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<br />shrub. This curve number was determined using vegetation and soil information <br />contained in the permit application. This curve number results in a design of no runoff <br />from these areas. <br />Enclosed is a copy of an aerial photo that appears to show that some of these upland <br />areas do not have the vegetative cover type or percent cover that was described in the <br />reference areas, particularly to the north of the bench area and those areas that have <br />roads. Some of these areas appear to be a mix of oak and grassland, with a cover that <br />may be described as 'fair" rather than "good. ". The road areas are grassed or bare <br />earth. <br />The Division believes that it is reasonable to assume that some of these areas will have <br />runoff. /f the upper diversion ditch is reclaimed, this runoff would flow to the sediment <br />ponds. In fact, the hydrology design for the West Mine upper diversion ditch, found in <br />Volume 8 under the "culvert capacity" tab, used a curve number of 60 for the drainage <br />area, which results in runoff being accounted for in the hydrology designs. Please <br />comment. <br />The Division has no further concerns. BRL changed the hydrology pazameters for the oak <br />and mixed shrub areas in the hydrology designs. The hydrologic condition was changed <br />from good to fair and the curve number was changed from 41 to 60. The pond designs, <br />including design drawings, were revised in the submittal dated September 13, 2001 and <br />received at the Division on September 17, 2001. <br />4. Bowie intends to apply mulch io the reclaimed area. The capacities of the two proposed <br />sedimentation ponds are based on this mulch ground cover. However, the Division is <br />concerned that several months will elapse benveen the construction of the ponds and the <br />application of the mulch to the fully backfil[ed and topsoiled reclaimed area. The <br />Division believes that the two sedimentation ponds should be designed for the interim <br />period when no mulch has been applied. Please provide revised pond designs or explain <br />why Bowie considers the present plan acceptable. <br />BRL changed the hydrologic design parameters to reflect the field condition before mulch <br />is applied. The hydrologic condition was changed from fair to poor and the curve number <br />was changed from 81 to 87. However, it would appear that the sedimentology parameters <br />for the disturbed areas also need changing. For each pond design, the cropping <br />management factor, "C", remains at 0.1. This value is applicable for the mulched <br />condition but not for the pre-mulched condition. Please revise the submittal to take into <br />account a cropping management factor for the pre-mulch condition for the disturbed <br />areas. <br />5. Bowie intends to apply mulch, at a rare of 1.5 tons per acre, to the reclaimed area. Please <br />add to the permit text what the anchoring method for the mulch will be. <br />2 <br />