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-5- <br />Rule 2.05.3 <br />Hydrology <br />There are discrepancies between Figure 1 of the October 1993 submittal and Map C-4 <br />with regard to which areas drain to the ponds and which are diverted. Specifically <br />the east natural area shown dreirting to the east pond is apparently much smaller than <br />what is shown. This would decrease the east pond watershed and increase the clean <br />water diversion watershed. Also, reach 10 is shown on Figure 1 as a new pipe but <br />text and site inspection apparently indicates open channel for a portion of this reach. <br />The permit boundary must also be shown on any map which is bisected by portions of <br />the permit boundary (Rule 2.10.1(3)). Also, Map C-4 part 1 and C-4 part 2 do not <br />match with regard to contoured elevation (off by 100' one way or another). <br />2. The Division questions the curve numbers used by the operator. Inspection of the <br />soils map shows a D soil for most of the area and aerial photo interpretation <br />indicates variable canopy cover and very little ground cover. The Division believes <br />realistic curve numbers to be as follows: <br />Natural south facing slopes, I,azear Soil CN = 77 <br />Disturbed yard CN = 86 <br />Natural, north facing mountain shrub CN = 73-77 <br />Please justify the curve numbers utilized or adopt the Division's recommended curve <br />numbers and reverify volume amounts. <br />3. Sediment ponds are not required to store the 10-year 24-hour event. Rule <br />4.05.6(3)(a) requires "adequate capacity to contain or treat the nmoff from inflow <br />entering the pond as a result of a 10-year, 24-hour precipitation event...". In the case <br />of King Coal, this will be accomplished by using aself-dewatering principal spillway. <br />An emergency spillway to safely pass the 25-year, 24-hour event will also be <br />employed. In order to properly evaluate the performance of the ponds, King Coal <br />needs to supply accurate information with regard to what is to exist. Currently there <br />are numerous discrepancies between as-built plans for the east and west ponds and the <br />October 1993 text. Some of them are as follows: <br />a. Are the 10-year spillways near the pond bottoms or are they at the elevation <br />shown on the as-built? Be advised, the elevation of the 2.5" and 1.5" orifices <br />are the 10-year spillway elevations. <br />