Hoover Dam & Bypass Bridge

Arizona / Nevada

Hoover Dam, once known as Boulder Dam, is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the US states of Arizona and Nevada. It was constructed between 1931 and 1936 during the Great Depression and was dedicated on September 30, 1935, by President Franklin Roosevelt. Its construction was the result of a massive effort involving thousands of workers, and cost over one hundred lives.
The dam was controversially named in honor of President Herbert Hoover.
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 the project. The winning bid to build the dam was submitted by a consortium called Six Companies, Inc., which began construction on the dam in early 1931.
 Such a large concrete structure had never been built before, and some of the techniques were unproven. The torrid summer weather and the lack of facilities near the site also presented difficulties. Nevertheless, Six Companies turned over the dam to the federal government on March 1, 1936, more than two years ahead of schedule.
Hoover Dam impounds Lake Mead, and is located near Boulder City, Nevada, a municipality originally constructed for workers on the construction project, about 25 mi (40 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; nearly a million people tour the dam each year. Heavily travelled U.S. 93 ran along the dam's crest until October 2010, when the Hoover Dam Bypass opened.
Contour map of Hoover Dam; 1930
Longitudinal Section, pamphlet “The Story of Hoover Dam;” 1961
A lone tree
September 30, 1935—a crew of 500 men remained after the dedication 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.
Standing in front of a section of the stark red ochre mountain along the pedestrian walkway is the “Winged Figure of the Republic”. The two 30-foot bronzed statues flank a 142-foot flagpole and sit atop six-foot tall pedestals of gleaming black diorite rock. The statues represent “that eternal vigilance which is the price of liberty.” Nearby is a plaque that commemorates those who conceived the Dam and those who labored to build it. There is also a bronze plaque memorializing the 96 workers who died during Dam construction with an inscription that proclaims “They died to make the desert bloom.”
Construction Deaths

There were 112 deaths associated with the construction of the dam. Included in that total was J. G. Tierney, a surveyor who drowned on December 20, 1922, while looking for an ideal spot for the dam.
He is generally counted as the first man to die in the construction of Hoover Dam. His son, Patrick W. Tierney, was the last man to die working on the dam's construction, 13 years to the day later.
 Ninety-six of the deaths occurred during construction at the site. Of the 112 fatalities, 91 were Six Companies employees, three were BOR employees, and one was a visitor to the site, with the remainder employees of various contractors not part of Six Companies.
Not included in the official fatalities number 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 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; none were listed as having died from carbon monoxide poisoning.
No deaths of non-workers from pneumonia were recorded in Boulder City during the construction period

Nevada Time
Before water from Lake Mead reaches the turbines, it enters the intake towers and enters 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 the Colorado River 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 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 only used to drain water from the penstocks for maintenance

The first concrete was poured into the dam on June 6, 1933, 18 months ahead of schedule.
The concrete was delivered in huge steel buckets 7 feet (2.1 m) high and almost 7 feet (2.1 m) in diameter—Crowe was awarded two patents for their design. These buckets, which weighed 20 short tons (18 t) 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 the dam (from pea-sized gravel to 9 inch (230 mm) stones), it was vital that the bucket be maneuvered to the proper column. Once the bottom of the bucket opened up, disgorging 8 cubic yards (6.1 m3) of concrete, a team of men worked it throughout the form.
A total of 3,250,000 cubic yards (2,480,000 m3) of concrete was used in the dam before concrete pouring ceased on May 29, 1935. In addition, 1,110,000 cubic yards (850,000 m3) were used in the power plant and other works. More than 582 miles (937 km) of cooling pipes were placed within the concrete. Overall, there is enough concrete in the dam to pave a two-lane highway from San Francisco to New York.[45] 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".[61] Hoover Dam concrete 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.

The old ticket counter

The old ticket counter

Brass Doors

Arizona Time

Survey Markers 1935

Survey Markers No Date

Power Lines
Hoover Dam Bypass

Discoloration around the banks of Lake Mead shows how much the water level has declined over the years
Last Reading: 1125.69 on Nov 29, 2011

Elevation & Content

Lake Mead is 93.91 feet below Full Pool (Elevation 1219.60 )
By content, Lake Mead is 53.79% of Full Pool (25,877,000 af)

Water Inflow Data

Total inflows for water year 2012: 2,172,712 acre feet
This is 250.73% of the November 29th average of 866,540 acre feet
Hoover Dam Release Data
Total releases for water year 2012: 985,720 acre feet
This is 10.95% of minimum required release of 9,000,000 acre feet

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 ft (30 m) long and 16 ft (4.9 m) high steel drum gates.
Each gate weighs 5,000,000 pounds (2,300,000 kg) and can be operated manually or automatically.
Gates are raised and lowered depending upon water levels in the reservoir and flood conditions.
The gates cannot completely stop water from entering the spillways but can help maintain an extra 16 ft (4.9 m) of lake level.
Water flowing over the spillways drops sharply into 600 ft (180 m) long, 50 ft (15 m) wide spillway tunnels before connecting to the outer diversion tunnels, and reentering the main river channel below the dam.
This complex spillway entrance arrangement combined with the approximate 700 ft (210 m) elevation drop from the top of the reservoir to the river below was a difficult engineering problem and posed several design challenges.
Each spillway's capacity of 200,000 cu ft/s (5,700 m3/s) was empirically verified in post construction tests in 1941

In the latter half of 1936, water levels in Lake Mead were high enough to permit power generation, and the first three 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 the maximum generating capacity to 1345 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.

