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.
“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.
 |
| 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)
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)
_______________________________________________________________
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
_______________________________________________________________
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