2010-12-17_REVISION - C1981019 (153)

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40 Surface water C �' 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. Information not presented includes: • geologic maps; • map showing the delineation of surface watersheds and direction of shallow groundwater flow; • map showing lands that are or were flood irrigated, including diversions, etc. (report says only historic irrigation in Jubb, but the hay meadow on Morgan Creek is irrigated today); • map showing lands subject to agricultural activities and different types of agricultural lands, etc; • documentation of areas not sub irrigated (discussion in text is reasonable, but the CDMG may want some data); and C documentation that areas are or are not flood irrigable (discussion in text is sufficient for Collom Gulch but does not mention current irrigation on Morgan Creek). The conclusions reached by the 1980 study are reasonable but probably need to be supported - by more recent data. This is most significant in terms of the hay field in Morgan Gulch. It is likely that the CDMG will require more information documenting current agricultural activities and their significance to the existing farming 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 are likely to meet the AVF definition and are therefore only potential AVFs. Further study is necessary on a site - specific basis to make the final determination. The OSM study covers any area potentially affected by the Collom Mine operation.. Potential AVFs were identified in Morgan and Collom Gulches and in Jubb and Wilson Creeks in areas similar to those identified in the 1980 D &M report. All of these areas are located downstream of, and not within, the proposed pit limit. The OSM report does not determine if they are or are not significant to farming. • 2572 -R2 Colowyo Coal Company Water Management Consultants