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Mr, Roland G. Obeying - 2 - June 20, 1989 <br />3. What is the reclamation plan for the silt retention facilitv2 How long <br />will it be maintained with respect to the minino and reclamation <br />timetable? Will it be removed at the completion of surface stabilization <br />and reveoetation of the Phase IIT area? <br />4. No time-of-concentration parameter value was provided in the appendix for <br />the drainage area designated 8-0, Please provide. <br />5. An R-factor of 75 was used in the LISLE calculation of soil Loss. Fioure <br />1 1n "A Guide for Predicting Soil Loss from Water Erosion in Colorado, <br />Technical Note 50", Revised February 1984, So11 Conservation Service, <br />indicates Manitou Springs is right on the border between values of 50 and <br />80, so the use of 75 aooears conservative. Please identify how the <br />R-value was derived, <br />6. A particle size of 40 microns was chosen as the level far control in the <br />sediment pond design, A settling efficiency of 70 percent was assigned. <br />These values are similar to those used in the reference provided. Please <br />describe briefly how these values were chosen in relation to the particle <br />sizes expected to be encountered at the mine site, <br />7, Sheet 1 of 2 provided with the report shows a silt fence to be <br />constructed extending west from the embankment of the pond. An area <br />exists downslope from this fence which will be disturbed by mining. The <br />Division recommends the silt fence be placed at the extreme base of the <br />bottom of the disturbed area and a berm be used to direct runoff to the <br />siltation facility. This berm would be located at the same general <br />location of the fence as shown on the map. Please comment on this <br />recommendation. <br />8, the embankment is designed to be excavated to grade. The principle <br />spillway is located at the base of the embankment. This requires a notch <br />be excavated in the embankment, What measures will be used to insure the <br />integrity of embankment stability from seepage in this location? <br />9. The Division recommends a marker be placed to identify the maximum <br />sediment storage level for field inspection, Please comment, <br />10, It aooears a Colorado Discharge Permit System (COPS) permit will be <br />required for this facility. You are advised to cgntact the Colorado <br />Water quality Control Division in this regard, <br />The additional elements of the plan including culvert crossings, silt fences <br />and site berming have been reviewed. The Division concurs with the designs <br />suggested. These will work well with the sediments control system a5 a <br />whole. T would also like to commend you on the direct and explicit approach <br />taken in the design and documentation provided in the report. <br />