PEWAUKEE, Wis. – American Transmission Co. on May 15 was recognized by Wisconsin Manufacturers & Commerce for environmental innovation on the Rockdale-West Middleton Transmission Line Project. The 32-mile, 345-kilovolt line provides an important transmission connection between eastern and western Dane County, Wis. The line was energized in early 2013.
ATC received the Environmental Innovation Award for its work designing and building transmission structures in the Yahara wetlands along the Beltline Highway in Madison, Wis. Award winners were selected by an independent panel of judges representing industry, the Department of Natural Resources, the University of Wisconsin and environmental groups.
“Placing structures in the wetlands required the team to address the challenges of accessing the wetland right-of-way and setting structures without causing significant or long-term environmental impacts,” said Environmental Project Manager Amy Lee. “To do this, the team undertook a multidisciplinary evaluation to consider foundation and structure design, construction methods, cost and environmental impacts.”
Construction access and timing
Crews used 2.8 acres of construction matting to access work areas at the edges of the marsh where ground was more stable and used low ground-pressure vehicles called marsh buggies to travel further into the marsh. Because of their wide tracks, these vehicles exert very low ground pressure, even less than a human foot.
Helicopters also were used on multiple occasions to move material and equipment to areas without mat roads. The project team carefully planned construction timing; completing work in the wetlands during the winter months and limiting construction timeframes to avoid spring and fall bird migration and spring fish spawning. Together, these methods eliminated the need for a mat road in the unstable portions of the marsh to provide access for traditional large cranes and heavy concrete trucks.
Foundation installation
ATC engineers and contractors designed and installed 16 helical pier foundations to hold the weight of the structures and have minimal impact on the Yahara wetlands.
“Helical pier foundations are much different from typical concrete foundations,” said Lee. “These hollow foundations screw into the ground and can be unscrewed in the event that they ever have to be decommissioned. They also required no excavation, generated no drilling spoils, and the portable installation equipment was moved with low-impact marsh buggies, barges and skids.”
Setting structures and stringing wires
Heavy-lift helicopters allowed the team to set eight H-frame structures in less than a day, which is much faster than conventional methods. After structure setting was complete, a smaller helicopter was used to string pull rope and move insulators into permanent positions on the structures.
Protecting habitat for migrating and breeding birds
“To protect birds, we placed bird flight diverters in this area, along with three other locations along the route,” said Lee. “Bird flight diverters make shield wire more visible, increasing the likelihood that the birds will see the wire and adjust their flight pattern to avoid it. Using H-frame structures also allowed us to place wires in a horizontal configuration, which minimizes the obstacle for birds in flight.”
In addition to innovation in design and construction of the line, the project also achieved the following environmental milestones:
30 waterways and 5.6 miles of wetlands crossed and only 0.054 acre of wetlands filled
5 miles of mats used to preserve wetlands and protect agricultural lands
Excellent compliance, with no environmental violations or fines
More efficient line eliminates 34,000 to 140,000 metric tons of carbon emissions each year from coal plants not having to operate
“We are committed to environmental stewardship and innovation in all aspects of our business,” said Environmental and Local Relations Manager Greg Levesque. “This is evidenced by our participation in the Department of Natural Resource’s Green Tier program, Clean Corporate Citizen designation in Michigan, as well as the policies and actions that guide our construction projects.”
Additional project information, including a final route map and video of work in the Yahara wetlands, is available at www.RockdaleWestMiddleton.com.
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