2010-12-17_REVISION - C1981019 (161)

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The wetlands along the project area stream courses are typical of Colorado mountain valley wetlands ranging from moist and wet meadows (within alluvial deposition areas) to heavily vegetated herbaceous strips (along stream banks). These wetlands are typically heavily vegetated herbaceous meadows to moist meadow communities because they receive moisture from lateral subirrigation along the stream channel. On occasion, wetlands developing along the margins of older more stable stock tanks exhibit emergent wetland communities. The majority of the wetlands within the project area occur over a rather broad continuum, especially lower in the watershed where stream courses flow over (or more typically have excised into) alluvial / colluvial floodplains. It is in these lower areas where the six larger wetlands were observed. It appears that most of these larger wetland areas receive their primary maintenance water from perched groundwater discharge in the form. of seeps and springs located along the margins of the alluvium / colluvium, but also from subirrigation due to the porous soil materials (sands and gravels) underlying the surface soils as well as run-on from the side slopes and flood flows escaping the confines of active channels. In most circumstances, sufficient moisture was observed to be delivered to these wetlands because areas of standing water were readily apparent. To the contrary, one of these six larger wetland areas (Wetland #4) located in the East Fork of Jubb Creek just above the confluence with the West Fork, is in a state of transition to upland. It appears that primary hydrology must have come as saturation of alluvial materials and subirrigation from flood flows. However, given stock tank development upgradient of this wetland, flood flows and/or subirrigation no longer saturate the surface with sufficient periodicity to preclude invasion by upland taxa. Because of the "problematic" nature of this apparent wetland, a soil pit (using a backhoe) was excavated in a central location dominated by wetland vegetation to a depth of six feet. Though soil mottling was "very abundant" and "strong" in the upper 6 inches of the profile, the pit was dry throughout the exposed profile of 6 feet. Given other corroborating characteristics observed about the area, it was concluded that alluvial moisture moving through the system must be at a depth greater than six feet and that the hydrology driving the wetland must have come from periodic flood flows (until the upstream stock tanks were constructed). The majority of study area wetlands tend to exhibit similar properties with very dark soil matrix colors, bright mottles, typical saturation to the surface or near surface, and dominance by sedges and wetland grasses and forbs. Areas transitional to upland are typically governed by elevation, slope, and soil textures that preclude ponding or subirrigation of soils in the upper 12 inches of the soil profile. The most notable characteristic governing the location of (or simply correlated to) the wetland / upland boundaries, especially along the transitional margins of these fluvial areas, is the often not so CEDAR CRIEEKASSOC?AMS, INC. Page 7 Colowyo Coal Co. - Collom Project Wetlands