BC Hydro knew 30 years before it started building the Site C dam that its chosen location for the most expensive publicly-funded infrastructure project in British Columbia’s history had big problems.
By the 1980s, it had done tests showing that the ground at Site C had serious flaws “due to the very weak sedimentary rock” in the area.
The revelation is contained in a report co-written by six professional engineers, including two working for BC Hydro and four working for major corporations — Klohn Crippen Berger Ltd. and SNC Lavalin — hired by the Crown corporation to provide design services at Site C.
The two BC Hydro engineers were Andrew Watson and Rod Carter. BC Hydro board member John Nunn, who was the chief engineer on the Site C project and chairs the project assurance board overseeing construction, was also an author.
Their report was presented to delegates attending the Canadian Dam Association conference in Halifax, N.S., in October 2016, just 15 months after construction of the multi-billion-dollar project began.
Nunn, Watson, Carter and their associates also reported that BC Hydro knew that certain “bedding planes” between the layers of sedimentary shale at Site C had poor shear strength, meaning they could suddenly shift under modest amounts of force.
Those daunting geological realities prompted BC Hydro to embrace a radical redesign of the dam, changing it from a fairly conventional straight-across-the-valley structure to a highly unusual L-shape that broke with convention and that was, in the engineers’ own words, a “unique concept” for an earthfill dam.
Now, four years after that presentation and with years remaining before Site C is finished — if it can be safely completed at all — the unique design that was supposed to avoid troubles is itself mired in problems, raising questions about the wisdom of BC Hydro in choosing to build such an unusual structure in such a geologically fraught location.
The project budget, originally estimated at $6.6 billion, has ballooned to an estimated $12 billion. And that’s before the current geotechnical problems, which BC Hydro characterizes as “project risk,” are dealt with.
A shale of a problem
“If I was going to pick a rock that was the least likely to be my friend, it would be shale,” says Anthony Ingraffea, an expert on rock mechanics.
A professor emeritus in civil and environmental engineering at Cornell University in New York state, Ingraffea is also deeply knowledgeable about fracking and what it does to shale rock formations. In addition, he has studied cracking and stresses in dams in three countries.
Ingraffea says shale is a particularly problematic material to build a dam on. And if the dam is in a wider shale zone where fossil fuel companies drill and frack for natural gas and oil, triggering thousands of earthquakes in the process, the risks of something going horribly wrong only increase, he says. And Site C clearly fits that bill.
Making matters worse, the material that BC Hydro engineers describe as weak “rock” is not really rock at all, at least not in the conventional understanding of the word, according to a late civil engineer.
Robert Hardy, a civil engineer and eventual dean of engineering at the University of Alberta, studied the region’s unusual and problematic shale after a spectacular collapse of a suspension bridge in 1957 at Taylor, not far downstream from the Site C project. The disaster occurred just 15 years after construction.
In a report that dissected the region’s geology, Hardy characterized the Peace River’s shale as “soft rock” that only remained rock-like due to the tremendous force exerted on it by ice sheets over thousands of years. When that shale is liberated from all that weight, it can “rebound” or swell under certain circumstances, becoming clay-like. The transformation can have devastating consequences for major civil works like bridges or dams.
In the case of the Taylor Bridge, workers had to jackhammer a ledge into the dry shale to pour the bridge footings because the shale was so hard.
But when that same shale was exposed to the elements due to the construction activities, it swelled in the presence of water, making the ground unstable and causing the bridge to collapse.
Perhaps prophetically for the Site C project, Hardy offered this description.
“Normal construction practices appear to have had the result of greatly accelerating the disintegration of these rocks. The result has been that within a period of only a fraction of the normal potential life of the structure, deterioration of the strength characteristics proceeded to the point where disastrous failure of the engineering works occurred.”
Going to L
In their 2016 report to the Canadian Dam Association, Nunn, Watson, Carter and the other team members noted that BC Hydro had conducted extensive testing at the Site C location by drilling through the shale. What it found was that critical zones between the layers of the shale were highly unstable — a finding that does not surprise Ingraffea.
Sedimentary rock forms when fine particles like silt accumulate on the beds of ancient lakes, oceans or other bodies of water, and are then pressed together under tremendous force over time. Eventually, over millions of years, layer upon layer of sedimentary shale forms, much like rows of bricks in a wall.
The thin planes between those layers are somewhat like the mortar in a brick wall, but they may contain other materials like sand particles, gravel, rock chips, mud or inorganic dirt and they are often not evenly distributed. This “discontinuous” material, as Ingraffea describes it, can shear under pressure, causing the layers to move.
