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• The progression of development, mining, backfill and reclamation that is detailed in <br />other documents associated with MLE2. The Storm water Plan has been adjusted to <br />accommodate each annual change in boundary so that storm water controls will <br />always be in place before mining disturbance occurs. <br />• The technical procedures used in the formation of the MLE1, Amendment 9 Storm <br />water Plan (Ref. Footnote 1) were reviewed and accepted by participants in the <br />review of that 2008 application. Those same procedures have been replicated in the <br />assessments for MLE2. <br />• A custom soils report was downloaded from the National Resource Conservation <br />Service ( "NRCS ") site for the site specific area around Cripple Creek and Victor. <br />Properties of the soils described in that survey were used to form the basis of the <br />Storm water Design. <br />• As with the MLE1 design, SEDCAD4 was used to calculate runoff discharge rates <br />and volumes using SCS Curve Number infiltration methods. The input models used <br />for MLE1 were updated to reflect changes in the Mine Plan that will affect the <br />hydrology. <br />1. STORM WATER HYDROLOGY <br />INFLOW DESIGN STORMS AND DESIGN CRITERIA <br />The Inflow Design Storm (IDS) criteria include two simulated storm events. The <br />precipitation depth /duration values for both events are derived from the NOAA Atlas, <br />which is universally used for moderate storm determinations. The capacity of each <br />terminal detention pond will be twice the volume of a single 10- year /24 -hour storm (2.7 <br />inches). A "terminal" detention pond is defined as one that would release storm water to <br />basins external to the mine, as compared to "internal" detention ponds whose release <br />would report to a downstream terminal pond. The spillways from those ponds and <br />engineered diversion channels are designed to discharge the runoff from a 100- year /24- <br />hour storm with a total precipitation depth of 3.5 inches in 24- hours. <br />RUNOFF COEFFICIENTS <br />The excess precipitation, or runoff, from each storm water basin is calculated by <br />the SEDCAD4 model and also independently on an EXCEL spreadsheet model. The <br />2 Custom Soil Resource Report for Teller -Park Area, Colorado, Parts of Park and Teller <br />Counties, A product of the National Cooperative Soil Survey, a joint effort of the United States <br />Department of Agriculture and other Federal agencies, State agencies including the Agricultural <br />Experiment Stations, and local participants <br />Client: CC &V Gold Mining Co. 2/2/12 <br />Title: Storm Water Management, MLE2 Page 2 <br />