Laserfiche WebLink
• EXHIBIT 7, ITEM 20, PART E <br />PERMANENT CHANNEL DESIGN <br />There are four permanent primary channels and eight permanent secondary channels associated <br />with the South Taylor Mine Plan. The primary and secondary channels are permanent channels <br />that convey runoff from the areas near the watershed divide near the southernmost extension of <br />the mining activity. The four primary channels are associated with drainage from the face of the <br />permanent fills in Sections 16 and 17. Their purpose is to convey water to the north from the <br />head of the watershed in Sections 19 and 20 toward East Taylor Sediment Pond and West Taylor <br />Sedimentation Pond as shown on Map 41A. The secondary channels drain reclaimed pit areas <br />near the watershed divide in Sections 16, 20 and 21 to the southeast toward Section 16 <br />Sedimentation Pond and Section 28 Sedimentation Pond. <br />The secondary ditches rely on several temporary ditches to convey the runoff to the respective <br />sedimentation ponds until reclamation is complete and the ponds are no longer needed. These <br />temporary ditches are described in other exhibits. Two of these temporary ditches, described in <br />Exhibit 7, Item 20, Part D are the Section 29 Collector Ditch and the Section 28 Collector Ditch. <br />However, the designs of these ditches did not require modification for TR -81. <br />Another temporary ditch, the Section 16 Pond Ditch also receives flow from some of the <br />secondary channels. It is described in Volume 2C, Exh 7 -14B, but it requires no modification <br />pursuant to TR -81. The remaining temporary ditch that collects flow from the secondary <br />channels described in this Part E is the Section Sixteen Pond Ditch Extension. This temporary <br />ditch has been slightly modified pursuant to TR -81 and is described in Volume 2C, Exh. 7 -140. <br />All of these ditches are shown on Map 41 A. Channel profiles for these channels are presented <br />on Map 33B. <br />Primary Channels <br />The four primary channels are the following: <br />• East Taylor, East Tributary Ditch <br />• East Taylor, West Tributary Ditch <br />• West Taylor, East Tributary Ditch <br />• West Taylor, West Tributary Ditch <br />The design basis for each ditch is identified on the following Table 1. By inspection, the area <br />contributory to each ditch is less than one square mile, making the appropriate design storm the <br />10 year, 24 hour event as specified in Rule 4.05.3. However, portions of these ditches pass over <br />permanent fills, so the design event required by Rule 4.09.2 becomes the 100 year, 24 hour <br />event. For simplicity of design, the entire channel for each ditch is designed to this larger event. <br />Exhibit 7, Item 14 as modified pursuant to TR -87 describes the hydrologic design methodology <br />used at the mine. For channels protected by a riprap liner, selection of minimum rip rap size is <br />done using the Simmons /OSM method in SEDCAD. For channels to be protected by a <br />vegetative liner, the permissible velocities are also determined using SEDCAD's routines. <br />Exh. 7 -20E -1 Revision Date: 6/6/11 <br />Revision No.: TR -81 <br />