Court documents and FOI materials show BC Hydro knew shale would move at troubled construction project, yet Hydro proceeded with river diversion


BC Hydro approved the pouring of massive amounts of concrete to build a buttress at its problem-plagued Site C dam project months before a critical drainage tunnel was completed to draw water away from the imposing structure and prevent it moving too much. 

In fact, the first concrete was poured well over a year before the tunnel was finished as workers struggled in unsafe conditions below ground with dust so thick at times that they couldn’t see their hands when they stretched their arms out in front of them. 

Now, that out-of-synch schedule, combined with well-known problems with the soft sedimentary shale at the construction site, appears to have landed BC Hydro in big trouble as “project risk” geotechnical problems emerge at the massive construction project. 

New details on those problems have been pieced together by the Canadian Centre for Policy Alternatives (CCPA) using documents obtained through a Freedom of Information request to WorkSafe BC, as well as a review of documents filed in BC Supreme Court. 

The new information shows for the first time not only how delays in building the tunnel may have contributed to the significant geotechnical problems at the construction site, but raises further questions about why BC Hydro chose to situate the project where it did. 

Many prominent British Columbians, including former president and CEO of BC Hydro, Marc Eliesen, say those geotechnical problems are of such concern that the provincial government  should order an immediate halt to the project while an independent team of professionals reviews the problems at the site. 

Bound to rebound 

The documents filed in BC Supreme Court and analyzed by the CCPA show that BC Hydro knew from the outset that the concrete buttress would move as excavation work exposed the Peace River valley’s soft shale rock, which is little more than compressed clay. 

But just how much movement or “rebound” has occurred already, and may yet occur, remains unknown due to the lack of transparency and public accountability surrounding the project. 

The court documents include an expert report filed in support of the West Moberly First Nations in June 2018. At the time, the Nations were seeking an injunction to stop work from occurring in critical areas covered by Treaty 8 that could be irreversibly impacted by the dam’s completion and subsequent flooding of their lands (their effort was ultimately unsuccessful). 

The expert report in support of the West Moberly court filing was prepared by Harvey Elwin, a Washington State-based civil engineer with five decades experience on hydroelectric projects around the world. An appendix to Elwin’s report includes two reports delivered by the Site C project’s independent engineer Tim Little to British Columbia’s deputy comptroller of water rights, Bruce O’Neill. 

As a condition of receiving the water licences it needed to build Site C, BC Hydro was required to nominate an independent engineer to oversee the project and file reports with the BC government detailing the project’s progress and any notable problems. 

In Little’s report to O’Neill on June 2, 2017, the importance of the drainage tunnel on the south side of the river is highlighted. 

A tunnel’s slow progress 

“The right bank drainage tunnel, currently under construction, will extend through bedrock below most of the length of the RCC [roller compacted concrete] buttress. The tunnel and drain holes to be drilled from it were intended to provide foundation drainage, both in advance of buttress construction and for the long term. The tunnel will also house instrumentation that was intended to serve as a tool to assess the behavior of the RCC buttress foundation during excavation and later, to monitor long term performance of the buttress,” Little wrote. 

However, Little went on, “due to slow progress of the tunnel construction,” the first of the concrete was to be poured well before the tunnel was completed. As a result, the tunnel wouldn’t be there to drain away water that might cause the region’s notoriously unstable shale rock to move even further. As a stopgap measure, Little reported that BC Hydro intended to install “alternative instruments” to monitor how the rock behaved and what movements might occur. 

Little recommended that the planned course of action was appropriate and should be allowed to proceed, and his recommendation was immediately endorsed by O’Neill. 

BC Hydro had already known for some time that movement would occur at the site. A 2006 engineering review conducted for BC Hydro stated that “rebound of the shale bedrock in the foundations of the right bank structures at Site C” would be “a significant design issue” for the megaproject. 

The review warned that the shale underneath the spillway’s headworks and chute and the dam’s intakes and penstocks could move by up to one third of a metre; while the movement under the spillway’s stilling basin and powerhouse could move up to four tenths of a metre. 

“The rebound will result from the reduction of stress in the bedrock due to the excavations,” noted the engineers, adding: “The right bank structures will have to be designed so that they can accommodate the anticipated rebound without adversely effecting (sic.) the operation of the project.” 

The 2006 review was prepared by engineers with Klohn Crippen and SNC Lavalin. Among them was John Nunn—who went on to become chief engineer on the Site C project and who currently sits on BC Hydro’s board of directors and heads the Site C Project Assurance Board. 

In 2016, Nunn was one of six professional engineers to issue another document noting how well known weaknesses in the shale “rock” at the project site had prompted a redesign of the dam to its current, highly unorthodox L-shape. The redesign was intended to avoid geotechnical problems associated with trying to anchor the dam to the weak shale on the river’s south bank. 

