THE NORTH SPUR: WARNINGS IGNORED

Guest Post by David Vardy
Many warnings about the North Spur have been ignored.

Dr. Lennart Elfgren and Dr. Stig Bernander, both full professors at the Lulea University of Technology in Sweden, wrote the Minister of Natural Resources on August 1, 2019.  In their technical report entitled A Downward Progressive Failure of the North Spur at Muskrat Falls - A Possibility that ought to be investigated and mitigated, dated July 25, 2019, submitted to the Minister, they said that “The most critical inclined progressive downward failure surfaces of the North Spur at Muskrat Falls have not been properly investigated. Relevant stress/strain properties of the metastable soil layers have not been made available, and no independent external experts seem to have reviewed this aspect of the stabilization work.”

They said that old methodology was used to assess the safety of the North Spur, the same model which had been used unsuccessfully at other failure sites, such as Mount Polley, a copper/gold tailings pond owned by Imperial Metals and located in central British Columbia. They repeated their call for an independent panel of experts to undertake the research and to assess the need for further remedial work.

NORTH SPUR: JIM GORDON TRIES AGAIN TO GET SIOBHAN COADY'S ATTENTION

Dr. Stig Bernander

Editor's Note: Canadian Hydro Engineer, Jim Gordon has worked hard to get successive Ministers of Natural Resources, including more recently Siobhan Coady, to take seriously the geotechnical analysis conducted by Swedish scientists Dr. Stig Bernander and Dr. Lennart Elfgren in relation to the North Spur, but without success. 

The Spur is a natural formation which forms part of the dam structure for the Muskrat Falls project. The feature contains clays defined by experts as "sensitive" because under certain circumstances they have the capacity to liquefy and to collapse. The issue is increasingly urgent because Nalcor, in a matter of days, will begin filling the Muskrat reservoir to the 39 meter level. 

VARDY/PENNEY SEEK EXPERT PANEL ON NORTH SPUR

Guest Post by David Vardy and Ron Penney

The recently released SNC Lavalin risk assessment report identifies the dearth of geo-technical investigations as one of the highest risks of the Muskrat Falls project. In his Uncle Gnarley post of June 29, 2017 Cabot Martin cites this report to confirm his claim that the North Spur is one of the major threats to the project and to the people living and working close to the site. The SNC report refers to “major scope change.” Cabot states:

Now “major scope change“ with regard to an admittedly unstable dam component like the North Spur is engineer code for “Your proposed North Spur stabilization design could be unsafe and to make it safe will require as yet unknown and un-costed extra work.”

And also unstated is that geotechnical conditions may be found (like Quick Clay) which will in effect be impossible to cure.

MUSKRAT: WHY A REVIEW BOARD IS ESSENTIAL FOR THE NORTH SPUR

Guest Post by James L. Gordon, P. Eng. (Ret'd)

I have mentioned several times that a review board is essential for the North Spur. 

Perhaps I should summarise the reasons particularly since the Owner’s engineering consultancy - Hatch - has made the same recommendation.

It is acknowledged that the North Spur natural dam is the first time a dam containing marine clay and founded on a deep deposit of marine clay has been used in a hydro dam. All major “firsts” always have a review board to add assurance to the design. I have worked on three dam “firsts” and all had review boards, and all benefited from their advice.

The first was at Duncan in BC, which is founded on a deep deposit of unconsolidated liquefiable silt. It holds the world record for settlement as predicted, at now over 6m. We had a 4-man review board which made significant changes to the project layout, adding to security.

The second was at Bighorn in Alberta, where the deepest (to date) cut-off through gravel and boulders was part of the dam. There we had a 2-man review board, including Dr. A. Casagrande from Harvard. He made a major change in the dam design which, on hindsight, avoided a possible dam failure.