Hoover dam is a fun family place to visit if you come to Las Vegas more than once or twice. It is a major tourist attraction, nearly a million people tour the dam each year. It has been compared to the Acropolis of Ancient Greece and the Coliseum of Imperial Rome. Rising 726 feet above the waters of the Colorado River, it was called by the man whose name it bears “the greatest engineering work of its character ever attempted by the hand of man.” In fact, Hoover Dam reflected the engineering genius and design philosophy of the time. And, in the middle of the Great Depression, it was a symbol of hope for the dispossessed.
Hoover Dam employees worked under dangerous conditions 7 days a week with 2 days off (unpaid) a year. For two years, workers poured concrete 24 hours a day, seven days a week. Working conditions were dangerous, pay was low, housing inadequate. But it was the Depression, and many were grateful to have work. Five thousand men and their families settled in the Nevada desert. There were two mess halls, each seating 600 and the dishwasher was sixteen feet long. In 1935 the job was finished under budget and ahead of schedule. But Hoover Dam also raised policy questions about the economic and environmental impact of large scale irrigation throughout the West.
By the time it was officially dedicated on September 30, 1935, the colossal dam project on the Southern Nevada portion of the Colorado river had been called by several different names. In the exploratory stage, the project was referred to as the Boulder Canyon Project. Boulder Canyon was replaced by Black Canyon, when Black Canyon was discovered to be a more suitable spot to place the dam. Having started its legislative life under the moniker of Boulder Canyon, the dam project simply adopted the title Boulder Dam. All of that changed, temporarily at least, on September 17, 1930, when Secretary of the Interior Ray Lyman Wilbur journeyed to the Nevada desert to drive the spike marking the project’s official start. Sweating profusely through his inappropriate wool suit, Wilbur announced, “I have the honor and privilege of giving a name to this new structure. In Black Canyon, under the Boulder Canyon Project Act, it shall be called the Hoover Dam.”
Hoover dam is about 30 minutes outside Las Vegas, just beyond Boulder Nevada, the town that was built to house the workers on the dam. On the way, you pass by Lake Mead, the lake that was created when Hoover dam was created. It is a huge lake, popular for boating and fishing. One problem has been that the water level changes so much that there really isn't a good shore or beach.
It used to be that the only way to get from Nevada to Arizona was to go across the top of the dam. Constructed in 2005 and opened 5 years later, the Mike O'Callaghan – Pat Tillman Memorial Bridge was the perfect bypass to avoid gridlock that caused painful US 93 bumper to bumper traffic. The bridge not only allows you to avoid the traffic, it's a great place to get out and walk and get the best view of the Hoover Dam. Easily the best vista point for getting a picture of it without having to rent a helicopter. When the bridge opened to traffic, the roadway over Hoover Dam was closed to through traffic, and all visitor access to the dam was routed to the Nevada side; vehicles are still allowed to drive across the dam to the Arizona side following a security inspection, but must return to the Nevada side to return to US 93.
The bridge was the first concrete-steel composite arch bridge built in the United States and it incorporates the widest concrete arch in the Western Hemisphere. At 840 feet (260 m) above the Colorado River, it is the second-highest bridge in the United States, following the Royal Gorge Bridge. The arches are made of 106 pieces—53 per arch—mostly 24 ft (7.3 m) cast in place sections. The arch was constructed from both sides of the bridge concurrently, supported by diagonal cable stays strung from temporary towers. When the two halves of the arch were completed in August 2009, they were only 3/8 inches (9.5 mm) apart, and the gap was filled with a block of reinforced concrete.
There's a small parking lot for people who wish to walk on the pedestrian path. Parking can be competitive, and there's no parking allowed on the highway if the lot is full. There are no fees to park, and there's no admission price to go up and walk on the bridge. You can get up to the bridge by either stairs or a really long ramp that isn't steep to climb. The pedestrian walkway on the bridge is about 5 feet wide. The railing along the edge is a little lower than shoulder-high with no fence blocking your view or photo ops. There's a thick concrete barrier separating you from the high speed traffic. When a big truck goes over the bridge, it feels like a mini earthquake.
To get to the dam you go down the old US 93, winding down into the canyon through a virtual thicket of power lines eminating from the dam. You end up in the parking garage, carved into the walls of the canyon.
They have a brand new visitors center along with some plaques and this pair of angels, “Winged Figures of the Republic”. Norwegian sculptor Oskar Hansen, responsible for most of the dam's various heroic and mythical artwork, made the figures from more than four tons of bronze. They sit on bases of black diorite, flanking a 142 ft. high flag pole. This stylish monument to the dam was dedicated in 1935. The figures have weathered to a green patina, but the toes are burnished to a soft gold by countless tourist hands.
This diagram shows the parts of the working dam, most of which is hidden from the casual observer. The spillways, used if the dam gets too full, are a set of 50 foot diameter pipes leading to the river below.
The large spillway tunnels have only been used twice, for testing in 1941 and because of flooding in 1983. Both times, in inspecting the tunnels after the spillways were used, engineers found major damage to the concrete linings and underlying rock. The 1983 damage, due to cavitation, led to the installation of aerators in the spillways.
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 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.
If you take the tour you will get to see the actual electric power generators. 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. 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 Pelton generator is seen in the lower right corner above. The operating turbines are seen with the orange light on. 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 multi-million dollar yearly maintenance budget. Power is generated in step with and only with the release of water in response to downstream water demands. About 25% of the generated power goes to Las Vegas.
To get to the generators, you take a long elevator down, then walk along corridors carved in the rock. 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.
The Las Vegas valley gets its water through two long channels drilled through the rock. The first taps the lake at 1,050 feet (320 metres) above sea level, the second at 1,000 feet. Lake Mead's water level is now near its record low, at 1,086 feet. Within a few years it could leave Las Vegas's first intake, or even both, dry. They are currently digging a third intake at 890 feet. Given the weight of the water on top, this is fiendishly difficult and will not be ready until 2014. The main reason why Lake Mead, currently only 40% full, has been getting emptier is a decade-long drought. Whether this is a cyclical and normal event, or an early sign of climate change, is unclear.
If you think Hoover dam looks a little dated, consider this reinterpretation from Yheu-Shen Chua from the United Kingdom for a project that re-imagines the Hoover Dam in the U.S. as an inhabitable skyscraper that unifies the power plant with a gallery, aquarium, and viewing platform that engages the falling water directly. I doubt they will rebuild it but this looks pretty cool.
Well that's all for now, thanks for reading.
Bustler 2011 Skyscraper Competition: http://www.bustler.net/index.php/article/evolo_unveils_winners_of_the_2011_skyscraper_competition
Bureau of the Interior: http://www.usbr.gov/lc/hooverdam/