Isabella Lake Dam

The Isabella Lake Dam Safety Modification project, led by the FlatironDragados and Sukut joint venture, enhanced the safety and operational capacity of the Isabella Lake dams for the U.S. Army Corps of Engineers. 

In 2006, a USACE study found the dam vulnerable to three potential failure modes: overtopping, seepage and seismic damage, naming Isabella the “most dangerous dam in America.” The project addressed each of these issues.

Key elements included:  

• Main and auxiliary dams raised by 16 feet 
• Construction of 300-foot-wide emergency spillway with 28-foot-high labyrinth weir
• Existing spillway reconstructed; new emergency spillway fortified with 35-foot-long anchor bolts
• Filtering and drainage systems enhanced

The project, completed in 2023, ensures long-term flood-risk management and reinforces the dam’s structural integrity, benefitting the 300,000 people living and working downstream. 

• 2023 Dam Safety Award, National Rehabilitation Project of the Year, Association of State Dam Safety Officials
• 2023 CMAA Project Achievement Award, Environmental: Construction Value Greater than $50 Million, Construction Management Association of America
• 2023 Excellence in a Constructed Project of the Year, United States Society of Dams