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, "".40j....., OJ_v~. Alternatives, Including Proposed Action 2-7 2.1.2.2 Penstock The penstock would be new construction. It would be installed in an excavated trench. The pipe diameter would vary depending on the design flow capacity of the AB Lateral facility and position along the alignment (generally 8 to 10 1/2 feet diameter). Steel pipe would be used, and the thickness of the steel would be determined according to the pressure in the pipe. The pipe would be thicker at the lower end of the penstock, near the powerhouse, than at the upper end near the intake, because the pressure at the lower end is greater. The joints between different sections of pipe would be welded. The Sponsors would inspect each joint during construction. After the penstock is constructed, the Sponsors would test the entire pipe before beginning operation of the Project. The penstock intake design would include features to prevent rocks and floating debris from entering the penstock and turbine. The intake design would also incorporate features to isolate the penstock from water flows during maintenance and inspection or in case of emergency. The selected route for the penstock and typical construction details are shown in Figure 2-3. 2.1.2.3 Powerhouse The powerhouse, to be located in northwest Montrose as shown in Figure 2-3, also would be new construction. It would house the turbines and generators, along with control panels and conventional support equipment. In case of an unplanned shutdown, water would continue to pass through the turbines but would be deflected away from the turbine runner, allowing the continuous flow of irrigation water to downstream canal systems and preventing sudden water-level fluctuations in the Gunnison and Uncompahgre Rivers. Figure 2-4 shows the facilities at the powerhouse site, based on the conceptual design. 2.1.2.4 Stilling Basin and Tailrace Water leaving the powerhouse would enter a stilling basin designed to slow the water velocity. The stilling basin would be lined with riprap to prevent erosion. An earth or concrete-lined tailrace would be constructed to convey water away from the powerhouse to the Uncompahgre River. Riprap at its confluence with the river would prevent bank erosion and channel degradation. Figure 2-5 shows the alignment, sections, and bank stabilization details. 2.1.2.5 Transmission Line Power from the new powerhouse substation would be transmitted through a new 115- kilovolt (kV) transmission line. Figure 2-6 shows the location of the proposed new line and the existing powerlines, including a segment that would be upgraded to 115 kV. The proposed line could feed power either direction (north or south) increasing local reliability. Total length of the new line is approximately 4 miles. AS Lateral Hydropower Project July 2000 , ..~I . .~~i..=.>J.",jj " ,.......