Muskrat Falls cofferdam leaks could be worse than Nalcor is admitting

Photo obtained by The Independent reveals what one hydroelectric engineering expert says is a “very serious” problem for Nalcor and subcontractors working on the site.

Nalcor has begun lowering water levels in the Muskrat Falls reservoir following a series of leaks in the project’s cofferdam this week that The Independent has learned could be much more significant than the Crown energy corporation has acknowledged.

On Friday morning Nalcor, which is in charge of the controversial hydroelectric megaproject, issued a statement saying there was “increased seepage” in the upstream cofferdam, which prompted the project’s engineering team to recommend that water levels in the reservoir be reduced “to mitigate risk associated with the increased flow and to maintain the integrity of the cofferdam.”

The statement also said that opening the spillway gates “has increased water flows and levels downstream of Muskrat Falls,” but that there is “no risk of flooding in any of the surrounding communities…and water levels and flow rates in the river will be consistent with spring flow conditions.”

At the time of publication Environment and Climate Change Canada’s Wateroffice was reporting that water levels in the river six kilometres below Muskrat Falls had risen almost a full metre. 

The first phase of reservoir flooding began earlier this month, following a series of protests during which hundreds of people province-wide took to the streets, while land protectors in Labrador blockaded the Muskrat Falls site and and eventually occupied the project’s workers’ camp to express concerns that, among others, the Grand River cannot be safely dammed.

In a statement issued to media on Wednesday Nalcor explained “water seeping through the rock cofferdam and collecting between the upstream rock dam and the downstream rock dam…is not uncommon and the cofferdam is operating as designed and as expected.”

But The Independent learned around that same time that another leak in the cofferdam—which was not noted by Nalor—was observed by workers on Tuesday and may indicate the problem is much more serious than the corporation has disclosed.

The cofferdam is a temporary structure comprised of rock, sand and clay to divert the river’s water flow so that the dam’s permanent components can be built.

While most cofferdams experience some water seepage, a photo obtained by The Independent reveals the problem at Muskrat Falls’ cofferdam could be “very serious,” according to an expert who has analyzed the photo.

The image shows brown-coloured water shooting up into the air under pressure from the downstream side of the project’s cofferdam, a scenario that retired hydropower engineer Jim Gordon says could get much worse if the problem isn’t immediately and sufficiently dealt with.

Gordon says the colour of the water indicates that the water in the photo comprising the fountain at the downstream side of the cofferdam “can only come from the upstream water level through what is called a ‘natural pipe’ that is eroded by the water through both cofferdams.”

The image also shows what appears to be a partial washout on the road atop where the water is flowing beneath, or what what Gordon says could be an “erosion channel”.

The Montreal-based former engineer, who has worked on dozens of dams in his lifetime and won a host of awards for his work, says he believes the water has formed a pathway through the cofferdam and is eroding the clay sediment, carrying it out into the river below the structure.

He also said if the problem isn’t immediately dealt with—if the contractor, Barnard Pennecon, isn’t able to successfully seal off the tunnel of water from the upstream side of the upstream cofferdam—the problem could result in a “failure” of the structure.

Independent file photo.
This view of the Muskrat Falls construction site, from a photo taken in October 2016, illustrates the places where the brown-coloured water fountain was reportedly observed, as well as the place where the initial and reportedly continued flow of water from the upstream side of the cofferdam is emerging in the middle of the cofferdam structure. Independent file photo.

“The fact that the water is coming out under pressure, rising above the crest of the downstream cofferdam is very serious,” Gordon explains. “And it indicates that the water flow is eroding more of the upstream clay, which is the waterproof barrier, out from the upstream cofferdam. This means the flow will increase with time and could eventually result in a failure. But how long that process will take, I just don’t know.”

On Wednesday Nalcor issued a press release saying “water was pumped out [from between the upper and lower cofferdams] and water levels are back to normal.” Further, the statement read, “experts inspected the cofferdam and have advised that the structure is safe and stable and operating as expected and designed.”

A worker on site, on condition of anonymity, told The Independent that on Tuesday morning workers from other areas of the project site were asked to help with efforts to pump water out from between the two sides of the cofferdam.

