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What Are the Biggest Dams in the U.S.?

October 23, 2020

Building a dam is an engineering feat. Even for those not in the construction industry, a big dam project can be jaw-dropping. 

The structures are massive, and the amount of concrete in the Hoover Dam would pave a highway from San Francisco to New York City.

The force of the water is extreme, and the base of the Hoover Dam sustains 45,000 pounds per square foot of pressure. That's the weight of 12 cars pressing on each square foot. 

Dams also need to perform well under changing conditions, including drought and flood. Cracked concrete in a dam can be just as problematic as it is for the foundation of a house. 

And a poorly maintained dam could cause safety risks if the dam fails. That's why the largest dams need to be constructed to meet high standards, have built-in safety measures, and be designed to allow for effective inspection. 

Where Are the Tallest Dams?

Some dams are as tall as skyscrapers. In the U.S., the tallest dams are out west. The steep grades of the landscape require this type of dam design. 

The Oroville Dam on California's Feather River is the tallest dam in the country at 770 feet. Comparatively, the tallest dam in the eastern half of the country is Fontana Dam in North Carolina at 480 feet. 

tallest and biggest dam projects in U.S.

5 Tallest Dams in the U.S.

  • Oroville Dam (California): 770 feet
  • Hoover Dam (Nevada/Arizona): 726 feet
  • Dworshak Dam (Idaho): 717 feet
  • Glen Canyon Dam (Arizona): 710 feet
  • New Bullards Bar Dam (California): 645 feet

Of this list of the tallest dams, Idaho's Dworshak Dam is the newest, constructed in 1973. The Hoover Dam is the oldest, built during the Great Depression. When it was finished in 1936, it was the tallest dam in the world. 

The height of the Hoover dam contributes to its ability to generate a large amount of electricity. The taller the dam, the more energy that can be captured as the water falls. The hydroelectric generation plant at the Hoover Dam generates enough electricity to serve 1.3 million people throughout California, Nevada, and Arizona. 

Which Dams Hold the Most Water?

Water is a strong force, and some of the largest dams have created the largest reservoirs. The volume of water a dam can hold indicates its structural strength. 

Keep in mind that the tallest dams aren't necessarily in sync with the dams that hold the most water. These tall dams could be next to smaller reservoirs. For example, the Oroville Dam may be the tallest in the country, but Lake Oroville's surface area is just 15,805 acres, giving it a total water capacity of 1.05 cubic miles. 

The five dams below are the strongest dams in the United States that can hold back the most water. 

strongest dams in the U.S. that can hold back the most water

5 Dams in the U.S. that Hold the Most Water

  • Hoover Dam (Nevada/Arizona): 8.95 cubic miles
  • Glen Canyon Dam (Arizona): 8.53 cubic miles
  • Garrison Dam (North Dakota): 7.05 cubic miles
  • Oahe Dam (South Dakota): 6.98 cubic miles
  • Fort Peck Dam (Montana): 5.52 cubic miles

What's At Stake For Dam Safety?

A dam's job is to hold back water or redirect it. As building experts, Groundworks understands the powerful force that water can have. When we looked at the worst cities for hurricane damage, we calculated that each cubic yard of seawater is equivalent to a live oak tree crashing into your home's foundation. 

According to the National Inventory of Dams from the U.S. Army Corps of Engineers, 17 percent of the country's dams have a high hazard potential, meaning that loss of human life is likely if the dam fails. Those within the inundation zone are not just facing a flood. They could be facing the complete submersion of buildings and neighborhoods. During the 2017 Oroville dam crisis, the California floods damaged the spillway and more than 188,000 people were evacuated from nearby areas. 

Just as many homeowners face foundation damage or cracking concrete, the infrastructure of the country's 91,000 dams is starting to crumble. The issue is that infrastructure is aging while weather patterns and rainstorms are getting more extreme. 

An analysis from AP found that there are at least 1,688 dams in poor or unsatisfactory condition and will cause loss of life if they fail. The Association of Dam Safety reports that it would cost $23.8 billion to repair the country's high-hazard dams where a structural failure results in loss of life. 

During economic downturns, investing in infrastructure often becomes a priority for governments and homeowners. 

Some of the country's major dam projects date back to the Great Depression and the Public Works Administration projects that were put into place by Franklin D. Roosevelt. The Grand Coulee Dam on the Columbia River is a key example of an infrastructure project that created many jobs. Nearly a century later, and after ongoing updates, the Bureau of Reclamation says it is the largest-capacity hydroelectric power project in the United States.

We may see this push for infrastructure projects come through in public policy during COVID-19, but we're already seeing the trend for single-family homes. 

During COVID-19, 29 percent of homeowners are using money from canceled vacations to invest in their homes. About half of these people are making structural repairs such as a new roof, foundation repair, or basement waterproofing.

Is your home at risk of flooding or basement moisture? A free inspection from the country's leading foundation repair experts can help homeowners protect their homes.