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• REPORT ON TECHNICAL IDENTIFICATION AND <br />STUDY OF ALLUVIAL VALLEY FLOORS <br />Methodology <br />During the week of May 11, 1980, Wyoming Fuel Company <br />personnel conducted a field examination and mapping procedure <br />to outline potential alluvial valley floors within a two mile <br />radius of its proposed surface mine on Federal Coal Lease No. <br />C-27931. All active flood plains and terraces underlain by <br />unconsolidated material were mapped, as were identifiable stream <br />channels. A regional map illustrating these unconsolidated <br />deposits is found in Exhibit 20. All drainage courses depicted <br />on the U.S.G.S. 7~" quadrangle sheets were examined for potential <br />alluvial valley floors within a two mile radius of the proposed <br />operation. Prior to the field examination, aerial photographs, <br />U.S.G.S. geologic maps, U.S.G.S. topographic maps and Soil <br />• Conservation Service maps were consulted as clues to areas con- <br />taining potential alluvial valley floors. <br />During March, 1981, Wyoming Fuel again studied the vicinity <br />described above in conjunction with the Pit 2 area (Federal Coal <br />Lease No. C-30168), paying particular attention as to the extent <br />of a potential alluvial valley floor up Bolton Draw near the <br />vicinity to be mined. The North Fork of Bolton Draw was walked <br />in order to determine the presence of a channel, flood plains or <br />other alluvial features. Subirrigation was studied. An analysis <br />was made of all exploration drill holes within the North Fork <br />vicinity to determine the presence of unconsolidated stream laid <br />deposits or the presence of alluvial groundwater. A careful <br />analysis of groundwater levels from both monitor wells and explor- <br />ation holes was made to determine if a water table aquifer exists <br />near the region to be mined. <br />• <br />-106- <br />