Inside one of the greatest engineering achievements in human history

From the top of Hoover Dam, the Colorado River looks suitably tamed. Famed for its whitewater tumult upstream, the Colorado is funnelled between the stark, towering walls of Black Canyon. Then the giant dam holds firm, the largest man-made lake in the United States sprawling behind it.

Hoover Dam is one of engineering’s greatest achievements – perhaps even the greatest. When construction began in 1931, no dam on this scale had ever been attempted. Hoover Dam is 221 metres high, with Black Canyon blocked by 2.49 million cubic metres of concrete. What many visitors don’t realise, however, is that it is possible to go inside the dam.

The Hoover Dam might be the greatest engineering achievement in history.Credit: Getty Images

From outside, Hoover Dam is about size, scale and spectacle. Once inside, it becomes more about appreciating how this great barrier works and holds together.

Tours start with a video presentation about the history of the dam – how six companies merged into one to tackle the task, how 21,000 men from all over the US worked on it, how the city of Boulder, Nevada, was built to accommodate the workforce.

The next stop is one of the two power plants – there’s one either side of the Nevada-Arizona border. Between them are 17 giant turbines, each connected to a generator, collectively providing enough hydroelectric power for 1.3 million people across Nevada, Arizona and California.

The enormous hall containing the eight on the Nevada side gives off huge Bond villain vibes. The generators look like giant boring machines, drilling down towards the centre of Earth, and it would not be a surprise to see the hall teeming with bio-suited henchmen.

At the base, Hoover Dam is 200 metres thick – you just can’t see most of it because it’s underwater.Credit: iStock

Less dramatic-looking, but arguably more impressive, is one of the four diversion tunnels that were carved inside the mountain. During construction, the Colorado River was re-routed through these tunnels, allowing for all that concrete to be put in place.

They aren’t the only tunnels inside Hoover Dam, however – and there’s much more to it than just concrete.

The network of service tunnels passes through the dam, with blocks of concrete numbered so that workers know where they are. It soon becomes apparent that the dam is even bigger than it looks from the outside.

At the base, Hoover Dam is 200 metres thick – you just can’t see most of it because it’s underwater.

“There’s 450 feet [140 metres] of concrete between us and the reservoir,” says the guide, twigging that a few members of the tour party are concerned about Lake Mead breaking through and rushing in.

Turbines in the dam’s generator room provide power for more than 1 million people.Credit: iStock

Some water does get in, however. Every tunnel within the dam has its own drain for seepage. “That’s not a leak,” says the guide. “We try not to say the L-word here.”

The seepage also creates lines of calcium carbonate along the tunnel walls. The dam is not as sealed-off as the outsider might imagine.

This is the sort of thing that spooks the public, but not engineers. It’s an inevitability and is built into the design, along with two spillways for when heavy snowfall in the Rockies makes for high water levels.

Some of the concrete, poured several decades ago, is still setting. A much higher proportion would still be wet if 937 kilometres of cooling pipes hadn’t been built in. River water was pumped through the pipes to help the concrete blocks set quickly, and avoid the cracking and crumbling that would come from allowing nature to complete the process over an estimated 125 years.

Inside a tunnel on the Hoover Dam tour.Credit: Travel Nevada

There are also ventilation tunnels and, on the way to the Arizona border in the middle of the dam, we’re allowed to venture down one. There’s a window, offering an extraordinary view of the river from inside the dam wall.

Going inside Hoover Dam should be about engineering greatness. This is a modern wonder that transformed desert land across the south-west of the US into some of the most productive horticultural land on Earth.

But it becomes far more interesting for the imperfections and workarounds. Peel away the cloak of magisterial greatness, and it’s a maze of pragmatic functionality.

THE DETAILS

VISIT
Hoover Dam is a 35-minute drive from Las Vegas. Tours cost $US30 ($45) and have to be booked on-site, rather than online. See usbr.gov/lc/hooverdam

FLY
United has one-stop flights from Melbourne and Sydney to Las Vegas, changing planes in Los Angeles or San Francisco. See united.com

STAY
The Best Western Hoover Dam Hotel in Boulder City offers comfortable motel-style rooms from $US88.50, including breakfast. See bestwestern.com

The writer was a guest of Travel Nevada, see travelnevada.com