It’s not just the North Spur we have to worry about

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By now most readers will have heard that the North Spur is a naturally formed dam that forces the Churchill River to veer south, around Spirit Mountain and to flow over Muskrat Falls.

Telegram letters

On Jan. 2, Jim Gordon, in his letter “Muskrat Falls and the North Spur controversy,” wrote — and rightly so — that “If the North Spur fails, Muskrat Falls will disappear and be left high and dry. The Muskrat Hydro facility would become a stranded asset, with (if feasible) a repair cost well over several billion dollars.”

While it is true that the North Spur helps create and maintain Muskrat Falls, it is neither safe nor cost efficient to have a sole, isolated focus on the North Spur.

As the Churchill River flows eastward, it approaches a very wide U-shaped (200 metres deep) subsurface, sand/silt/clay-filled valley (only two thirds of which is made up of the natural dam called the North Spur). If any part of this much larger sand/silt/clay-filled valley (not just the North Spur) should fail, “... Muskrat Falls will disappear and be left high and dry.”

The entire subsurface valley spans a full 2,500 metres from the south side of the Trans-Labrador Highway to Spirit Mountain and the one third portion that runs from the river’s north bank to the Kettle Lakes gorge (and that is not part of the North Spur) already shows evidence of landslides.

While Nalcor has conducted borehole and other geotechnical studies along the two thirds of the valley that makes up the North Spur (spending many millions of dollars in an attempt to reduce the risk of a North Spur failure), there is little or no evidence that similar extensive geotechnical studies have ever been conducted along the remaining one third of the subsurface, sand/silt/clay-filled valley.

Since there is no evidence that Nalcor is designing a plan to stabilize the remaining one third (800 metres) of the 2,500 metre long sub-surface, sand/silt/clay-filled valley, on what basis has Nalcor been able to make a rational decision that the one third portion of the U-shaped valley running between the upstream north bank and the Kettle Lakes gorge area already has a natural safety factor equal to or better than the North Spur after stabilization?

While there appears to be little or no evidence that the north bank to Kettle Lakes gorge area is already safe, there does appear to be some evidence that the area may be less safe than previously thought.

Before 2013, Nalcor’s stratigraphic interpretations of the upstream north bank to Kettle Lakes area described the subsurface as having two (presumably more stable, coarser) sand layers between the two existing upper and the one lower clay layer — Figure 7 of Nalcor and SNC-Lavalin’s poster presentation to the 1st International Workshop on Landslides in Sensitive Clays at the University of Laval on Oct. 28-30, 2013. (

However, Nalcor’s post-2013 interpretation describes the same subsurface area as follows: “Figure 7 and 8 present a cross section between (the) upstream side and the Kettle Lakes. The intermediate sand strata previously encountered, is now described as a sandy-silt or silty-sand with a fine content greater than 25 per cent” (see previously referenced poster).

Furthermore, it should also be noted that although the area was previously described as having a total of only six layers of sand and clay, and while the area is now described as having a more complex total of 10 layers of sand, clay, sandy/silt or silty/sand (both silt and clay categorized in the fine particles category), and along with the above-referenced more recent 2013 interpretations, where is the analyses that confirms that this area has the same stabilized potential as previously thought?

In addition to stratification issues, will strengthening the North Spur without strengthening the north bank to Kettle Lakes area increase the risk of failure along the north bank to Kettle Lakes gorge?

Historically, the upstream water elevation generally remains below 18 metres above sea level. Accordingly, the river places no horizontal water (infiltration) pressure on any of the 2,500 metre long subsurface sand/silt/clay-filled valley that is at or above the 18 metre mark.

However, once the Muskrat Falls dams are built and the reservoir is filled to its planned 39 metre elevation, the horizontal water pressure at the 18 metre mark will increase according to the square of the increased depth of the water.

That will increase horizontal water infiltration pressure at the 18 metre mark from zero to nearly one half million pounds per metre along the length of the North Spur and the upstream north bank (and approaching almost one million pounds per metre when the reservoir reaches a maximum flood level of 45 metres).

Furthermore, the North Spur stabilization works are designed to keep water in the north bank to Kettle Lakes gorge area from infiltrating the North Spur. Would this not impede the north bank to Kettle Lakes area from keeping its saturation at a safe level?

If the North Spur stabilization fails, Muskrat Falls will disappear and be left high and dry. But if stabilization helps ensure that the North Spur does not fail and instead the north bank to Kettle Lakes gorge area fails, Muskrat Falls will still disappear and be left high and dry.

For these and other reasons, and in addition to Mr. Gordon’s request that the government’s review be “... expanded to include the geotechnical design of the North Spur dam...,” I would also ask that government include in its review any potential risk/safety and cost implications associated with the entire subsurface, sand/silt/clay-filled valley that extends from the south side of the Trans-Labrador Highway to Spirit Mountain, or as a minimum, from the south side of the Trans-Labrador Highway to where Nalcor’s North Spur stabilization works turn northeastward, away from the reservoir’s north bank.


