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ATTACHMENT A, CALCULATION METHODS <br />Calculation Methods <br />I. Given Criteria <br />a. Design storm for pond size is 2.4 inches (P,o, Q,o,V,o) or 10yr/24hr storm. <br />Pond size is 2 times that runoff volume <br />b. Design storm for channels is 3.5 inches, or 100yr/24hr storm (P,oo, Q,oo. <br />Vioo) , <br />c. Riprap design using Simon method for 10-year flow (Figure 3), or <br />PARDAR method for 100-year flow <br />II. Criteria <br />a. Land use Curve Numbers <br />i. Operations and pre-mining <br />1. CN for grass= 71 <br />2. CN for forest= 66 <br />ii. Stripped areas <br />1. CN= 71 <br />iii. Rock fill, loose dumped <br />1. CN= 50 <br />iv. Post Reclamation <br />1. CN for Grassed Areas = 71 <br />2. CN for low Permeability ECOSA = 75 <br />b. Antecedent moisture, Type II distribution <br />c. Calculation models <br />i. SEDCAD4/TR55 for tabular hydrograph routing and Time of <br />Concentration (T~) by TR55 method <br />ii. SCS Methodology for determining volume of runoff (implicit in <br />TR55) but tabulated on Table I by direct calculation <br />III.- Calculation Method (reference Table I) <br />a. Storm volume for pond sizing <br />i. Rio= (Pio-0.25)Z/(P+0.85) <br />S= (1000/CN)-10 <br />Client:CC&V Gold Mining Co. 4/11/08 <br />Title: Storm Water Management, MLE Page 17 <br />