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I I I I I I I I I I I I I I I I I I I ES ENGINEERING-SCIENCE 34.8,37.5, and 50.5 acres for Scenarios B, C, and D, respectively (Table 1). A small 3 to 5-acre increase in riparian area could be expected with Scenario A as a lower lake level makes new plant growing sites available along the former shoreline. Such resource losses resulting from Scenarios B, C, and D would probably be considered significant adverse environmental impacts by the Corps and other federal and state agencies charged with protecting and managing these resources. Given the generally high quality of these areas as wildlife habitat, the U.S. Fish and Wildlife Service (FWS) and Colorado Division of Wildlife (CDOW) (among others) would be reluctant to endorse activities or actions that would cause wetland or riparian losses. If, however, water storage is authorized, substantial mitigation for these losses would probably be required. Increases in riparian area (because of Scenario A) would be generally considered a favorable resource and wildlife habitat change. Mitigation Potential Potential opportunities for developing onsite and in-kind mitigation areas were observed during the field surveys of both the Turkey Creek and Bear Creek drainages. Potentially suitable upland areas are generally located outside wetland and riparian areas and appear to be reasonably well suited for wetland development activities (e.g., land excavation, routing water through the excavated area, and revegetating with wetland and/or riparian plants). Existing topographic conditions suggest that construction of new wetlands might be feasible along the new lake perimeters of the larger storage scenarios (Scenarios C and D at elevations 5,576 and 5,585, respectively) by excavating shallow-sloping land to the ground water table. Whether sufficient area is available to satisfy all mitigation needs would be a function of the approved mitigation objectives, required mitigation ratios, and total acreage requiring replacement. These considerations are discussed in a subsequent section. It is also likely that alluvial fans would redevelop at the mouth of each creek if watershed erosion continues at present rates. New willow, sedge, and cottonwood wetlands would develop on the sandbars and sand deposits, partially compensating for inundation losses. Since water impoundment began in 1977, willow wetlands have d~veloped at the mouth of both creeks and have extend into the upper end of the lake. REGULATORY IMPLICATIONS The preceding section demonstrates that storing additional water in the lake could result in inundation impacts to approximately 31.7 to 41.3 acres of probable jurisdictional wetlands, depending on the storage scenario selected. Jurisdictional wetlands are those areas which satisfy the legal definition of wetland (described previously) as used .in the admini.tration of Section 404 of the Federal Water Pollution Control Act of 1972 and the Clean Water Act of 1977, as amended. The Clean Water Act's Section 404 dredge and fill permit program is the major statutory -10- BI6-~3