2008-08-11_PERMIT FILE - C1992080A

Home Browse Search

Surface water control within the permit area employs a series of collection ditches and channels, berms, and two sediment ponds to direct and control sediment laden surface waters. In general, surface water runoff from the South Pit and area to the east and south, is conveyed via the East Collection Channel to Sediment Pond No. 1, which has been adequately designed and constructed to contain the design storm event flow and runoff. The East Collection Channel above the Permanently Reclaimed Spoils Area is the original Carbon Junction Canyon drainage channel. Runoff from the joint use area is conveyed via the East Collection Ditch around the east end of the facilities area to Sediment Pond No. 1. Surface water drainage from the permanently reclaimed spoils area, the south half of the reclaimed North Pit the reclaimed North Pit haul road is conveyed via the West Collection Ditch to Sediment Pond No. 2. Sediment Pond No. 2 was originally designed and constructed to handle flows from a larger area, and as such is currently oversized. Designs for all elements of the sediment control plan are contained in Exhibit N of Appendix 2.05. and Map 5 -10. Sediment Ponds • The general plan calls for two sediment ponds controlling surface drainage from the sources described above. Based upon the latest two foot topography, the current volume of Sediment Pond #1 is 4.4 acre -feet. Design Volume Calculations Sediment Pond # 1 Area Drainage Area (acres) 11.19 Design Event 10 yr. storm Design Precipitation 2.4 Average CN 86 Calculated S 1.62790697674 Description Exposed loose soil some vegetation Calculated Runoff Volume (Q) 1.16 Calculated Runoff Volume (acre -ft.) 1.08 Ponding Percentage 0.00 Actual Runoff Volume (acre /ft.) 1.08 Adding 0.4 ac -ft for sediment storage yields a total volume of 1.48 acre -feet needed in the pond above the spillway. The pond has 4.4 acre feet, therefore, it is more than adequate. The pond will Abridged Permit Document 5 -5 Feb 2008