Maurice E. Adams


Organizations: Trans-Labrador Highway, SNC-LAVALIN, University of Laval

Geographic location: North Spur, Muskrat Falls, Kettle Lakes Spirit Mountain Churchill River Sensitive Clays

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Recent comments

  • Fred
    January 19, 2016 - 14:26

    Clearly the folks at Nalcor are incompetent for not considering the remainder of the river. After all, they are only interested in the reservoir and the power house. I suppose they could have put the generator anywhere eh Maurice?

    • Maurice E. Adams
      January 20, 2016 - 09:45

      They probably could have put it here in Sin John's --- the hot air rising over their headquarters building would have provided all the power we needed --- and enough left over for Nova Scotia.

  • Lucien Beauregard
    Lucien Beauregard
    January 19, 2016 - 12:22

    Uninteruptable Power Flow In the event that Muskrat Falls Power Plant is left high and dry, could we expect that remaining electrical infrastructure, like switchyards and transmission lines from Churchill Falls, will be able to by-pass the Muskrat Falls Power plant and take over the supply of power to Newfoundland Island ?

  • Winston
    January 19, 2016 - 11:38

    Maurice is right, I believe, to be concerned about the area beyond the immediate North Spur. A view of the aerial photos of this area suggests it is vulnerable from past activity, and the elevated water levels later will add to the risk. Perhaps they intend to assess and monitor that area later once the system is operating at the high river water levels? Surely it shows poor risk assessment that should have been done before sanction. (Retired engineer)

    • Fred
      January 19, 2016 - 19:07

      Do you know what risk assessment was done prior to sanction? (active engineer)

    • Maurice E. Adams
      January 20, 2016 - 08:46

      Fred, we know that whatever data (or lack thereof) was relied on, Nalcor concluded that no stabilization was required. So let Nalcor release the data. ---------------- They won't even release the geotechnical studies on which the North Spur design fix (?) is based.-------------- Why not?

    • Winston
      January 20, 2016 - 14:08

      Fred, I have read that Acres Canadian Bechtel, I believe, in the 1960's assessed Muskrat as a risky site due to marine clay problems and suggested it could cost 10 percent of the total project cost to stabilize it. Later assessments reduced the 10 percent to a much lower percentage. This leaves one to wonder if the risk is adequately addressed with the present design, especially given the more recent knowledge of the higher risk known from failures in other parts of the world and the technical understanding of the science of this marine clay and how it is vulnerable to liquefy and fail. You ask do I know what risk assessment was done prior to sanction. No. Can you tell me? I am sure Mr Gordon and others would like to know. If I were living downstream of Muskrat, my concern would be even greater that the risk assessment have a reasonable safety factor.

  • Errol
    January 19, 2016 - 10:22

    Thank you Maurice. Government needs to start listening to others besides the one man show that has lead Nalcor and Hydro for too long. A reading of the 'Oversight Committee' minutes provides no comfort at all to the Public. These minutes read like a bureaucratic get together, with the only result being a commitment to have more meetings. The Committee is a waste of time and effort.

  • roy206
    January 19, 2016 - 10:03

    Although it has been commented to death, the north spur situation is very real. Look no further than the Daniels Harbor slides of 2006 and 2007..( google it ) . Cbc footage shows that plastic flow of the saturated fine sand ( like North Spur)....This sand was stable as far back as anyone can remember. .There were also landslides within sight of MF over the years...( retired engineer)

  • Anthony Rockel
    January 19, 2016 - 09:24

    Readers with a modicum of curiosity might also be interested to read about the effects of landslides into a dam, no matter how far upstream from the dam the landslide might occur. A landslide into a confined body of water will create a tsunami. Read about the Vajont dam disaster. Read about the 3 Gorges tsunami. Landslides are happening quite frequently upstream from the Muskrat Falls project and they will become much more frequent as the water level rises with filling of the reservoir. Water enters fissures in the walls of the reservoir, loosening the already unstable rocks and soil. With glacial mud, the possibility of massive failure is even mote immediate. Does Nalcor plan to stablize the walls of the reservoir too?

  • Tired of Muskrat
    January 19, 2016 - 06:52

    Here comes Maurice yet again going on and on about Muskrat Falls. The naysayers need to realise that the project is not going to stop. The naysayers were wrong about Nalcor's demand growth, the naysayers were wrong about the impacts of shale oil, the naysayers were wrong about Nalcor's ability to hold the DG3 budget, the naysayers were wrong about Nalcor's ability to deliver to the project schedule. Oh shit... Maurice and the naysayers were perhaps right more times than Nalcor were!! Maybe we should be listening to the chorus of educated critics on the North Spur as well.

  • Maurice E. Adams
    January 19, 2016 - 06:06

    When you use the above-pasted link to the Nalcor poster, scroll down just a little (the 2nd article) and click on 'poster presentation'.