2008-09-08_REVISION - C1994082 - Laserfiche WebLink

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Technical Revision 37 Response to Adequacy Comments Page 4 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. Response: Exhibit 13-12.1, Yoast Mine Watersheds, shows a conservative watershed area estimate that was used by SCC for the designs of Ponds 012, 013 and 014. These designs were all completed in 1999 in accordance with Rule 2.05.3(4) of the Regulations of the Colorado Mined Land Reclamation Board for Coal Mining. The rule reads (a) General `A general plan and detailed design plan shall be submitted for each sediment pond, impoundment, other treatment fadko, and diversion proposed (emphasis added) to be constructed within the permit area. " (a) (i) (B) "Contain a description, map, prepared according to 2. 10,... " Exhibit 13-4B, Pond 010 - Existing Watershed Conditions August 2006 (emphasis added) was also prepared in accordance of Rule 2.05.3(4). As noted in the title, the drawing shows conditions as of August 2006. Attachment 13-3A Part II contains references to this exhibit. These drawings are needed to support design and as-built documentation in accordance with Rule 2.05.3(4). Consequently SCC believes that it is inappropriate to remove, or update, either exhibit. Finally, Channel YPM-22 is shown on Exhibit 13-12.1A, Permanent Channel and Pond Watersheds. Exhibit 13-3A, Part I (prepared for TR-37 [with a revision date of 02/08]) indicates that drainage areas used in the SEDCAD demonstrations were measured from Exhibit 13-12.1A (see page 13-3A.1-2). Again, there is no need to revise Exhibit 134B since the plan view of YPM-22 is shown on both Exhibit 13-12.1A and Exhibit 20-2, Postmining Topography Map. 10. Please revise Appendix 13-12.3 with an updated channel design(s) for the YPM4, 4-1, 4-2, YPM-17 and Diversion 13A rystem of channels that flow into Pond 013. There were no previous existing designs for Diversion 13A and it appears that that the existing channel information to be retained for YPM4, 4-1, and YPM-17 do not match the new Pond 013 As-Built SEDCAD design information for contributing areas and peak discharger • Response: As noted above in SCC's response to Comment No. 3, Appendix 13-12.3 contains channel des s. The approved designs are representative of the minimum configuration needed to convey the estimated runoff from a proposed topography. Consequently, the approved demonstrations in this appendix should be designs for YPM-4, 4-1 and 17, not the as-builts. Unfortunately, neither SCC nor the Division recognized that "designs" and "as-built" were different earlier in the permit revision process. If SCC had recognized this issue earlier it would have proposed leaving the original "designs" in Attachment 13-12 and, would have subsequently prepared as-built demonstrations (which would have superseded the design demonstrations) as part of the bond release process. To assure consistency with material currently in the PAP (e.g., the revised "designs" inserted into Attachment 13-12 as part of TR-36 and TR-37, as well as, the inputs that were used for pond permanent feature demonstrations) the channel demonstrations for YPM-4 and 4-1 have been revised. The design for YPM-4-2 was submitted as part of the March 2008 TR-37 package; the SEDCAD demonstration and channel designs start on page 13-12.3-241. An updated as-built demonstration for YPM-17 which includes Diversion 13A was also included in the March 2008 TR-37 package (see page 13-12.3-169). The original ditch design for Diversion 13A is found in the Pond 013 design demonstration (see Appendix 13-12.1, Sediment Pond SEDCAD4 Design Results, starting on page 13-12.1-98). Diversion 13A is included in the model network as Structure #2. 11. Since the recent slide activity at Pond 012, the configuration of the pond has obviously changed This was confirmed by the pond storage capacity survey submitted May 28, 2008 forAbatement Step 1 of NOV CV-2008-001. In the new certified As-Built Report for Pond 012 (Option 1) page 13-12A-1.4, SCC indicates that `Exhibit 13-6, As-Built Pond 012, presents the existing impoundments configuration and structure elevations" This statement is no longer correct since the slide occurred after the submittal of TR-37 and the configurations and stnrcture elevations have changed Please remove the revised Attachment 13-12A As-Built Report fmm the revision application since this report is no longer appmpriate. As stated above in Item S, we recommend the two pond option (012 and 012A in series) that should be designed in concert with the slide remediation plan and takes into consideration a smaller dimension for Pond 012. Please resubmit a new design for the two pond system accordingly. New certified As-Built Report and new As-Built Map far the two pond option (012 and 012A design) will be required following construction.