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AMERICAN SODA, L.L.P. WILDLIFE MITIGATION PLAN MIGRATORY BIRDS Concern has been expressed by the U.S. Bureau of Land Management (BLM), the Colorado Division of Wildlife (CDOW), and the U.S. Fish and Wildlife Service (FWS) about potential migratory bird losses as a result of exposure to evaporation and other process ponds that will be part of the Yankee Gulch Sodium Minerals Project (Yankee Gulch Project) Piceance Site and Parachute Site facilities. It is suspected that TDS levels, especially sodium levels, and possibly other chemical conditions will warrant netting of the ponds to protect migratory birds. The primary sources of data on potential impacts due to effluent from sodium mining operations are studies conducted at trona operations in Wyoming and at other water bodies with high salinity. These data indicate that ponds with high salinity levels can cause bird mortality for a number of reasons, including salt toxicosis if sodium concentrations are over 17,1;00 mg/l (Rameriz 1992, Roffe personal communication 1998, Windingstad et al. 1y87, Wobeser 1981). Studies show that brain sodium concentrations above 1,800 ppm are considered toxic to birds. Sodium can also crystallize on the Feathers of waterfowl using highly saline ponds, which destroys thermoregulatory and buoyancy functions. The high salinity can also destroy oils in the skin used for preening, which is required to maintain the insulating qualities of the feathers. The end result is that birds may die of hypothermia or drowning. Although residence time, availability of nearby sources of fresh water, and the life stage of visiting birds may positively influence the survival of waterfowl exposed to highly saline waters, it appears that the best way to protect birds is to use 17,000 mg/1 as the threshold for when birds will be adversely affected. American Soda's mine plan for the Yankee Gulch Project includes a 13-acre evaporation pond system at the Piceance Site and a 15-acre evaporation pond system and a 21-acre MVR (mechanical vapor recompressor) purge pond system at the Parachute Site. These ponds, termed process ponds, would hold process waters that could have high sodium content and possibly other chemical conditions that could be hazardous to waterfowl. Therefore, these ponds are considered to have the potential to adversely affect migratory birds, and the following mitigation measures have been designed in consultation with the BLM, the CDOW, and the FWS to minimize this potential. First, American Soda will attempt to minimize or eliminate inflow streams to the process ponds wherever possible. [n final design, American Soda will attempt to Wildlife Mitigation Plan 3-1 Yankee Gulch Sodium Minerals Project American Soda, L.L.P.