When Michigan passed its Clean, Renewable and Efficient Energy Act in 2008, it created the Wind Energy Resource Zone Board. The board identified four regions for wind development; Region 4, in the state’s Thumb, had the highest potential for wind generation. ITC submitted a plan to build out the transmission infrastructure to accommodate wind development in the region.
In 2011, the board authorized ITC to begin construction. The Thumb Loop Project consists of approximately 140 miles of double-circuit 345-kV lines and four new substations, plus additional lines and facilities as generation resources go into service. The system is designed to support a maximum capacity of about 5,000 MW of generation.
ITC engaged Burns & McDonnell for all substation and transmission line design and support of construction observation for the project, which was constructed in three phases.
In addition to the new transmission lines, work included replacement or modifications of multiple 120-kV circuits. Before transmission line design, our team provided transmission line routing and siting services, including the public involvement process requiring multiple open houses. Additionally, our routing specialists provided expert testimony to the Michigan Public Service Commission.
Our full transmission line design services included preliminary and final structure spotting; detailed PLS-CADD design; development of structure loads and structure designs including new ITC standard double circuit 345-kV transmission structures; foundation design; hardware design; grounding design; and preparation of detailed construction drawings and specifications. Additionally, we supported right-of-way acquisition required for the transmission line by working closely with right-of-way agents to spot structures in locations acceptable to landowners, and assisted in permitting.
Three new 345-kV greenfield substations, a major 345-kV addition to an existing station, and multiple 345-kV and 120-kV upgrade projects to ancillary stations were included in the project. For all substation work, we were responsible for the electrical, civil and structural design — including one-lines, schematics and wiring diagrams — to all aspects of physical design including foundations, raceway, grounding, lightning protection, steel structures, control buildings, site grading, drainage, oil containment and the implementation of all associated equipment. This included preparation of drawings, specifications, standards and bills of material for the civil and electrical constructions.
Transmission line routing and public involvement processes
Preliminary and detailed transmission line engineering design
Substation engineering design
Civil and structural design
One unique component of the project was to look to the past and creatively reclaim structures, foundations and conductor on one 4-mile stretch of transmission line, saving millions of dollars and months of schedule time.
Lattice steel towers and a single-circuit extra-high voltage transmission line that were installed for a planned nuclear power plant more than four decades earlier are now used in a critical stretch of the Thumb Loop. The transmission transformation — turning single-circuit 765-kV towers into double-circuit 345-kV — is a first-of-its-kind conversion.
Using existing towers, materials and right-of-way shaved months off the expected project schedule. That meant no need to acquire new easements, buy new structures, string new wire or drill and pour new foundations. Reusing conductor from the single-circuit quad-bundle line meant buying fewer new materials. Using a bucket truck, a crew could convert one tower per day from single- to double-circuit. Not having to acquire new right-of-way, demolish existing infrastructure, build new towers or string new lines increased efficiency.