On a hot summer afternoon, the North Maitland River in Southwestern Ontario trickles lazily past crumbling concrete. The Gorrie Dam – what’s left of it –awaits removal.
Its destruction had been long foretold. Following a damaging flood in 1974, engineers concluded that neither its spillways nor its earthen dikes had been constructed properly; the silty sand and gravel on which they rested allowed water to seep through. An engineer from the Ministry of Natural Resources concluded that the dam would eventually fail.
In 2017, amid heavy rains leading to the second highest flows on the river in half a century, it finally did. Flood waters overtopped and eroded its emergency spillway, and damaged its concrete structure.
Luckily, this failure unfolded gradually; it didn’t release a massive pulse of water that might have damaged other infrastructure downstream. As it was, other owners throughout the area were struggling to prevent failures of their own dams, a fate that was narrowly avoided.
Such incidents will likely arrive more frequently as Canada’s aging dams continue on a collision course with a warming climate.
There are more than 14,000 dams across Canada, with significant concentrations in Quebec, Ontario and British Columbia. Many date from the early and mid-20th century. While some are well-maintained and were built to withstand extreme events, others have deteriorated beyond hope of restoration.
They are at risk of failing even during moderate rainfall, let alone the massive deluges that are becoming increasingly commonplace.
The extent of the problem is obscured by a massive data gap. Dams fall largely under provincial jurisdiction, and while the rigour of supervision varies considerably, most provinces publish little information that could be used to identify poorly maintained dams, or assess what might happen if they fail.
But the available evidence suggests the Gorrie Dam was no anomaly. A report by engineering firm Greck and Associates Ltd. following its failure noted that Ontario alone has more than 5,000 dams and weirs. “Many dams are approaching or have exceeded their normal life expectancy,” the report noted. “They are in poor condition and no longer provide their originally intended function. They present risks to public safety, owner liability issues, and impacts to the natural environment.”
Evidence from around the globe establishes that ignoring dams until they fail can be a costly and hazardous error. An alternative – decommissioning and removing them – is often cheapest. But it’s also politically unpopular, and hasn’t yet caught on in Canada.
In May, the Edenville Dam and Sanford Dam in Michigan breached amid heavy rainfall, leading to flooding and evacuations of nearby towns. The New York Times reported that the flood waters inundated parts of a large chemical complex and threatened the site of a major toxic cleanup.
Failures of this magnitude are mercifully rare: According to a 2018 study by the National Performance of Dams Program at Stanford University, since 1980 the U.S. has experienced an average of 24 failures annually. When they do occur, however, major failures prompt re-evaluations. The Michigan incident sparked a flurry of reports reminding Americans that their country is littered with vulnerable dams. According to a national inventory maintained by the U.S. Army Corps of Engineers, nearly 25,000 of the more than 90,000 dams in the country have hazard ratings of “high” or “significant,” meaning their failures might cause loss of human life, property damage or environmental destruction.
Critics complain that the true extent of the problem in the U.S. is obscured by a lack of data. But if the U.S. has blind spots, Canada is almost entirely blind.
To begin with, Canada lacks a national inventory and has no body equivalent to the Army Corps of Engineers. The closest thing Canadians have is a list from the Canadian Dam Association of fewer than 1,200 “large” dams – a classification that includes dams higher than 15 metres, or smaller ones that impound large volumes of water. That wouldn’t be such a problem if provinces published their own comparable inventories. Some (such as Quebec and Alberta) do, but there are considerable gaps. Ontario’s inventory, for example, provides little more than names and locations of dams.
This is just one indication of how little attention some Canadian regulators pay. According to a report released in August by the Intact Centre on Climate Adaptation at the University of Waterloo, most provinces and territories don’t require owners to conduct flood risk assessments for their dams. Without them, it’s difficult to identify decrepit dams whose failure would seriously threaten people and property. "This may pose a potential threat to the safety of Canadians,” the report noted, “as it may lead to outdated or inaccurate dam safety information.”
Not all provinces are blind. Alberta and British Columbia, for example, classify dams based on the hazard they present. That information is crucial if regulators want to prioritize where to focus their attention. It also helps emergency responders; for example, it could help prioritize where to issue evacuation orders during a major flood or earthquake.
Apart from the 400 dams it owns, Ontario says it doesn’t keep information on hazard potential classifications for dams within its borders. “There’s no legislation that requires dam owners, large or small, to do the engineering analysis to determine what happens if these dams fail,” said Jeff Graham, president of GSS Engineering Consultants Ltd. in Owen Sound, Ont.
Ontario also lacks a system for verifying whether dams are properly maintained. British Columbia, in contrast, audits high and extreme consequence dams at least once every five years for compliance with provincial regulations; significant consequence dams are revisited every decade. B.C. employs dam safety officers who perform this work.
B.C. also requires dam owners to report annually on the status of their dam safety programs. Nothing like that exists in Ontario. B.C. publishes annual reports about its enforcement activities, which include audits to ensure dam owners comply with regulations. (Through these audits, the B.C. government has learned that “many dam owners are not following through with the work indicated on their report.”) Ontario doesn’t.
