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4. The postmining channel designs do not take into account the disturbance associated with <br />haul roads, access roads and topsoil piles to be reclaimed at the Seneca 11 Mine. Seneca <br />modeled all of these azeas as vegetated using a CN of 62. The roads that aze not included <br />include the narrowed portions of the postmining road, a portion of haul road A2, haul <br />road F1, haul road B1, haul road EIA, all access roads leading to ponds and topsoil piles, <br />and the footprints of topsoil piles located on site. Please revise the drainage designs to <br />take into account the disturbance associated with reclamation of these roads and topsoil <br />piles. <br />Seneca designed the postmining drainage channels to pass through a number of culverts <br />on site. Due to the minimal use of the postmining road, Seneca should consider dry <br />stream crossings to divert runoff rather than culverts. Please reevaluate the use of dry <br />stream crossings rather than utilizing culverts for culverts 3A, 15A, 18A, 19A, 24A and <br />45A. <br />6. Seneca used a CN of 62 for all reclaimed azeas at the Seneca II Mine. The 1997 Annual <br />Reclamation Report (ARR) reveals a total vegetation cover of 60.2% for the 1990 <br />reclaimed azea and 69.7% for the Wadge Pasture. In the Seneca II permit (Appendix 7-6, <br />Table 7-6-1), has a range of Soil Conservation Service (SCS) curve numbers for <br />vegetated cover between 50% and 80%. The CN's range from 69 for a B type soil to 83 <br />for a D type soil. It is not cleaz how Seneca derived the CN of 62 for all of the reclaimed <br />portions of the mine. Please inform the Division how the CN of 62 was derived, and <br />adjust the modeling accordingly. <br />Seneca used a curve number (CN) of 62 for the SIIPM-7 and SIIPM-17 channel designs. <br />Roughly 8 acres of the watershed boundary is located in the non-vegetated area (freshly <br />graded). Please revise the CN in the model to reflect the portions of disturbance located <br />in watersheds SIIPM-7 and SIIPM-17. <br />8. Seneca's model did not take into account the disturbance associated with reclamation of <br />the solid waste disposal site or the corral azea. Seneca depicts these azeas as vegetated, <br />but they have yet to be reclaimed. Please revise the designs for SIIPM-1 and SIIPM-10 <br />to account the disturbance associate with the solid waste disposal site and the corral azea. <br />9. Seneca used a CN 62 for SIIPM-15, which collects runoff from the pre-law azea. This <br />azea has less total cover than the reclaimed portions of the site, but the same curve <br />number was used. Please justify the use of CN 62 for runoff and the channel design of <br />SIIPM-15. <br />10. On page 7-] 2-5, Seneca states that newly designed channels will be lined if the flow <br />velocity exceeds 6 fps. The limiting velocity for open channels is generally 5 fps on <br />newly reclaimed channels. Please inform the Division how Seneca derived the limiting <br />velocity of 6 fps for the reclaimed channels. <br />