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DRMS Comment <br />8. COLL #5 is very near the Atlas Drainage. <br />a. Provide assurance that COLL #5 will not be undermined by the Atlas Drainage. <br />b. Provide assurance that the 90 degree bend in COLL #5 as it approaches the Atlas <br />Drainage will be armored such that it will not breach and flow into the Atlas <br />Drainage. <br />SMO Response <br />Coll #5 will not be undermined by the Atlas drainage, since as part of the regrading of the old <br />mine waste involves pulling the toe back from its previous location 10 feet horizontally. <br />Additionally, regular inspections and maintenance of the ditch system will be conducted to <br />ensure its integrity. Any sharp turns will be armored with large rock (likely 12 inch +) to protect <br />against breaches into the Atlas Drainage. <br />DRMS Comment <br />Map G -2: Sediment Pond 1 <br />9. There appears to be a typographical error for the Sediment Pond 1 Spillway Design <br />principal spillway outlet elevation. The stated elevation makes the pipe have no elevation <br />drop. Please provide a corrected elevation. <br />10. The stated storage capacity of Sediment Pond 1 is 1.05 ac -ft. Section 4.5 (Exhibit G) <br />states the pond will store both the 10 -, and 25 -year, 24 -hour design storm runoff volumes. <br />However, the sum of the 10- and 25 -year runoff volumes (1.39 ac -ft) on the Stage - <br />Storage curve exceeds 1.05 ac -ft. Only runoff volume calculations for the 100 -year <br />design storm were provided. Please provide runoff volume calculations for the 10 -, and <br />25 -year, 24 -hour design storms. <br />11. As the site is a DMO, any embankment fill is considered an EPF. Please reference <br />embankment material fill and compaction specifications on Map G -6. <br />12. Please provide hydraulic calculations for the emergency spillway. <br />SMO Response <br />Map G -2 has been revised to accurately show the spillway elevations, and a reference to the <br />embankment specifications on Map G -6 has been added. The stage storage curve now shows the <br />10 -YR, 25 -YR, and 100 -YR runoff volumes for the area draining to the pond, and Exhibit G <br />Section 4.5 has been revised to explain that the ponds are designed to hold up to the 100 -YR <br />event runoff. Hydraulic calculations for the emergency spillways for all three sediment ponds <br />can be found in Table 6 -1 in Appendix 6. <br />