In my experience, the safety of the 100,000-plus dams located in North America and Canada is just one of many things the average person takes for granted. And I suppose I was the same way for many years.
For more than a decade of my early formative years, I lived on Grand Lake O’ the Cherokee in northeastern Oklahoma. This lake has a surface area of more than 59,000 acres and an average depth of 36 feet, with a total water volume of more than 1.5 million acre-feet. Grand Lake is impounded by Pensacola Dam, the longest multiple-arch dam in the world. Its main span is 5,145 feet long and consists of 51 arches. Construction on this Works Progress Administration project began in 1938 and it was completed in 1940.
The potential downstream consequences of a sudden release of this reservoir could be catastrophic to people and the environment. But, you know, I never really gave it much thought at the time.
Now that I’m older and have worked providing information to the hydroelectric power industry for more than a decade, I am sometimes quite amazed when I see structures (houses primarily) located almost at the base of dams. Because, you know, some dams fail. The Association of State Dam Safety Officials in the U.S. says that while “no one knows precisely how many dam failures have occurred in the U.S.,” dam failures have been documented in every state. From Jan. 1, 2005, through June 2013, state dam safety programs reported 173 dam failures, ASDSO says.
Luckily for all those who live mostly unaware, those failures are few and far between (at about 20 per year based on the above statistics). And, they primarily occur at smaller dams, where the consequences may be less severe.
In a presentation made to the Federal Emergency Management Agency’s National Dam Safety Program, the Canadian Dam Association said there have only been five recorded dam failures in that country that resulted in loss of life, the most recent one in 1966.
FEMA, in the U.S., says dams can fail for one or a combination of the following reasons:
- Overtopping caused by floods that exceed the capacity of the dam
- Deliberate acts of sabotage
- Structural failure of materials used in dam construction
- Movement and/or failure of the foundation supporting the dam
- Settlement and cracking of concrete or embankment dams
- Piping and internal erosion of soil in embankment dams
- Inadequate maintenance and upkeep
Wanapum Dam, on the Columbia River in Washington State, is an example of a dam that faced potential failure … but was saved through timely intervention and extensive repair work. Read the article on page 10 to see how the crack was discovered, measures taken to ensure stability, and work completed to return the dam to proper working order and the 1,092-MW powerhouse to full operation.
In addition, every issue of the magazine contains the Dam Safety & Security department (page 52) to keep you up to date on the latest news. And we have a “topic center” on our HydroWorld.com website – Dams/Civil Structures – that contains even more information on this important topic.
Safe dams = safe people … even if they take that safety for granted.