A headworks gantry crane (right) looms over the Robert H. Saunders Generating Station, one of Ontario Power Generation’s largest hydroelectric dams on the St. Lawrence River, on April 10.Matthew McClearn/The Globe and Mail
One afternoon in April, inside the control room at the Robert H. Saunders Generating Station west of Cornwall, Ont., a team of roughly half a dozen people monitor hydroelectric units at dams throughout southeastern Ontario. On a large digital screen, Saunders units G9 and G1 are depicted in red, signifying they’re out of service. The other 14 units are green, supplying electricity to the grid.
G9 has been out of service for more than a year for a major overhaul. After it returns to service (scheduled for August), G16 will undergo the same process: Its upstream and downstream gates will be shut, and the water removed. Then workers will begin removing and overhauling major components such as rotors and turbines. Many of them will be sent to machine shops for reconditioning. Over the next 16 years, this will be repeated for all 16 units at the 1,045-megawatt station.
While newer technologies such as battery storage, renewables and next-generation nuclear reactors garner much attention, aging hydro dams typically attract little. Many are located in remote locations, and even if they spectacularly blew their budgets during construction, such controversies are soon forgotten. As for the three dozen hydro stations operated by Ontario Power Generation (OPG) – some more than a century old – these escape notice almost entirely.
But dams still generate about 60 per cent of Canada’s electricity, four times the global average. And they require overhauls roughly every 25 to 40 years to keep them in service. These are major capital projects, with price tags to match: Saunders’ overhaul is budgeted to cost more than half a billion dollars. The Ontario government announced in April it had earmarked $1-billion to refurbish the Sir Adam Beck Complex at Niagara Falls.
Energy Minister Todd Smith said the Beck overhaul was necessary to “ensure we have the power we need for the next major international investment, the new homes we are building and industries as they grow and electrify.”
But while these megaprojects sometimes result in modest increases in generating capacity, that’s not what they’re really about. Even as politicians speak of doubling or tripling power generation by mid-century, utilities face technically demanding, costly undertakings simply to maintain what they already have.
New life for old powerhouse
This cross-section of the Robert H. Saunders Generating Station highlights major components. The station's overhaul focuses on its drivetrain, which includes the generator assembly, the main shaft and a stainless steel ring around the turbine runner. Each unit will put out the same 67 megawatts as before, using less water.
Powerhouse
Lake St. Lawrence
River
Inspection tunnel
Penstock
300-tonne powerhouse
gantry crane (with 2 x 15 tonne auxiliary “jib” cranes)
Turbine runner assembly
(21-foot diametre propeller
style runner blades)
Headgate (3 gates/unit)
Generator breaker
Generator assembly
(rotor and stator)
Main output transformer
Stay vanes and wicket
gates (yellow),
main shaft (orange)
john sopinski, murat yükselir and matthew mcclearn/
the globe and mail, Source: opg
New life for old powerhouse
This cross-section of the Robert H. Saunders Generating Station highlights major components. The station's overhaul focuses on its drivetrain, which includes the generator assembly, the main shaft and a stainless steel ring around the turbine runner. Each unit will put out the same 67 megawatts as before, using less water.
Powerhouse
Lake St. Lawrence
River
Inspection tunnel
Penstock
300-tonne powerhouse
gantry crane (with 2 x 15 tonne auxiliary “jib” cranes)
Turbine runner assembly
(21-foot diametre propeller
style runner blades)
Headgate (3 gates/unit)
Generator breaker
Generator assembly
(rotor and stator)
Main output transformer
Stay vanes and wicket
gates (yellow),
main shaft (orange)
john sopinski, murat yükselir and matthew mcclearn/
the globe and mail, Source: opg
New life for old powerhouse
This cross-section of the Robert H. Saunders Generating Station highlights major components. The station's overhaul focuses on its drivetrain, which includes the generator assembly, the main shaft and a stainless steel ring around the turbine runner. Each unit will put out the same 67 megawatts as before, using less water.
