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00106~ Final Environmental Assessment-Chapter 2-Alternatives Water Supply for Fish Ladder Because of downstream senior water rights, a flow of at least 520 cfs is present in this reach of the river under all but the most severe drought conditions. The Service also has up to 37,650 acre-feet of storage water available from upstream reservoirs for endangered fish uses in drought years. About 25 cfs of Colorado Rjver flow would be needed to operate the fish ladder. An additional 75 cfs would be used to provide attraction flows necessary to direct fish to the fish ladder entrance. Ifthe Jacobson Hydro No. 1 Project were independently constructed, the power plant's tailrace could also provide the necessary attraction flow. Downstream Rock Fish Passage This alternative was developed in response to public comments on the 1999 Draft EA with input from affected parties. The Downstream Rock Fish Passage Alternative would notch the Price-Stubb Diversion Dam and leave the Dam in place. A rock ramp fish passage would be constructed on river left2 of the downstream face of the dam. This type of fish passage would not prevent construction of the Jacobson Hydro No.1 Project; however, the proposed hydro project would require additional modification and design. Significant modifications include elimination of the 4- foot flashboards on the dam and moving the hydro plant downstream or extending the hydro plant discharge to the downstream entrance of the fish passage. Similar rock fish passages were constructed in the San Juan River by the San Juan River Basin Recovery Implementation Program to restore endangered fish passage. An "in- river" rock fish passage was constructed in 2002 at the Hogback Diversion Dam on the San Juan River in near Shiprock, New Mexico (Figure 4). An "out-of-channel" rock fish passage with selective fish passage (fish trap) was constructed in 2003 at the Public Service Company of New Mexico Diversion Dam on the San Juan River near Fruitland, New Mexico (Figure 5). Fish passage use by Colorado pikeminnow and razorback sucker has been documented at the Public Service Company of New Mexico fish passage. Design Conceptual designs (Figure 6) propose placing fill material on the downstream face of the Price-Stubb Diversion Dam to create fish passage. The fish passage would consist of 1) a 30 foot-wide by 550 foot-long downstream fish passage channel with a 2.5 percent gradient along the river-left bank of the Colorado River, 2) a 80 cfs low flow fish passage notch in the Price-Stubb Diversion Dam, 3) the remaining 250-foot-width ofthe dam would be stabilized with riprap material to create a 2.5% sloped ramp, 4) a divider-berm constructed between the fish passage channel and the 2.5% ramp to protect the fish passage, and 5) a rock barrier or sheet pile barrier to assist in directing fish to the passage 2 River left refers to the left side of the river as viewed when looking downstream. 11