American Transmission Co. projects

Project website for a Wisconsin-based company that owns and operates the high-voltage electric transmission system that powers communities in portions of the Upper Midwest.

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News release: Underground power line study leads to route options off Beltline highway, through neighborhoods

ATC will not propose underground construction for proposed Rockdale-West Middleton project

MADISON, Wis.—The conclusion of a study on constructing the proposed Rockdale – West Middleton high voltage transmission line underground is that Madison’s Beltline highway is not a suitable location for underground facilities.

The locations identified as the most feasible include routes off the Beltline on city streets and frontage roads. “Although we assumed the Beltline might offer undergrounding possibilities, the routes we found the most feasible from a construction standpoint deviate from the Beltline between Verona Rd. and west to the West Middleton Substation,” said Mark Williamson, vice president of Major Projects. “The routing guidelines are different for underground facilities. Portions of the Beltline were found to be unsuitable for underground construction because of access issues from private property, volume and speed of traffic and steep slope conditions along the edge of the Beltline right-of-way. All combine to make this type of construction along the Beltline impractical.”

ATC conducted the underground study—the first to be conducted by the company for a 345-kilovolt line—in response to requests from the Public Service Commission of Wisconsin and several local governments to evaluate options for undergrounding the proposed transmission line near the Beltline and in parts of Fitchburg. According to Williamson, the company will not be recommending underground construction because of operational and cost concerns. “It is simply imprudent to construct underground lines at a cost many times greater than overhead lines knowing the trade-off is greater operational limitations,” he said. “It’s like paying a premium for a high-end coffee maker that makes worse coffee than a more economical model.”

Williamson explained that Wisconsin currently doesn’t have any power lines of this voltage underground. “The findings will be useful for future 345-kV proposals. The results we have now offer a comprehensive analysis of underground routing and construction feasibility for a line at this voltage. More detailed studies on the reliability of the specific underground line proposals are ongoing and results will be provided as part of ATC’s filing with the PSC.”

In its application to the PSC, ATC will provide the study’s final results including cost, route and feasibility analyses on a segment by segment basis. The analysis was performed in segments to allow state regulators the option of designating that certain segments be constructed underground while constructing others overhead. One such segment is the area between South Towne Dr. and Verona Rd., which has been the focus of many questions from adjoining landowners. The analysis of this six-mile segment shows the cost to construct the line overhead is estimated to be $20 million, while the cost to construct the same route underground is estimated to be $128 million, or almost 6 times more costly.

Among those who have a stake in the study results are property owners along the newly identified underground routes. “Most of these property owners have not been previously involved in the two-year public process leading up this point,” said Williamson. “It is our obligation to notify these landowners of the possible impact an underground line could have on their property and their neighborhoods if the PSC were to require portions to be placed underground.”

ATC will host open house meetings on June 11, 12, and 13 to discuss the underground line route proposals. “We want to introduce the overall project to people who are new to this process and give them an opportunity to ask questions,” explained Williamson. “Since it ultimately will be up to the PSC to determine if and where the line is built—and whether or not it should go overhead or underground it is prudent to make sure the public is aware of all the possibilities.”

The company expects to announce its final overhead routes for the transmission line project in late July of this year and file for the necessary approvals from state regulators in October.

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ATC is a Wisconsin-based company that moves energy along the regional electric grid in parts of Wisconsin, Michigan, Minnesota and Illinois, serving more than 5 million electric consumers. We are experts at what we do: planning, maintaining, operating and protecting the grid. As the electric industry moves toward renewable generation sources, we are transforming our system to continue delivering energy reliably and safely. We proudly support STEM education programs that empower youth with the skills needed to succeed in tomorrow’s energy workforce. For more information, visit and follow us on LinkedIn and X (Twitter).