Powerhouse
300-tonne powerhouse
gantry crane (with 2 x 15 tonne auxiliary “jib” cranes)
Headgate (3 gates/unit)
Generator assembly
(rotor and stator)
Lake St. Lawrence
Stay vanes and wicket
gates (yellow),
main shaft (orange)
River
Inspection tunnel
Turbine runner assembly
(21-foot diametre propeller
style runner blades)
Penstock
Generator breaker
Main output transformer
john sopinski, murat yükselir and matthew mcclearn/the globe and mail, Source: opg
OPG’s refurbishment plan is extensive, encompassing about half its fleet of 66 hydroelectric stations in the next 15 years. Barrett Chute and Otto Holden stations, which like the Saunders facility are in eastern Ontario, are also in line. So are Healy Falls, Ear Falls, Eugenia and Aguasabon in the west of the province.
“We’ve got three on the go right now,” said Amanda Griener, director of assets and project management for OPG’s southeastern region. “In our near future, we’ve got as many as five planned.”
Canada’s largest hydroelectric-focused utility, Hydro Quebec, spent $3.3-billion last year – more than two-thirds of its budget for property, plant and equipment – on what it called “large-scale asset sustainment initiatives.” (Those assets include not only dams but also transmission lines.) The ongoing refurbishment of its Rapide-Blanc generating station in Maurice, Que., is expected to cost more than $600-million. Overhauling its much larger Carillon station on the Outaouais River, intended to increase capacity from 753 MW to 795 MW, is in the planning stage. Hydro Quebec reports that its “sustainment” spending has risen rapidly in the last few years.
Manitoba Hydro is refurbishing its Pointe du Bois dam, which dates from 1911. It originally had 16 units; this refurbishment will install eight modern turbines and generating units. That’s expected to cost $314-million and wrap up in 2027. Only three of its original units will operate beyond 2030.
This is the second major overhaul at Saunders; of the dozens of people who worked on the first, in the 1990s, only four remain employed at OPG.
Preparatory work begins up to five years in advance, with an assessment of the plant’s condition and of opportunities for increasing its output. Some infrastructure may need to be upgraded. Saunders’ 300-tonne gantry crane, critical for moving heavy components, was recently replaced, as were the panels that distribute electricity to pumps, motors and other systems.
A dam’s concrete structure tends to be its life-limiting factor; the surrounding environment will eventually deteriorate it past the point of no return. At Saunders, about 18 inches of the exterior deck – the topping slab – was recently replaced.
Built in the 1950s, the station represents half of the Robert Moses-Robert H. Saunders dam which spans across the Saint Lawrence River and straddles the Canada-U.S. border. The New York Power Authority operates 16 units on the American side, constructed using aggregate sourced from New York State. Canada’s aggregate came from a pit north of Cornwall, was of different composition. Though it wasn’t appreciated at the time, this subtle difference was to have profound implications for the Canadian portion.
A hydroelectric behemoth
The Saunders dam is one component of a large hydroelectric project on the St. Lawrence River shared between Canada and the U.S. It includes the Iroquois Dam, which controls water levels for the entire project, and the Long Sault Spillway.
Cornwall
ONTARIO
CANADA
Lake St. Lawrence
U.S.
Iroquois Dam
Long Sault
Spillway
Moses-Saunders
Power Dam
NEW YORK
10 KM
THE GLOBE AND MAIL, SOURCE: OPENSTREETMAP
A hydroelectric behemoth
The Saunders dam is one component of a large hydroelectric project on the St. Lawrence River shared between Canada and the U.S. It includes the Iroquois Dam, which controls water levels for the entire project, and the Long Sault Spillway.
Cornwall
ONTARIO
CANADA
Lake St. Lawrence
U.S.
Iroquois Dam
Long Sault
Spillway
Moses-Saunders
Power Dam
NEW YORK
10 KM
THE GLOBE AND MAIL, SOURCE: OPENSTREETMAP
A hydroelectric behemoth
The Saunders dam is one component of a large hydroelectric project on the St. Lawrence River shared between Canada and the U.S. It includes the Iroquois Dam, which controls water levels for the entire project, and the Long Sault Spillway.
Cornwall
ONTARIO
CANADA
Lake St. Lawrence
U.S.
