-6f-1 Revised 08/21/91 <br />