Mudslides and Band-Aids

Published on September 2, 2014

In last weekend’s Telegram we were treated to an interview with Nalcor’s Gilbert Bennett on the subject of landslides at Muskrat Falls.

Of July’s landslide that sent clay hundreds of metres out into the river, Bennett had this to say: “Five kilometres away is a long distance away. If we look at the conditions upstream and downstream, we know that those slides have happened at multiple locations, and we’re not too interested in those. They’re going to continue to happen.”

From the tone of his responses you’d get the impression that he actually welcomes these events: I can almost hear him saying “bring them on.”

If past events in historic and prehistoric times are anything to go by, the “world class experts” at Nalcor should be taking a much more serious look at these landslides. They should also acquaint themselves with the literature on tsunamis.

 The tsunamis most people hear about occur in our oceans. When the seabed moves up or down during an earthquake, or when an undersea landslide occurs, the overlying ocean is displaced, creating a disturbance that moves out in all directions, getting bigger and bigger as it reaches shallow water, frequently with catastrophic results.

There are other less well publicized types of tsunami: these occur when a landslide empties itself into a body of water in a confined space, such as a bay, a lake or dam.

When a large body of water is impacted this way, the effects can be dramatic, resulting in what are called mega-tsunamis, with wave heights of several tens, or even hundreds of metres.

Just ask the two survivors of the 1958 event in Lituya Bay, Alaska. Their fishing boat actually rode out a 520-metre high wave, created by a mountainside falling into the bay.

This wave swept away the trees along the shore and scoured away the topsoil down to bedrock. Of more immediate relevance, we have the 1963 disaster at Northern Italy’s Vajont dam.

Here, a landslide entering the reservoir created a 250-metre high wall of water that overtopped the dam, destroying five communities downstream and killing nearly 2,000 people.

The engineers knew in advance that in filling the reservoir, the water seeping into the walls of the gorge could destabilize the rockface, so they tried raising and lowering the water level several times, in hopes of creating a series of “gentle” rock-falls before filling the reservoir permanently. Obviously this approach left something to be desired.

Upriver from Muskrat Falls, we have a 35-kilometre valley (incidentally, a pristine ecosystem and a unique haven for wildlife) that Nalcor plans to flood in order to create a reservoir.

As with the North Spur, parts of the walls and uphill slopes of this valley are made of glacio-marine clay, which is notoriously unstable. It can suddenly liquefy, especially when its chemical composition is changed by prolonged exposure to fresh water, or during an earthquake.


We can fix this, no worries

In the inimitable Nalcor fashion, Bennett assures us that none of this is a problem. They can fix all this with a bit of landscaping, some rock, and a concrete wall along the North Spur, extending downwards 45 metres below water level.

This wall, we are told, will prevent water from migrating through the spur from the reservoir. How exactly will it do this when the glacial mud is 65 metres deeper than lower edge of the proposed wall? What’s to stop the water from going under this wall?

Nalcor also neglects to mention that beneath this glacial mud there are 150 metres of sand and gravel before you reach bedrock. How do you stabilize a 45-metre high concrete wall when it sits in mud 220 metres above bedrock? How do you prevent it from sinking? And what will be the cost of this gargantuan undertaking? The peasant populace of Newfoundland and Labrador is not allowed to know.

Bennett tells us this “should” (not “will”) stabilize the North Spur.

How reassuring!

The proposed wall appears to be about as potentially effective as a Band-Aid on a mud pile.

The North Spur is only part of the problem. What will happen to the sides of this 35-kilometre valley when it is flooded? Remember, many parts of it are glacial mud, known for its instability when exposed to fresh water.

And as we’ve learned from the Vajont disaster, even rockfaces can weaken when they’re constantly immersed in water.

This flooding is guaranteed to produce many more and bigger slides than have already happened along the Churchill River.

 Many previous slides, both upriver and downriver from the North Spur have been huge, some of them more than 20 million cubic metres in volume. A slide such as one of these into a river is one thing, but a slide of this magnitude into a reservoir is something else entirely (remember Vajont?).

What kind of wave would it produce? It would only need to be 15 metres high to overtop the North Spur, likely washing away a lot of topsoil and opening a breach in the dam. On the slopes above the North Spur there is a five-square-kilometre area of potentially unstable marine clay.

Just think about that.

Bennett tells us that the North Spur has been studied since the 1960s. What are the results of these studies, and what are their conclusions?

Nalcor’s geotechnical engineer admits that in hydro-engineering there’s nothing comparable to the North Spur anywhere in the world. Where is Nalcor’s Landslide Risk Assessment, and if it exists, why aren’t we allowed to see it?

Do you believe in magic?

Apparently in the wonderful Disney-like, make-believe world of Nalcor, the laws of physics don’t apply, just as cost overruns never happen and we don’t have winter blackouts, so we really haven’t a thing to worry about. Perhaps, as a sign of good faith, Bennett and his colleagues could undertake to build summer cottages downriver from Muskrat Falls and spend lots of time in them once the dam is up and running.

Meanwhile, our provincial politicians of all stripes, like hypnotized chickens at a travelling side-show, remain mesmerized by the bafflegab of robotic Ed Martin and glib Gil Bennett, both of whom can yammer on for hours without saying a thing, while our interim premier goes on and on about “transparency” as he takes orders from Nalcor, one of the most secretive and arrogant organizations on the planet.

Nothing about Muskrat Falls makes economic or engineering sense to anyone except King Danny and his cabal.

History will not be kind to the perpetrators responsible for pushing so hard for it.

But then, they obviously have no shame.


Anthony Rockel