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 The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid watershed that encompasses parts of seven U.S. s ...

drainage to the eastern

Front Range The Front Range is a mountain range of the Southern Rocky Mountains of North America located in the central portion of the U.S. State of Colorado, and southeastern portion of the U.S. State of Wyoming. It is the first mountain range encountered ...

of Colorado. It is long, with a concrete lined diameter of . The tunnel drops in elevation along its length and runs in a straight line under the Continental Divide from west to east, passing under Rocky Mountain National Park. At its deepest point, the tunnel is about below the surface of the mountain peaks. Construction began on 15 June 1940, but was suspended as a result of

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

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

drainages to

Lake Granby Lake Granby is the third largest body of water in Colorado. It was created by the erection of Granby Dam, completed in 1950, as part of the Bureau of Reclamation's Colorado-Big Thompson Project. Water from Lake Granby is pumped via the Farr Pump ...

. 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 largest reservoir in the state of Colorado, with a nominal capacity of . Once the water reaches the

on the eastern side of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...

, it is used to generate electricity as it falls almost half a mile (0.8 km) through five power plants on its way down the Front Range.C-BT and Alva B. Adams tunnel syste

Accessed 7 September 2011 To get the power from the

power plants back to the pumps on the western slope, a diameter watertight nitrogen-filled conduit carrying a 69,000 volt electric power transmission line is mounted on the roof of the tunnel. This power is used to run the pumps on the western side of the tunnel, while surplus power is sold. West slope water is stored on the Front Range in Mary's Lake, Lake Estes, Carter Lake Dam, Carter Lake (all reservoirs), Flatiron Reservoir, Horsetooth Reservoir and Boulder Reservoir for power generation or release after the peak snow melt months of May to July. The tunnel is capable of carrying a water flowrate of . An average annual total of of water is transported through the tunnel each year. The tunnel can transport as much as in one day. The water transferred through the tunnel is considered part of Colorado's

water allocation of per year as agreed to in the

Colorado River Compact The Colorado River Compact is a 1922 agreement among the seven southwest U.S. states that fall within the Colorado River drainage basin. The pact governs the allocation of the river's water rights. The agreement, originally proposed by attorn ...

. Entrance (West Portal, Underwater)
Exit (East Portal)

References

{{Rocky Mountain National Park Water tunnels in the United States Transportation buildings and structures in Grand County, Colorado Transportation buildings and structures in Larimer County, Colorado Buildings and structures in Rocky Mountain National Park Tunnels completed in 1947 1947 establishments in Colorado