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maximum flow is only 11.5 acre feet for a full dam break, it is not enough to cause the water to <br />exceed the channel and flow uphill to the Enstrom structures. Once the water goes downstream <br />in the tributary channel, it enters Tuttle Draw a short distance downstream and there are no <br />structures that could be affected by a small volume in Tuttle Draw since it is large enough to <br />handle substantial peak flows, as shown on Map 2.05.3(3)-1. For these reasons, Pond 011 is <br />given a Class A designation. <br />Ponds 012 and 013 - As seen on Map 2.05.3(3)-1 Surface Hydrology, Ponds 012 and 013 are <br />located immediately outside the floodplain of Tuttle Draw. Any dam break of these ponds would <br />discharge water directly into Tuttle Draw. There is no chance the water could harm anything or <br />anyone at other locations. There are no structures that could be affected by a small volume in <br />Tuttle Draw since it is large enough to handle substantial peak flows, as shown on Map <br />2.05.3(3)-1. For these reasons, Ponds 012 and 013 are given a Class A designation. <br />Ponds 015, 016, and 018 - Since these small partly to fully incised ponds are designed to contain <br />the flow from a 100 year 24 hour event they would only contribute a couple acre-feet to a <br />drainage from overflow or embankment failure. Thus, these ponds are given a Class A <br />designation. <br />G. Pond 008 through 018 Designs <br />Tables 2.05.3(3)-1, 2.05.3(3)-lA, and 2.05.3(3)-2 list the values of CN and "k" for different soil <br />and vegetation types. The tables have been revised to address new soils found in the area west of <br />2700 Road. <br />The curve number (CN) and "k" factor for each of the ponds is determined as a weighted <br />average. The undisturbed area curve number and "k" factor information is based on the soils and <br />vegetation information found within Sections 2.04.9 and 2.04.10, respectively, of the New <br />Horizon mine permit application. <br />The pond volumes are calculated by first using the Curve Number and Runoff Routine within the <br />Hydrology module of Carlson Software and then using the USLE sediment storage routine <br />within the Hydrology module of Carlson Software. The LS factors for the USLE are determined <br />from the 3D CAD grid model of the drainage areas for each pond. The water volume is <br />determined from the weighted average CN for the watershed based on the worst case conditions <br />over the life of the mine and the appropriate design storm rainfall. Curve numbers used are from <br />78 to 90 based on the existing conditions, level of disturbance and the hydrologic soil type of <br />each watershed. Once the required volume of sediment and storm inflow is known, these two are <br />combined to get the total required volume. Carlson Software was then used to design ponds in <br />Page 2.05.3(3)-16 January 2016 (TR -70) <br />