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Photo Courtesy of Manitoba HydroFive thousand piles set Manitoba's Keewatinohk converter station on solid foundations

By Lily Slain 

It’s been about 2,000 years since the Romans ruled the earth, but their magnificent aqueducts can still be found across Europe; a few are even still in use. If the modern world has a comparable achievement, it might be our hydro corridors.

The Romans were transporting water across great distances; now we harness the power of water to create electricity that is transported over hundreds of kilometres. The Romans themselves would have admired contemporary projects like Bipole III, currently underway in Manitoba. It’s one of the largest projects of its kind in North America and one of the biggest capital projects that Manitoba Hydro, the province’s energy utility, has ever undertaken.

 

The Bipole III Transmission Reliability Project is a new high-voltage direct current (HVDC) transmission system that will carry power from Manitoba Hydro’s northern generating stations located on the Nelson River to southern Manitoba. The almost 1,400-kilometre transmission line is being built to serve as a back-up to the Bipole I and Bipole II HVDC transmission lines, which were constructed in the 1970s. Currently, more than 70 per cent of the electricity generated by Manitoba Hydro’s northern generating stations is delivered to customers using the two HVDC lines.

Bipole III will create an alternate route to bring electricity to the south of the province, strengthening the overall reliability of Manitoba’s electricity supply. It will also provide additional capacity to deliver renewable energy from the 695-megawatt Keeyask Generating Station currently under construction on the Nelson River in northern Manitoba.

The construction of Bipole III transmission line includes building two converter stations. The northern terminus of Bipole III is the Keewatinohk Converter Station, which is about 80 kilometres northeast of the town of Gillam. The southern end of Bipole III is the Riel Converter Station, east of Winnipeg.

Manitoba Hydro’s generating stations produce alternating current (AC) electricity. For transmission over Bipole III, AC will be converted to direct current (DC) electricity through the rectification process at the Keewatinohk Converter Station. DC is more economical to transmit over long distances. At Riel, DC will be converted back to AC through the inversion process to supply to customers. Most of the electricity used in the world is AC.

Bruce Owen, public affairs officer with Manitoba Hydro, says that the Bipole III Reliability Project will help meet the growing needs of Manitoba residents.

“Bipole III is essential to enhance the long-term reliability of Manitoba Hydro’s power grid, and provides additional capacity to bring electricity from new hydro projects in the north to southern Manitoba,” said Owen. “The additional capacity also accommodates increased future export sales that will help to pay for important system upgrades and moderate rates.”

The construction process

At Keewatinohk, the site takes up 25 hectares and includes a 10,000-square-metre HVDC converter building. The converter station will also include a 230-kilovolt (kV) AC switchyard and several auxiliary and process buildings.

Preparation of the Keewatinohk site started in early 2014 and Keewatinohk Lodge, the main construction accommodations where workers stay, officially opened in September 2015. Construction on the converter station foundation infrastructure started the following month. Work to install piles will continue throughout this winter with the majority of the foundation work scheduled to be completed through the summer and early fall of 2016.

At the same time, the Bipole III project requires about 4,300 piles at the Riel Converter Station, most of which are pre-cast concrete piles, and another approximately 2,600 cast-in-place and 4,000 helical piles to support the transmission line towers between Keewatinohk and Riel. The Riel and Keewatinohk stations are expected to be completed and ready for operation in the summer of 2018, when the entire Bipole III transmission line is put into service.

Construction at Keewatinohk is primarily being undertaken by three separate contractors, each of whom are subcontracting piling work specific to their scope of the project. The HVDC facilities are being overseen by a consortium of Siemens Canada and Mortenson Construction. On that part of the project, Graham Brothers was contracted to supply and install APE HD helical piles.

SNC-Lavalin is responsible for construction of the 230-kV AC switchyard; their subcontractor is Pacer, which is handling driven piling and pile cap welding. The auxiliary buildings are being constructed by PCL Constructors Ltd., who turned to Agra Foundations Limited for deep cast-in-place piles, some of which extend up to 22 metres below ground and require double casing, splicing of cages over the holes and the construction and installation of greases and poly wrapped sono-tube. 