Instead, the L-shaped makeover has resulted in a whole suite of problems, precisely where all that mass of concrete now sits. BC Hydro says anticipated enhancements to address those significant geotechnical problems include improvements to the spillways and power house 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 that problematic shale. 

Little made no mention of the L-shape in another report he sent to O’Neill in April 2018. Despite 10 months passing since his earlier report, Little told O’Neil that the problematic tunnel still remained far from done. In fact, the tunnel would not be completed until February 2019, when Peace River Hydro Partners issued a press release trumpeting the “breakthrough achievement.” 

Choked with dust 

Little’s April 2018 report noted that “piezometric pressure” or water pressure could be a serious issue for Site C’s roller-compacted concrete structures. 

“Movements within the bedrock foundation can be influenced by piezometric pressures, and it was intended that the right bank drainage tunnel and drain holes drilled from the tunnel would be completed prior to excavations for the overlying RCC [roller compacted concrete] buttress sections. It was also intended that instrumentation to be installed from the tunnel would monitor piezometric pressures and rock movements in response to surface excavations,” Little wrote. 

But with work on the troubled tunnel still advancing “more slowly than originally expected,” BC Hydro elected in the tunnel’s absence to drill temporary “drain holes” to reduce water pressure on the buttress’s foundation, Little said. Instruments were also installed to monitor “the behavior” of the foundation in response to the excavation at the site. 

Little’s report provided no detail on why the tunnel took so long to complete. But documents obtained through a Freedom of Information request filed with WorkSafe BC paint a grim picture of the conditions faced by workers as they drilled through the weak shale. 

In the initial weeks of drilling the tunnel, workers were exposed to potentially dangerous levels of silica or rock dust in the tunnels. The work went on for weeks without Peace River Hydro Partners putting in place proper dust-control measures. 

In a report dated April 6, 2017, WorkSafe BC inspector Troy Lockhart noted that Peace River Hydro Partners had sent workers into the tunnel “without the proper work processes in place to ensure air contaminants were not going to put workers at risk of occupational disease.” 

In fact, the company did no air sampling in the dust-choked tunnel for “more than 30 days” after work first commenced. 

A subsequent WorkSafe report noted that “crystaline silica dust is a known carcinogen” and that Peace River Hydro Partners had a responsibility to keep workers’ exposure to that dust “at the lowest level that is reasonably achievable.” 

WorkSafe subsequently ordered the company to inform its workers of their rights to file formal notices with a “hazard registry” set up under the Workers Compensation Act. The registry is designed to compensate workers “now or in the future” for exposure to hazards in the workplace. 

Raining concrete 

The dust problems at the tunnel would lead to months of delay. But those were far from the only problems. Chunks of the tunnel’s concrete lining crashed to the tunnel floor, resulting in work suspensions, but, thankfully, no injuries or fatalities. (Similar incidents also occurred in the diversion tunnels drilled on the opposite bank, leading to lengthy delays.) 

In order to secure the concrete to the walls of the tunnel, holes had to be drilled into the weak shale so that anchor bolts could be installed. Spraying water as those holes were drilled kept the troublesome dust down, but it introduced a new problem. It softened the shale, making it more clay-like and less able to hold the bolts, which were critical to keeping the concrete attached to the tunnel walls. So for at least part of the time, the drilling was done “dry” rather than “wet.” 

A WorkSafe memo on the issue clearly indicates that the primary reason for drilling dry was that if the shale was too wet the bolts could lose their grips and fail. (The same phenomenon of exposed shale “rock” turning soft in the presence of water, played a critical role in the failure of the Taylor bridge not far downstream from the Site C project in 1957.) 

“The reason given for drilling without water for the anchor bolt holes is that pull tests conducted found that the anchors were not reliable when the holes for the anchors were drilled using water,” WorkSafe’s occupational safety officer, Dale MacDonald noted in an inspection report on June 4, 2018. 

Not observing the observation method 

Little’s memos to O’Neill also flag two other important issues involving the anticipated movement of the massive buttress. 

First, BC Hydro planned to build the formidable buttress structure in three phases. 

Essentially, a big hole would be dug down into the shale in the winter and a section of roller-compacted concrete buttress built the following summer. The same pattern would be repeated in each of the next two years. The powerhouse buttress excavation and concrete pour would occur in 2016-2017, the spillway buttress excavation and pour would occur in 2017-2018 and the dam and core buttress excavation and pour would happen in 2018-2019. 

The work would be done in stages, Little told O’Neill, as “the shale bedrock at Site C” was expected to move or rebound both vertically and horizontally as the holes were dug. “Bedrock excavations and RCC (roller-compacted concrete) placements of the RCC buttress will be done in a sequential manner to minimize potential movements within the buttress foundation,” Little wrote. His report also indicated it was possible there could be differences in the movements depending on how the shale responded during each excavation. 

