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Clear answers required on design of North Spur dam


Dear editor: I was reacting to an interview on the design of the North Spur Dam between Gilbert Bennett, V.P. Lower Churchill Projects (Nalcor) and James McLeod, TC Media.

The impression I got was that Bennett had little understanding of the challenges posed by sensitive clay underlying North Spur. He seemed to be relying upon the advice of an “independent engineer responsible for project oversight” who had apparently approved the design approach.

This gave me no comfort as this person was not identified and no information was given about his/her qualifications and experience. My recommendation at the time was that Nalcor/SNC-Lavalin should engage world class geotechnical experts to review the adequacy of the design being developed.

Also I asked that the findings of such experts be discussed in an appropriate public arena.

I am pleased to note that Nalcor/SNC-Lavalin have engaged two excellent experts Dr. Leroueil of Laval University and Dr. I.M. Idriss emeritus professor in geotechnical engineering at University of California - Davis.

Dr. Leroueil’s memo report has been published on Nalcor’s website but Nalcor’s Public Relations Dept. has not provided any information on Dr. Idriss’s findings.

It should be noted that Dr. Leroueil’s report was ambivalent. He mentioned that his expertise did not extent to analyses of dynamic behaviour of the North Spur Works. Presumably Dr. Idriss was called upon to give advice on this aspect of design. 

I call upon Nalcor to give an account of Dr. Idriss’s review of the North Spur design. In particular I would like answers to the following questions:

Please give a summary of Dr. Idriss’s expertise for interest of the public at large.

What was the scope of Dr. Idriss’s services and did his services include a site visit?

Were other notable experts consulted, perhaps an expert on construction in sensitive clays?

What factors of safety were adopted and how do they compare to conventional FOS such as recommended by the Canadian Dam Association?

Was a monitoring program recommended to observe behaviour of the structure during construction and has this program been implemented? Have there been any surprises?

Does Nalcor plan to retain, extend or upgrade the system of drainage wells installed following the landslide of 1978 as an additional protective system?

Given the great interest and concern of the Newfoundland public about the design of this structure and the fact that this is a pioneering effort in dam construction on sensitive clay foundations I do not think it is too much to ask that Nalcor provide clear answers at least to the above questions. May I suggest that these replies be provided to the public via the medium of TC Media.

Phil Helwig, St. John’s

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