Iroquois Dam
Long Sault
Spillway
Moses-Saunders
Power Dam
NEW YORK
10 KM
THE GLOBE AND MAIL, SOURCE: OPENSTREETMAP
By the 1970s, engineers understood that the two million tons of concrete in the Saunders dam was suffering from a phenomenon known as Alkali Aggregate Reactivity (AAR). In a nutshell, certain components in the aggregate combined with alkali hydroxides in the concrete to form a gel, which absorbs water and swells. Over time, the resulting pressure deformed the concrete, to the point where it interferes with turbine movement. At Saunders, one victim was the 21-foot-wide stainless steel ring in which the turbine runners spin; components started to rub against one another.
OPG officials say AAR is manageable. But it has already compelled it to reopen the expansion joints which divide Saunder’s massive units to relieve pressure. During this overhaul they’ll need to replace that stainless steel ring.
“It’s a major undertaking for OPG – probably only done that a handful of times in history,” said Scott Gagnon, director of plant operations at Saunders.
During the busiest moments at Saunders, up to 80 laborers, electricians, boilermakers and other tradespeople will be at work overhauling various components simultaneously. They won’t always be comfortable.
Saunders is a “California-style” dam: There’s no powerhouse covering its generators – it was quicker to build the facility without one – so workers are exposed to the elements more often. Another downside is the limited space for storing components that have been removed for servicing.
The price tag on an overhaul can seem steep, at least until alternatives are considered. Existing dams are among the cheapest sources for power generation. Provinces that rely on them heavily, notably Quebec and Manitoba, typically enjoy the lowest electricity costs. Megawatt to megawatt, refurbishing a hydroelectric plant is far cheaper than extending the life of a nuclear plant.
Perhaps that helps explain why the Independent Electricity System Operator, for planning purposes, assumes hydroelectric dams will continue operating in perpetuity, regardless of how old they are or who owns them. OPG officials say they have no plans to retire any power dams.
Costs, though, have risen significantly since Saunders was last overhauled.
“I can’t tell you off the top of my head the cost of overhauling in 1990, but I imagine it’s gone up tenfold,” Mr. Robertson said.
Like many other projects, hydro refurbishments have also been plagued by supply chain issues – particularly since the COVID-19 pandemic.
“Just because we want to replace something doesn’t mean we can get it in our hands,” he said.
Though Canada’s golden age of dam construction is a distant memory, some are still being built. Last year, Hydro Quebec completed the 1,550-MW Romaine hydroelectric complex, capping 15 years of construction. OPG’s small 28-MW Peter Sutherland Sr. station entered service in 2017.
There might be room for further growth. The International Hydropower Association estimates Canada has 160 gigawatts of unharnessed hydropower potential.
But dams have high up-front capital costs and must compete against other renewables such as wind and solar, which can often be built far more rapidly. Dams also disrupt river systems, and sometimes communities. (The Saunders headpond, known as Lake St. Lawrence, flooded several small towns and villages when it was filled in 1958, forcing thousands of residents to relocate. Today, utilities generally don’t possess such awesome powers of expropriation.)
Many projections suggest hydroelectricity will lose ground. According to modelling by the Canada Energy Regulator, which regulates pipelines and energy development, hydro generation could grow by about a quarter between 2021 and mid-century. But since other generation types are expected to grow much more rapidly, hydropower’s share of total generation could diminish to less than 40 per cent by mid-century.
Dams don’t simply generate power – they also provide other vital services. In electricity systems, production must be balanced in real time with consumption. Intermittent sources such as wind and solar can’t provide that balance, nor can large nuclear plants. Hydroelectric dams, though, can adjust their output rapidly to compensate for those ever-changing requirements: Saunders units can go from producing no power whatsoever to their full 67 MW in under five minutes.
For old hydro hands, the implications of diminishing the balancing services provided by hydro dams are worrisome.
“We hear estimates of the requirement [for electricity] doubling in the next 15 or 20 years,” Mr. Robertson said. “We need to think about what a change in the proportion of those generation mixes are going to do to our ability to manage the grid.”