A project to restore and repair a 100-year-old dam near Duluth received a 2021 Grand Award in Engineering Excellence from the American Council of Engineering Companies of Minnesota. The award was presented at ACEC/MN’s virtual awards gala on February 26.
The Island Lake Dam Gate Upgrade project restored and repaired a unique, century-old dam that supports Minnesota’s largest hydropower system and provides important community and environmental benefits. Minnesota Power hired Barr to devise and implement a solution to repair or replace the Island Lake Dam’s aging sluice gates, which reduced power generation and posed operational, environmental, and safety risks. The dam supports the Island Lake Reservoir, north of Duluth.
“Barr’s technical expertise, collaborative approach, and innovation resulted in a safe, reliable design that modernized the operation of the gates,” said Minnesota Power’s supervising engineer Daniel W. Nordling, P.E. “The design accommodated normal operation throughout construction and maintained aquatic habitats and recreational activities on this 10,800‐acre reservoir.”
Designing and implementing repairs to the dam called for precision at every step. A major complicating factor was the gates’ location, 50 feet below the water’s surface. Divers could not safely access the gates for repairs. Further, while the dam’s original design called for partial drainage of the reservoir to access the gates, this option was no longer feasible.
Close collaboration among Minnesota Power, Barr, and construction contractor J.F. Brennan Company, Inc., along with the use of a three-dimensional model, enabled development of a final design and detailed construction plans. The design configuration extended the end walls and piers vertically by 30 feet. New bracing and framing were added to distribute loads. Bulk-head slots, incorporated on the upstream end of the walls and piers, accommodated steel bulkheads for dewatering. Finite-element models were used to assess load stresses and size new elements to assure structural integrity and stability. The project was completed in the fall of 2019.
“We appreciate Barr’s partnership and expertise on this important project,” said Chris Rousseau, Minnesota Power’s manager of renewable business operations. “Our roots in renewable energy run deep—Minnesota Power got its start more than 100 years ago with clean, renewable hydropower.”
“Barr was honored to assist Minnesota Power in proactively improving critical infrastructure and contributing to a more sustainable future by supporting the safe, reliable, and efficient operations of the state’s largest hydropower system,” said Barr’s president and CEO, John Lee.
For more, check out the project team’s acceptance video from ACEC/MN’s virtual gala event.