2011-05-12_PERMIT FILE - M2011028 (2)

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CHAPTER 3 AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES Mitigation for Refined Alternative 4 Special Status Species Impact 4: Reclamation would operate ' Navajo Reservoir and the Durango Pumping Plant to mimic the natural hydrograph of the San Juan River for the benefit of the Colorado pikeminnow and razorback sucker. The result of the seven-year research study was a flow recommendation for modified operation of Navajo Dam releases (Holden 1999). Reclamation is preparing an EIS to address the long-term environmental consequences of the reoperation of Navajo Dam. The Service and Reclamation would review these flow recommendations and a new Biological Opinion would be prepared on the modified operation of Navajo Dam incorporating these flow recommendations. Refined Alternative 4 Special Status Species Impact 5 - Potentially Significant: Survival and recovery of endangered fish in the San Juan River could be jeopardized by competitive interaction with non-native fish released from Ridges Basin Reservoir to the Animas River. A possible impact to the endangered fish in the San Juan River is the interaction with nonnative fish species escaping from Ridges Basin Reservoir. The proposed CDOW stocking of trout in Ridges Basin Reservoir would pose no threat to either the Colorado pikeminnow or razorback sucker in the San Juan River. However, the possibility does exist that other nonnative species that might compete with the San Juan River endangered species may be illegally stocked into the reservoir and subsequently escape. Because the majority of reservoirs in the area have received illegal stockings of nonnative species, it is assumed that Ridges Basin Reservoir would also. Mitigation for Refined Alternative 4 Special Status Species Impact 5: The reservoir outlet system would be designed and operated to eliminate survival of predatory or competitive fish from escaping the reservoir. To minimize entrainment of fish, the dam outlets would be located as deep in the reservoir as possible to draw primarily anoxic hypolimnetic water, a zone likely to be devoid of fish in summer and winter. Water released from the reservoir would be directed at a high velocity splash pool to ensure mortality of any escaping fish. Reclamation may also consider adopting other, more effective measures if such are deemed feasible. Water released through a delivery system from the reservoir would also be released from as deep in the reservoir as possible. This water could also be physically treated to ensure mortality of any escaping fish. Small volumes of water (i.e., less than 50 cfs) could be passed through a sand/gravel filter, particularly if the water is to flow into any existing surface waters, such as the La Plata River. Water destined for a water treatment plant would be treated to eliminate fish as part of the treatment process. 3.7.4.2 Refined Alternative 6 Implementation of Refined Alternative 6 is expected to have no effect on the Colorado pikeminow and razorback sucker in the San Juan River. The increase in mean flows transferred down the Pine River to Navajo Reservoir would not change the flow statistics over that of Refined Alternative 4. Under Refined Alternative 6, there would be no Ridges Basin Reservoir, as the alternative would avoid the potentially significant impact of releasing competing non-native fish from the reservoir to the Animas River, with the risk of the fish adversely interacting with the Colorado pikeminnow and razorback sucker in the San Juan River. This section discusses the potential effect of Alternative 6 on the bald eagle and southwestern willow flycatcher. Weeminuche Construction Authority 3.7 SPECIAL STATUS SPECIES 3-120 P.O. Box F: - Tolxacc CO 8133 ',:i, ?tV t f>•'+q S Gt.Ac t?Y? GRsa tt L- ' L , i _ F_,}c. t-t t C? l T l-E - PC1G ? ({ - Qt 3 ..