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Response to General Stormwater Comments on March 01, 2011 <br />Response #6 <br />Soil and vegetation characteristics were considered for the entire drainage basin. The soils <br />and vegetation data is presented in exhibit I and J respectively. <br />Adequacy Issue #7 <br />Please clarify the meaning of, or remove "Sq feet" under the column labeled "Rainfall Amount" <br />and "Acres" under the column labeled "Runoff' as necessary on page 1 of Tables SWMP A, B, <br />C, D, G, and H. <br />Response #7 <br />As requested, "Sp Feet" was removed from all referenced tables. <br />Adeauacv Issue #8 <br />Culvert Designs - Tables SWMP D, E, and F: Page one of each table references Haested's <br />CulvertMaster software package. However, it appears that Haested's FlowMaster software was <br />used to perform the culvert analyses. A full-slow pipe analysis is not appropriate for culvert <br />design or analyses. This approach fails to account for head loss at the culvert entrance and outlet. <br />It should be noted that a considerable amount of head is required to force a culvert on a relatively <br />steep slope (e.g. 3% in Tables SWMP D & F) to flow full. Standard engineering practice for <br />allowable head at a culvert entrance is 1.5 times the culvert diameter. Please use appropriate <br />methodology and engineering practice to size culverts. <br />Response #8 <br />Culverts are designed in accordance with referenced documents. The allowable head at <br />culvert entrance has been limited to less than 1.5 times the culvert diameter. All culvert <br />slopes are less than 2% and D50 riprap has been specified. All culverts are designed with <br />controlled inlets and outlets with appropriately sized riprap. <br />Adequacy Issue #9 <br />Please correlate or use consistent nomenclature for the storm water management structures <br />shown in Figure SWMP-1 with the elements designed in Tables SWMP 1 and SWMP A through <br />M. For example, is the structure labeled "CUL-A" on Figure SWMP-I the same as the culvert <br />analyzed in Table SWMP D? Also, for what purpose are the values calculated in Tables SWMP <br />A through C. <br />May Day Idaho Mine Complex 112(d) Permit Application <br />Revised: April 14, 2011 <br />4