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124-540: Glen Canyon National Recreation Area (shortened to Glen Canyon NRA or GCNRA ) is a national recreation area and conservation unit of the United States National Park Service that encompasses the area around Lake Powell and lower Cataract Canyon in Utah and Arizona , covering 1,254,429 acres (5,076.49 km) of mostly rugged high desert terrain. The recreation area is named for Glen Canyon , which
248-557: A $ 3,000-per-day fine to be assessed for any delay. To meet the deadline, Six Companies had to complete work by early 1933, since only in late fall and winter was the water level in the river low enough to safely divert. Tunneling began at the lower portals of the Nevada tunnels in May 1931. Shortly afterward, work began on two similar tunnels in the Arizona canyon wall. In March 1932, work began on lining
372-482: A 40-foot (12 m) rock dam which could generate 10,000 horsepower (7,500 kW). However, at the time , the limit of transmission of electric power was 80 miles (130 km), and there were few customers (mostly mines) within that limit. Edison allowed land options it held on the river to lapse—including an option for what became the site of Hoover Dam. In the following years, the Bureau of Reclamation (BOR), known as
496-705: A desolate area Beatty named the Imperial Valley . Though water from the Alamo Canal allowed for the widespread settlement of the valley, the canal proved expensive to operate. After a catastrophic breach that caused the Colorado River to fill the Salton Sea , the Southern Pacific Railroad spent $ 3 million in 1906–07 to stabilize the waterway, an amount it hoped in vain that it would be reimbursed for by
620-491: A flash flood while looking for an ideal spot for the dam was the second person. The official list's final death occurred on December 20, 1935, when Patrick Tierney, electrician's helper and the son of J.G. Tierney, fell from one of the two Arizona-side intake towers. Included in the fatality list are three workers who took their own lives on site, one in 1932 and two in 1933. Of the 112 fatalities, 91 were Six Companies employees, three were Bureau of Reclamation employees, and one
744-449: A form by only 1 inch (25 mm), and Six Companies engineers would not have permitted a flaw caused by the presence of a human body. A total of 3,250,000 cubic yards (2,480,000 cubic meters) of concrete was used in the dam before concrete pouring ceased on May 29, 1935. In addition, 1,110,000 cu yd (850,000 m ) were used in the power plant and other works. More than 582 miles (937 km) of cooling pipes were placed within
868-424: A minimum size, ability to attract a significant number of visitors from nearby and beyond its state, and filling a regional need with recreation as the dominant purpose. The policy also called for national recreation areas to be established by acts of Congress and for them to be able to be managed by multiple agencies as necessary, including as partnerships with states. The Bureau of Outdoor Recreation (rather than
992-588: A new record low elevation of 1,071.61 feet (326.63 m) on July 1, 2016, before beginning to rebound slowly. Under its original design, the dam would no longer be able to generate power once the water level fell below 1,050 feet (320 m), which might have occurred in 2017 had water restrictions not been enforced. To lower the minimum power pool elevation from 1,050 to 950 feet (320 to 290 m), five wide-head turbines, designed to work efficiently with less flow, were installed. Water levels were maintained at over 1,075 feet (328 m) in 2018 and 2019, but fell to
1116-443: A new record low of 1,071.55 feet (326.61 m) on June 10, 2021 and were projected to fall below 1,066 feet (325 m) by the end of 2021. Control of water was the primary concern in the building of the dam. Power generation has allowed the dam project to be self-sustaining: proceeds from the sale of power repaid the 50-year construction loan, and those revenues also finance the multimillion-dollar yearly maintenance budget. Power
1240-620: A policy that recognized the need for and established criteria for establishing NRAs. The council recommended that NRAs should focus on growing "recreation demand" more than preservation, conservation, or development; have significant natural and recreational quality greater than that of state lands, even if not as unique as other parts of the National Park System; and provide opportunity for recreation consistent with other federal public lands programs. It outlined seven mandatory criteria and six secondary criteria for establishing NRAs, including
1364-413: A pumping station 20 miles (32 km) downriver. Electricity from the dam's powerhouse was originally sold pursuant to a fifty-year contract, authorized by Congress in 1934, which ran from 1937 to 1987. In 1984, Congress passed a new statute which set power allocations to southern California, Arizona, and Nevada from the dam from 1987 to 2017. The powerhouse was run under the original authorization by
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#17328516542961488-493: A set of 1-inch (25 mm) steel pipes; cool river water would be poured through the pipes, followed by ice-cold water from a refrigeration plant. When an individual block had cured and had stopped contracting, the pipes were filled with grout . Grout was also used to fill the hairline spaces between columns, which were grooved to increase the strength of the joints. The concrete was delivered in huge steel buckets 7 feet high (2.1 m) and almost 7 feet in diameter; Crowe
1612-464: A variety of activities for visitors, including hiking, camping, boating, fishing, swimming, biking, horseback riding, and wildlife viewing, in areas that include multiple-use management for both conservation and limited utilization of natural resources. They have diverse features and contexts, being established around reservoirs, in urban areas, and within forests. Due to their size, diversity of activities, and proximity to population centers, NRAs are among
1736-499: A wider range of activities. Through the 1950s, many traditionalists at the NPS saw recreation areas championed by Wirth as distractions with open questions of how to manage and square them with the broader aims of the agency. As increased visitation forced answers to these, Lake Mead served as a model for administration at other recreational units, experiencing changing demands of the public, with more day-use visitors. Wirth advocated for changing
1860-743: Is National Park Service. The NPS sites are stand-alone units of the National Park System , while the USFS sites are all part of national forests except Land Between the Lakes . Several of the larger USFS NRAs are managed equivalent to a ranger district , but most are designated areas within one. The Green Mountain National Forest is the only one with two NRAs. The Forest Service manages its NRAs as "showcases" of its management standards so that their programs, services, and facilities should be better than and models for its other recreation sites. The USBR operates dams in
