2018-09-07_REVISION - C1981010 (2)

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This is a review of the design plans submitted for sediment ponds. The above rule is adequately addressed with the exception of: As built designs for the 12 ponds. Many of these design drawings were illegible, the font was less than 10 point and in some cases no elevations were called out on contour maps. Specific designs that were problematic comprise: Johnson System, Middle Pyeatt System, No Name System, and Ute Pond. Ute Pond had no elevations called out on the plan view. As the Middle Pyeatt system may receive runoff from the disturbed area associated with the development of Nighthawk Pit, DRMS requests as built design drawings meeting that are legible and have the information needed in order to do an adequate review. DRMS is not able to verify the inputs used for the sedcad runs associated with Middle and East Pyeatt systems and performed in 1993. As these runs are outdated given current conditions and future anticipated disturbance, rerunning these models for the proposed PR9 disturbance is appears necessary. 14. Please, update and resubmit the Middle Pyeatt System as built drawings to meet the general requirements of Rule 2.10.1, with specific emphasis on legibility, and completeness of information. Trapper Response to Comment 14: The requested and enclosed as -built drawings referenced above for all 12 ponds have been modified and edited for better clarity of information with this adequacy response. 15. Please recalculate the sedcad runs to reflect conditions addressing the anticipated effects of disturbance for: 16. Middle Pyeatt 17. East Pyeatt systems Trapper Response to Comments 15-17: The two drainages have been modeled with current topographical boundaries and projected future disturbances to look at planned future conditions, versus those that existed when the "worst case" scenarios were developed for these two drainages. Enclosed with these comments are the Engineering Certifications and site drawings for both East Pyeatt and Middle Pyeatt Drainages. The Engineering Certifications testify to the fact that both drainages and series of ponds project that the 24 hour average settleable solids concentration released from the lower most ponds in each drainage is 0.0 mUl, well below the 0.5 mUl settleable solids standard and that all ponds have in excess of 1.0 feet of freeboard for a 25year/24 hour rainfall event as required. 1S. Please discuss to what extend extent if any, the No Name Pond system may be affected by the changes in topography proposed at the D Pit? Trapper Response to Comment 18: No impacts are anticipated to occur to the NO -Name Pond system as the post mining topography has not changed from the previous submittal of map M 12 with PR -07. 19. Will there be any water routing structures to construct or modify?