CapX2020 Mississippi River T-Line Crossing
Hanson and POWER Engineers Inc. provided transmission line design services that helped Xcel Energy Inc. complete a critical Mississippi River crossing of the CapX2020 Hampton-Rochester-La Crosse 345-kilovolt project.
The goal of the CapX2020 program is to provide reliable and affordable electric service to Wisconsin, Minnesota and the surrounding region while expanding access to new power generation, including renewable energy. It involves the design and construction of about 800 miles of 230- and 345-kilovolt transmission lines at a cost of more than $2 billion. Eleven utilities, including Xcel Energy, are partners in CapX2020, which is the largest development of new transmission capacity in the region in more than 40 years. Xcel Energy is the managing partner for the 150-mile Hampton-Rochester-La Crosse transmission line.
The crossing, which was completed in February 2015 and cost $18 million, presented many challenges. The crossing is within the Upper Mississippi River National Wildlife and Fish Refuge, which is part of a primary bird migration route called the Mississippi Flyway. Vertical limitations for the line’s towers required that the conductors be at least 90 feet above water and the towers be below 200 feet in height. To minimize span lengths, one tower was placed on an island and another on a peninsula; transporting equipment and materials to those sites was done by barges and towboats. Helicopters pulled ropes across the river to string transmission lines and dropped off linemen on top of the towers.
Hanson’s design for the five tower foundations factored in the site’s harsh environment, providing scour protection and supporting the towers against wind, river flooding and ice. POWER’s team helped develop the overhead line design to meet CapX2020 requirements and environmental and navigation requirements from the U.S. Fish and Wildlife Service and U.S. Army Corps of Engineers. The new crossing improved the protection of birds along the flyway and has less potential for bird strikes.