1984-619: Is for recreation as well as preservation (whereas a national park may carry more emphasis on natural preservation). As such, the area has been developed for access to Lake Powell via five marinas, four public campgrounds, two small airports, and numerous houseboat rental concessions. The geology of the area is dominated by the Glen Canyon Group , consisting of the Navajo Sandstone , Kayenta Formation , and Wingate Sandstone . The entire stratigraphic section includes rocks dating from
2108-512: Is generated in step with and only with the release of water in response to downstream water demands. Lake Mead and downstream releases from the dam also provide water for both municipal and irrigation uses. Water released from the Hoover Dam eventually reaches several canals. The Colorado River Aqueduct and Central Arizona Project branch off Lake Havasu while the All-American Canal
2232-416: Is located near Boulder City, Nevada , a municipality originally constructed for workers on the construction project, about 30 mi (48 km) southeast of Las Vegas , Nevada. The dam's generators provide power for public and private utilities in Nevada, Arizona, and California. Hoover Dam is a major tourist attraction, with 7 million tourists a year. The heavily traveled U.S. Route 93 (US 93) ran along
2356-448: Is not subject to alkali–silica reaction (ASR), as the Hoover Dam builders happened to use nonreactive aggregate, unlike that at downstream Parker Dam , where ASR has caused measurable deterioration. With most work finished on the dam itself (the powerhouse remained uncompleted), a formal dedication ceremony was arranged for September 30, 1935, to coincide with a western tour being made by President Franklin D. Roosevelt . The morning of
2480-559: Is supplied by the Imperial Dam . In total, water from Lake Mead serves 18 million people in Arizona, Nevada, and California and supplies the irrigation of over 1,000,000 acres (400,000 ha) of land. In 2018, the Los Angeles Department of Water and Power (LADWP) proposed a $ 3 billion pumped-storage hydroelectricity project—a "battery" of sorts—that would use wind and solar power to recirculate water back up to Lake Mead from
2604-585: The Black Canyon of the Colorado River , on the border between the U.S. states of Nevada and Arizona . Constructed between 1931 and 1936, during the Great Depression , it was dedicated on September 30, 1935, by President Franklin D. Roosevelt . Its construction was the result of a massive effort involving thousands of workers, and cost over 100 lives. In bills passed by Congress during its construction, it
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#17328516542962728-655: The Cretaceous to Pennsylvanian periods. A well-known rock formation named the Double Arch existed over Lake Powell. It collapsed on August 8, 2024. Lake Powell has nearly 2,000 miles (3,200 km) of fish-holding shoreline and provides opportunities to fish for largemouth bass, smallmouth bass, and striped bass that swim in the waters of the recreation area. Several local marinas and sports outfitters provide houseboats, powerboats, jet skis, kayaks, fishing gear, and related equipment to visitors. With millions of visitors to
2852-807: The Hetch Hetchy Reservoir that flooded a scenic valley in Yosemite National Park , the National Park Service sought to balance its conservation and recreation efforts with dams, and it could provide the expertise for such visitor infrastructure at the Boulder Canyon Project. A proposed 8,000 sq mi (21,000 km ) Virgin National Park in that region promoted by Secretary of the Interior Ray Lyman Wilbur
2976-762: The National Park Service Organic Act . A bill to establish it was introduced in Congress in 1933 with mixed support and failed to advance, while Albright reluctantly agreed to support the USBR with visitor services. As part of the New Deal , President Franklin D. Roosevelt strongly promoted tourism to a growing NPS, with increased emphasis on recreation at facilities constructed by the job-creating Civilian Conservation Corps . The Park Service, now under Director Arno B. Cammerer , took advantage of federal funds to claim
3100-540: The Navajo Nation on the southeast. The southwestern end of Glen Canyon NRA in Arizona can be accessed via U.S. Route 89 and State Route 98 . State Route 95 and State Route 276 lead to the northeastern end of the recreation area in Utah. Glen Canyon NRA was established in 1972 "to provide for public use and enjoyment and to preserve the area's scientific, historic, and scenic features." The stated purpose of Glen Canyon NRA
3224-526: The Parker , Shasta and Grand Coulee dams and power plants. True's work on the Hoover Dam was humorously referred to in a poem published in The New Yorker , part of which read, "lose the spark, and justify the dream; but also worthy of remark will be the color scheme". Complementing Kaufmann and True's work, sculptor Oskar J. W. Hansen designed many of the sculptures on and around the dam. His works include
3348-538: The United States Forest Service and other agencies, being more efficient for management. USFS took over Shasta Lake Recreation Area in Shasta National Forest in 1948 as its first. The Forest Service had traditionally focused on forestry for timber and custodial management, and the 1950s saw debate among the agencies, extraction interests, and conservationists as demand for recreation increased
3472-407: The "Wobblies", they formed a committee to represent them with the company. The committee drew up a list of demands that evening and presented them to Crowe the following morning. He was noncommittal. The workers hoped that Crowe, the general superintendent of the job, would be sympathetic; instead, he gave a scathing interview to a newspaper, describing the workers as "malcontents". On the morning of
3596-591: The 1940s, under the leadership of associate director Conrad L. Wirth , the NPS prepared a National Recreation Plan and conducted a number of studies with the USBR and the United States Army Corps of Engineers (USACE) assessing the natural impact, recreational opportunities, and significance of proposed reservoirs. In 1947 the Boulder Dam Recreation Area was renamed Lake Mead National Recreation Area and expanded to include Lake Mohave above
3720-418: The 9th, Crowe met with the committee and told them that management refused their demands, was stopping all work, and was laying off the entire work force, except for a few office workers and carpenters. The workers were given until 5 p.m. to vacate the premises. Concerned that a violent confrontation was imminent, most workers took their paychecks and left for Las Vegas to await developments. Two days later,
3844-489: The Boulder Dam Recreation Area, and the NPS quickly built significant infrastructure for sightseeing visitors and contracted with concessionaires. This was a major compromise and precedent that expanded the Park Service's mission beyond the strict conservation of national parks and monuments to include broader outdoor recreation that coexists with other land uses. The Park, Parkway, and Recreation Area Study Act of 1936 had
