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Technical Revision 37 <br />Response to Adequacy Comments <br />Page 3 <br />• Division believes that building Pond 012A is warranted SCC has presented two options with this revision; Postmine Topography <br />Option 1 (Pond 012 only) and Option 2 (Pond 012A and Pond 012 in series). Since the slope above Pond 012 remains unstable the <br />Division recommends Option 2. Please revise all text, channel designs and appropriate maps to indicate Option 2 only. As part of <br />Option 2, the Division believes that there may be some advantage to reducing the dimension of Pond 012 to allow for lengthening the toe <br />of the unstable slope above and to the east of the pond and to provide more mom and soil material forgrading and stabilization to the <br />east of Pond 012. The Division asks that SCCgive this some consideration when developing the slide remediation plan required in <br />Abatement Step 2 of NOV CV-2008-001. <br />Response: SCC has revised the TR-37 material so it only includes "Option 2" (Pond 012A and Pond 012 in series). <br />SCC will review the certified geotechnical engineer's recommendations before determining the configuration and <br />volume for Pond 012 following the slide remediation. <br />6. Hydroh g g <br />gic input parameters includin ori <br />inal approved curve numbers (Table 13-1) for Ponds 010 and 011 were initially given in <br />Tab 13 Facilities section. Attachment 13-12 was subsequently prepared for the Yoast South area (Ponds 012, 013, and 014) and <br />contained a second modified curve number table. With TR-37 Attachment 13-12 was sign ficantly modified and Table 13-12.1 Yoast <br />Mine Curve Numbers was substantially expanded We now have two lengthy curve number tables in two different parts of the permit. <br />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 <br />location in the permit for approved curve numbers. Please update the appropriate sections of the permit document appropriately. <br />Response: SCC representatives discussed this comment with Mr. Michael Boulay on June 24, 2008. It was agreed that <br />Table 13-1 needs to stay in the PAP because the curve number values in this table were used for the original design and <br />as-built demonstrations found in Attachments 13-3 and 13-4. Mr. Boulay and the SCC representatives agreed it is <br />inappropriate to remove this table unless the design and as-built packages found in these two attachments were also <br />40 removed. The PAP needs to retain the design packages to assure SCC remains in compliance with Rule 2.05.3(4) of the <br />Regulations of the Colorado Mined Land Reclamation Board for Coal Mining. Table 13-12.1 (found in Attachment 13- <br />12) was developed in 1999 to support the expansion of the Yoast Mine into the south mine, area. The values in the <br />1999 version of the table were thought to be sufficient for future hydrologic designs by both SCC and Division <br />representatives. However, recent SEDCAD modeling experience has shown that a wider range of curve number values <br />for undisturbed conditions was needed to accurately estimate the hydrologic response of the various watersheds. <br />Consequently, SCC has modified Table 13-12.1 to include the'approved curve number values from Table 13-1. At Mr. <br />Boulay's request, Table 13-12.1 has also been footnoted to help the reviewer reconcile any differences between the two <br />tables. <br />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 <br />given as 11-313%. Please make the necessary corrections to Figure 13-12.3. <br />Response: Figure 13-12.3 has been revised to eliminate the errors noted in this comment. In addition, references to <br />any channel configurations included with Pond 012 "Option 2" have been removed. <br />8. On new Exhibit 13-12. lA and revised Exhibit 20-2, Postmine Channel YPM-3-2A is missing. Please include this channel on the <br />exhibit. <br />Response: Exhibit 13-12.1A and 20-2 have been revised. <br />9. The watershed boundary designations have become confusing and difficult to correlate between channel and pond designs and the exhibits <br />that show the watershed boundaries and designations. For example, it appears that the designations shown on Exhibit 13-12.1 no <br />longer correlate with the Watershed Identifications and the hydrologic input parameters for the postmine channel and pond design <br />SEDCAD urns for the Yoast South area. It also appears the Exhibit 134B needs to be updated with the current watershed <br />• conditions as of September 2007 and with new Channel YPM-22. If appropriate, remove Exhibits 13-12.1 and 134B and replace