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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 />each location which had the parameters described in the previous section. All ponds were <br />designed to fully contain the 25 year, 24 hour event. Ponds 015, 016, and 018 are designed to <br />contain the 100 year, 24 hour event. <br />Shown on the following two pages are the calculations used by Carlson Software in determining <br />typical pond volumes. <br />Universal Soil Loss Equation: Used by Carlson Software <br />-------------------- <br />Required User Input: <br />Note: The following values are to be entered by the user for each area in the watershed. The <br />method for obtaining these parameters is left to the user. <br />Rainfall Factor (R): Default = 50; <br />Erodability Factor (K): Default = 0.37 <br />C Factor (C): Default = 0.5 <br />P Factor (P): Default = 1.0 <br />Geometric Information: <br />Area (sq units): Can be entered by the user or the program calculates the area of a user -selected <br />closed polyline. The user also has the option to enter the area in different units. <br />Section 2.05.3(3) Page 16 February 2017 (TR -78) <br />