PERMFILE112237 - Laserfiche WebLink

Home Browse Search

In reference to Areas 9 and 10, and 31, no repair is required for the Swale • and Swale-like feature in these areas. Water Engineering and Technology Inc. has prepared a report (see Appendix II) which demonstrates that these areas comply with the backfilling and regrading requirements of the regulations. A section of the report in Appendix II utilizes hypsometric analysis to show that three AOC requirements leave been met at the CYCC operation. As part of this analysis, the mine areas were initially combined to form a drainage basin. However, the combined mine areas consisting of Areas 31,7, 51 and 41 can be divided into five watersheds (i.e. first-order basins). Analysis on a basin scale is justified by the contention by many that a drainage basin is the smallest fundamental hydrologic or geometric unit. For instance, Gregory and Walling (1973, preface) state that the drainage basin, "... is visualized increasingly as the fundamental unit of study in fluvial geomorphology...". Ritter (1978, p. 169) describes basins as, " excellent fundamental units of geomorphic systems." Charley et al. (1987, p. 3i6) point out that the drainage basin,"... has been recognized as a viable process-response unit since the beginning of the last century." It is concluded then, that comparison of mine areas smaller than a first order basin is inappropriate because it is a comparison of only a portion of the basic geomorphic system unit. The five watersheds are approximately the size of first-order basins and they extend from the lowermost portions of the mine adjacent to South Foidel Creek to the top cf the mine. Approximate drainage divides were drawn • between adjacent watersheds that remain fixed on both existing and approved topographic maps so that the same area is measured for both conditions. Contour interval for the analysis is 50 feet except in the area of the Swale where contour interval is 25 feet. Hypsometric curves for existing and approved topography within the five watersheds (Figs. 1 through 5) are similar indicating, as did the analysis presented in our report, that spoil material has not been significantly re-arranged by mining. Figure 6 shows the relative locations of mine areas, stream channels, and watershed areas. in addition, portions of the Swale in Areas 9 and 10 have been topsoiled and revegetated. It tiould not be prudent to disturb these revegetated areas when no benefit would be gained by such an action. Likewise, for the Swale-like feature in Nrea 31, the entire area iias been topsoiled and revegetated. Disturbing this area to eliminate a Swale-like feature is not warranted. It should be noted that the 4later Engineering and Technology report included procedures that thie Wyoming Department of Environmental Quality (DEQ) has proposed for determining pre- and post-mining surface configurations. A copy of the DEQ memorandum is contained in Appendix III. In addition, the postmining land use is for both rangeland and wildlife. The creation of topographic diversity, i.e. swales, certainly benefit the utilization of the reclaimed areas by wildlife. ~. - 53 - Revised 04/11/88