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138,000 volt (138 kV) line which runs from Zilwaukee to Mio, became increasingly unreliable as growing demand and outdated infrastructure taxed its service capabilities, especially during peak-demand summer months.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.