Ontario doesn’t even know how often dams fail within its borders because it doesn’t maintain records or data. Contrast that with Stanford University, which maintains a database of dam failures for the entire United States.
Dams do fail in Canada, regardless of whether anyone is keeping track. Last year, water overtopped the Glen Miller hydropower plant near Quinte West, Ont., following a power outage that caused the dam’s doors to close. Downstream, a road collapsed and a home was flooded. Worse still was the failure of a dike in Sainte-Marthe-sur-le-Lac near Montreal, which flooded dozens of residential streets and forced around 6,500 people to evacuate.
Dianne Saxe, Ontario’s former environment commissioner, doesn’t mince words. “The clear impression I was given was that the Ministry of Natural Resources was not paying attention.”
Such inattention could become a bigger problem if, as many climatologists expect, Canada is condemned to more frequent and devastating floods.
According to a paper published this year by Megan C. Kirchmeier-Young and Xuebin Zhang, researchers with Environment and Climate Change Canada’s climate research division, extreme precipitation is already on a clear upward trend in North America, one that will likely continue. As the earth’s climate continues to warm, it evaporates more water into the atmosphere. This can produce heavier downpours, leading to flash floods.
“There is lots and lots of data around the world showing that the intensity of storms is increasing,” said Ms. Saxe. “Which is exactly what you’d expect from the basic physics.”
Continuing loss of wetlands and other natural buffers exacerbates flooding in some areas. Paradoxically, climate change may also lead to more and longer droughts. And that’s not good news for dams, either: Under such conditions, earthen dams and levees may crack due to drying, subsidence and erosion.
Properly maintained and upgraded, even an aging dam may continue to operate safely and reliably. Consider Ontario Power Generation’s fleet of 241 dams. According to Tony Bennett, OPG’s director of dam safety, the utility inspects many dam components – such as spillway gates and the hoists that lift stop logs – annually. Fences, safety booms and buoys are regularly maintained to keep people out of harm’s way. And OPG also needs to keep its emergency plans current for all 24 river systems on which it operates.
That OPG goes to all this bother is hardly surprising: Its dams produced more than 32 terawatt hours of electricity last year. Similarly, owners of flood control structures have strong incentives to keep their dams in good working order.
But it’s a different story with so-called “deadbeat dams” – those that have outlived their usefulness. These include dams built for log driving or to provide mechanical power for mills. Some are owned by municipalities, mining companies and private owners who may lack adequate resources, and may not even know about emerging problems because they’re not inspecting.
And that’s to say nothing of “orphan dams” – ones that effectively have no owner at all. If they are in remote areas, the very existence of some earthen dams has been forgotten, and they may be so overgrown with vegetation as to have become unrecognizable.
“The great majority of dams really have no active maintenance,” said Mr. Graham, “so they just slowly deteriorate.”
The Gorrie Dam is a prime example. The nearby Maitland Mill’s windows are either shuttered or broken, its clapboard weathered and disintegrating, its cogs rusted and motionless. Built in the 1850s, its equipment was once powered by water diverted by the dam into the sluiceway, which is now clogged with algae. (The current dam dates from 1929.)
The mill closed in 1962. That’s when the Maitland Valley Conservation Authority bought the dam. General manager Phil Beard said that at the time, the provincial government provided funding to its conservation authorities to buy up such properties to establish parks, campgrounds and other amenities. Since then the dam’s sole purpose has been to create a small pond for recreational purposes in the warmer months.
But owing to subsequent budget cuts, particularly during the 1990s, Mr. Beard said conservation authorities lack the funding to conduct major maintenance. “Everything has a lifespan,” he said. “And these structures weren’t designed to deal with the impacts of a changing climate. So it’s a double whammy.”
Just kilometres downstream of the Gorrie Dam, in the Township of North Huron, anglers hop a chain-link fence to hang their fishing rods. They do so against all advice: The structure they’re standing on, the Howson Dam, makes its failed upstream cousin appear robust by comparison.
Its piers are etched with webs of deep cracks that the rude slogans and genitalia spray-painted on them can’t conceal. Originally designed to do double duty as a bridge, it’s been closed to traffic for two decades. As early as the 1980s, evaluations determined that the concrete was in poor condition; another, in 2018, found that the concrete from three vertical core holes was “extensively deteriorated with fractures present throughout.”
A document produced by the Township of North Huron warned that the Howson Dam “represents a liability to the municipality” and “has degenerated to the point that it can no longer be ignored.”
Only recently, however, did the municipality become aware of what would be at stake if it failed. The first-ever safety review, in 2018, recommended that its hazard potential classification be listed as high because “the dam is located in a populated area susceptible to flooding during large floods.” The Maitland Valley Conservation Authority has warned the town that it’s “a bottleneck in the floodplain” that could flood the area immediately upstream.
“A lot of these old dams are really precarious,” Mr. Graham said. “There’s a good chance that these dams will fail in the next 50 years or so, due to really big flood events that will likely occur as a result of climate change, or maybe just bad luck.”
BREACH OF KNOWLEDGE
The Testalinden Dam was a privately owned earthen dam in B.C. Completed in 1937 for irrigation, it failed in June, 2010, releasing torrents of mud and debris that damaged a handful of homes and farms downstream.
