Alcona-Twining Transmission Line Rebuild

Portions of the electric transmission grid in northeastern Michigan date back to the 1950s and have experienced minimal investment since that time. The Au Sable circuit, a 110-mile, 138,000 volt (138 kV) line which runs from Zilwaukee to Mio, became increasingly unreliable as growing demand and outdated infrastructure taxed its service capabilities, especially during peak-demand summer months. Some sections contained obsolete copper wire, and many of the structures supporting the line were in poor condition and needed to be replaced.

Because the Au Sable Circuit is important to electric reliability in the region, Michigan Electric Transmission Company, LLC (METC) has been rebuilding it in stages over a period of several years. Upgrading this line to current design and construction standards, including engineered steel monopoles and steel-aluminum conductors (wires), will increase its capacity and reliability and improve lightning protection.

The 38-mile Alcona to Twining section was the final segment scheduled for reconstruction. Work began during the summer of 2013 and was completed in June of 2014.




  • Why is this project necessary?
    Much of the transmission system serving northeastern Michigan was built in the mid-1950s and needs to be upgraded to meet increasing electrical demand. The lines, poles and towers on the Alcona-Twining section of the Au Sable circuit have reached their design capacity limits and have become difficult to maintain. ITC subsidiary Michigan Electric Transmission Company, LLC (METC) will upgrade this 38-mile section in order to improve reliability and to meet current design and construction standards, including increased lightning protection..
  • Where is this project located?
    The Alcona-Twining section of the Au Sable 138,000 volt (138 kV) transmission line in located in Alcona, Iosco and Arenac counties. It runs approximately 38 miles from the Alcona substation in Curtis Township south into Iosco County, through Plainfield and Oscoda townships to the Whittemore substation in Reno Township. From there it continues south through Grant, Sherman and Burleigh townships, crossing into Arenac County and passing through Turner Township and the Village of Turner to the Twining substation in the Village of Twining.
  • What do the new lines and towers look like?
    The new towers are steel monopoles which are stronger and more reliable than the existing three-legged steel structures. ITC will replace the existing copper lines with new steel-aluminum conductors capable of carrying more electricity safely and reliably. The new structures will allow for the addition of a second circuit to meet additional demand for energy in the future.
  • When did this project start, and how long did it take?
    Construction began during the summer of 2013 and was completed in June 2014.
  • What efforts did ITC make to protect the environment in the area?
    ITC works with appropriate federal state and local organizations, including the U.S. Forest Service and the Michigan DNRE, to review project plans and obtain appropriate permits to erect towers and lines through this region.
  • What local permits, if any, did ITC have to obtain to reconstruct this transmission line?
    ITC coordinates with all federal, state and local agencies as well as local municipalities to ensure that all required permits such as road crossings, drain crossings and soil and erosion permits are obtained. Local zoning approvals are not necessary because the reconstruction process is taking place entirely within our existing rights of way and easements.



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