Manitoba Hydro is an integrated, government-run utility owned by the Province of Manitoba and based in Winnipeg, Canada. As the province’s major electricity and natural gas provider, it serves nearly 587,000 electric customers throughout the province and 285,000 natural gas customers in southern Manitoba. One of the lowest-cost providers of electricity in Canada, Manitoba Hydro also exports electricity to utilities in the provinces of Saskatchewan and Ontario, Canada, as well as the U.S.
In fact, the utility recently completed the Manitoba-Minnesota transmission project (MMTP), a 213-km (132-mile), 500-kV ac transmission line built to deliver additional electricity to its neighbor Minnesota Power over the next 15 years. The new line increases Manitoba Hydro’s capability to export surplus energy to the U.S. by 50%, expanding export access to other markets in the Midwest.
The new interconnection also improves grid stability in the Province of Manitoba by increasing the capacity to import power from the U.S. from 700 MW to 1400 MW. The additional capacity will help in emergencies, like equipment failure, storm damage and droughts, when less water is available for the utility’s hydroelectric facilities.
Planning and Approvals
Planning for MMTP began over 12 years ago, with construction kicking off in the fall of 2019. The planning phase included public and indigenous consultation, determination of a route, development of an environmental protection plan and a long approval process at both the provincial and federal levels, which entailed public hearings and scrutiny. Manitoba Hydro’s in-house groups developed designs and drawings of foundations and towers, selected the conductor and hardware, and procured the materials. The utility’s construction team tendered, awarded and oversaw the construction contracts.
Because MMTP would extend over the Canada-U.S. border at Minnesota and connect with Minnesota Power’s Great Northern transmission line, the new line required both provincial and federal approvals. The federal approval included a review by an independent regulatory agency called the National Energy Board of Canada (NEB), now named the Canada Energy Regulator. This additional review step is not typical of most Manitoba Hydro projects.
Recognizing its responsibility to its customers and the environment, Manitoba Hydro implemented extensive strategies to mitigate negative environmental impacts of the project and seek out positive opportunities for Indigenous Manitobans to participate and work on the project. Extensive mitigation measures were taken as part of the environmental protection plan during the project planning and construction phases.
For example, retaining certain vegetation (instead of removing all trees and shrubs) on the right-of-way (ROW) was a mitigation measure applied in wetlands, riparian areas and the habitat of the threatened golden-winged warbler bird to reduce environmental impacts. The utility also developed a clearing management plan indicating the specific removal and retention of certain types of trees within the golden-winged warbler region, which improved the bird’s habitat and ensured compliance with the Canadian Species at Risk Act.
The final preferred route for MMTP was announced in September 2015, following two years of public engagement, environmental assessment and other technical considerations. The utility submitted its environmental impact statement (EIS) with mitigation plans to Manitoba Sustainable Development for provincial regulatory review. The provincial approvals were typical of a Manitoba Hydro project, but the utility also had to gain federal approval at the same time.
It filed an application with the NEB in December 2016; public hearings were required at both provincial and federal levels separately, which occurred in 2017 and 2018, respectively. Finally, in August 2019, Manitoba Hydro received all the required approvals and was cleared to start construction of MMTP. Originally, the utility estimated construction would begin in 2017, but it did not actually start until well into 2019.
Accessibility and Foundation Challenges
Once all regulatory approvals were in place, construction on MMTP began in mid-August 2019, almost four years after Manitoba Hydro had publicly announced the preferred route. To make up this time, the utility aimed to compress its original two- to three-year construction schedule to less than a year. The work required developing access to remote areas, clearing vegetation, geotechnical investigation, installing foundations and anchors, assembling and erecting towers, burying existing distribution line crossings, and stringing three-phase triple-bundle conductor, overhead ground wire (OHGW) and optical ground wire (OPGW).
Manitoba Hydro separated MMTP into two contracted sections:
- Muskeko Joint Venture, an Indigenous-led partnership with Voltage Power Ltd., on section 1, totaling 93 km (58 miles).
- Valard Construction on section 2, totaling 120 km (75 miles).
No sooner had construction started in September 2019, the project was faced with heavy precipitation in several days and a snowstorm in October which affected the progress of work.
Although a significant portion of MMTP is on open fields and private land, soft ground made some areas difficult to access with heavy construction equipment. Some areas were soft and muddy, so work was not permissible; the equipment would have caused large ruts in the mud, which is not permitted by the environmental restrictions. Sometimes construction mats, placed on the ground to disperse the weight of the equipment, were used to prevent rutting. Where matting was not sufficient to facilitate access, crews had to move and work in other areas. Accessibility in section 2 was considerably worse than what was experienced in section 1.
Construction in bogs, which existed throughout section 2 of the MMTP’s ROW, was limited to frozen ground conditions, both as a licensing requirement to minimize ground disturbance and as a practical consideration to prevent equipment from sinking. Depending on temperatures and snowfall in the prior months, in Manitoba, it might take until February to freeze the required ground access in those areas. The Winnipeg area experiences a wide range of temperatures, from 30°C (86°F) in the summer to -30°C (-22°F) in the winter. Below freezing temperatures occur mostly from November through March. It was important for it to be cold during these five winter months, so the ground would freeze.
With winter setting in, areas that had experieced heavy precipitation were now frozen, and boggy areas — which stay wet year-round — finally were accessible. In section 2, Manitoba Hydro immediately had to collect geotechnical data in the bogs for tower foundation design. Most of MMTP would be accessible for several months, but these bogs would only be frozen for two or three.