Brian Frost, Manitoba Hydro’s converter engineering and procurement department manager, says crews at Keewatinohk have been installing about 40 to 60 piles per day through the winter; heated shelters and pre-cast beams allow them to work even in sub-zero temperatures.

Frost says the project will require about 5,000 piles to be set into the ground at Keewatinohk this winter and into the spring. Of these, about 2,800 are helical piles that are being installed with a CAT 374 and HD 200 drive head, two CAT 349E hydraulic excavators and Quebec a Komatsu 490, each with a HD 80 drive head for pre-boring operations.

About 2,000 driven steel piles are being installed with a Junttan PM22 pile driving rig, with two Soilmec SR-30 hydraulic drilling rigs for pre-boring and drilling. About 200 piles are being cast in place; these have to be kept warm under heated tarps until they have set.

Feels like home

Throughout this winter, about 35 workers have been directly involved with piling operations at Keewatinohk.

Workers on the project stay nearby at the recently opened Keewatinohk Lodge, which has the capacity to house up to 600 people. The workforce will be needed as construction ramps up on the converter station.

The Keewatinohk Lodge is operated by a joint venture of Fox Lake Cree Nation and Sodexo, and includes private bedrooms and washrooms, modern amenities including cable television and Internet, and a full-service kitchen and dining room that prepare fresh meals onsite daily.

A recreation centre, which will include fitness facilities and a full-size basketball court, is currently being constructed.

“If people are working in isolated conditions, we want them to have the best services and the best food,” said Owen. 

Any project of this size presents unique challenges, and for Keewatinohk, the cold weather is on the list. 

“We’re working in the north and in the winter and almost around the clock,” said Owen. “That cold rush of arctic air that folks and machinery are dealing with on a daily basis can create some challenges,” adding that contractors and Manitoba Hydro employees are used to working in winter conditions. 

The remote location does come with some positives, however. Frost says Keetwinohk’s location allows construction to continue into the evening hours, unlike some urban projects. 

“Lights can go on and people can work into the evening as construction noise is not generally as big of an issue,” said Frost. “Work at Keewantinohk is proceeding as planned.”

Below ground

Frost says a second challenge is the ground Keewatinohk is being built upon. That ground includes discontinuous permafrost, which offers a challenging base for the foundations and within the station.

“When you’re setting these piles for the foundations, you’ve got to account for the fact that the long-term settling will be uneven,” said Frost. “Although this settling will take place over a number of years, you’ve got to account for it, because Keewatinohk is expected to be in operation for more than 50 years.”

Environmental impact

Frost says Keetwinohk’s location allows construction to continue into the evening hours, unlike some urban projects.

“Lights can go on and people can work into the evening as construction noise is not generally as big of an issue,” said Frost. “Work at Keewantinohk is proceeding as planned.”

The entire Bipole III project was subject to a detailed environmental impact review by the Manitoba Clean Environment Commission.

During construction, contractors are required to follow a Heritage Resource Protection Plan in case ancient human remains are found. To date, none have been located. Should crews make such a discovery, work would be stopped until the remains could be recovered and removed for interred at a site approved by Fox Lake Cree Nation.

Another consideration is preservation of permafrost. Manitoba Hydro will avoid burning slash on permafrost soils adjacent to the Keewatinohk Converter Station and northern ground electrode sites, and during construction, workers will avoid stripping through organic layers on permafrost-affected soils.

The logistical considerations and planning that have gone into Keewatinohk and the rest of the Bipole III project are staggering in scale and scope. However, the effort is small compared to the impact of a power line that will travel hundreds of kilometres and last for a human lifetime. No doubt the Romans would have approved.

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Piling Canada is the premier national voice for the Canadian deep foundation construction industry. Each issue is dedicated to providing readers with current and informative editorial, including project updates, company profiles, technological advancements, safety news, environmental information, HR advice, pertinent legal issues and more.