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August 2000 CRWYCD * Yampz Reur Basin Small Rew wi- Study - Phase 2 Report -Page ? 25 ' dam at this location would impact at least one and likely two existing irrigation ditches. If the lower ditch was to be serviced from this reservoir, it would require maintaining a minimum pool of 20 feet to feed the ditch during the irrigation season. ' A portion of Moffat County Road 27 would have to be relocated to allow construction of the reservoir. Based on initial site reconnaissance, the road could be relocated to the south and east of the reservoir site and tie into the existing road along the northeast side of the reservoir. This portion of County Road 27 is an improved gravel road that could be relocated without substantial cost impacts to the reservoir project. ' The geologic setting for the dam would be in the lower portion of the Wasatch formation (see Figure 9). The Wasatch formation consists of fluvial sandstone, mudstone, and conglomerate. During the site reconnaissance for Little Bear 1, each of these geologic strata was noted at the site. From a review of the surficial geology map, Figure 8, it appears that the upper end of the Little Bear 1 ' Reservoir could inundate an area of historic landslide activity. Further discussion pertaining to landslide activities in the Fortification Creek drainage is presented in Section 4.2. ' Soils in the Little Bear 1 reservoir area have been identified as Abor silty clay loam, Bulkley stoney loam, Herm-Fughes complex, Lander loam, and Morapos Loam. These soils are typically residuum or colluvium derived from shale with a moderate to high shrink-swell potential. The typical profile for ' these soils grades into clays ranging from low to high plasticity. The upstream side of the knob that would form the right side of the foundation is an over steepened slope, approximately 1:1, and would present a stability problem during drawdown of the reservoir. ' This area would likely have to be stripped of surficial soils, or buttressed with reject material during dam construction to prevent development of instability in this area during reservoir operation. ' Ecological Evaluation Riparian and wetland habitats along Little Bear Creek are dominated by willow (Salix spp.)/alder ' (Alnus irr ) communities in the vicinity of the proposed dam site and within the potential reservoir basin. Linear stands of narrow-leaf cottonwood (Popuhm artgustifolia) also exist in the drainage bottom in the upper portion of the reservoir basin and create additional riparian habitat diversity. Many of these trees were partially decadent or appeared to be dying indicating a possible reduction in historic ' water levels or that the tree stands in this area are reaching their maximum age. Cattle grazing in the area appears to have limited the recruitment of young narrow-leaf cottonwood trees at the Little Bear 1 reservoir site. Wetlands along the creek are not extensive and are confined primarily within the stream's embankments. However, there are some areas of Baltic rush Vwxw baldcw) /sedge (Caxex spp.) / ' grass wetlands outside of the stream embankments primarily in what appeared to be old, isolated oxbow creek sections on the west side of the existing creek channel. ' Other habitats along the creek are mixed shrub communities of big sagebrush (Artenisia trr mow), snowberry (Syrnphorkarpos sp.), Gambel oak (Qte= gvnbe t), and chokecherry (Pn#tus vi*ui vw) as well as big sagebrush / grass communities. Dominant grasses are smooth brome (B7 s inenis), Great Basin wildrye (E6mw cm mw), orchard grass (Da* gbimata), Kentucky bluegrass (Poa praunsis), and timothy (Phkum praom). Side slopes of the reservoir basin area support primarily sagebrush / grass communities and mixed shrub communities of big sagebrush, Gambel oak, ' snowberry, and serviceberry (Amelan&ieralnifalia). Photo LBear#1-1 (refer to Appendix B) shows a representative view of vegetation communities supported within the reservoir basin area. Mor Wreery Watson * P.O. Box 774018 * SteamEroat Sprijgs, Colorado 80477 * (970) 879-6260 ' W/WPPoSS/pGaie7 Repws OB/30/OOjr?