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Environmental Scientists and Engineers, LLC Dames & Moore, 1980 Study The original body of work delineating potentially affected AVFs was performed by Dames and Moore (D &M) in 1980. Areal photographs and topographic maps were used to identify potential AVFs based primarily on geomorphic characteristics in portions of: • Wilson Creek • Jubb Creek • Collom Gulch • Straight Gulch • Morgan Gulch These areas were then field evaluated, and observations on vegetation, soils, hydrology, and historic land use were made. The report concluded, "that the upper reaches of these drainages could be classified as AVFs." The study concluded that these potential AVFs "have limited economic and agricultural significance to the present ranching and agricultural operations in the area." The study area for the 1980 evaluation consisted of lands within a 2 -mile radius of a project, which would have mined, primarily in Sections 25, 35, and 36 of T4N, R94W. The currently proposed lease area is expected to operate in areas further south than was the subject of the 1980 Dames and Moore study, including mining in Sections 1 through 4, 11, and 12, T3N, R94W. The D &M study area includes all of Sections 1 through 3 and most of Sections 4 and 10 through 12. This study appears to cover the area potentially affected by the Collom Mine adequately. Any AVF south of the D &M study area would be located upstream of the proposed operation and, thus, the proposed operation is unlikely to affect either farming or water supplies. • While the 1980 study included the basic disciplines and types of evaluations that are required to make an AVF determination, the specific data and maps "required" by the regulations are not included. The conclusions reached by the 1980 study are reasonable but probably need to be supported by more recent data. This is important in terms of the hay field in Morgan Gulch. It is likely that the CCDMG will require more information documenting current agricultural activities and their significance to the existing fanning operation in order to make their finding. OSM, 1985 Study The OSM report presents maps that identify potential AVFs on a reconnaissance -level only. Published reports, aerial photography, Landsat imagery, geologic and soils data, and irrigation and agricultural practices in the region were evaluated. This report cautions that the maps presented represent only a reconnaissance -level identification of areas that P PROJECTS (ofm, OISS ,raLlA.M- ,- EACo6„i3Op8 ni uo. J•' 23