Ever since it was completed in the 1930s, this wall of concrete on the Colorado River has impressed everyone with its size and function.
By Tom and Joanne O’Toole
January 2006
A two-lane road from Las Vegas, Nevada, to Hoover Dam snakes across the countryside, through landscape that hasn’t changed in thousands of years. As you crest a knoll, Lake Mead looms ahead like an enormous oasis in the middle of the desert. In the distance are mountain ranges, and above it all are billowing clouds in a rich blue sky.
Hoover Dam originally was named in honor of President Herbert Hoover, who pushed for its creation during his tenure as U.S. Secretary of Commerce, and later as president. After Franklin Delano Roosevelt defeated Hoover in the 1932 presidential election, his secretary of the interior changed the structure’s name to Boulder Dam. President Harry Truman renamed it Hoover Dam permanently via an act of Congress in 1947.
Let’s clear up the one big myth about Hoover Dam right now. There are no bodies buried in the concrete of this colossal structure that holds back the Colorado River. However, a number of plaques and a monument near the visitors center honor the men who built the dam, and the 110 workers who died in the process.
The dam straddles the states of Nevada and Arizona. Many visitors walk across the dam from one state to the other, and the roadway atop the dam is highly traveled U.S. 93, which is a main artery in this part of the United States. Traffic goes across slowly, and the sidewalk is comfortably wide.
However, walking along the top of the structure and peering over the edge of the face of the dam is a stomach-churning experience. A number of small platforms hang out over the top of this concrete monster, allowing you to look down its sloping face.
The front of the dam sweeps down and away, and a number of people have taken the plunge “” either by accident or through compulsion. If you’re afraid of heights, you might want to skip this view. The back, or water side, of the dam is much more serene.
The broad expanse of concrete atop the dam features different areas with memorial art and graceful sculptures. Most of the art is located on the Nevada side close to the abutment. Most conspicuous is the 142-foot-high flagpole, flanked by two winged statues called “Figures of the Republic.” Other art-deco works include the large compass surrounded by the 12 signs of the zodiac. As you gaze upon these, you’ll be walking on an intricate terrazzo floor and its interesting star map.
This huge dam and hydroelectric power plant is one of the engineering marvels of the 20th century. The cylindrical-shaped visitors center built into the Nevada side of the canyon wall is a storehouse of information about the dam, its history, and construction. It includes a topographical model of the Colorado River Basin, showing how the dam benefits the West. Everyone who stops at the Hoover Dam site should go first to the visitors center.
To visit the center, you may want to use the $7 cash-only multilevel parking garage that is tucked into the upper rocks of the canyon wall. This is by far the most convenient parking area at the visitors center (for towed vehicles). Or, you can take advantage of free outdoor parking on the Arizona side of the dam.
The center is a three-level, 110-foot-diameter circular concrete structure with a rooftop overlook. Take the Discovery Tour, and you can explore exhibits, sights, and even go down inside the dam. From the reception lobby, access to the rotating theater is provided, which is divided into three 145-seat sections, along with audiovisual programs and construction memorabilia and photographs.
The Discovery Tour has replaced the traditional and hard-hat tours previously conducted in the power house. This tour includes a film called How The West Was Won, which details how the Bureau of Reclamation has helped to harness the power of nature for the country’s good.
Next, you take an elevator down into the wall of Black Canyon and walk through a 250-foot-long tunnel drilled out of the rock to see the Nevada wing of the power plant, including its eight huge generators.
Since the Arizona-Nevada border runs down the middle of the Colorado River, each state has a set of turbines inside the base of the structure. The water passing through these turbines generates low-cost hydroelectric power for use in Nevada, Arizona, and California. The energy is marketed to both public and private agencies under contracts that expire in 2017. The four biggest users by percentage are the Metropolitan Water District of Southern California (28.5 percent); the state of Nevada (23.4 percent); the state of Arizona (19 percent); and the city of Los Angeles (15.4 percent).
The dam was created to control flooding on the Colorado River as well as to generate power. Black Canyon was selected as the best site for the dam, because it was narrow, and the sheer walls of more than 800 feet provided the needed strength. With the Great Depression sweeping the country, finding men eager to do the backbreaking and often dangerous work was no problem. Work officially began in May 1931. By 1933 the concrete began to pour day and night, and continued for two years. When the dam was finished, more than 4.4 million yards of concrete were in place.
Bid in at just shy of $49 million “” the largest construction contract by the federal government up to that time “” Hoover Dam was completed in 4½ years “” 2½ years ahead of schedule, and millions of dollars under budget. Imagine that happening today! The overall cost of the project, including the dam, power plants, and related structures, was $165 million.