Manitoba Hydro’s civil design department designed a suite of foundation and anchor types, selected based on ground conditions. The types of foundations and anchors included were precast concrete, cast-in-place concrete (CIP), micropile, overburden grouted and helical pile.
In places where seepage and sloughing were extensive, or with several meters of spongy peat instead of firm soil, the precast concrete foundation was challenging or infeasible to install. In these cases, other foundation types that do not require excavation were more suitable. Manitoba Hydro designers used knowledge from their previous experience building the Bipole III HVDC transmission line to determine which foundations worked best in different soil conditions for MMTP.
Valard Construction suggested a driven pile solution, which Manitoba Hydro had never used before. It was used successfully for MMTP following testing. The utility found having many foundation options increased the variety of personnel, equipment and crews, which improved production and reduced risk of delays.
Floodway Crossing Logistics
Another challenge unique to Manitoba was MMTP crosses the Red River Floodway south of Winnipeg. Following severe flooding to the city in 1950, the Province of Manitoba built a diversion to protect it from future water damage. It was further expanded in the aftermath of a flood in 1997, referred to as the “Flood of the Century.” Because of the significance of the Red River Floodway to Winnipeg, Manitoba Hydro had to follow stringent requirements for placing towers on either side of it.
When the floodway is in use, the MMTP tower footprints could be submerged. As a result, in collaboration with the provincial floodway authority, Manitoba Hydro designed foundations that would be elevated to clear a once-in-150-year flood level. The utility’s in-house designers had to design one of the largest CIP foundations used on a transmission line project in Manitoba. The pile was 3 m (9 ft 10 inches) in diameter and installed 12 m (39 ft 5 inches) below grade, with an extremely high top-of-foundation height of approximately 6.5 m (21 ft 4 inches). The piles were fully cased with permanent steel sleeving to protect the foundation from ice and took approximately three months to install.
Tower Assembly and Erection
Tower assembly typically was performed by multiple crews, at approximately eight people per crew. Depending on the type of tower and extension, each crew could take between one day to two days to assemble a single tower. There generally are two main types of towers used on MMTP: self-supporting towers have four legs, each bearing on a foundation, and guyed towers are placed on one central foundation and stabilized by four guy wires anchored to the ground. The Manitoba Hydro-designed towers on MMTP consisted of 373 self-supporting lattice structures, 127 guyed-lattice structures and two tubular structures. Once foundations were in the ground and towers assembled, tower erection quickly followed.
In all of section 1 and some of section 2, towers were assembled at the tower locations on the ROW and lifted into position using conventional cranes. In section 2, many of the tower locations were not accessible during the fall, so the contractor assembled a large portion of the towers at accessible fly yards near the ROW. When the tower sites became accessible in the winter (and after the foundations were completed), the contractor flew the towers to the ROW using a heavy-lift helicopter, also known as a sky crane.
The sky crane requires three pilots to operate the helicopter and crane, which lifts and lowers the tower onto a small target where the tower connects to the foundation. Self-supporting towers typically are lifted in sections, whereas guyed structures are lifted as a whole.
Conductor and OPGW stringing began as towers were erected to keep pace with the tight schedule. MMTP has a three-phase triple-bundle conductor, OHGW and OPGW, all supplied to contractors by Manitoba Hydro. The conductor used on MMTP is 1192.5 MCM 45/7 ACSR “Bunting.”
Stringing crews prioritized the wetland areas as soon as tower erection was complete, leaving the accessible parts of the line to be strung later in spring. All major activities in these wetland areas were completed in the one and only window of opportunity where frozen ground conditions would occur, between January and March.
At the peak of construction, Manitoba Hydro’s contractors had a total of approximately 700 personnel on-site. The utility had approximately 60 of its own personnel managing the project and performing field inspections. Late in March 2020, toward the end of the construction season, the project was faced with the COVID-19 pandemic. Despite the pandemic, the project was not delayed. Manitoba Hydro and its contractors quickly implemented new screening, distancing, cleaning and stay-at-home-if-sick procedures at their offices and camps to reduce risk of the virus spreading.
The originally anticipated two- to three-year construction schedule was reduced to eight months, with MMTP con-struction completed by mid-April 2020. Commissioning was completed successfully by the June 1, 2020, target in-service date.
MMTP was a major achievement for Manitoba Hydro despite challenging weather conditions, a narrow construction window, boggy terrain and the COVID-19 pandemic. This project required the utility to proactively identify and manage risks quickly to ensure the work would not be interrupted, considering the condensed construction schedule. The project team had to be agile in adapting to sudden challenges and communicate closely with team members to resolve problems quickly. MMTP was an opportunity to demonstrate the utility’s ability to work together effectively and overcome challenges quickly for a successful project completion.
Editor’s Note: For MMTP construction videos, visit www.youtube.com/user/ManitobaHydro/search?query=MMTP.
Nahome Birru ([email protected]a) is a civil engineer with Manitoba Hydro in Winnipeg, Manitoba, Canada. He graduated with a BSCE degree from the University of Manitoba in 2012. He led contract management of the 240-km (150-mile) N1 section of the Bipole III transmission line project until its completion in spring 2018. After completion of Bipole III, Birru led the contract management of section 1 of the Manitoba-Minnesota transmission project.
Michelle Bakkelund ([email protected]) is a civil engineer with Manitoba Hydro in Winnipeg, Manitoba, Canada. She graduated with a BSCE degree from the University of Manitoba in 2013. She led contract management of the 200-km (125-mile) N4 section of the Bipole III transmission line project until its completion in spring 2018. After completion of Bipole III, Bakkelund led the contract management of section 2 of the Manitoba-Minnesota transmission project.