| Bridge Canyon Dam | |
|---|---|
Map showing proposed location of the dam and reservoir |
|
|
|
|
| Country | United States |
| Location | Mohave County, Arizona |
| Coordinates | [1] |
| Status | Proposed |
| Construction cost | $500 million (est.) |
| Owner(s) | U.S. Bureau of Reclamation |
| Dam and spillways | |
| Height | 740 feet (230 m) |
| Length | 1,700 feet (520 m) |
| Impounds | Colorado River |
| Reservoir | |
| Creates | Bridge Canyon Reservoir |
| Capacity | 3,700,000 acre feet (4.6 km3) |
| Catchment area | 140,000 square miles (360,000 km2) |
| Surface area | 24,000 acres (9,700 ha) |
| Power station | |
| Hydraulic head | 672 feet (205 m) |
| Installed capacity | 900-2,000 MW |
Bridge Canyon Dam is a proposed dam in the lower Grand Canyon of the Colorado River, in northern Arizona in the United States. It would be located near Bridge Canyon Rapids in an extremely rugged and isolated portion of the canyon, roughly 235 miles (378 km) downstream of Lee's Ferry and 30 miles (48 km) upstream of the current extent of Lake Mead.
The project was considered seriously by the U.S. Bureau of Reclamation for a period of over twenty years from the early 1950s to 1968. If built, the dam would tower 740 feet (230 m) high, forming a reservoir stretching more than ninety miles (150 km) upstream, including thirteen miles (21 km) inside Grand Canyon National Park. The dam would serve mainly for hydropower production and sediment retention in conjunction with several others further upstream including Marble Canyon Dam, on the Colorado, Green and other rivers.
Due to its enormous potential for environmental destruction and the dwindling flows of the Colorado River, the project stalled in 1968 after years of public opposition. However, the location is considered one of the best remaining sites for a large dam in the western United States.
Contents |
The Colorado River has one of the steepest gradients among major rivers in the United States in relation with its flow. In the late 1800s and the early part of the 1900s, the river's annual discharge exceeded 22,000 cubic feet per second (620 m3/s). From Glen Canyon to the mouth of the Grand Canyon (Lower Granite Gorge) near present-day Lake Mead, the Colorado drops a total of 1,950 feet (590 m), giving it tremendous potential for hydroelectricity generation.
Bridge Canyon Dam was first seriously considered in the 1940s as part of the Bureau of Reclamation's cascade of high power dams along the Colorado River system. Up to seven dams were proposed on the Colorado River alone, including Hoover, Bridge Canyon, Marble Canyon (Redwall) and Glen Canyon, and perhaps an additional one or two within Grand Canyon National Park. However, only Hoover and Glen Canyon were eventually built, as well as several others on tributaries.
In the 1940s, Reclamation began investigating potential sites for a dam in the lower Grand Canyon near the river's confluence with Diamond Creek, 25 to 40 miles (40 to 64 km) upstream of Lake Mead. A small tent city was erected along the Colorado River near Bridge Canyon, complete with "a tar-paper cook shack with tables, a walk-in refrigerator attached, and tents or sleeping accommodations for the men… a small generating plant which furnished lights and fans for the swamp-type air conditioners which were a necessity in this canyon."[2] The site was only accessible by a 30-mile (48 km) boat trip up the Colorado River from Lake Mead, and was plagued by torrid heat, poor access, floods and long working hours.[2]
After more than four potential damsites were investigated, the best one was found at a location called the "Lower Gneiss" site below the confluence of Gneiss Canyon, a small tributary, and 19 miles (31 km) northwest of the small town of Peach Springs. The dam was proposed as a concrete arch-gravity structure 736 to 740 feet (224 to 230 m) high above its foundations, with a hydraulic head from 666 to 672 feet (203 to 205 m). It would raise the water behind it for 93 miles (150 km) upstream to an elevation of 1,876 feet (572 m) just below the mouth of Kanab Creek.[3]
The dam was also considered part of a massive proposal designed to bring Colorado River southwards out of the Grand Canyon into the Salt River Valley in central Arizona known as the Central Arizona Project, the most expensive single project constructed by the Bureau of Reclamation. Along with Marble Canyon Dam further upstream, it would generate a portion of the massive power required to pump-lift the Colorado River five thousand feet out of the Grand Canyon. From there, the water would flow via a gravity canal south towards Arizona's primary agricultural regions in the Salt and Gila River valleys.[4]
After proposals for the dam surfaced, they met with almost immediate opposition from environmental groups such as the Sierra Club, as well as an outcry from recreation-minded general public. The reason for this was because the dam would back water up for 13 miles (21 km) into Grand Canyon National Park, and 40 miles (64 km) through Grand Canyon National Monument. The resistance was strengthened by previous controversies pertaining to the construction of dams in national parks, such as the O'Shaughnessy Dam in Yosemite National Park which was built in 1925.[5]
All of the proposals thus far for the dam have failed for one reason or another. In 1938, the state of Arizona attempted to gain federal permission to build the dam.[4] Again in 1950, a bill was introduced in Congress for a Bridge Canyon Dam that would serve the water diversion purposes of the CAP. This time, it was not activists who killed it but rather representatives from California in the United States House of Representatives. This was because California did not want Arizona's utilization of its share of the Colorado River to increase, which would mean possible shortfall of water supplies in that state.[6]
Even though the hypothetical dam and its reservoir lie along a remote, seldom seen or visited reach of the Colorado River, it would still destroy many well-known landmarks and points of interest. These include lower Havasu Creek, famed for its travertine formations and waterfalls, and Lava Falls, one of the most spectacular rapids on the Colorado.[7] Opponents state that the meager storage capacity of the dam, as well as its potential to evaporate more than 85,000 acre feet (105,000,000 m3) of water per year, do not justify the dam's destruction of natural features and disruption to both the river ecology and recreational activities.
Because of the high silt load of the Colorado, the Bridge Canyon Reservoir would eventually fill with sediment, rendering it useless. Estimates by the Sierra Club suggest a useful life span of 60–160 years, while the Bureau of Reclamation predicts 163 years.[8] Reclamation suggested building additional dams on Kanab Creek, the Little Colorado River and Paria River to act as silt traps in order to prolong the life span up to 250 years.[9] These proposals, however, were not enough to save the dam. As a result, the Bridge Canyon project officially stalled in 1984.[10]