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3968-595: The Colorado River as a federal concern because the river's basin covered several states, and the river eventually entered Mexico. Though the Fall-Davis report called for a dam "at or near Boulder Canyon", the Reclamation Service (which was renamed the Bureau of Reclamation the following year) found that canyon unsuitable. One potential site at Boulder Canyon was bisected by a geologic fault ; two others were so narrow there
4092-433: The Colorado River usually passes through the turbines. The spillways and outlet works (jet-flow gates) are rarely used. The jet-flow gates, located in concrete structures 180 feet (55 m) above the river and also at the outlets of the inner diversion tunnels at river level, may be used to divert water around the dam in emergency or flood conditions, but have never done so, and in practice are used only to drain water from
4216-539: The Lake Mead's designation to "national recreation park," which would emphasize its importance with autonomy from the USBR. His Mission 66 vision provided capital investment for construction of visitor services and infrastructure across the park system. In 1963, the Recreation Advisory Council, created by executive order of President John F. Kennedy and composed of five major government officials, issued
4340-491: The Los Angeles Department of Water and Power and Southern California Edison; in 1987, the Bureau of Reclamation assumed control. In 2011, Congress enacted legislation extending the current contracts until 2067, after setting aside 5% of Hoover Dam's power for sale to Native American tribes, electric cooperatives, and other entities. The new arrangement began on October 1, 2017. The Bureau of Reclamation reports that
4464-417: The NPS analyze the needs for outdoor recreation and collaborate with state and local governments, officially expanding its mission beyond national parks. With skepticism remaining among agency veterans, planning at the area still emphasized scenery and preservation. The Act's mandates and provision for interagency cooperation however resulted in more versatile land acquisition as the NPS defined its mission. In
4588-443: The NPS's 18 sites, 12 are based around large reservoirs emphasizing water recreation, 5 are near urban areas and include both historic preservation and outdoor recreation, and the last is at a river where a reservoir was planned but not built. Of the USFS's 22 sites, 5 are at or near reservoirs, and the rest are other exemplary recreation sites within national forests. The 40 NRAs are located in 26 states; California and Washington have
4712-562: The NPS) was charged with studying proposals and referring them to the council for recommendation. This process gave flexibility to the NPS and USFS to develop their own guidelines for unmet future recreational needs. In response Congress made Lake Mead National Recreation Area the first such area to be established by statute in October 1964, finally resolving the complicated co-management of USBR land as sole NPS jurisdiction. It eventually codified most of
4836-474: The NRAs but are classified by the NPS with the national rivers and are not listed here. The USFS has four additional designated "recreation areas" that have similar management practices but are not listed here. The USFS and BLM do not collect visitor data for most sites, marked with an asterisk. 551,000 (USFS) Download coordinates as: Hoover Dam Hoover Dam is a concrete arch-gravity dam in
4960-569: The President's speech, in which he avoided mentioning the name of former President Hoover, who was not invited to the ceremony. To mark the occasion, a three-cent stamp was issued by the United States Post Office Department —bearing the name "Boulder Dam", the official name of the dam between 1933 and 1947. After the ceremony, Roosevelt made the first visit by any American president to Las Vegas. Most work had been completed by
5084-490: The Reclamation Service at the time, also considered the Lower Colorado as the site for a dam. Service chief Arthur Powell Davis proposed using dynamite to collapse the walls of Boulder Canyon, 20 miles (32 km) north of the eventual dam site, into the river. The river would carry off the smaller pieces of debris, and a dam would be built incorporating the remaining rubble. In 1922, after considering it for several years,
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5208-476: The Reclamation Service finally rejected the proposal, citing doubts about the unproven technique and questions as to whether it would, in fact, save money. In 1922, the Reclamation Service presented a report calling for the development of a dam on the Colorado River for flood control and electric power generation. The report was principally authored by Davis and was called the Fall-Davis report after Interior Secretary Albert Fall . The Fall-Davis report cited use of
5332-586: The Republic , were both formed in a continuous pour. To put such large bronzes into place without marring the highly polished bronze surface, they were placed on ice and guided into position as the ice melted. Hansen's bas-relief on the Nevada elevator tower depicts the benefits of the dam: flood control, navigation, irrigation, water storage, and power. The bas-relief on the Arizona elevator depicts, in his words, "the visages of those Indian tribes who have inhabited mountains and plains from ages distant." Excavation for
5456-483: The Salton Sea. The Board cautioned: "To avoid such possibilities, the proposed dam should be constructed on conservative if not ultra-conservative lines." On December 21, 1928, President Coolidge signed the bill authorizing the dam. The Boulder Canyon Project Act appropriated $ 165 million for the project along with the downstream Imperial Dam and All-American Canal , a replacement for Beatty's canal entirely on
5580-522: The Supreme Court handed down the Wyoming v. Colorado decision undermining the claims of the upstream states, they became anxious to reach an agreement. The resulting Colorado River Compact was signed on November 24, 1922. Legislation to authorize the dam was introduced repeatedly by two California Republicans, Representative Phil Swing and Senator Hiram Johnson , but representatives from other parts of
5704-432: The U.S. side of the border. It also permitted the compact to go into effect when at least six of the seven states approved it. This occurred on March 6, 1929, with Utah's ratification; Arizona did not approve it until 1944. Even before Congress approved the Boulder Canyon Project, the Bureau of Reclamation was considering what kind of dam should be used. Officials eventually decided on a massive concrete arch-gravity dam ,
