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Page 2 June 8, 1979 • • attainable will not be known until the operation is begun and experience gained on the groundwater fluctuations and their effect on the sand deposit. It is recognized that there will be stream channel erosion into the pit which is formed from excavation of the sand, and it is intended to observe this action as it occurs periodically from surface flows. Although large drop structures are depicted on the reclamation map, it may be necessary to utilize several smaller drop structures in each channel to more effectively contain the scouring actions. The structure located on Murphy Creek will be determined and installed approximately seven years after the operation commences when Tract #3 is excavated (Item #11-27 Map of Mined and Affected Areas), but it is anticipated that the two structures located on Coal Creek will not be required until after twenty years of operation. The conditions of Picadilly Road and its effect on the channel could change completely in that time period, e. g. abridge crossing structure could be built. At the present time the improved surface of Picadilly Road acts as a dam to the scouring effects of surface flows and must be cleared of sand after each occurrence. The construction of the drop structures needed in the channels will be assured by reason of the bond requirement as part of the permit procedures of the Mined Land Reclamation Board. Atypical design of the drop structures as depicted on the reclamation map could be prepared, but in fact would contain conjectures because of the unknowns etiumcrated above. The proper channel design should be ascertained when the operation has been underway for a few seasons. Regarding erosion downstream because of discharge of sediment- free water from the pit during floods, such a condition is possible as the pit becomes larger in area, and sheet piling may be required in the channel at the pit outlet to reduce erosion effects. At the same time, a Larger area in the pit will reduce the frequency of downstream flooding by decaying or eliminating the lesser surface flows. Finally, it is planned to use afour-strand barbed wire fence to secure the area against trespassers. This type fence should not obstruct the flows of any flood waters. We wish to assure you that the features of the area as an open drainageway have been assessed in preparing our report for the rezoning petition and that the final layout of the reclamation plan must recognize this continued use as stated in Item yll-23 A Reclamation Plan and Maps; the operator wil! also continue to be made aware of these conditions because of periodic surface flows in the channel as excavation of the effected area progresses upstream.