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Dan Mathews <br />Page 2 <br />August 8, 2005 <br />4. There appeazs to be several minor inconsistencies or typographical errors on the Hydrologic <br />Input Parameter Tables submitted with the Post mining Channel designs and stock pond <br />information with regard to runoff curve numbers. Approved curve numbers and related <br />information are contained on page 3 of Attachment 13-SB Drainage and Sediment Control <br />Plan II-W South Extension. The cover type Aspen/Mountain Shrub is described as Aspen <br />Mountain Brush numerous times in most of the Hydrologic Input Parameters Tables, and <br />for the Reclaimed cover type the Hydrologic Condition should be listed as Good (>70%) <br />and the Hydrologic Soil Group should C rather than B. Please revise all Hydrologic Input <br />Parameters Tables accordingly to ensure consistency with Table 1 of Attachment 13-SB. <br />Please provide a Hydrologic Input Parameters Table for Stock Pond T-25. <br />6. It does not appear that all of the watershed boundaries aze drawn on Exhibit 20-2A. Please <br />ensure that all of the watershed boundaries are drawn on Exhibit 20-2A and clearly labeled. <br />Please also include the watershed boundaries designation in the Legend of Exhibit 20-2A. <br />Please update and revise Section 6.0 of Attachment 13-SB Drainage and Sediment Control <br />Plan II-W South Extension to include the new and revised information submitted with <br />Permit Revision No. 5. <br />8. Insufficient design information was submitted for proposed Stock Ponds T-25, T-26, and T- <br />27. The design, construction, and maintenance of all impoundments shall be in compliance <br />with Rule 4.05.9. The Division will require a certified design for each proposed stock pond <br />and a stock pond stability analysis. The certified design should at a minimum include the <br />following information: a spillway cross-sectional profile, an embankment and pond cross- <br />section profile (with side slope information), plan view drawing, and astage/capacity table. <br />Please provide certified stock pond designs for T-25, T-26, and T-27. <br />Please revise the SEDCAD demonstrations to include for each stock pond a detailed <br />discharge table showing the spillway elevation and peak stage elevation to demonstrate <br />compliance with 4.05.9(7)(d). <br />A generic stability analysis has been accepted in the past for stock ponds at the Seneca II <br />Mine. A generic stability analysis may also be appropriate for the Seneca II-W Mine. <br />Please provide a stability analysis for each stock pond or provide a generic stability analysis <br />specific to the Seneca II-W Mine for the proposed worst-case stock pond embankment <br />geometry. <br />Let me know if you have any questions regarding my review of PR-O5. <br />c: Sandy Brown <br />