Alva B. Adams Tunnel

The Alva B. Adams Tunnel is the principal component of the largest transmountain water project in Colorado, the Colorado-Big Thompson Project (C-BT). The tunnel transfers water from the western slope of the Colorado River drainage to the eastern Front Range of Colorado. It is 13.1 miles (21.1 km) long, with a concrete lined diameter of 9.75 feet (2.97 m). The tunnel drops 109 feet (33 m) in elevation along its length and runs in a straight line under the Continental Divide from west to east, passing under Otis Peak in Rocky Mountain National Park. At its deepest point, the tunnel is about 3,800 feet (1, 200 m) below the surface of the mountain peaks. Construction began on 15 June 1940, but was suspended as a result of World War II priorities, from the end of 1942 to August 1943. The tunnel was holed through on 31 March 1944, an event that was broadcast throughout the United States by NBC Radio. The tunnel was posthumously named for its chief advocate, US Senator Alva B. Adams. West of the Continental Divide, the input of the tunnel is water pumped from Windy Gap Reservoir, Willow Creek Reservoir and other North Fork of the Colorado River drainages to Lake Granby. From Lake Granby, the water is pumped into Shadow Mountain reservoir and then flows by gravity to Grand Lake, Colorado's largest natural body of water, from where it pours through the tunnel. Lake Granby is the second l

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