Photo By Patrick Adelmann | An overhead view of the Lewisville Lake spillway. Construction crews have installed more than 70 high-capacity post-tensioned anchors through the spillway weir and into the underlying bedrock. These anchors increase the spillway's resistance to uplift forces and improve overall structural stability. In addition, engineers installed an upstream geomembrane blanket designed to limit seepage beneath the spillway, reducing water pressures that can develop beneath the concrete during flood operations. Additional improvements include reinforcing portions of the spillway apron with 936 rock dowels and restoring disturbed areas once construction is complete. see less
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Lewisville Lake Spillway Modification Strengthens Dam Safety for Future Generations
One of North Texas' most critical pieces of flood risk management infrastructure is nearing completion as the U.S. Army Corps of Engineers’ Fort Worth District completes extensive modifications to the Lewisville Lake spillway. The project represents the latest milestone in the long-term Lewisville Dam Safety Modification Program, ensuring the dam continues to safely serve the millions of people who live and work downstream.
Completed in 1955, Lewisville Dam plays a vital role in reducing flood risk throughout the Dallas-Fort Worth Metroplex and Trinity River watershed while also providing municipal water supply, recreation, and environmental benefits. As one of the largest earthen dams in the nation, its continued reliability is essential to the region's public safety and economic vitality.
The spillway modification project addresses structural stability concerns identified through the Corps' Dam Safety Program. Detailed engineering evaluations determined that improvements were needed to strengthen the spillway foundation and reduce the potential for uplift pressures caused by water seepage beneath the concrete structure during high-water events. Rather than responding to an immediate hazard, the district is proactively investing in infrastructure that will extend the service life of the dam while reducing long-term risk.
“The dam and spillway were stable before we began the project,” said Stacy Gray, the initial project manager. “But after Hurricane Katrina, we realized that we had to change the way we looked at things. The structure can be doing everything it's supposed to do, but the potential consequences to life and infrastructure needed to be part of our risk equation going forward.”
In 2022, the Fort Worth District awarded a $76.5 million construction contract to Shimmick Construction Company to perform the spillway modifications. The contract followed completion of an earlier phase of the Dam Safety Modification Project that focused on reducing seepage risks within the embankment and foundation, work that concluded in 2021. Together, these projects form a comprehensive effort to modernize the dam while maintaining its critical flood risk management mission.
Construction crews have installed more than 70 high-capacity post-tensioned anchors through the spillway weir and into the underlying bedrock. These anchors increase the spillway's resistance to uplift forces and improve overall structural stability. In addition, engineers installed an upstream geomembrane blanket designed to limit seepage beneath the spillway, reducing water pressures that can develop beneath the concrete during flood operations. Additional improvements include reinforcing portions of the spillway apron with 936 rock dowels and restoring disturbed areas once construction is complete.
“The key to the project is locking all the pieces and parts into place and preventing uplift and sliding,” said Gray. “Both the weir anchors and the apron dowels are key, as they reduce those risks. And the rest of it is building in resiliency, redundancy, and robustness into the structure. But the key mechanism was the anchors locking those concrete structures into place and preventing the uplift.”
Although construction has required temporary road closures, changes to recreational access, and modifications within the Lewisville Lake Environmental Learning Area, the dam has remained fully operational throughout the project. Flood risk management and water supply operations have continued uninterrupted while crews safely completed work in phases.
"The Lewisville Dam Safety Modification Project demonstrates our commitment to efficiently deliver critical infrastructure before problems become emergencies,” said Col. Calvin Kroeger, the Commander of the Fort Worth District. “These improvements ensure Lewisville Dam will continue providing reliable flood risk management and water supply for the North Texas region for decades to come."
The spillway modifications are part of the approximately $166 million Lewisville Dam Safety Modification Project, which was approved after years of engineering analysis and funded through federal appropriations. The investment reflects the importance of maintaining aging water infrastructure across the country while ensuring continued protection for rapidly growing communities downstream.
“With all the anchors, rock dowels, and drilled piers that are now in the foundation, the structural integrity of the spillway is more profound than it was in the 1950s. The modifications significantly improve the structure's long-term performance and resilience,” said Tony Mendolia, the project manager since May 2024. “This is significant when it comes to the downstream communities like Dallas as well as the potential economic consequences there as well.”
For residents throughout North Texas, much of the work remains invisible beneath the surface. Yet the engineering improvements being installed today will help ensure Lewisville Dam continues performing as designed during future flood events. Every anchor installed and every seepage mitigation measure completed strengthens the resilience of one of the region's most important flood control structures.
“Our ‘Building Infrastructure, Not Paperwork’ initiative will ensure available resources are
allocated to the most critical water resources projects that will deliver the greatest benefits
to our country,” said Adam Telle, Assistant Secretary of the Army for Civil Works. “Aligned with President Trump’s vision of American excellence, the U.S. Army Corps of Engineers will accelerate project delivery with smarter contracting, higher design standards, and a reformed partnership pipeline to build the infrastructure America needs, faster.”
As the project nears completion, the Lewisville spillway will stand as an example of proactive infrastructure investment—combining modern engineering with decades of operational experience to preserve a structure that protects lives, safeguards property, and supports the continued growth of one of the nation's fastest-growing metropolitan regions.