5828-624: The USBR's new Davis Dam . This interagency partnership was successful in creating many recreation areas at reservoirs: nine more were created by agreement with USBR and two more with other dam agencies in the next two decades under the leadership of Wirth as director. However, it contributed to the controversial proposals of Echo Park Dam and Bridge Canyon Dam in existing NPS areas that were canceled after considerable opposition from environmentalists. These new sites were mainly designated as just "recreation areas" since they did not necessarily have national significance. Several would be transferred to
5952-552: The West, with eleven NRAs built around them, while the USACE primarily operates dams in the East, with reservoirs or areas near four part of NRAs; three more are based around reservoirs operated by other agencies. As the primary focus of land management is recreation (rather than conservation), limited land use such as grazing, logging, and mineral leasing is permitted only if it does not interfere with
6076-546: The World (IWW or "Wobblies"), though much-reduced from their heyday as militant labor organizers in the early years of the century, hoped to unionize the Six Companies workers by capitalizing on their discontent. They sent eleven organizers, several of whom were arrested by Las Vegas police. On August 7, 1931, the company cut wages for all tunnel workers. Although the workers sent the organizers away, not wanting to be associated with
6200-476: The arch-gravity as was proposed for the Black Canyon dam, opponents claimed that the Black Canyon dam's safety could not be guaranteed. Congress authorized a board of engineers to review plans for the proposed dam. The Colorado River Board found the project feasible, but warned that should the dam fail, every downstream Colorado River community would be destroyed, and that the river might change course and empty into
6324-547: The assistance of the National Laboratory of Anthropology, True researched authentic decorative motifs from Indian sand paintings, textiles, baskets and ceramics. The images and colors are based on Native American visions of rain, lightning, water, clouds, and local animals—lizards, serpents, birds—and on the Southwestern landscape of stepped mesas. In these works, which are integrated into the walkways and interior halls of
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#17328516542966448-416: The bid documents in nearly as much detail as the dam itself. The upper cofferdam was 96 ft (29 m) high, and 750 feet (230 m) thick at its base, thicker than the dam itself. It contained 650,000 cubic yards (500,000 m ) of material. When the cofferdams were in place and the construction site was drained of water, excavation for the dam foundation began. For the dam to rest on solid rock, it
6572-461: The bottom, narrowing to 45 ft (14 m) at the top, leaving room for a highway connecting Nevada and Arizona. On January 10, 1931, the Bureau made the bid documents available to interested parties, at five dollars a copy. The government was to provide the materials, and the contractor was to prepare the site and build the dam. The dam was described in minute detail, covering 100 pages of text and 76 drawings. A $ 2 million bid bond
6696-461: The bypass tunnels, as the tunnel had to be used to take in irrigation water until the powerhouse went into operation. There were 112 deaths reported as associated with the construction of the dam. The first was Bureau of Reclamation employee Harold Connelly who died on May 15, 1921, after falling from a barge while surveying the Colorado River for an ideal spot for the dam. Surveyor John Gregory ("J.G.") Tierney, who drowned on December 20, 1922, in
6820-568: The canyon wall, to house 480 single men at what became known as River Camp. Workers with families were left to provide their own accommodations until Boulder City could be completed, and many lived in Ragtown. The site of Hoover Dam endures extremely hot weather, and the summer of 1931 was especially torrid, with the daytime high averaging 119.9 °F (48.8 °C). Sixteen workers and other riverbank residents died of heat prostration between June 25 and July 26, 1931. The Industrial Workers of
6944-486: The clocks display the same time for more than half the year. At Kaufmann's request, Denver artist Allen Tupper True was hired to handle the design and decoration of the walls and floors of the new dam. True's design scheme incorporated motifs of the Navajo and Pueblo tribes of the region. Although some were initially opposed to these designs, True was given the go-ahead and was officially appointed consulting artist. With
7068-419: The concrete. Overall, there is enough concrete in the dam to pave a two-lane highway from San Francisco to New York. Concrete cores were removed from the dam for testing in 1995; they showed that "Hoover Dam's concrete has continued to slowly gain strength" and the dam is composed of a "durable concrete having a compressive strength exceeding the range typically found in normal mass concrete". Hoover Dam concrete
7192-481: The construction period. The initial plans for the facade of the dam, the power plant, the outlet tunnels and ornaments clashed with the modern look of an arch dam. The Bureau of Reclamation, more concerned with the dam's functionality, adorned it with a Gothic -inspired balustrade and eagle statues. This initial design was criticized by many as being too plain and unremarkable for a project of such immense scale, so Los Angeles-based architect Gordon B. Kaufmann , then
7316-482: The country considered the project as hugely expensive and one that would mostly benefit California. The 1927 Mississippi flood made Midwestern and Southern congressmen and senators more sympathetic toward the dam project. On March 12, 1928, the failure of the St. Francis Dam , constructed by the city of Los Angeles, caused a disastrous flood that killed up to 600 people. As that dam was a curved-gravity type, similar in design to
7440-491: The creation of Cuyahoga Valley NRA south of Cleveland and Santa Monica Mountains NRA west of Los Angeles. The former was redesignated a national park in 2000. Chattahoochee River NRA north of Atlanta was created in 1978 and Boston Harbor Islands NRA in 1996. The Santa Monica Mountains and Boston Harbor Islands are partnerships with state parks and local agencies. Mount Hood is the newest NRA, designated in 2009. The Land and Water Conservation Fund provided funding for
7564-420: The creation of Grand Canyon National Monument (II) for the pristine upstream eastern section; it would later be incorporated into the park. Cramton proposed that the western section, which had less spectacular scenery, the dam and reservoir, livestock grazing, and mining, but nationally important recreational importance, be designated as the "Boulder Canyon National Reservation", consistent with terminology used in
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#17328516542967688-408: The dam (from pea-sized gravel to 9 inches [230 mm] stones), it was vital that the bucket be maneuvered to the proper column. When the bottom of the bucket opened up, disgorging 8 cu yd (6.1 m ) of concrete, a team of men worked it throughout the form. Although there are myths that men were caught in the pour and are entombed in the dam to this day, each bucket deepened the concrete in