An independent review conducted soon afterward found that beginning as early as the 1960s, inspections had revealed a series of deficiencies. One inspector wrote in 1977 that “the dam is in deplorable condition” and needed to be breached or rebuilt. Another report, a decade later, made nearly identical observations.
But while B.C.‘s dam safety program was able to detect poor maintenance, it failed to compel improvements. “There is no indication that the needed repairs were acted upon,” the 2010 review concluded, “but also no indication that the owner was being held accountable to make those repairs.”
Nor did the government warn the public. B.C.’s Information and Privacy Commissioner found in a 2013 report that while the government knew the dam was near the end of its life, it failed “to disclose information about the compromised state of the dam to residents downstream.”
But here’s the rub: B.C. was one of only four provinces that even had a dam safety program. Other provinces, like Ontario, are likely oblivious to such dams because they don’t require dam safety reviews except in rare circumstances, and often don’t possess or study them when they are produced.
Despite reforms introduced following the Testalinden Dam failure, some owners in B.C. continue to flout their obligations. According to audits conducted by B.C. dam safety officers, “many dam owners are not following through with the work indicated on their report.”
Take the Frank Lake Dam, located near the Canada-U.S. border. In 2018, provincial officials reported that the “unauthorized” dam “was exhibiting signs of instability on the upstream slope” and was holding back about 130,000 cubic metres of water. The government ordered that it be decommissioned by September, 2019.
According to a government spokesperson, the dam’s owner – Elkink Ranch Ltd. – has not complied. Elkink Ranch, the government noted, “formerly owned the Testalinden dam.”
A SIMPLE BUT UNPOPULAR SOLUTION
The good news is that there is a relatively straightforward remedy for the hazard presented by deadbeat dams: remove them.
It’s the solution favoured by a growing number of small non-governmental organizations. They’re often motivated more by hopes of restoring river ecosystems rather than improving public safety. The Ontario Rivers Alliance, a non-profit organization that focuses on restoring freshwater ecosystems, has begun approaching owners who might be interested in removal. “We’re exploring ways of finding more of these old and dysfunctional dams,” said its chair, Linda Heron.
Robert Huber, president of the Thames River Anglers Association in London, Ont., is also eager to encourage more decommissionings. He says he was inspired by large-scale decommissionings of hydroelectric projects on major U.S. river systems. “They’ve been even knocking them down in the States left, right and centre, and doing a really good job of it,” he said. “We looked at that and we’re like, we could do that here… We’re gonna keep trying to tear them out every chance we get.”
Financially, removing a deadbeat dam is often the cheapest option. For the cash-strapped Maitland Valley Conservation Authority, the calculation for the Gorrie Dam was fairly straightforward. An engineer’s study estimated removal would cost nearly $1-million. Replacing it, on the other hand, could cost as much as $3.5-million. (The Conservation Authority believes the decommissioning cost will be far lower than the initial estimate.)
Informed by that experience, in 2018 the Conservation Authority adopted a new policy for end-of-life dams: It will offer to transfer ownership to the municipalities in which they’re located for replacement. Failing that, the Conservation Authority will decommission them.
The Township of North Huron, which hasn’t decided yet what to do with the Howson Dam, faces similar math. By one estimate, removal would cost $436,000, versus between $2.8-million and $6.2-million to fix or rebuild.
Nevertheless, decommissioning is often a tough sell. While doing nothing may court significant legal liability in the event of subsequent failure, it is even cheaper (at least in the short term) than removal. And outside sources of funding are typically few. Ontario’s Conservation Authorities, for example, can call on the province’s Water Erosion Control Infrastructure program to fund removals, but at $5-million a year it is small and consistently oversubscribed.
To remedy this and encourage more removals, some have suggested government-funded schemes resembling recent efforts to remediate abandoned oil wells in Western Canada. To encourage removals, the Ontario Rivers Alliance offers to help owners raise money.
Even the most deadbeat of dams often has local defenders, who form “save the dam” groups to lobby local officials for rehabilitation. “Most people don’t want to lose their reservoirs or local ponds that have been created with these dams,” said Ms. Heron. “Sometimes we’re successful, most times we’re not.”
There are also regulatory obstacles. A curious aspect of Ontario’s Lakes and Rivers Improvement Act is that owners require provincial permits to repair or remove their dams, whereas there are few requirements for owners who choose to do nothing.
“The fascinating thing is, it’s harder to go through the process of removing it than it was to put it in there in the first place,” said Mr. Huber.
Since establishing his own engineering firm in 2013, Mr. Graham has helped several municipalities and conservation authorities remove small and medium-sized dams in Ontario. Last year GSS Engineering removed the Truax Dam on the Saugeen River in Walkerton, Ont. But he said the pace of removals in Canada is “glacial,” and far slower than that south of the border.
“If we only are able to achieve the removal of one or two or three or four of these dams per year in Ontario, we’ll never make a big dent in the total number,” said Mr. Graham. “I mean, we’re just scratching the surface.”
The coming deluges: More from Matthew McClearn
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