Second, Little noted that a key precautionary approach employed in major construction projects would not be followed during the first phase of excavation and concrete placement. That approach is known as “the observational method.” The method’s three cornerstones are to design what you are about to build based on what you know is going on at the site, to have a monitoring plan in place that verifies that what you are building and the environment you are building it in is behaving “acceptably” and to have a contingency plan in place “if defined limits of acceptable behavior are exceeded.” 

Knowing that its excavations would likely cause the shale to move, BC Hydro had the option of placing instrumentation in the first hole it dug and then waiting for a sufficiently long time period to see exactly how much the shale moved before laying down the first of what would eventually be more than 1.7 milion cubic metres of concrete. 

But instead of waiting, BC Hydro elected to lay down the first layers of concrete and place “movement joints” in the structure that would accommodate any predicted uplift or shifting in the shale that subsequently occurred. The observation would wait until later. 

“For the powerhouse buttress, RCC placement is scheduled to happen shortly after the excavation is completed and the actual time available to observe the response of the rock due to excavation is less than anticipated at the time of design,” Little reported to O’Neill. “Based on the recommendations of the designer-of-record (Klohn Crippen Berger/SNC Lavalin) that there is insufficient data to confidently remove the joints, BC Hydro has directed PRHP  [Peace River Hydro Partners] to proceed with construction of the movement joints for the powerhouse buttress. Decisions on the need for movement joints for other buttresses will be made later when more information is available on the response of the bedrock to the excavation.” 

What Little was essentially saying was this: BC Hydro doesn’t want to wait. It wants to build Phase One before seeing what the actual shale movements are. It’s told the contractor to put in movement joints based on what it thinks those movements will be. And down the road it will see what the actual movements are. 

Delaying information 

Early in 2020, the CCPA published two lengthy reports based on Freedom of Information documents released by BC Hydro. 

The documents showed that several BC Hydro dam safety officials and engineers knew of weak bedrock underlying the Peace Canyon dam upstream of the Site C project, and that the dam’s less than desirable foundation of shale “rock” made the dam vulnerable to damage by earthquakes triggered by nearby natural gas company fracking and disposal well operations. 

As a then-senior employee with BC Hydro, Little was told in 2009 ­­by the Crown corporation’s top dam safety official that a magnitude 5.5 earthquake right near the dam could have serious consequences for the structure. Since then, the CCPA reported on the occurrence of thousands of fracking-related earthquakes in the geologically sensitive region that included the Site C project. 

Upon learning earlier this year that Little had been named Site C’s independent engineer, the CCPA contacted the provincial Ministry of Forests, Lands, Natural Resource Operations and Rural Development to request copies of all reports that Little had made to the Water Comptroller’s office.

The CCPA was told that the documents would take some time to gather. During a seven-week wait, the CCPA was told repeatedly that the documents were coming. But then, at the end of that wait, the Ministry said “a mistake” had been made and it could not release the documents. If the CCPA still wanted them, it would have to file a formal Freedom of Information request, a process that can take months to complete and that may not result in the requested documents actually being released. The CCPA has yet to file that request, but soon will in an attempt to find out what else Little has told the provincial government about ongoing geotechnical challenges at the Site C project. 

Diversion begins 

Despite all the foundational problems at the concrete buttress—which BC Hydro has yet to say publicly how it will resolve—the Crown corporation has steamed ahead with a critical component of its dam-building plans. Last week it diverted the Peace river around the area where it will build the largest portion of the actual dam itself, the massive earth-filled wall that will stretch across the river valley from the north side to join the concrete buttress. 

The diversion, which was accompanied by a brief and muted press release announcing the major event, began on October 3. 

Former BC Hydro CEO Marc Eliesen said in an email that proceeding with the diversion was “scandalous” under the circumstances, in which geotechnical issues remain unresolved and a provincial election campaign is under full swing. 

BC Hydro would not comment on matters raised in this piece. Its Site C spokesperson Dave Conway said it would be inappropriate under the circumstances. “As you know the writ period for the provincial election has begun,” Conway wrote in an email. “As part of our obligation to remain impartial during this time, we are not able to respond to media requests unless the information is publicly available on our website.”

This research is supported by the Social Science and Humanities Research Council of Canada (SSHRC) and the Minor Foundation for Major Challenges.


Author: Ben Parfitt

Ben is the resource policy analyst with the Canadian Centre for Policy Alternatives – BC Office. He has received numerous awards for his investigative journalism, is a co-author and author of two books on forestry, and is a long-established researcher and policy analyst specializing in natural resource management and environmental issues. Reports and analysis for the CCPA–BC include Fracking, First Nations and Water: Respecting Indigenous rights and better protecting our shared resources (June 2017); A Dam Big Problem: Regulatory breakdown as fracking companies in BC’s northeast build dozens of unauthorized dams (May 2017); From disenfranchised to revitalized: Ten proposals to set our forests and BC’s rural communities on a new course (March 2016); Counting Every Drop: The case for water use reporting in BC (June 2013); and Fracking Up Our Water, Hydro Power and Climate: BC’s reckless pursuit of shale gas (November 2011).