7812-550: The dam could be built, the Colorado River needed to be diverted away from the construction site. To accomplish this, four diversion tunnels were driven through the canyon walls, two on the Nevada side and two on the Arizona side. These tunnels were 56 ft (17 m) in diameter. Their combined length was nearly 16,000 ft, or more than 3 miles (5 km). The contract required these tunnels to be completed by October 1, 1933, with
7936-617: The dam feared endless litigation. Delph Carpenter, a Colorado attorney, proposed that the seven states which fell within the river's basin (California, Nevada, Arizona, Utah, New Mexico, Colorado and Wyoming) form an interstate compact , with the approval of Congress. Such compacts were authorized by Article I of the United States Constitution but had never been concluded among more than two states. In 1922, representatives of seven states met with then- Secretary of Commerce Herbert Hoover . Initial talks produced no result, but when
8060-399: The dam site was reinforced with grout , forming a grout curtain . Holes were driven into the walls and base of the canyon, as deep as 150 feet (46 m) into the rock, and any cavities encountered were to be filled with grout. This was done to stabilize the rock, to prevent water from seeping past the dam through the canyon rock, and to limit "uplift"—upward pressure from water seeping under
8184-400: The dam was authorized, increasing numbers of unemployed people converged on southern Nevada. Las Vegas, then a small city of some 5,000, saw between 10,000 and 20,000 unemployed descend on it. A government camp was established for surveyors and other personnel near the dam site; this soon became surrounded by a squatters' camp. Known as McKeeversville, the camp was home to men hoping for work on
8308-461: The dam wound down. When a Six Companies manager altered working times to force workers to take lunch on their own time, workers responded with a strike. Emboldened by Crowe's reversal of the lunch decree, workers raised their demands to include a $ 1-per-day raise. The company agreed to ask the Federal government to supplement the pay, but no money was forthcoming from Washington. The strike ended. Before
8432-696: The dam's crest until October 2010, when the Hoover Dam Bypass opened. As the United States developed the Southwest, the Colorado River was seen as a potential source of irrigation water. An initial attempt at diverting the river for irrigation purposes occurred in the late 1890s, when land speculator William Beatty built the Alamo Canal just north of the Mexican border; the canal dipped into Mexico before running to
8556-444: The dam's total power output was placed on the grid and made arbitrarily distributable. Before water from Lake Mead reaches the turbines, it enters the intake towers and then four gradually narrowing penstocks which funnel the water down towards the powerhouse. The intakes provide a maximum hydraulic head (water pressure) of 590 ft (180 m) as the water reaches a speed of about 85 mph (140 km/h). The entire flow of
8680-405: The dam, True also reflected on the machinery of the operation, making the symbolic patterns appear both ancient and modern. With the agreement of Kaufmann and the engineers, True also devised for the pipes and machinery an innovative color-coding which was implemented throughout all BOR projects. True's consulting artist job lasted through 1942; it was extended so he could complete design work for
8804-409: The dam. The workers were under severe time constraints due to the beginning of the concrete pour. When they encountered hot springs or cavities too large to readily fill, they moved on without resolving the problem. A total of 58 of the 393 holes were incompletely filled. After the dam was completed and the lake began to fill, large numbers of significant leaks caused the Bureau of Reclamation to examine
8928-559: The daring." Hansen's dedication plaza, on the Nevada abutment, contains a sculpture of two winged figures flanking a flagpole. Surrounding the base of the monument is a terrazzo floor embedded with a "star map". The map depicts the Northern Hemisphere sky at the moment of President Roosevelt's dedication of the dam. This is intended to help future astronomers, if necessary, calculate the exact date of dedication. The 30-foot-high (9.1 m) bronze figures, dubbed Winged Figures of
9052-467: The dedication, and Six Companies negotiated with the government through late 1935 and early 1936 to settle all claims and arrange for the formal transfer of the dam to the Federal Government. The parties came to an agreement and on March 1, 1936, Secretary Ickes formally accepted the dam on behalf of the government. Six Companies was not required to complete work on one item, a concrete plug for one of
9176-513: The dedication, it was moved forward three hours from 2 p.m. Pacific time to 11 a.m.; this was done because Secretary of the Interior Harold L. Ickes had reserved a radio slot for the President for 2 p.m. but officials did not realize until the day of the ceremony that the slot was for 2 p.m. Eastern Time. Despite the change in the ceremony time, and temperatures of 102 °F (39 °C), 10,000 people were present for
9300-411: The design of which was overseen by the Bureau's chief design engineer John L. Savage . The monolithic dam would be thick at the bottom and thin near the top and would present a convex face towards the water above the dam. The curving arch of the dam would transmit the water's force into the abutments, in this case the rock walls of the canyon. The wedge-shaped dam would be 660 ft (200 m) thick at
9424-535: The diversion tunnels), and a classification used by Six Companies to avoid paying compensation claims. The site's diversion tunnels frequently reached 140 °F (60 °C), enveloped in thick plumes of vehicle exhaust gases. A total of 42 workers were recorded as having died from pneumonia and were not included in the above total; none were listed as having died from carbon monoxide poisoning. No deaths of non-workers from pneumonia were recorded in Boulder City during
9548-596: The dominant resource objective, but with multiple intensive uses allowed. But because most units contained a combination of natural, historic, and recreational lands, the General Authorities Act of 1970 made all areas equal within the National Park System ; separate policy manuals for each were replaced in 1975 with one that would tailor policies in each park respective to the purpose of zones within. In 1972 Congress established two NRAs in urban areas as
9672-590: The energy generated under the contracts ending in 2017 was allocated as follows: The dam is protected against over-topping by two spillways . The spillway entrances are located behind each dam abutment , running roughly parallel to the canyon walls. The spillway entrance arrangement forms a classic side-flow weir with each spillway containing four 100-foot-long (30 m) and 16-foot-wide (4.9 m) steel-drum gates. Each gate weighs 5,000,000 pounds (2,300 metric tons) and can be operated manually or automatically. Gates are raised and lowered depending on water levels in