BC Hydro’s tests in the 1980s showed that there were many bedding planes at Site C “that were found to have very low shear strength values.” These planes were numbered BP-8, BP-12, BP-25, BP-28, BP-31 and BP-33. But it was BP-25 that was the most problematic.
“BP-25 is located on both valley walls at an elevation just above river level,” Nunn and his colleagues reported. “Laboratory tests revealed that this bedding plane has the lowest shear strength of all the bedding planes found at the site. BP-25… is considered to be the most important bedding plane for the design of the [Site C dam’s] headworks structures, which are located on the right [south] bank.” (A hydroelectric dam’s headworks are where the powerhouse and water intakes for the turbines are located.)
The presence of weak bedding planes in such a critical location meant that BC Hydro had to abandon plans to build a fairly conventional dam across the valley.
To avoid the problematic south bank, the dam design was transformed. In 2010, when then premier Gordon Campbell jetted north for an elaborate press conference at the W.A.C. Bennett dam (the first of two dams up-river of Site C) to announce his government’s intention to proceed with Site C, illustrations for the proposed project showed an almost straight valley crossing.
But only a year later, the dam design underwent an extreme makeover to its current, striking L-shape.
Today’s illustrations for Site C depict a large earth-filled dam wall cutting straight across the valley from the north bank (construction of the wall has not begun). As it approaches the south bank it makes a 90-degree turn to the left to parallel the problematic south bank. That part of the dam is to be built out of roller-compacted concrete.
L-shaped earthfill dams? Name one
BC Hydro Site C spokesperson David Conway says the new design makes for a stronger structure. The spillway, which drains water if the reservoir is too full, as well as the powerhouse are now on the short branch of the L-shape paralleling the south bank.
This design “improved the stability and seismic performance to the previous design model,” Conway said in an email.
Asked to provide examples of other earthfill dams with such an unorthodox configuration, Conway couldn’t name one.
“While not an earthfill dam, an example of an L-shaped layout is the Grand Coulee dam on the Columbia River in Washington state. Also, the Sir Adam Beck generating station in Ontario has a similar arrangement of flow rounding a corner to get to the power intake,” Conway said.
Both those dams are massive concrete and steel edifices tied into tough bedrock, and not sitting atop fickle shale. And the Adam Beck generating station near Niagara Falls is far from an L-shape.
Shortly after Site C’s extreme makeover, the Alaska Highway News interviewed BC Hydro engineer Andrew Watson, one of the authors of the 2016 report. Watson told the newspaper that geotechnical challenges prompted the redesign. The newspaper reported that Watson said “the new design will minimize the depth of the excavation required under the generating station, which will reduce concerns about foundation stability.”
Clearly, the engineers were not enamoured with the idea of digging deep into that shale “rock.”
Yet now, concerns about “foundation stability” are emerging again despite the revised design. And BC Premier John Horgan is voicing his “disappointment” at the horrendous cost implications.
According to BC Hydro’s recent Site C progress report filing with the BC Utilities Commission, big problems have emerged on that branch of the L-shape. Problems now made far, far more complex by the fact that millions of tonnes of concrete are already in place, pressing down on weak shale rock, that may also be prone to swelling in the presence of water.
On the last day of July, BC Hydro CEO Chris O’Riley wrote David Morton, the BCUC’s chair, to inform him that a “project risk” had emerged at Site C.
“Towards the end of December 2019, investigations and analysis of geological mapping and monitoring activities completed during construction identified that some foundation enhancements would be required to increase the stability below the powerhouse, spillway and future dam core areas,” O’Riley wrote — which is precisely where all that concrete is now poured.
“By the end of the March 31 reporting period, we had learned more about these geological challenges,” O’Riley continued. “Based on further engineering analysis of the proposed mitigation measures, the foundation enhancement costs are anticipated to be more substantial than initially expected in January. BC Hydro continues to work with the independent Site C Technical Advisory Board and the Project Assurance Board to determine the appropriate enhancement measures.”
In its report to the BCUC, BC Hydro said that the anticipated “enhancements” include “improvements to the spillways and powerhouse roller-compacted concrete buttresses.” A “shear key” is also proposed for the right bank of the earthfill dam itself, which would involve drilling down into the problematic shale.
The report went on to say that “several options” were being evaluated to determine what would work, but costs will be “much higher than initially expected” as recently as January.
