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2016-05-03_PERMIT FILE - C1981008A (17)
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2016-05-03_PERMIT FILE - C1981008A (17)
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Last modified
8/5/2019 9:59:25 AM
Creation date
6/14/2016 11:23:52 AM
Metadata
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Template:
DRMS Permit Index
Permit No
C1981008A
IBM Index Class Name
Permit File
Doc Date
5/3/2016
Doc Name
Pond 013 Postmining SEDCAD Modeling
Section_Exhibit Name
Section 2.05.3(3) Attachment 2.05.3(3)-32
Media Type
D
Archive
Yes
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SEDCAD model allows for an estimate of the annual sediment collected in the pond. The <br />methodology is described on page 64 of the SEDCAD User's Manual, and requires an Annual R <br />factor (rainfall -erosivity factor). The value of R at 27 can be interpolated from Figure 5.3 <br />presented in Barfield, Warner and Haan (1981). In addition the total tonnage of sediment from <br />the modeled storm, in this case 10 year, 24 hour storm, is required. This is obtained from the <br />SEDCAD output by subtracting from tons flowing into the pond (63.7 tons) the sediment <br />tonnage into the null below the pond (21.2 tons). <br />The net 42.5 tons from a single 10 year, 24 hour storm is converted to annual tons via the method <br />described in the SEDCAD Users Manual to 60.9 tons. This weight is then converted to volume, <br />using a density of 78 lb/cu ft, to arrive at the projected annual volume collected in the pond of <br />0.036 ac -ft. According to the stage -storage curve, there are 2.40 ac ft of available storage <br />between the pond floor (elevation 5549) and the invert of the twin 6 -inch valves on the riser. <br />Thus, over a period of 10 years approximately 0.36 ac -ft of sediment would be accumulated in <br />the pond bottom with the watershed in its current revegetated condition. This is small enough to <br />not significantly affect the trap efficiency of this pond. <br />The SEDCAD printout shows the 10 year, 24 hour storm flows in Ditch C9 to be 4.65 cfs in the <br />10 year storm, and flowing at a velocity of 2.3 fps, well below the allowable velocity of 7 fps for <br />the grass lined channels at these conditions. <br />Following establishment of the postmining topography to final grade, an inlet ditch into the pond <br />will be excavated as shown on Map 1. Details of this inlet channel, along with dimensions and <br />erosion protection details and other information is also provided for this feature. <br />REFERENCES <br />Barfield, Warner, & Haan (1981). "Applied Hydrology and Sedimentology for Disturbed Areas". <br />Oklahoma Technical Press, Stillwater, OK. <br />Renard, K.G., G.R. Foster, G.A. Weesies, D.K. McCool, and D.C. Yoder (1996). "Predicting <br />Soil Erosion by Water: A Guide to Conservation Planning with the Revised Universal Soil <br />Loss Equation (RUSLE)". Agricultural Handbook No. 703. U.S. Department of <br />Agriculture. Washington, DC. <br />Schwab and Warner (1998). "SEDCAD4 Users Manual". Civil Software Design. Lexington, KY. <br />Soil Conservation Service (1986). "Urban Hydrology for Small Watersheds (TR -SS)". Soil <br />Conservation Service. Washington, DC. <br />Striffler and Rhodes (1981). "Hydrologic and Erosional Characteristics of Regraded Surface <br />Coal Mined Lands in Colorado', Dept. of Earth Resources, Colorado State University, Ft. <br />Collins, CO. <br />USDA (January 2009), National Resources Conservation Service, National Engineering <br />Handbook (NEH), Chapter 7, "Hydrologic Soil Groups" <br />Attachment 2.05.3(3)-32 Revision Date: 3/09/2016 <br />Page 5 Revision No.: TR -70 <br />
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