9796-477: The existing recreation areas under the new national designation ( Lake Roosevelt and Curecanti NRAs are the only NPS areas that have not been permanently established by Congress or the president ). Lake Mead is still the largest NRA and is the most visited among those at reservoirs. The first new NRA under USFS administration was Spruce Knob–Seneca Rocks National Recreation Area , established in 1965. Congress initially authorized Delaware Water Gap NRA in 1965 with
9920-965: The expectation that the Tocks Island Reservoir would serve the New York and Philadelphia areas as the first NRA east of the Mississippi River, but local and environmental opposition led to the dam's cancellation. The NRA remains as the forested area intended to be flooded by the Delaware River . Mount Rogers NRA was also delayed and downsized, losing a planned reservoir and ski area. A 1968 NPS publication outlined policies for administration of recreational areas, which were distinct from its natural and historical areas. This included not only NRAs but also national lakeshores and seashores , national parkways , and some national scenic riverways; at that time there were 22 such areas, and recreation would be
10044-527: The federal government. Even after the waterway was stabilized, it proved unsatisfactory because of constant disputes with landowners on the Mexican side of the border. As the technology of electric power transmission improved, the Lower Colorado was considered for its hydroelectric -power potential. In 1902, the Edison Electric Company of Los Angeles surveyed the river in the hope of building
10168-415: The first three Allis Chalmers built Francis turbine - generators , all on the Nevada side, began operating. In March 1937, one more Nevada generator went online and the first Arizona generator by August. By September 1939, four more generators were operating, and the dam's power plant became the largest hydroelectricity facility in the world. The final generator was not placed in service until 1961, bringing
10292-582: The first urban national parks: Golden Gate NRA in the San Francisco area and Gateway NRA in New York City, both with beaches, historic military sites, and natural conservation areas. Spearheaded by Director George Hartzog , this controversially expanded the Park Service's responsibilities into local urban recreation (in addition to the National Capital Parks ), and after he left, the NPS opposed
10416-525: The headquarters for the dam construction, closing its many speakeasies when the decision maker, Secretary of the Interior Ray Wilbur , came to town. Instead, Wilbur announced in early 1930 that a model city was to be built in the desert near the dam site. This town became known as Boulder City, Nevada . Construction of a rail line joining Las Vegas and the dam site began in September 1930. Soon after
10540-409: The maximum generating capacity to 1,345 megawatts at the time. Original plans called for 16 large generators, eight on each side of the river, but two smaller generators were installed instead of one large one on the Arizona side for a total of 17. The smaller generators were used to serve smaller communities at a time when the output of each generator was dedicated to a single municipality, before
10664-400: The monument of dedication plaza, a plaque to memorialize the workers killed and the bas-reliefs on the elevator towers. In his words, Hansen wanted his work to express "the immutable calm of intellectual resolution, and the enormous power of trained physical strength, equally enthroned in placid triumph of scientific accomplishment", because "[t]he building of Hoover Dam belongs to the sagas of
10788-473: The most common cause of death on the dam site; the high scalers' work thus helped ensure worker safety. One high scaler was able to save a life in a more direct manner: when a government inspector lost his grip on a safety line and began tumbling down a slope towards almost certain death, a high scaler was able to intercept him and pull him into the air. The construction site had become a magnet for tourists. The high scalers were prime attractions and showed off for
10912-478: The most visited units of the National Park System, with six among the thirty most visited sites. The first NRA was Lake Mead National Recreation Area , which was created by a 1936 agreement between the United States Bureau of Reclamation (USBR), which had built Hoover Dam , and the National Park Service (NPS), which had experience in managing visitors in the outdoors. Because the reservoir had disturbed
11036-411: The most, each with four. NRAs of the USFS have a total area of 3,261,818 acres (13,200 km ), and those of the NPS total 3,714,735 acres (15,033 km ). The BLM's one NRA is approximately 1,000,000 acres (4,000 km ). The U.S. Bureau of Reclamation was planning the construction of Boulder Dam (now Hoover Dam) on the Colorado River in the late 1920s and saw the potential for recreation at
11160-512: The name. The name was descriptive and was an inside joke among the San Franciscans in the bid, where "Six Companies" was also a Chinese benevolent association in the city . There were three valid bids, and Six Companies' bid of $ 48,890,955 was the lowest, within $ 24,000 of the confidential government estimate of what the dam would cost to build, and five million dollars less than the next-lowest bid. The city of Las Vegas had lobbied hard to be
11284-432: The nation's leading dam builder, Frank Crowe . They formed a joint venture to bid for the project with Pacific Bridge Company of Portland, Oregon ; Henry J. Kaiser & W. A. Bechtel Company of San Francisco; MacDonald & Kahn Ltd. of Los Angeles; and the J.F. Shea Company of Portland, Oregon. The joint venture was called Six Companies, Inc. as Bechtel and Kaiser were considered one company for purposes of Six in
11408-426: The natural state of the environment, a new designation was devised that allowed for more intensive land use while maintaining the NPS's role in conservation and historic preservation. The system of NRAs grew as the USBR constructed more dams near urban areas where there was a need for outdoor recreation. NRAs are managed by the NPS, the United States Forest Service (USFS), and the Bureau of Land Management (BLM). Of
11532-472: The need for multiple-use planning. The Multiple-Use Sustained-Yield Act of 1960 for the first time established recreation as well as wildlife as an equal priority for the Forest Service with range, timber, and watershed oversight. The Park Service took a utilitarian approach to its recreation areas, acknowledging their less-than-national significance and focused on providing useful facilities and allowing
