"NORTH SPUR IN A NUTSHELL" A CALL TO ACTION BY CANADIAN HYDRO ENGINEER

Introduction

“North Spur in a Nutshell” is an outstanding piece of work, not just for its conclusions, but also for the clear, evidence based call to action the analysis contains. 

The Quick Clay stability problem is described in the chillingly objective style of an engineer all too familiar with difficult, potentially costly, and project-threatening problems.

In this Piece, just released to the Uncle Gnarley Blog, the renowned Canadian engineer, James L. Gordon, reduces the problem to terms any layperson can understand.

And James.L.Gordon, P. Eng. (Retired), is no ordinary engineer.

James L. Gordon

During a career spanning more than six decades, he has worked on 113 hydro projects, six of which received awards “for excellence in design” by the Association of Consulting Engineers of Canada. 

Engineering projects have taken him to 15 countries; he has served for 9 years as Vice-President Hydro, Montreal Engineering, practiced as a private consultant, served on a number of Review Boards, including for Newfoundland and Labrador Hydro, authored or co-authored 86 papers, and wrote multiple columns published by Hydro Review Worldwide.

His professionalism is unassailable; his contribution to the discipline of civil engineering, especially in the hydro field, is simply vast.

Of course, like another distinguished engineer, James L. Gordon is not new to this Blog (see links below).

Readers will also recognize the name of Swedish scientist, Dr. Stig Bernander, a leading expert in new methodologies for assessing Quick Clay induced landslide risk, who performed fieldwork in Labrador and lectured here last year. 

It is not surprising that James Gordon took notice of Dr. Bernander’s concerns. As the Piece suggests, the two have exchanged information regarding the continuing risk inherent in the Muskrat development.

James Gordon is a long-time advocate of using Review Boards, composed of a small number of professionals, to assess specific complex issues, like the Quick Clay problem. Equally, as a writer and long-time columnist, he is a communicator and instructor.

His 14 point review of the North Spur is as disturbing as it is revealing.

If Jim Gordon’s clarity of prose, as well as purpose, fails to gird us to action, let there be no doubt that this Canadian icon, like the Swede Dr. Stig Bernander, tried his best to get our attention. - Des Sullivan

THE NORTH SPUR IN A NUTSHELL
By James L. Gordon, P. Eng. (Retired)

1. The North Spur is a natural hill 1,000m long connecting Spirit Mountain to the North shore at Muskrat Falls.

2. When the Muskrat reservoir is filled, this hill will form a natural dam containing the reservoir.

3. The hill consists of 3 layers of sand, and 2 layers of quick clay, sloping downstream, on a deep foundation of quick clay extending down to far below tidewater.

4. Quick clay is similar to quicksand. It liquefies when disturbed or when it becomes saturated with water.

5. There are numerous quick clay slides on the North shore upstream and downstream of Muskrat, including three large slides on the downstream slope of the North Spur.

6. As calculated by Dr. Bernander when the water level in the North Spur is 5m below ground level, the natural dam has a safety factor of 1.43. However, when saturated, the safety factor drops to 1.09. This is what would be expected in view of the numerous quick clay slides.

7. NALCOR intends to increase these factors by flattening the slopes, adding a downstream berm, adding pump wells, placing an upstream impervious blanket to close off the upper sand layers, and building a cut-off wall filled with an impervious material to close off the lower sand layer. All reasonable measures.

8. This means that the 2 layers of quick clay will remain within the body of the dam.

9. Dr. Bernander has questioned the use of a cut-off wall indicating that it may be detrimental to the safety factor.

10. To my knowledge, quick clay has never before been used to form part of a dam structure, nor has a dam been built on a quick clay foundation.

11. There is one dam built on a liquefiable silty sand foundation at Duncan Lake in BC. When designed in 1963, it was deemed safe. However, since then earthquake factors have increased, and it would liquefy during a severe earthquake. There is no economical repair.

12. If the North Spur dam fails, there is the likelihood of loss of life in Goose Bay and Happy Valley, and the river will divert to flow through the breach in the Spur.

13. If the North Spur fails, the Muskrat Falls will disappear and be dry. The Hydro facility would become a stranded asset, with a repair cost well over several billions. Power would be interrupted for several years.

14. Since the design of the North Spur dam is without precedent, and the consequences of a failure are catastrophic, it becomes imperative to have the design reviewed by an independent panel of experts – a Review Board, to provide added assurance that the design is acceptable.

Jim Gordon PEng. (Retired)
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Others related to this Post:

DAM BREAK STUDY NEEDS REVISION: HYDRO EXPERT

Confused Minister and a Canadian Solution for the North Spur

Letter From Cabot-Martin to Hon Dan Crummel July 2, 2015

Letter Hon. Dan Crummel to Cabot Martin July 30, 2015

SERIOUS FLAWS REVEALED IN CRUMMELL'S LETTER ON NORTH SPUR