 Diversion Tunnel No. 3 on the Arizona Side of Hoover Dam is shown under construction.

 Trucks excavating in river bed
General condition of river bottom after diversion; November 29, 1932
 Bottom row of concrete forms; June 27, 1933
 Mid-level progress on the dam; August 31, 1933
 Mid-level progress on the dam; April 1, 1934
Looking upstream toward Boulder Dam and power house; Sept 26, 1934
 Image shows some of the monolithic pour blocks, which accomodated up to five feet of mass
concrete at a time, before stopping to allow curing
 8 foot wide slot in the dam's centerline used to convey temporary cooling pipes to the dam's interior. This was grouted in 100 foot increments as the dam concrete cured. 
The last concrete placed in the dam was into this slot along the dam's crest on May 29, 1935.
 Memorandum for the press concerning bidding companies; March 4, 1931
 Excerpt from Memorandum for the press announcing construction has started; July 7, 1930
 Profile of Hoover Dam, “The Construction of Hoover Dam,” Wilbur M. Mead, published by Department of Interior; 1933
 Longitudinal Section, pamphlet “The Story of Hoover Dam;” 1961
 Electric shovel at mouth of diversion tunnel; March 7, 1932
 Bureau of Reclamation signs contract with Six Companies, Inc
 Pouring the 2 millionth cubic yard of concrete for the dam; June 2, 1934
 Men drilling face of tunnel; September 10, 1931
 Night shot of construction; June 19, 1934
 Making sound movies of the Colorado River near the damsite; September 16, 1930
 Jackhammer men drilling open cut excavation; November 29, 1931
Section of pipe in transit to site; 1934
A Memorial Tribute to Anson Smith
1860 – 1935
Editor and Publisher of the Mohave County Miner, acclaimed by President Herbert Hoover for his tireless efforts and support during construction of Boulder Canyon Project and the location of Hoover Dam at this site.
Anson Smith - For some of his friends, Anson H. Smith was the editor with the longest continuous tenure in the whole nation. For still others he was an ideal family man with 10 fine children, all of whom survived him. For all who knew him, he was a man of high ideals, strong convictions, an unfailing locality to his country and state, and a friend to everyone.

He was the founder and editor of the Mohave County Miner, a weekly newspaper launched on November 5, 1882 in one of the pioneer mining districts of Arizona. It began in Mineral Park and moved shortly after the arrival of the railroad to the new community of Kingman, where it became a bulwark of support for all worthwhile endeavors.

Anson Smith is widely recognized as the “father of the Boulder Dam.” As early as 1890, Smith became interested in the potential of the Colorado River as a source of power and of water for irrigation. Year after year, his newspaper advocated the building of a dam in Boulder Canyon. When he presented his ideas to Franklin K. Lane, Secretary of the Interior under President Woodrow Wilson, Lane wrote a reply in which he called Smith’s ideas “a wonderful dream of a wonderful undertaking” but warned that it was “just 50 years ahead of time.”
Smith later described as one of the biggest moments of his life the occasion on which, in June 1933, with the dam about one-third completed, he stood in the dry bed of the Colorado, its water flowing through diversion tunnels on either side. Secretary of Commerce Herbert Hoover, while presiding at the Santa Fe conference on the Colorado River Compact in 1922, called Anson Smith the “Father of the Boulder Dam.”

He was active in promotion of good roads, and at the time of his death he was endeavoring to obtain prompt completion of the highway from Kingman to Boulder (Hoover) Dam. Today there is a road in Kingman named after him.

Wire mesh holding the lose rocks back

 September 10, 1929 – March 5, 2004)
 He was the 23rd Governor of the U.S. state of Nevada from 1971 to 1979
November 6, 1976 – April 22, 2004
 Was an American football player who left his professional career and enlisted in the United States Army in June 2002 in the aftermath of the September 11, 2001, attacks. He joined the Army Rangers and served several tours in combat before he died in the mountains of Afghanistan. The Army at first reported that Tillman had been killed by enemy fire, and Lieutenant General Stanley A. McChrystal approved the award of a Silver Star. The actual cause of Tillman's death was later ruled by the Pentagon as friendly fire.
The key component to the Hoover Dam Bypass project, was the first concrete-steel composite arch bridge built in the United States, and it incorporates the longest concrete arch bridge in the Western Hemisphere.
Opened on October 19, 2010, this four-lane highway bridge provides a crossing of the Colorado River for U.S. Route 93, linking Nevada with Arizona about 1,600 feet (about 500 meters) downstream from the Hoover Dam.
This bridge is located about 30 miles (48 kilometers) southeast of Las Vegas, Nevada.
 At 840 feet (260 meters) above the Colorado River, this bridge is the second-highest one in the United States, following the Royal Gorge Bridge.
Built as part of the Hoover Dam Bypass Project, which was successfully completed within budget at a cost of $240 million, the bridge portion cost $114 million (2010 prices).

