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Response: Discussion of possible sediment pond seepage is provided <br /> in Response No. 8 of the main response letter. <br />e. The pond design should address discharges from the old mine <br />both in terms of quality and quantity. The regulations <br />require treatment if discharges exhibit a pH less than 6.0. <br />Response: Discharges from the adjacent underground mine north of <br />the sediment pond, vary dependent on the time of year. This <br />discharge will be routed to the sediment pond and the pH of the <br />pond will be monitored prior to discharge. If necessary, treatment <br />measures will be implemented to ensure that the pH of the effluent <br />is greater than 6.0. Treatment will typically entail addition of <br />lime to the pond or other measures. <br />f. Ditch designs for the two (2) unnamed ditches which flaw into <br />the sediment pond must be presented. In addition, it appears <br />that the ditch on the east side of the pond will short <br />circuit. Also, the east ditch drainage area does not appear <br />to be included in the disturbed area drainage of 28 acres. <br />Response: Calculations for the ditch from the east are attached. <br />The east ditch drainage is included in the disturbed area drainage <br />of 28 acres. Given the location of the east ditch discharge at the <br />northeast corner of the sediment pond, short circuiting will not <br />occur. <br />g. Why are peak flows for the 10 year, 24 hour event in Culvert <br />C-2, which flows into the pond, greater than peak flaws <br />calculated far the 25 year, 24 hour event for the sediment <br />~~ <br />Response: The methods utilized to estimate peak flow for Culvert <br />C-2 and the 25 year, 24 hour event flows for the sediment pond are <br />. slightly different in that routing was used on the sediment pond. <br />Peak flow for the sediment pond is 19 inches per inch of runoff or <br />34 cfs as compared to 28.8 cfs for Culvert C-2. <br />-11- <br />