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32 <br />Pond 001 Emergency Spillway Design <br />Criteria: 25 Year, 24 hr. Storm Event =3.4 inches <br />Minimal run -off into pond <br />Peak Mine Water Flow into pond = 4,000 gpm =8.9 cfs <br />Spillway Capacity >Mine Water Inflow + 25 yr 24 hr Storm Event <br />For open channel flow <br />Q =Cm/N A, e S"2 (modified Mannings equation) <br />Where: Q =Flow <br />Cm= Constant =1.49 (English units) <br />Al =area dedicated to mine water inflow <br />R= wetted perimeter <br />S= Channel Bottom Out slope <br />N= Mannings roughness factor--0.29 for gravel <br />A1= [8.6(48 +2(3.4)) + (8.6)(8.6)] / 144 Al = 3.79 Fig <br />R = 3.79/ [48 + 6.8 + 2(2(8.6)1*) / 12] R = 0.68 <br />Q = [(1.49) / 0.029] (3.79) (0.68)20 (0.1)12 Q = 35.1 cfs <br />Safety Factor = 35.1 cfs / 8.9 cfs SF = 3.9 <br />Additional discharges into Pond 007 will include sump discharge from the raw and <br />clean coal reclaim tunnel, and industrial building sump. These additional discharges <br />will be infrequent, of short duration and of relatively small magnitude. Total <br />estimated flow from these sources is 600 to 800 gpd. The surplus capacity in Pond <br />007 is more than adequate to handle the additional water volumes and sediment loads <br />generated by these sources. <br />Pond 006 will be placed in the New Elk preparation plant water -flow circuit as <br />shown on Figure 4. The plant will require 70.9 gpm of make -up water at a 400 ton <br />per hour feed rate. Pond 006 design is shown in Exhibit 19. Pond 006 will be a non- <br />discharging structure. The operator has amended the current NPDES permit to allow <br />for this. Installation of the Pond 006 emergency spillway is proposed to be completed <br />by January 1, 1989. The operator will also be utilizing pond 006 as a polishing pond <br />for the sewage treatment plant. <br />The operator submitted design specifications and received construction approval for <br />Section 2.05 TR -70 03/02/2015 <br />