The bypass was constructed to improve safety, security, and traffic capacity.
Through extensive studies, this bridge route was determined to be the best route for the bypass.
U.S. Highway 93, in conjunction with U.S. Highway 60 via Wickenburg, Arizona, is the primary highway between Phoenix, Arizona, and Las Vegas, Nevada, two cities that have seen great increases in population since the completion of the Hoover Dam.
 The section of U.S. 93 that approached and crossed Hoover Dam was not adequate for modern traffic needs. It was too narrow, with just one lane in each direction, it had many dangerous curves, including several hairpin turns, and it had poor lines-of-sight, especially at night.
Through highway traffic combined with sightseeing and pedestrian traffic at the dam, the traffic often came to a standstill. As a consequence of the heightened security measures following the September 11, 2001, attacks, truck traffic over the Hoover Dam was diverted south to a bridge crossing the river at Laughlin, Nevada, in an effort to safeguard the dam from hazardous spills or explosions.
This disruption, however, did not eliminate the threat of a possible attack on the dam, since regular traffic still passed over it. Hence, the new bypass and the bridge are intended to improve travel times, replace the dangerous roadway, and reduce the possibility of an attack or an accident at the site of the dam.
More than 17,000 cars and trucks are using the new bridge daily, a number expected to grow by 50 percent over the next 20 years.
 This bridge is a key component of the proposed Interstate 11 project.
The bridge has a length of 1,900 feet (579 m) and a 1,060 ft (320 m) span.
 The roadway is 900 ft (270 m) above the Colorado River and four lanes wide.
This is the first concrete-and-steel composite arch bridge built in the United States.
It includes the longest concrete arch in the Western Hemisphere and is also the second highest bridge in the nation, with the arch 840 ft (260 m) above the river.
The twin arch ribs are connected by steel struts.
Pedestrian access is provided over the bridge to tourists who wish to take in a different view of the nearby dam and river below, but the dam is not visible for those driving across it.
A parking area is provided near the bridge on the Nevada side at what was a staging area during construction. A set of stairs and disabled access ramps lead to the sidewalk across the bridge

Work began in 2003 on the approaches in both states and the construction contract for the arch bridge was awarded in October 2004.
 The largest obstacle to the project was the river crossing.
The bridge and the bypass were constructed by a consortium of different government agencies and contractors, among them the Federal Highway Administration, the Arizona Department of Transportation, and Nevada Department of Transportation, with RE Monks Construction and Vastco, Inc, constructing the Arizona Approach, Edward Kraemer & Sons, Inc, the Nevada Approach and Las Vegas Paving Corporation undertaking the roadway surfacing on both approaches.
The bridge itself was built by Obayashi Corporation and PSM Construction USA, Inc., while Frehner Construction Company, Inc. was responsible for completing the final roadway installations.
A permit problem between Clark County and the subcontractor Casino Ready Mix arose in May 2006 over the operation of a concrete-batch plant for the project, and this caused a four-month delay.

Road Bike Tube

The Hoover Dam Police are responsible for the enforcement of federal and state laws and regulations in the security zone in both Nevada and Arizona; and to provide assistance for local and federal law enforcement agencies, such as handling motor vehicle accidents, traffic violations, public assistance, and the apprehension of wanted persons.
Hoover Dam Police Officers perform a variety of duties and are skilled in law enforcement techniques, as well as public relations.
Their duties include traffic control, manning a stationary post, and conducting foot or roving vehicle patrols.
 Police Officers patrol perimeters, areas open to the public, and restricted access areas to detect violations and enforce laws and regulations, including trespass and other crimes against persons and property.
Police Officers assist other Federal and State law enforcement agencies with investigations.
Police Officers conduct routine physical security checks of buildings, parking areas, gates, fences, and restricted access areas throughout the facility.

Little Mike 

Pedestrian access is provided over the bridge to tourists who wish to take in a different view of the nearby dam and river below

Bypass Construction
 Image by Federal Highway Administration, Central Federal Lands Highway Division (FHWA/CFLHD)
 The dozens of criss-crossing cable stay anchorage sockets temporarily held the weight of the two arch halves above the river gorge. Kayakers float more than a thousand feet below
 Image by Federal Highway Administration
 The west approach is 328 feet (100 meters) high. Image by Federal Highway Administration
 Image by Federal Highway Administration

1 comment:

Anonymous said...

Great article, photos and review. We will be taking the trip with our family today. Thank you - Rob