New dam failure case studies and new 'lessons learned' have been uploaded to DamFailures.org. Thank you to the researchers and reviewers who contributed. The site now has more than 20 case studies and more than 10 lessons learned, as well as 5 ASDSO webinars that can be viewed free of charge as part of a Cooperating Technical Partnership between FEMA’s National Dam Safety Program and ASDSO.


 

May 2019

Case Study - Maple Grove Dam (Colorado, 1979)

Researcher: Ryan Schoolmeesters
Reviewer: Greg Richards

In an effort to increase water storage capacity and provide flood protection to the surrounding communities of Lakewood, Colorado, two inflatable Fabridams were added to the crest of Maple Grove Reservoir and spillway in 1977. Shortly before midnight on March 17, 1979, personnel of The Consolidated Mutual Water Company noticed one of the inflatable Fabridams was collapsing and allowing reservoir water to be released down the spillway. The sudden and unintentional spillway release prompted a midnight evacuation of approximately 2,000 people and caused damage to structures, streets, and culverts as well as stream bank erosion. Investigation into the cause of the rupture and failure of the Fabridam revealed the Fabridam’s vulnerability to vandalism. Though uncommon, additional investigation discovered similar cases of vandalism to Fabridams throughout the country further presenting a need for steps to be taken to avoid future incidents of vandalism. Precautionary measures to avoid future vandalism were taken at Maple Grove Reservoir including increased personnel surveillance, installation of alarm systems with visual and audio alerts, security lighting, and fencing to limit public access. As an additional precaution, an earthen fuse plug was constructed in the spillway approach channel to assure any unintentional deflation of the Fabridam would only release a minimal amount of water downstream. As the Fabridams reached the end of their service life in 2004, a decision was made to replace them altogether with two independent hydraulically-actuated steel crest gates. The crest gates are less susceptible to vandalism, provide greater confidence in the integrity of the Maple Grove Dam and Reservoir, and were determined to provide greater public safety.

 

Lesson Learned -  Site security is a critical aspect of dam safety that shouldn’t be overlooked or disregarded.

Researcher: Ryan Schoolmeesters
Reviewer: Frank Calcagno

More than 90,000 dams are included in the 2018 National Inventory of Dams (NID) database. According to the 2016 U.S. Department of Homeland Security (DHS) Dams Sector fact sheet, “Dams Sector assets irrigate at least 10 percent of U.S. cropland, help protect more than 43 percent of the U.S. population from flooding, and generate about 60 percent of electricity in the Pacific Northwest.” It is undeniable that the Dams Sector, including dams, levees, hydropower plants, and navigation locks, provide a wide range of economic, environmental, and social benefits, and serve a vital role in the national interest.

Unfortunately the economic, environmental, and public safety consequences of failure also makes the Dams Sector assets an attractive target for physical, cyber, and other deliberate attacks. Deliberate attacks are not new to the Dams Sector risk profile. There are well documented historical examples of deliberate physical attacks on Dams Sector assets, including the German Möhne and Eder Dams during World War II in 1943, the North Korean Sui-Ho Dam and hydroelectric facility during the Korean War in 1952, and numerous smaller scale domestic attacks on several U.S. dams as recent as 2016. In 2012, the U.S. DHS compiled and documented a list of over two dozen physical attacks on dams worldwide during the first decade of the twenty first century alone, with no indication of a drop in frequency during that time period. Adding complexity, the advent and growth of digital infrastructure and automated data collection with internet-facing components has opened the door to relatively new threats to the Dams Sector risk profile, as demonstrated by a cyber attack on a small U.S. dam in 2013. The evidence indicates that the Dams Sector assets will continue to be the target of deliberate attacks. It is therefore imperative that Dams Sector partners develop and implement appropriate risk reduction strategies to protect critical infrastructure. 


 

March 2019

Case StudyVajont Dam (Italy, 1963)

Researcher: Lee Mauney
Reviewer: Giorgia DeWolfe

In 1963, one of the most disastrous rockslides ever to occur, slid into the reservoir behind Vajont Dam in Italy, causing a massive wave to overtop the dam, destroying entire villages and causing more than 2,000 fatalities. Because of the magnitude of the event, the Vajont Dam incident is one of the most researched rockslides in the world, analyzed in technical papers, books and film. This case study can remind us of the hazards that exist at dams, even if a structure is considered safe and does not fail. In the years before the incident, the risk of a major rockslide and its consequences were normalized and as the event was proceeding, a clear, concise warning message was never issued. Vajont highlights the need for thorough geotechnical investigations during dam design, specifically reservoir slope stability analyses. Vajont Dam remains in place today and provides a unique and important educational opportunity for visitors. Compared with historic dam failure and incident case studies, Vajont is unique is many aspects, including:

• Vajont Dam did not fail and remains one of the highest dams in the world,

• The scale of the 1963 rockslide and resultant flood are unprecedented,

• Resultant flooding from the rockslide reached the population at risk almost immediately,

• The fatality rate is among the highest recorded dam failure or dam incident,

• Voluminous research has been conducted on the Vajont rockslide and surrounding geology since the incident.

 

Updated Lesson Learned - Dam incidents and failures can fundamentally be attributed to human factors.

Researcher: Irfan A. Alvi
Reviewer: Mark Baker

The field of “human factors” considers how and why systems meet or don’t meet performance expectations, with an emphasis on understanding and prevention of incidents and failures. The systems considered in human factors work, such as dams, typically include both human and physical aspects, and are sometimes referred to as “sociotechnical” systems. To prevent future dam failures, it is essential that dam safety professionals understand both physical factors and human factors, and how they contribute to failures or safety.

Thumbnail Photo: In 2017, the service spillway of Oroville Dam in California, the tallest dam in the US, failed to due to uplift of the slab and subsequent foundation erosion. This was followed by erosion and headcutting at the emergency spillway, which was used for the first time in its history during the incident, and prompted evacuation of about 188,000 people. A wide range of human factors contributed to the incident at individual, organizational, regulatory, and industry levels, starting with the design and construction of the project in the 1960s until the incident in 2017. (Photo Source: Irfan A. Alvi)


 

More 'lessons learned' and case studies coming in 2019!