2008-06-13_REVISION - C1994082 - Laserfiche WebLink

Home Browse Search

-1:. Mr. Dan Mathews June 13, 2008 Page 2 5. On page 1 of revised Attachment 13-12, SCC states that Pond 012A would be used "...if Pond 012 continues to lose capacity from upslope instability previously experienced adjacent to the pond area." "If the area stabilizes then Pond 012A will not be constructed." It does not appear that the area is going to stabilize given recent significant slide activity immediately adjacent to Pond 012. The Division believes that building Pond 012A is warranted. SCC has presented two options with this revision; Postmine Topography Option 1 (Pond 012 only) and Option 2 (Pond 012 and 012A in series). Since the slope above Pond 012 remains unstable the Division recommends Option 2. Please revise all text, channel designs and appropriate maps to indicate Option 2 only. As part of Option 2, the Division believes that there may be some advantage to reducing the dimension of Pond 012 to allow for lengthening the toe of the unstable slope above and to the east of the pond, and to provide more room and soil material for grading and stabilization to the east of Pond 012. The Division asks that SCC give this some consideration when developing the slide remediation plan required in Abatement Step 2 of NOV CV-2008- 001. 6. Hydrologic input parameters including original approved curve numbers (Table 13-1) for Ponds 010 and 011 were initially given in Tab 13 Facilities section. Attachment 13-12 was subsequently prepared for the Yoast South area (Ponds 012, 013, and 014) and contained a second modified curve number table. With TR-37 Attachment 13-12 was significantly modified and Table 13-12.1 Yoast Mine Curve Numbers was substantially expanded. We now have two lengthy curve number tables in two different sections of the permit. To avoid confusion, it would be helpful to have both curve number tables be consistent with each other, or refer the reader to just one location in the permit for approved curve numbers. Please update the appropriate sections of the permit document accordingly. 7. A couple of errors were noted on Figure 13-12.3. Channel YPM-6-2A was not included in the figure. Under YPM-18 the slope is given as 11-313%. Please make the necessary corrections to Figure 13-12.3. On new Exhibit 13-12.1A and revised Exhibit 20-2, Postmine Channel YPM-3-2A is missing. Please include this channel on the exhibit. 9. The watershed boundary designations have become confusing and difficult to correlate between the channel and pond designs and the exhibits that show the watershed boundaries and designations. For example, it appears that the designations shown on Exhibit 13-12.1 no longer correlate with the Watershed Identifications and the hydrologic input parameters for the postmine channel and pond design SEDCAD runs for the Yoast South area. It is also appears that Exhibit 13-413 needs to be updated with the current watershed condition as of September 2007 and with new Channel YPM-22. If appropriate, remove Exhibits 13-12.1 and 13-413 and replace them with a single map showing the revised watershed designations. Alternatively, the appropriate watershed designations could be added to the new Exhibit 13-12.1A. 10. Please revise Appendix 13-12.3 with an updated channel design(s) for the YPM-4, 4-1, 4-2, YPM-17 and Diversion 13A system of channels that flow into Pond 013. There were no previous existing designs for Diversion 13A and it appears that the existing channel