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Repair of the gullies was conducted by filling and roughening the gully areas, and at the • <br />same time, constmcting a meandering flow path along the length of the gully areas down to <br />Channel SIIPM-8. The channel areas were then re-seeded. <br />The Division inspected the area and requested SCC to either submit a channel design <br />similaz to all other constmcted channels or demonstrate that the meandering channel would <br />stabilize the slope. <br />The two (2) re-constmcted channels have been designated as SIIPM-8a and 8b and the <br />locations are shown on Exhibit 7-19, Postmining Drainage Control. Channel 8a consists of a <br />continuous meandering flow path while 8b combines an upper vegetated channel and a <br />lower meandering flow path. Following is a demonstration for the meandering flow path <br />design. <br />Hvdrol~ <br />Channel SIIPM-Sa <br />Watershed <br />Reclaimed >3yrs 30.2 acres CN= 62 <br />Reclaimed <3yrs 2.3 acres CN= 70 <br />Weighted average CN= 63 • <br />Design (Q) <br />10-year, 24-hour storm = 0.13 cfs, use default value = 1.0 cfs <br />Channel SIIPM-Sb <br />Watershed <br />Reclaimed >3yrs 9.1 acres CN= 62 <br />Reclaimed <3yrs 3.9 acres CN= 70 <br />Weighted average CN= 65 <br />Design (Q) <br />10-year, 24-hour storm = 0.13 cfs, use default value = 1.Ocfs <br />(SEDCAD4 hydrology printouts are attached.) <br />Channel DesiQrts <br />Existing Channels: The existing meandering channels were not originally designed. SCC <br />personnel have walked the length of the channels and a sketch of a typical 100' length is <br />provided. See Figure 8a, SIIPM-8a & Sb Typica] Channel Section. Although the lengths and <br />slopes of the meandering flow path change throughout the slope length of the channel, • <br />overall the slope of the channel is reduced from 18% - 31% to 16% - 21%. <br />TR-36 7-12-6 Revised 11/04 <br />