The multipurpose dam was built to harness the Colorado River for (in order of importance) flood control, navigation, irrigation, water storage, and power. In the bargain the project was to be self-supporting, financed entirely through the sale of hydroelectric power.
The arch-gravity structure rises more than 726 feet from bedrock, is 660 feet thick at the base, and 45 feet thick at the top; its crest stretches 1,244 feet across the canyon, rim to rim. More than five miles of maintenance and inspection tunnels wind through the structure, and many are lined with ceramic tile and American Indian designs.
How do you build a dam like this? First, diversion tunnels were drilled and blasted through solid rock in the walls along either side of the river. These massive tunnels were 4,000 feet long, 56 feet in diameter, and surrounded by three feet of concrete.
Then a cofferdam was built to divert the river into the tunnels. Farther downstream, behind where the tunnels emptied out into the riverbed again, another cofferdam was built to prevent water from backing up into the proposed dam site.
The area between the two cofferdams was pumped dry, the riverbed was excavated 135 feet to bedrock, and construction of Hoover Dam was under way.
One of the innovative ideas used during the dam’s construction was cooling the concrete. Without artificial cooling, it would have taken more than a century for the dam to lose the heat created by the setting concrete, and it would have shrunk and cracked as it cooled. The solution, engineers determined, was to build the dam in pier-like blocks and cool the concrete by running ice-cold water through a network of copper pipes embedded in the blocks. As the blocks contracted and gaps appeared between them, concrete grout was pumped into the breaches, making the structure monolithic “” of one piece. The copper tubes then were filled with concrete as the material cured, assuring structural integrity.
Water from Lake Mead (which took 6½ years to fill) has never crested the dam. Instead, it runs around it, and detailed engineering diverts the flow to the power-producing generators at the base of both canyon walls. The power plants at Hoover Dam have 17 large generators with a capacity of more than 1.3 million kilowatts.
Two spillways on either side are 27 feet lower than the walk and roadway atop the dam.
Back in 1941 the lake was permitted to rise so the spillways could be tested. Mother Nature provided another successful test of the spillways when snowmelt reached record levels in 1983. A white line along the canyon walls behind the dam shows the maximum level reached.
Lake Mead extends more than 110 miles upstream from the dam and is one of the West’s most popular recreation areas, with a 12-month season that attracts almost 10 million annual visitors for swimming, boating, waterskiing, and fishing. Recreation-related boat and equipment rental firms have been licensed by the government, and satellite businesses are everywhere.
The lake’s 550 miles of shoreline are mostly edged with green vegetation and stands of trees, while snuggled along the shore are marinas and a smattering of lodges.
The lake and surrounding area are administered by the National Park Service, as part of the Lake Mead National Recreation Area.
Hoover Dam is the third-most popular tourist attraction in the United States under the control of the federal government. When you visit, you’ll be one of the nearly 1 million people who go there each year. It’s also the most popular day-trip from Las Vegas. In 1985 Hoover Dam was designated a National Historic Landmark by the Department of the Interior.
Visitors who come away from this engineering marvel usually find it difficult to comprehend the enormity of it all “” much like not fully understanding the national debt. You know it’s there, but you’re not quite sure how it all came to be.
Further Info
The Discovery Tour at Hoover Dam costs $11 for adults, $9 for seniors age 62 and over, $6 for children ages 7 to 16, and is free for children 6 and under. Golden Eagle or Golden Age Passports are not accepted for admission to the visitors center or tour.
If you wish to drive across Hoover Dam, you must pass through an inspection checkpoint. Arriving from the north, the checkpoint is located on U.S. 93 one mile north of the dam. If arriving from Arizona, the point is nine miles south of the dam. Any vehicle may be fully inspected prior to being permitted to cross the dam. Motorhomes, rental trucks, and similar types of vehicles are always inspected, so plan on being delayed and having your coach searched.
Semi-tractor trucks, commercial buses, vans, and enclosed trucks are not permitted to cross the dam at all. Stopping on top of the dam in any vehicle is prohibited.
A new Hoover Dam bypass bridge is being constructed, and this may cause traffic delays on U.S. 93. When completed, the bypass will be a four-lane, 3½-mile divided highway flanking the innovative arch bridge. It will route traffic away from the top of the dam, relieving bottlenecks and adding greater security. It is scheduled for completion in 2008. Updated information about crossing the dam is available by calling (888) 248-1259.
For free brochures, contact:
Hoover Dam Visitor Services
P.O. Box 60400
Boulder City, NV 89006-0400
(702) 494-2517
www.usbr.gov/lc/hooverdam