Demanding Conditions, 24/7 Schedule at Keeyask
Keeyask Generating Station Construction Site
The Keeyask Generating Station Project is a 695-megawatt hydroelectric generating station being developed by the Keeyask Hydropower Limited Partnership — a partnership between Manitoba Hydro and four Manitoba First Nations (Tataskweyak Cree Nation, War Lake First Nation, York Factory First Nation, and Fox Lake Cree Nation).
Located approximately 725 km north of Winnipeg on the lower Nelson River, the Keeyask Generating Station Project involves massive cast-in-place concrete structures—chiefly a seven-bay spillway and seven-unit powerhouse and service bay structure—totaling more than 350,000 cubic meters. Other major project components include more than two kilometers of dams and 23 kilometers of dikes built on the North and South side of the reservoir. Construction is expected to take eight years. The project’s remote location and, at times, extreme weather conditions called for the expertise of experienced general civil contractors, BBE Hydro Constructors LP – a joint venture between global construction leader Bechtel, Montana-based Barnard Construction company and Canadian contractor Ellis Don.
More than 2,500 personnel are housed on site at any one time, including a dedicated group of concrete pumping professionals working in demanding conditions.
While construction of the access road to the site and associated infrastructure (the work camp, contractor yards, water and sewage treatment plants and other required facilities) began in 2012, it was not until 2014 that BBE first began laying the groundwork for the Powerhouse facility and construction commenced. As the project’s centerpiece, its seven turbine units will provide enough renewable energy to power 400,000 homes. In-stream construction activities began in July 2014, with the construction of temporary dikes that are used to create dry work areas for the powerhouse, spillway and other structures. Behind the spillway and powerhouse cofferdams, rock excavation for the spillway and powerhouse continued through the winter of 2015 and concrete placement began in early 2016.
BBE developed a construction plan that included completing concrete placements with crane and bucket, telescopic belt conveyors, truck boom pumps and trailer pumps with towers and placing booms. Initial large volume and large aggregate placements were performed with conveyor belts but as the structures increased in height, pumping is now the primary placement method.
Developing the project’s concrete pumping program was a collaborative mission between the BBE team, Rob’s Concrete Pumping, Regina, Saskatchewan, and Schwing America. At first, the BBE construction team was concerned that the mixes – containing 40mm rock – could be pumped effectively. “The granite crushed on-site is very angular,” says Mitch Eden, co-owner of Rob’s Concrete Pumping, “But I did a simulated pumping demo in our yard of similar concrete and they were on board.
In addition to three Schwing placing booms and stationary pumps, BBE elected to supplement concrete placement with boom pumps. “We had some smaller booms on the project in 2016 but BBE decided they needed some longer booms and we currently have three Schwing S 58 SX boom pumps on the project,” explains Eden.
To pump the harsh mixes at high volume, BBE specified six-inch lines on the separate placing booms. “We modified our four-section SPB 35 placing booms by shortening the tip section to accommodate the weight of the pipe and concrete,” according to Tom Oury, Schwing regional manager. Schwing had recently developed an adapter to mount their placing booms with the Linden Comansa MT12 pin lattice towers used by the five tower cranes at Keeyask. The adapter utilizes the standard Schwing four-pin quick-connect system.
The SP 8800 2018-7 150/90 all-hydraulic concrete pumps are dedicated to their individual placing booms. “One pump feeds a boom downstream from the dam that hops between two towers,” explains Paul Anderson, BBE powerhouse construction manager. “The other two pumps are on the upstream side where we have four towers for two booms.” The SP 8800s are capable of pumping up to 94 cubic meters per hour. Sections are added to the towers as the height of the powerhouse rises. The booms can free stand up to 80 feet without guy wires or bracing systems and are mounted on ballasted cross frames. High strength concrete is batched on site in a two drum 450 cubic meter per hour plant. Truck mixers deliver to the pumps. The operation goes on 24 hours a day, seven days a week.
With more than 150,000 cubic meters of structural concrete remaining to be pumped, the project will extend into 2019. “We plan for 17 pours per week on the powerhouse portion, “ explains Anderson, “Last week we planned for 2400 cubic meters in place and did 3200 cubic meters in 24 pours so things are going very well.” Concrete pumps will also be used to complete the service bays, transitions, wing walls and spillways.
The three S 58 SX boom pumps working steadily on the project are refurbished units from Schwing-owned Concrete Pump Repair. Dental concrete used for soil stabilization is also being placed by the boom pumps in addition to the belts.
With the Keeyask site covering 135 square kilometers and the massive workforce required for the project, it is the seventh largest ongoing Canadian construction project in 2017. The environmental benefit of the renewable, clean energy produced by Keeyask’s 4400 Gigawatt hours of annual capacity is the equivalent of burning one million tons of oil. “It all adds up to the job of a lifetime,” states Eden, “My greatest thrill is working with the professionals from BBE and Schwing.”
Owner: Manitoba Hydro, Winnipeg, Manitoba
Contractor: BBE Hydro Constructors LP, Winnipeg, Manitoba
Pumping Contractor: Rob’s Concrete Pumping, Regina, Saskatchewan
Pumping equipment: Three Schwing separate placing booms, three Schwing SP 8800 stationary concrete pumps and three Schwing S 58 SX concrete pumps with placing booms.