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u Mr. Brent Anderson - 5 - VII. April 24, 1991 22. The Division accepts the methodology utilized in performing the sedimentation analyses, but rejects some of the assumptions. We are unable to evaluate the results of this section until the following assumptions are modified: a. The response to question 7 indicates that vegetative cover values representative of pre-mine conditions were used, yet the sedimentoiogy analysis uses cover values from the sagebrush reference area. The Division agrees with the use of the sagebrush reference area but requests that Rodccastle use Table 2.2 d, UDSA-SCS TR-55, sagebrush with grass understory, good conditions, to derive the curve numbers for the pre-mine conditions. Post-mine curve numbers are appropriately described by either the herbaceous cover type or the dryland pasture or range values in good condition from Tables 2-2d or 2-2c. Good conditions were utilized as the tables use cover values derived from litter, grasses, forties and brush and Mr. Croft's sampling shows that all the pits and the reference area have cover exceeding 80%. b. The pre-mine slope length of 150' seems short. The Division would accept 250'. c. The Division apparently utilizes Table 5.5c on CP factors differently from ACZ. The canopy cover column should reflect the living cover (herbaceous and woody) and the cover that contacts the surface column reflects all cover (herbaceous, woody, litter and rock) . 21. As the drainage submittals were partially prepared to satisfy the Division's concerns associated with NOV C-89-034, it is pertinent to review the status of the issues identified in that NOV. lA. See Question 2 on page 2, above. i8. See Question 1 on page 2, above. If you plan to make this a permanent structure, note that the drainage divide on the Pit 6 upper diversion ditch (6-2) differs from that shown on the map. (See NOV C-89-034). 1C. It is net clear whether this ditch was reclaimed in conjunction with reclamation of the shop. Please clarify this situation. 1D. This information has been provided. 2A, and 2B. These will be eliminated by a positive sedimentology demonstration. 2C. The current design of Ditch 5-1 appears to exclude the area disturbed by overburden and topsoil stockpiles. Ditch 5-1 needs to be extended to the west and re-designed to respond to 2C. 2D. See Question 11 on page 3, above. 2E. Accurate designs of Ditch 5-1 will provide sufficient information to respond to this issue. 3A. and 38. The California crossings address these items. t