Laserfiche WebLink
shown on Map 2.05.3(3) -1. For these reasons, Ponds 012 and 013 are given a Class A <br />designation. <br />Ponds 014 and 015 -These ponds are meant to handle the flow from a 100 year 24 hour <br />event. They are also incised ponds without any real embankment structure. Also, their small <br />volume and location would not result in any damage to property or life. For these reasons, <br />Ponds 014 and 015 are given a Class A designation. <br />7. Pond 008 through 015 Designs <br />As shown above for Sediment Pond 007, Tables 2.05.3(3) -1 and 2.05.3(3) -2 list the values of <br />CN and "k" for different soil and vegetation types at the New Horizon Mine. The tables have <br />been revised to address new soils found in the area west of 2700 Rd <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 <br />soils and vegetation information found within Sections 2.04.9 and 2.04.10, respectively, of <br />the New Horizon mine permit application. <br />The pond volumes are calculated by first using the Curve Number and Runoff Routine within <br />the Hydrology module of the SURVCADD software and then using the USLE sediment <br />storage routine within the Hydrology module of the SURVCADD 2000 software. The LS <br />factors for the USLE are determined from the 3D CAD grid model of the drainage areas for <br />each pond. The water volume is determined from the weighted average CN for the <br />watershed based on the worst case conditions over the life of the mine and the appropriate <br />design storm rainfall. Curve numbers used are from 78 to 90 based on the existing <br />conditions, level of disturbance and the hydrologic soil type of each watershed. Once the <br />required volume of sediment and storm inflow is known, these two are combined to get the <br />total required volume. SURVCADD was then used to design ponds in each location which <br />had the parameters described in the previous section. All ponds were designed to fully <br />contain the 25 year 24 hour event. Pond 015 is designed to contain the 100 year 24 hour <br />event. <br />Shown on the following two pages are the calculations used by the SURVCADD Program in <br />determining typical pond volumes. <br />(Revised June 2010) 2.05.3(3) -17 <br />