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<br />Mr. Dan Mathews <br />June 13, 2008 <br />Page 3 <br />information to be retained for YPM-4, 4-1, and YPM-17 do not match the new Pond 013 As- <br />Built SEDCAD design information for contributing areas and peak discharges. <br />11. Since the recent slide activity at Pond 012, the configuration of the pond has obviously <br />changed. This was confirmed by the pond storage capacity survey submitted May 28, 2008 for <br />Abatement Step 1 of NOV CV -2008-001. In the new certified As-Built Report for Pond 012 <br />(Option 1) page 13-12A-1.4, SCC indicates that "Exhibit 13-6, As-Built Pond 012, presents the <br />existing impoundments configuration and structure elevations". This statement is no longer <br />correct since the slide occurred after the submittal of TR-37 and the configurations and <br />structure elevations have changed. Please remove the revised Attachment 13-12A As-Built <br />Report from the revision application since this report is no longer appropriate. As stated above <br />in Item 5, we recommend the two-pond option (012 and 012A in series) that should be <br />designed in concert with the slide remediation plan and takes into consideration a smaller <br />dimension for Pond 012. Please resubmit a new design for the two-pond system accordingly. <br />New certified As-Built Report and new As-Built Map for the two pond option (012 and 012A <br />design) will be required following construction. <br />12. There is an error on page 13-12A-1.3 regarding reference to (elevation difference between the <br />calculated top of the sediment storage and the principal spillway invert) being between 0.5 and <br />one (1) as recommended by Warner, et al., 1998. If a slow passive dewatering system is <br />employed (such as is the case with Pond 012) then the elevation can be reduced to 0.5 to 1.0 ft. <br />The second paragraph should be revised to read (elevation difference between the calculated <br />top of the sediment storage and the low-hole spillway/dewatering orifice). Please clarify this <br />discrepancy and revise page 13-12A-1.3. <br />13. In the SEDCAD 4 User's Guide (page 64) it is suggested that a minimum two foot elevation <br />difference exists between the invert of the principal spillway and the top of the sediment <br />storage area. This would apply to Pond 012A since there is no low-hole spillway. The original <br />approved design for 012A (TR-36) had less than the suggested elevation difference (1.49 feet). <br />With TR-37 page 13-12A-1-4.13 (Pond 012 and 012A System) shows a proposed elevation <br />difference between the top of sediment storage and the principal spillway of only.55 feet). A <br />more prudent design and to avoid re-suspension of sediment would be to allow for additional <br />space between the top of sediment storage and the principal spillway elevation. Please <br />reconsider the design for Pond 012A to allow for a minimum two foot elevation difference <br />between the invert of the principal spillway and the top of sediment storage. <br />14. Attachment 13-17 As-Built report for Pond 014 incorrectly references Pond 013 in the <br />Introduction and on page 13-17.1-1. Please correct these pages. <br />15. Culverts that are intended to be permanent as shown on the Post-Mining Topography Map 20-2 <br />should be added to the permanent structures and features discussion in Tab 20 and listed in <br />Attachment 20-1 Permanent Structures and Features. <br />16. In some instances the slope information for the channels provided on Figure 13-12.3 Yoast Post <br />Mining Channel Designs does not match the slope and profile information provided for Post- <br />Mining Channel Profiles Exhibit 20-2B. Please check the following profiles on Exhibit 20-213;