11656-538: The number of black people employed by Six Companies never exceeded thirty, mostly lowest-pay-scale laborers in a segregated crew, who were issued separate water buckets. As part of the contract, Six Companies, Inc. was to build Boulder City to house the workers. The original timetable called for Boulder City to be built before the dam project began, but President Hoover ordered work on the dam to begin in March 1931 rather than in October. The company built bunkhouses, attached to
11780-440: The penstocks for maintenance. Following an uprating project from 1986 to 1993, the total gross power rating for the plant, including two 2.4 megawatt Pelton turbine -generators that power Hoover Dam's own operations is a maximum capacity of 2080 megawatts. The annual generation of Hoover Dam varies. The maximum net generation was 10.348 TWh in 1984, and the minimum since 1940 was 2.648 TWh in 1956. The average power generated
11904-531: The potential for uneven cooling and contraction of the concrete posed a serious problem. Bureau of Reclamation engineers calculated that if the dam were to be built in a single continuous pour, the concrete would take 125 years to cool, and the resulting stresses would cause the dam to crack and crumble. Instead, the ground where the dam would rise was marked with rectangles, and concrete blocks in columns were poured, some as large as 50 ft square (15 m) and 5 feet (1.5 m) high. Each five-foot form contained
12028-471: The powerhouse was carried out simultaneously with the excavation for the dam foundation and abutments. The excavation of this U-shaped structure located at the downstream toe of the dam was completed in late 1933 with the first concrete placed in November 1933. Filling of Lake Mead began February 1, 1935, even before the last of the concrete was poured that May. The powerhouse was one of the projects uncompleted at
12152-475: The project, together with their families. Another camp, on the flats along the Colorado River, was officially called Williamsville, but was known to its inhabitants as "Ragtown". When construction began, Six Companies hired large numbers of workers, with more than 3,000 on the payroll by 1932 and with employment peaking at 5,251 in July 1934. "Mongolian" (Chinese) labor was prevented by the construction contract, while
12276-513: The project. The winning bid to build the dam was submitted by a consortium named Six Companies, Inc. , which began construction in early 1931. Such a large concrete structure had never been built before, and some of the techniques used were unproven. The torrid summer weather and lack of facilities near the site also presented difficulties. Nevertheless, Six Companies turned the dam over to the federal government on March 1, 1936, more than two years ahead of schedule. Hoover Dam impounds Lake Mead and
12400-429: The public lands. A 1932 study by Yellowstone National Park superintendent Roger Toll evaluated the region and recognized some sites of interest but again dismissed it as inconsistent with national parks' and monuments' standards and purpose of preservation. Separately that year the secretary's advisor Louis C. Cramton led further studies of the area between the dam site and Grand Canyon National Park and recommended
12524-577: The purchase of land at several NRAs. Three federal agencies manage the 40 NRAs. The National Park Service, in the Department of the Interior , manages 18, the U.S. Forest Service , in the Department of Agriculture , manages 22, and the Bureau of Land Management , in the Department of the Interior, manages one. One NRA, Whiskeytown–Shasta–Trinity , comprises three units, two of which are Forest Service and one
12648-571: The recreation area each year, it is inevitable that vandals will deface the rock faces of the canyon. Glen Canyon NRA has implemented a voluntourism program wherein volunteers sign up for a five-day houseboat trip during which they help remove graffiti from the canyon walls. National recreation area A national recreation area ( NRA ) is a protected area in the United States established by an Act of Congress to preserve enhanced recreational opportunities in places with significant natural and scenic resources. There are 40 NRAs, which emphasize
12772-568: The recreational use of the land. The establishing legislation of each NRA usually specifies multiple purposes of the designation. Hunting is by default banned in areas of the National Park Service unless explicitly permitted by law; 15 of 18 NRAs of the NPS allow hunting – and it is generally permitted in National Forest lands – in accordance with local rules. The Mississippi National River and Recreation Area and Big South Fork National River and Recreation Area share many features with
12896-445: The remainder were talked into leaving by law enforcement. On August 13, the company began hiring workers again, and two days later, the strike was called off. While the workers received none of their demands, the company guaranteed there would be no further reductions in wages. Living conditions began to improve as the first residents moved into Boulder City in late 1931. A second labor action took place in July 1935, as construction on
13020-553: The reservoir area and highlight natural features and development needs. Despite the lack of legislation establishing the reservation, the USBR's inability to manage the influx of tourists at the newly finished Lake Mead led Interior Secretary Harold L. Ickes to direct for negotiation of a memorandum of agreement that gave the NPS responsibility for the reserved lands and surface of the lake, but not Boulder Dam itself, maintaining mining and grazing so long as they did not disrupt recreation. Ickes signed it on October 13, 1936, establishing
13144-403: The scenic area in Nevada and Arizona around the future Lake Mead , to then be the world's largest reservoir. The car was expanding access to travel in the growing Southwest and the USBR wanted to bring about the outdoor activities that would be enabled by its enormous project, but it lacked the experience and desire to provide facilities and services for recreation. Following the controversy of
13268-504: The side-walls were also excavated to reach virgin rock, as weathered rock might provide pathways for water seepage. Shovels for the excavation came from the Marion Power Shovel Company . The men who removed this rock were called "high scalers". While suspended from the top of the canyon with ropes, the high-scalers climbed down the canyon walls and removed the loose rock with jackhammers and dynamite . Falling objects were
13392-477: The situation. It found that the work had been incompletely done, and was based on less than a full understanding of the canyon's geology. New holes were drilled from inspection galleries inside the dam into the surrounding bedrock. It took nine years (1938–47) under relative secrecy to complete the supplemental grout curtain. The first concrete was poured into the dam on June 6, 1933, 18 months ahead of schedule. Since concrete heats and contracts as it cures,
