Ribbon Cutting at Isabella Lake Dam Safety Modification Project

Once considered the “most dangerous dam in America,” Phase II of the Isabella Lake Dam Safety Modification Project is now complete. Flatiron and its joint venture partners Dragados USA and Sukut Construction completed the project under budget at $323 million.

Isabella Dam has a main and auxiliary dam just north of Lake Isabella, California. The US Army Corps of Engineers (USACE) owns and operates the dam. In 2006, a USACE study found the dam vulnerable to three potential failure modes: overtopping, seepage and seismic damage. Water leaked at its base, and a fault line previously believed to be inactive was found to have been active within recent (5,000 years) geologic time.

Dam improvements, begun in late 2017, were designed to address these issues. The fortified structure features:

• Labyrinth weir designed to channel water during significant flood events
• Additional emergency spillway constructed
• Primary and emergency spillways strengthened with 35′ long anchor bolts 
• Main and auxiliary dams raised by 16 feet
• Improved filtering and drainage systems

Several dignitaries attended the ribbon-cutting ceremony in early April, including Speaker of the House and Representative of California’s 20th Congressional District, Representative Kevin McCarty:

Today’s ceremony is the culmination of the relentless work of countless individuals who have dedicated years to see this project through. Finally, all the reviews, studies, environmental work, and major construction are complete, and our community will undoubtedly reap the benefits.

Local station KGET News explains the project in full detail in this YouTube video.

About Flatiron

Flatiron is the trusted partner to deliver innovative solutions to infrastructure challenges across the U.S. and Canada. Flatiron collaborates with public and private clients to deliver heavy civil infrastructure including highways and bridges; aviation, rail and transit; dams and water treatment facilities; and underground projects. For more on how Flatiron is transforming infrastructure, visit www.flatironcorp.com. Flatiron is a subsidiary of HOCHTIEF, an engineering-led global infrastructure group.