‘You can’t put a bandage on a crack’
Ingraffea says that shale is not a rock of choice for dam building for good reasons. You have the bedding planes that generally run horizontally between the layers of shale. But you also have faults or cracks that can run near vertically. Again, think of bricks in a wall. There’s mortar between the rows of bricks, and there’s also mortar running vertically between each brick.
Now think about a dam cutting across a river valley and impounding a whole bunch of water.
Dams must be built to withstand the tremendous water pressure exerted on them. They must also be built to withstand water coming up from below.
“Water seeps down through joints and the faults, migrates along bedding planes, lubricates them and can rise upwards again and get into the bottom of the dam,” Ingraffea says. “And when the water goes upward into the bottom of the dam, you’re making the dam unstable because you’re trying to lift the dam up under the water pressure. So the dam has to withstand horizontal pressure from the reservoir, it also has to withstand upward pressure from the water under it.”
Upping the ante for the Site C project, more than 10,000 earthquakes associated with fracking operations in the same zone where Site C is located occurred in 2017 and 2018 alone. One of those earthquakes in November 2018 registered 4.5 magnitude and jolted the ground so hard at the Site C project that construction workers were evacuated from the site.
“Is it possible that all this natural gas development in the area… could generate an earthquake close enough and large enough to have very serious structural effects on one of those dams? Absolutely,” Ingraffea says.
Ingraffea says it’s reasonable to think problems are already visible at the project.
“In my professional opinion, having been called to dam sites in three different countries, the reason why the call goes out for action is inevitably some form of apparent distress. Usually, but not always, cracking where it is unexpected,” Ingraffea says.
“If you already have damage in the structure, and it’s not even complete, how are you going to repair it?” Ingraffea asks. “You can’t put a bandage on a crack.”
Ingraffea also said that if any “enhancement” work is required at the point where the dam makes its dramatic right-angle turn, the engineering challenges will be considerable because the corner is “under different kinds of stresses” than other parts of the structure.
Doubling the costs for ratepayers and taxpayers
All major hydroelectric projects have one troubling thing in common. They almost always go way over budget. And that is precisely where Site C is headed.
In Newfoundland and Labrador, where an $8-billion debt associated with the hugely over-budget Muskrat Falls dam threatens to push the provincial government to the brink of bankruptcy, the first witness to testify before a provincial inquiry into the controversial hydroelectric project was Bent Flyvbjerg of Oxford University.
Flyvbjerg told the inquiry that a report he had co-authored looked at 274 hydro dam projects around the world. The report was “the largest academic data set” of its kind and found that on average nearly 300 dams came in at virtually double their originally estimated costs.
Only nuclear power plant installations had worse cost overruns, Flyvbjerg said.
David Vardy, former head of Newfoundland and Labrador’s public utilities board, said it is essential that there is rigorous public oversight of such large projects by independent bodies. But with both Muskrat Falls and Site C, the provincial governments removed oversight of the projects by independent provincial utilities regulators, leaving the public in the dark.
Vardy says that had rigorous oversight been in place the plug could have been pulled on Muskrat Falls at least five years ago, when it was apparent that about $5 billion of the project’s original $6.2-billion budget had already been spent and the dam was nowhere near done. Now Muskrat Falls’ price tag sits at $13 billion, more than twice its originally estimated cost.
The costs already sunk on a megaproject can’t be recovered, Vardy says. But the future costs can be controlled. And if those costs show signs of vastly exceeding the project’s original budget, then the savings associated with stopping the project must be considered.
But in order to make that kind of call, you need proper oversight, Vardy says.
“When you’re dealing with a megaproject, you do need to have a thorough process, you need to have a public process.”
While BC Hydro provides quarterly reports to the BCUC, the allegedly “independent” project assurance board is tasked by the B.C. government with overseeing Site C and ensuring the interests of British Columbians are safeguarded.
Former BC Hydro CEO Marc Eliesen says that is not how it should be. Like Vardy, he believes that a project of Site C’s magnitude must be regulated independently.
But that is not what the government did.
"In December 2017, when Premier Horgan decided to continue the construction of Site C, he announced a new project assurance board. The board would provide ‘enhanced oversight’ on costs and schedule,” Eliesen said.
But the premier “violated one of the basic principles of arms-length review,” Eliesen said. “He appointed individuals to the board who had a vested interest, including John Nunn, who was Site C’s project engineer along with Ministry of Finance and Ministry of Energy officials who had been actively involved in promoting the project.”
Eliesen said the revelations of foundational problems at Site C cry out for “an immediate halt” to all work at the project and a sober assessment of whether or not it’s in the public interest to continue.
This is the time to decide once and for all whether an unusually designed dam has any place in such hostile terrain.