13516-442: The supervising architect to the Bureau of Reclamation, was brought in to redesign the exteriors. Kaufmann greatly streamlined the design and applied an elegant Art Deco style to the entire project. He designed sculpted turrets rising seamlessly from the dam face and clock faces on the intake towers set for the time in Nevada and Arizona—both states are in different time zones, but since Arizona does not observe daylight saving time ,
13640-418: The time of the formal dedication on September 30, 1935; a crew of 500 men remained to finish it and other structures. To make the powerhouse roof bombproof, it was constructed of layers of concrete, rock, and steel with a total thickness of about 3.5 feet (1.1 m), topped with layers of sand and tar. In the latter half of 1936, water levels in Lake Mead were high enough to permit power generation, and
13764-447: The tunnels for maintenance. To protect the construction site from the Colorado River and to facilitate the river's diversion, two cofferdams were constructed. Work on the upper cofferdam began in September 1932, even though the river had not yet been diverted. The cofferdams were designed to protect against the possibility of the river's flooding a site at which two thousand men might be at work, and their specifications were covered in
13888-451: The tunnels with concrete. First the base, or invert, was poured. Gantry cranes , running on rails through the entire length of each tunnel were used to place the concrete. The sidewalls were poured next. Movable sections of steel forms were used for the sidewalls. Finally, using pneumatic guns, the overheads were filled in. The concrete lining is 3 feet (1 m) thick, reducing the finished tunnel diameter to 50 ft (15 m). The river
14012-422: The tunnels with large concrete plugs. The downstream halves of the tunnels following the inner plugs are now the main bodies of the spillway tunnels. The inner diversion tunnels were plugged at approximately one-third of their length, beyond which they now carry steel pipes connecting the intake towers to the power plant and outlet works. The inner tunnels' outlets are equipped with gates that can be closed to drain
14136-615: The watchers. The high scalers received considerable media attention, with one worker dubbed the "Human Pendulum" for swinging co-workers (and, at other times, cases of dynamite) across the canyon. To protect themselves against falling objects, some high scalers dipped cloth hats in tar and allowed them to harden. When workers wearing such headgear were struck hard enough to inflict broken jaws, they sustained no skull damage. Six Companies ordered thousands of what initially were called "hard boiled hats" (later " hard hats ") and strongly encouraged their use. The cleared, underlying rock foundation of
14260-432: Was 4.2 TWh/year for 1947–2008. In 2015, the dam generated 3.6 TWh. The amount of electricity generated by Hoover Dam has been decreasing along with the falling water level in Lake Mead due to the prolonged drought since year 2000 and high demand for the Colorado River's water. By 2014 its generating capacity was downrated by 23% to 1592 MW and was providing power only during periods of peak demand. Lake Mead fell to
14384-418: Was a visitor to the site; the remainder were employees of various contractors not part of Six Companies. Ninety-six of the deaths occurred during construction at the site. Not included in the official number of fatalities were deaths that were recorded as pneumonia . Workers alleged that this diagnosis was a cover for death from carbon monoxide poisoning (brought on by the use of gasoline-fueled vehicles in
14508-446: Was awarded two patents for their design. These buckets, which weighed 20 short tons (18.1 t; 17.9 long tons) when full, were filled at two massive concrete plants on the Nevada side, and were delivered to the site in special railcars . The buckets were then suspended from aerial cableways which were used to deliver the bucket to a specific column. As the required grade of aggregate in the concrete differed depending on placement in
14632-428: Was diverted into the two Arizona tunnels on November 13, 1932; the Nevada tunnels were kept in reserve for high water. This was done by exploding a temporary cofferdam protecting the Arizona tunnels while at the same time dumping rubble into the river until its natural course was blocked. Following the completion of the dam, the entrances to the two outer diversion tunnels were sealed at the opening and halfway through
14756-460: Was flooded by the Glen Canyon Dam , completed in 1966, and is now mostly submerged beneath the waters of Lake Powell. Glen Canyon NRA borders Capitol Reef National Park and Canyonlands National Park on the north, Grand Staircase–Escalante National Monument on the west, Vermilion Cliffs National Monument and the northeasternmost reaches of Grand Canyon National Park on the southwest, and
14880-469: Was necessary to remove accumulated erosion soils and other loose materials in the riverbed until sound bedrock was reached. Work on the foundation excavations was completed in June 1933. During this excavation, approximately 1,500,000 cu yd (1,100,000 m ) of material was removed. Since the dam was an arch-gravity type, the side-walls of the canyon would bear the force of the impounded lake. Therefore,
15004-507: Was no space for a construction camp at the bottom of the canyon or for a spillway. The Service investigated Black Canyon and found it ideal; a railway could be laid from the railhead in Las Vegas to the top of the dam site. Despite the site change, the dam project was referred to as the "Boulder Canyon Project". With little guidance on water allocation from the Supreme Court , proponents of
15128-481: Was praised for its scenic and historic resources but rejected in 1930 by NPS Director Horace M. Albright due to a reservoir's inherent lack of a natural landscape expected for a national park . The political leaders at the Department of the Interior nevertheless wanted to manage the significant lands for tourism and recreation. Farming interests in the Arizona Strip area also wanted to keep their grazing access to
15252-479: Was referred to as the Hoover Dam, after President Herbert Hoover , but was named Boulder Dam by the Roosevelt administration. In 1947, the name Hoover Dam was restored by Congress . Since about 1900, the Black Canyon and nearby Boulder Canyon had been investigated for their potential to support a dam that would control floods, provide irrigation water, and produce hydroelectric power . In 1928, Congress authorized
15376-512: Was to accompany each bid; the winner would have to post a $ 5 million performance bond . The contractor had seven years to build the dam, or penalties would ensue. The Wattis Brothers , heads of the Utah Construction Company , were interested in bidding on the project, but lacked the money for the performance bond. They lacked sufficient resources even in combination with their longtime partners, Morrison-Knudsen , which employed
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