The fact that the water is coming out under pressure, rising above the crest of the downstream cofferdam is very serious. — Jim Gordon

The worker said they were told by a colleague that a steady flow of clear water that has been penetrating the cofferdam as long as the structure has existed—and was being removed with pumps—suddenly turned brown and intensified Monday night.

The worker also said the fountain of brown water on the downstream side of the cofferdam only stopped when that part of the structure collapsed on itself.

The Independent shared the photo with Nalcor spokesperson Karen O’Neill and sent multiple emails seeking comment on Thursday, but received no response by the time of publication on Friday.

On Friday, following Nalcor’s announcement that another leak had penetrated the cofferdam, a source told The Independent that the new water was also brown.

Gordon said there are “two interpretations” of the claim that the water tunnel leading to the fountain of brow water on the downstream side of the cofferdam collapsed on itself.

“If the contractor has dumped sufficient material upstream of the upstream cofferdam to shut off the flow, that’s great — they’ve almost won the battle,” he said.

“If, on the other hand, the downstream cofferdam has collapsed to such an extent [that the fountain has stopped], all it means is that the flow is no longer emerging where it was emerging before, against a rock and shooting up. It’s now emerging further down, perhaps underwater, and you can’t see it.”

Gordon estimated that adequately sealing off the intake on the upstream side of the cofferdam could take time — “not hours or days, but weeks or months,” he said, explaining that the proper equipment and significant amounts of materials will likely be required.

In its statement Friday morning Nalcor said the corporation “followed its Emergency Preparedness Plan prepared for the impoundment process for the project and notified communities and stakeholders in the area of the potential for increased water flows associated with this condition.”

Mud Lake resident Craig Chaulk said those he spoke with in his community, which sits adjacent the mouth of Grand River from Happy Valley-Goose Bay and is accessible only by boat this time of year, weren’t aware of Nalcor’s decision to release water from the reservoir.

Chaulk, whose family commutes by boat to Happy Valley-Goose Bay for work on a daily basis, said there has been noticeably more debris, including trees, floating down river since the first phase of reservoir flooding began earlier this month, and that he has heard reports that there is even more debris present in the water today since the dam’s spillway gates have been opened.

“We often have to go across in the dark at night, so that’s concerning,” he said, explaining lights can illuminate ice in the water ahead of the boat, but that trees, logs and other debris now flowing down from Muskrat Falls are much less visible.

A worker from the Muskrat Falls site who has worked on the cofferdam since last summer said he’s less concerned about workers’ safety on site under the present circumstances than he is about what the cofferdam leaks mean for the project on the whole.

They hurried up to get the cofferdam done to match their projected flood date [and] the quality [of the work] is taking a hit for it. — Muskrat Falls worker

Nalcor and its subcontractors are “doing a rush job” in order to meet deadlines, they said, adding “they hurried up to get the cofferdam done to match their projected flood date,” and that “the quality [of the work] is taking a hit for it.”

The worker said they are not worried the cofferdam will give without first growing noticeably worse, thereby giving workers time to evacuate the area, but that they’re worried what Nalcor and Barnard Pennecon’s management of the cofferdam construction could indicate for other parts of the project, like the North Spur.

“If they’re not being thorough on the pre-work that we’re doing now, how can I be assured of the confidence of Nalcor to start doing the proper work to make sure the job is done right?

“I just don’t believe that the quality control is even close to being accurate or trustworthy,” they continued. “I don’t believe anything they say, and that goes for almost everybody I ever spoke to [on the project].

“We should be able to go home at night and tell our family we did a great job [at work]. We should be able to say, there’s no way this thing is letting go, and this is why. Instead everybody’s like, Jesus b’y.”

On Friday morning, moments after receiving news that the gates had been opened and water levels downstream were on the rise, Happy Valley-Goose Bay Mayor Jamie Snook told The Independent that the Town will be “monitoring today and reiterating our urgent and shared support for a symposium on the North Spur,” saying the cofferdam problems and subsequent last-minute decision to release water from the reservoir reveals a need for “more transparency period.”

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