2010-12-30_PERMIT FILE - P2010026 (5)

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Yamac loam comprises approximately 85 percent of the map unit. Other soils series that may occur within this map unit include the Forelle, Piceance, Redcreek, and Rentsac series. Yamac is classified as a "Fine-loamy, mixed, frigid Ustic Haplocambids". The representative Yamac loam sample site was located approximately 2,322 feet east, 1,809 feet south of the NW corner of Section 4, T2S, R98W. The landscape at the sample site was a 4% slope with a northeast aspect. Vegetation included big sagebrush, rubber rabbitbrush, and a variety of mixed grasses and forbs, including western wheatgrass, needleandthread, and winterfat. The surface was stable with no visible evidence of disturbance or erosion. However, two significant drainage channels draining to the south dissected the Yamac map unit. Approximately 21 acres of Yamac were mapped in the study area (14% of total). Yamac typically has an "A" horizon surface layer that is brown sandy loam about 4 inches thick. The upper 8 inches of "B" horizon subsoil is brown loam, and the lower 10 inches is highly calcareous loam or sandy loam. The upper 26 inches of the "C" horizon substratum is a very pale brown loam, and the lower part to a depth of 60 inches or more is a pale brown loam. Permeability of Yamac is moderate, runoff is medium, and the available water holding capacity is moderate to high. The effective rooting depth is 60 inches or more. The hazard of water erosion is slight to moderate. Yamac is not considered Highly Erodible Land (HEL). There is no current Official Soil Series Description available for Yamac. However, an outdated PDF copy was obtained from the Colorado NRCS state office for submittal with this report (Hahn 2009). Yamac is a series that originated in the Plains of Montana. However, it was correlated in Rio Blanco County in 1979 and the official description at the time was modified to include the Colorado version of Yamac. In 1984, after the publication of the original Soil Survey of Rio Blanco County Area in 1982, it was determined that the Yamac series (and name) did not belong in western Colorado. Therefore the Yamo series was established as a Colorado-counterpart to the Montana Yamac. Other northwest Colorado counties in which the soil survey has been recently updated have already officially made this switch. When soil mapping is updated in Rio Blanco County in the future it can be assumed that the Yamac series will be recorrelated to the Yamo series (Hahn 2009). Disturbed Land (DL) Minor areas of Disturbed Land (DL) occur in the study area. Range revegetation research has been ongoing for over 40 years in the study area and many studies involved activities that disturbed the land surface. Study plots stripped of topsoil and/or subsoil were regraded to match the surrounding landscape. Retorted shale may have been tilled or graded onto the study plot surface. These areas may have been cultivated, reseeded, fertilized, and/or irrigated. Years of vegetative regrowth has made these plots difficult to distinguish from the surrounding landscape. Remnants of these studies remain as stockpiled berms of topsoil and/or subsoil that have not yet been reclaimed. Other than this evidence, it is difficult to determine how much of the study area has been disturbed and to what degree. 8