Hells Canyon Dam is a concrete gravity dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 on the Snake River

Snake River

The Snake is a major river of the greater Pacific Northwest in the United States. At long, it is the largest tributary of the Columbia River, the largest North American river that empties into the Pacific Ocean...

 (river mile

River mile

In the United States, a River mile is a measure of distance in miles along a river from its mouth. River mile numbers begin at zero and increase further upstream. The corresponding metric unit using kilometers is the River kilometer...

 247) in Hells Canyon

Hells Canyon

Hells Canyon is a wide canyon located along the border of eastern Oregon and western Idaho in the United States. It is North America's deepest river gorge at and part of the Hells Canyon National Recreation Area....

 on the Idaho

Idaho

Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....

-Oregon

Oregon

Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

 border. The dam impounds the Snake River in Hells Canyon Reservoir; its spillway elevation is 512 m (1,680 ft) above sea level.

It is the third and final hydroelectric

Hydroelectricity

Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...

 dam of the Hells Canyon Project, which includes Brownlee Dam

Brownlee Dam

Brownlee Dam is a hydroelectric earth fill embankment dam on the Snake River on the Idaho-Oregon border, in Hells Canyon . It impounds the Snake River in the long Brownlee Reservoir...

 (1959) and Oxbow Dam

Oxbow Dam

Oxbow Dam is a hydroelectric run-of-the-river rockfill dam on the Snake River on the Idaho-Oregon border, in Hells Canyon . It is part of the Hells Canyon Project that also includes Hells Canyon Dam and Brownlee Dam, built and operated by Idaho Power Company.The dam's powerhouse contains four...

 (1961), all built and operated by Idaho Power Company

Idaho Power Company

Idaho Power Company is a regulated electrical power utility. Its business involves the purchase, sale, generation, transmission and distribution of electricity in eastern Oregon and southern Idaho. It is a subsidiary of IDACORP, Inc...

. The Hells Canyon Complex on the Snake River is the largest privately owned hydroelectric power complex in the nation, according to the US Energy Information Administration. The contractor for the Hells Canyon Dam was Morrison-Knudsen.

The Hells Canyon Dam powerhouse contains three generating units, with a total nameplate capacity

Nameplate capacity

Nameplate capacity, also known as the rated capacity, nominal capacity, installed capacity or maximum effect, refers to the intended technical full–load sustained output of a facility such as a power plant, a chemical plant, fuel plant, metal refinery, mine, and many others.For dispatchable power,...

 of . Power generation began with two units in 1967, the third came on line the following year.

Lacking passage for migrating salmon

Salmon

Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...

, the three dams of the Hells Canyon Project blocked access by anadromous salmonids to a stretch of the Snake River drainage basin

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 from Hells Canyon Dam up to Shoshone Falls

Shoshone Falls

Shoshone Falls is a waterfall on the Snake River located approximately five miles east of Twin Falls, Idaho. Sometimes called the "Niagara of the West," Shoshone Falls is 212 feet high—45 feet higher than Niagara Falls—and flows over a rim 1,000 feet wide.A park overlooking the waterfall is...

, which naturally prevents any upstream fish passage to the upper Snake River basin.

High dam proposal

As built, Hells Canyon Dam is significantly lower than it was originally proposed in the 1940s, with three dams (Hells Canyon, Brownlee Dam and Oxbow Dam) taking the place of a single 710 feet (216.4 m) high dam. As proposed by the U.S. Army Corps of Engineers, the Hells Canyon High Dam would have been a straight-profile concrete gravity dam with two gate-controlled tunnel spillways, one in each abutment. The proposed reservoir was planned to have a capacity of 4050000 acre.ft with an area of 23500 acres (9,510.1 ha). The reservoir was to extend 89 miles (143.2 km) upstream. The power plant was to be capable of generating 850 MW using ten units. The project included provisions for fish hatcheries, with the intention of maintaining salmon runs. Project cost was estimated at $342,076,000. The high dam project was not pursued.

External links

• Hells Canyon Dam, Northwest Power and Conservation Council
• Hells Canyon Complex, Idaho Power