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7. Three diversion ditches are included in the drainage system as designed. <br />A review of Map 6 indicates that the undisturbed area runoff captured by <br />Ditch No. 3 wi]] topographical]y flow into Ditch No. 2. This presents a <br />problem because the sizing of Ditch No. 2, the culverts in Ditch No. 2 <br />and the sediment pond have not been sized to include this runoff volume. <br />The outlet of Ditch No, 3 occurs on a steep hillside and will cause <br />erosion. The application should be revised to either: <br />A. Provide a drainage design which describes how the undisturbed flow <br />(Ditch No. 3) can be routed separately from the disturbed area flow <br />to Hay Gulch; <br />B. redesign the present system to size the pond, Ditch No. 2 and the <br />culverts on Ditch No. 2 adequately to include the flow from Ditch <br />No. 3; or, <br />C. remove Ditch No. 3 from the design and still provide treatment for <br />all the runoff from the disturbed area. <br />8. Ditch No. 1, as designed, indicates a design flow velocity of 5.9 feet <br />per second. This velocity is erosive for the soils encountered at this <br />location. The ditch should be either: <br />A. Redesigned with different channel dimensions, or <br />8. riprapped with rock of sufficient size to control erosion. <br />9. No ditch or berm above the portals has been shown on Map 6 although this <br />is described on page 8-1 of Exhibit 8. This feature, and the bench <br />drainage feature described on page 2.06-2, should be included on Map 6. <br />10. The application states on page 4.05-5 that a rton-clogging dewatering <br />device will be located at a lower elevation than the maximum sediment <br />storage elevation. Design standards require that this dewatering device <br />be located above the maximum sediment storage level. This statement <br />should be revised as appropriate in the application and a description or <br />drawing of the device be provided which illustrates the non-clogging <br />aspects in the design. <br />11. In order to evaluate the adequacy of the pond, the applicant needs to <br />provide principal spillway size and location, a cross section of the pond <br />and the calculations used to demonstrate detention time. Pond drawings <br />need to be certified by a qualified registered professional engineer. <br />12. It is unclear from information provided in the permit application what <br />specific plan is being proposed for backfilling and grading the portal <br />area, the access road, and the lower facilities area. Certain portions <br />of the text (p. 2.05-24, p. 2.05-26, p. 2.05-27, and p. 2,05-28) <br />describe, in genera] terms, a backfilling scheme oriented towards the <br />achievement of approximate original or pre-mining contours. Other <br />portions of the text (pp. 2.05-33 - 35) describe a backfilling scheme <br />that essentially leaves the portal face-up or highwall artd possibly the <br />access road cuts in place as part of the proposed final contours. <br />-6- <br />