The Uncle Gnarley Blog has a new website. Click here to visit to view the latest posts!

Monday, 20 March 2017



Independent Dam Safety Review And Audit By Hatch
February, 2017

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

James L. Gordon, P. Eng.
I have read the "Hatch "Audit" released by Nalcor just a few days ago. The first issue that I noticed is that a company cannot “audit” its own work – it is a blaring conflict of interest, and I am surprised that Hatch accepted the assignment. Of course everything is perfect, why would Hatch say otherwise when commenting on their own work?

The second issue is that the report is limited to a review of the project management and operation – quote from slide 11 - “The objective of this presentation is to cover the results of a dam safety audit and overall review performed for the Muskrat Falls GS between January 29 – February 2, 2017” And – quote from slide 17 – “The review of the design of structures did not form part of this audit”.

So, the entire report can be deposited in File 13¹. Bearing this in mind – what is missing from the report? The immediate reply is no numbers! The entire report is based on the opinion of one geotechnical engineer, with no supporting documentation. I would have expected to see at least the following -

From the Executive Summary –

1.      Quote from Slide 5 - “Inspection and reporting – Extensive instrumentation, real time data and collection and assessment”. This is similar to a doctor asking an intern how the patient is progressing, and receiving a reply “Well, we are monitoring his heart, measuring blood pressure, pulse rate and oxygenation”. The intern’s reply does not tell the doctor whether the patient is progressing or on the verge of passing away. In the audit there is no data and no analysis of any data.

2.   Quote from Slide 5 - “Emergency preparedness – Well documented, dam break assessments performed, actual level 2 emergency response performed”. During the cofferdam incident last November, the emergency preparedness plan was found to be deficient when the residents of Mud Lake were not notified of the emergency. There is no mention of how this was rectified, nor any mention of a test of the system. Tests are essential, and usually reveal the weak links in the command structure.

3.    Quote from Slide 5 - “Operations, Maintenance and Surveillance – Number, quality of instruments and surveillance frequency exceeds typical industry best practices”. See comment #1. There is no mention of instrumentation data.

For example – some North Spur piezometers reacted to an increase in headpond level several years ago. How did the same piezometers react to the increased headpond level last November? Was there no reaction confirming the impermeability of the cut-off walls?

Another example – impermeable clay and till placed on the face of the North Spur and in the cofferdam needs to be compacted to 95% Proctor (a measure of the compaction) to attain the required impermeability. There is no mention of how many tests achieved this standard, and no mention of the percentage of tests below 95%.

And another example – the spillway and intake form part of the dam containing structures. There is no mention of the compression tests on concrete cylinders from each concrete pour – how many achieved the required strength and what % were below strength.

4.  Quote from Slide 6 – “Upstream cofferdam remedial program – Cofferdam instrumentation, monitoring and inspections sufficient to minimize risks while cofferdam is remediated” See comment #1. The only way to tell whether the remedial measures are effective is to monitor the volume of seepage. This is difficult in winter with everything covered in ice and snow.

There is mention on slide 51 that cofferdam seepage is currently being read once per day, and during impoundment the rate will increase to every 2 hours. This is reasonable, but the method of recording seepage should have been mentioned, and data provided for seepage flows since the completion of the two upstream temporary cofferdams.

The chart on Slide 43 shows piezometer water levels, with only one piezometer (0+291) showing any decrease as would be expected from the remedial measures. Without knowing the precise location of the piezometers, interpretation of the data is not possible. A drawing showing a cross-section through the cofferdam with piezometer locations is missing.

The next chart on Slide 44 shows the reaction of piezometers to the rising water levels. However, there is no link between piezometers to show the reaction of individual piezometers, which moved up, and where were the piezometers located with respect to the cofferdam cross-section.

Other miscellaneous comments on lack of numbers are –

5.      About the middle of the presentation, slide 33 shows a plan photo of the cofferdam taken last fall, before major seepage started. It clearly shows the green seepage flowing across the dewatered area between the cofferdams, and the green discharge from the downstream culvert. This seepage should have been stopped prior to placing the impervious fill between the two upstream temporary cofferdams, and is the reason for current difficulties. Impervious fill should have been placed on the face of the upstream cofferdam until the seepage stopped.

6.      On the cofferdams, there is the statement, from slide 35, quote – “Current levels of leakage in line with what would be expected for a cofferdam of this type” I would beg to differ. The seepage through the upstream cofferdam was excessive from the start, it was never staunched and resulting in depositing the impermeable clay through water, with the fine material coming in contact with the rock foundation being flushed downstream, resulting in the current seepage issues.

And from the same slide – quote – “Remediation program underway to deal with increased leakage that occurred on first impoundment ‒ Measures are appropriate and appear to be effective.” The continued grouting program, now extending for almost 4 months since the seepage increased on headpond filling and no decrease in piezometer water levels contradict this statement.

It would have been far preferable to engage a consultant with no prior contracts with NALCOR to undertake the audit. There are several such as Klohn Crippen Berger and Golder Associates with an office in St. Johns. If there is another audit, NALCOR should consider the above consultants.

To reiterate – it is not possible for a company to audit its own work – put the report in file 13 and forget about it.

Jim Gordon P.Eng.  (Retired)

1. "File 13" is a euphemism for the trash can.