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<br /> <br />Please refer to the permit application pages where these data <br />come from. <br />12. On pages 6 and 9 of Exhibit 8, an erosion control practice <br />factor, "P", of .75 is used. Please describe the specific <br />practices that will be employed at the mine site that would <br />reduce this "P" factor from 1.0 to .75. <br />13. On pages 7 and l0 of Exhibit 8, it is stated that riprap will <br />not be needed for the top of the emergency spillways for ponds <br />B and C, respectively. However, it is also stated that the <br />velocity of the discharge from the 25 year - 24 hour storm <br />event will be 5.25 feet per second. The Division would like to <br />comment that this velocity may be erosive, depending upon the <br />material used in the emergency spillways. The Division <br />recommends that some type of erosion control material be used <br />along the top of the emergency spillway. The material can be <br />an erosion control fabric, riprap of the size already <br />calculated on pages 7 and 10 of Exhibit 8 or some other <br />material. <br />14. On page 17 of Exhibit 8, a hydraulic length of 1516 feet and <br />an elevation change of 294 feet is given for the watershed # <br />B-5 Wetland. However, examination of Map 3, Vegetation, seems <br />to indicate that there are wetland areas at a hydraulic length <br />of about 3400 feet and an elevation change of about 1050 feet. <br />If you agree, please modify these two values and any resultant <br />calculations. If you do not agree, please justify the use of <br />these values. <br />15. Referring to page 21 of Exhibit 8 and Map 20, Sedimentation <br />Control Plan, it appears that the calculation of the total <br />drainage area for drainage area D did not take into account <br />the drainage area above the gob pile that is being diverted <br />around the gob pile and into drainage area D. If you agree, <br />please modify the peak flow calculations for drainage area D <br />and the design parameters for any structures affected by this <br />change. If you do not agree with the Division's opinion, <br />please explain your position on this matter. <br />16. On page 21 of Exhibit 8, an elevation change of 1690 feet is <br />listed for watershed # D-1 Disturbed. However, it appears that <br />the elevation change may be about 690 feet. Please change this <br />value, and any resultant calculation, if needed, or justify <br />the use of this value. <br />17. On page 21 of Exhibit 8, for watershed D-3 Juniper Woodland, <br />a hydraulic length of 1516 feet and an elevation change of 388 <br />feet is used. Referring to Map 3, Vegetation, and Map 20, <br />Sedimentation Control Plan, there appears to be a Juniper <br />woodland near the top of the drainage area, resulting in a <br />hydraulic length of about 3400 feet and an elevation change of <br />4 <br />