11 March 2013

Muskrat Falls weakness: the North Spur #nlpoli

The north side of the site of the future Muskrat Falls dam has a problem.  The soil is made up of clay that has a tendency to sheer away in landslides when it gets too wet. The North Spur, as it is known, is a key part of the reservoir.

Cabot Martin has documented the whole thing in a slide presentation based on documents released during the environmental reviews of the project.

According to Martin, Nalcor won’t have a potential solution to the problem or know the cost until sometime this year.

northspur martin

That’s a slide from Martin’s presentation.

Martin notes that the upstream section river, on the left side of the slide is about 18 metres above sea level naturally.  The Muskrat Falls dam will raise the water level to 35 metres above sea level.  The North Spur is thus a major part of the reservoir since it will be holding back the water in addition to the dam sections to be built on the lower falls (the lower right hand side of the slide)

A major landslide in 1978 prompted Newfoundland and Labrador Hydro to install a pump system to drain water from the downstream side of the spur.  In 2008,  Nalcor commissioned a review of the existing pumping system in an effort to determine how to keep the water pumping system working successfully for another decade.

Remember that in 2008, Muskrat Falls wasn’t a key part of the Lower Churchill project.  Nalcor was focused on building Gull Island.  Muskrat falls was something they might build, maybe, if needed.

To give a sense of the slides that these soil conditions can produce, take a look at this documentary of a slide in Norway almost 30 years ago.

What Martin is talking about here is not an issue Nalcor doesn’t know about or hasn’t address.

It is a significant issue, though. One of the factors that drove up the cost of the project was a major design change apparently to use the water at the site more efficiently.

The North Spur problem might be solved with continued use of wells and pumps. That’s the low-cost outcome of the deeper engineering studies.  At the other end of the cost spectrum, we could be looking at construction of a new dam on the upstream side of the North Spur.

Time will tell which it will be