How did 2.2 million m³ of sand and clay that lay atop the section of the lower Churchill Valley shown in the photo below disappear? The devastated one–square–kilometre site is located across from Edward’s Island — a short distance upstream from Muskrat Falls. Read on and you will find out.
|Site of landslide viewed across the Churchill River from Edward’s Island|
Spur stability problem — specifically Nalcor’s refusal to submit its “fix” for independent
review — still rankles those who have followed the sad
saga of the Muskrat Falls project.
The current $11.7 billion price tag is its
own testament to, among other issues, Nalcor’s incompetence. But its failure to
take every precaution to ensure the dam’s integrity — having been warned of the risks, having closed the door to expert analysis — is another in its list of indictments.
Spur instability problem isn’t about money anymore — that ship has sailed. But four years after project sanction, an independent
assessment of Nalcor’s remediation plan still eludes.
L. Gordon, the highly published Canadian hydro engineer and frequent writer on
this Blog: “every utility I have worked with has welcomed a review board, with
the exception of Nalcor…”
Recently, I revisited a series of photographs of the 2010 Edward’s Island landslide, taken in August 2015, only a few of which got published in a piece for this Blog entitled “Captured By A River Damned”.
The decision to do so now is one more try at killing the complacency that infects the provincial government on this issue. Nalcor has its own reasons for denying the seriousness of the issue. Even Stan Marshall, from whom much was expected, seems to have drunk the Kool-Aid.
The photos are a reminder that a potential collapse of
the North Spur, or large parts of its northern slope, is not a mere theoretical possibility.
Edward’s Island is located between kilometre 72 and 73 as measured from the mouth of the Churchill River, according to AMEC, a consultancy which performed a study of the landslide in 2011. The site is just 20 km or so upstream of the Muskrat Falls project.
comprises roughly 50% of the Muskrat Falls dam.
a 40–to–60m high trumpet–shaped deposit of sand and clay of 1000m length
measured from its north bank at the Trans Labrador Highway, terminating south
at a high rock knoll known by the Innu as Manitutshu Spirit Mountain.
falls are powerful, the landmass around which they flow is described as
geologically ‘sensitive’. Riverbank
calving and landslides along the Churchill River are matters of historical
record. The area is geologically complex, but underpinning this complexity is the threat of naturally occurring and
induced earth movements.
The problem that joins the Edward’s Island slide and the North Spur is a marine clay called ‘quick clay’.
As the nomenclature suggests, they are associated with the last period
of glaciation, popularly known as the Ice Age. The clays were deposited by
glacial melt which raised the level of the oceans. As the glacial ice
disappeared, releasing its enormous weight, the landmass rebounded at which
time the seas also receded, exposing the shorelines of today. In a 1997 scientific article entitled “Quaternary
Geology of the Goose Bay Area” D.G.E. Liverman writes:
last ice age, the whole Lower Churchill Valley was inundated by the sea up as
far as Gull Island and a bit beyond. Consequently, marine clays were laid down
in these areas, after which these clays were covered by more sediments as the
land uplifted. The general limit of glacio-marine clays along the Churchill
River Valley is 100m above sea-level.”
reshape the landscape.
reduced salt concentrations, due to leaching, influences its
sensitivity and causes it to transform rapidly into a liquid state — hence the
term ‘quick clay’. This excerpt from the AMEC Report on the Edward’s Island landslide sums it up nicely:
|Excerpt from AMEC Report on Edward’s Island landslide|
home to one of the largest and most famous quick clay induced landslides. The well-known “Rissa“ slide occurred when a farmer performed the seemingly innocuous task of
digging out his property for a new barn, dumping the clay onto the shoreline
of nearby Lake Botn. The excavation
served as a triggering event causing approximately 33 hectares of farmland to
liquefy and to flow into the Lake within a few hours. The entire devastating
event was caught on film. The video “The Quick Clay Landslide at Rissa – 1978 (English Commentary)” is well worth viewing.
Dunderdale Government sanctioned the Muskrat Falls project in December 2013, but
the words “quick clay” were slow to enter the public lexicon.
Cabot Martin called the North Spur “the weak link in Nalcor’s Muskrat Falls
|Dr. Stig Bernander|
Others, like Dr. Stig Bernander, an internationally renowned expert
on quick clay, and, later, hydro engineer James L. Gordon read Martin’s research and
were aghast that the issue had escaped detailed public examination.
the cost of a three-person panel of geoscientists to review the remediation plan? Likely it would equal a rounding error on the money Nalcor
wastes at Muskrat before breakfast on a single day.
caused Dr. Stig Bernander such concern that he flew from Sweden in 2014 to conduct field research at Muskrat Falls. From there, he returned to St. John’s to lecture at the
LSPU Hall and Memorial — and to warn Nalcor. What did he received for his “pro bono”
effort? Only a dressing down from Nalcor V-P Gil Bennett.
|AMEC Exhibit: See investigated area across Churchill River from Edward’s Island|
|Kayakng the Churchill River August 2015|
The Edward’s Island landslide is one half–day’s paddle from Muskrat Falls by kayak.
In my August 2015 trip
down the Churchill River, I
was accompanied by trip coordinator and kayaker Mark Dykeman.
I am grateful to Mark for permitting me to publish his photographs, which are presented along with some of mine and others selected from a 2014 PowerPoint Presentation by Cabot Martin entitled “Field Trip Report”, based upon the field work of Dr. Stig Bernander in the Lower Churchill Valley area. Other images are taken from the AMEC Report.
Together, they paint a fairly full picture of that landslide — one about
which the public would not be generally aware.
There are a number of possible triggers. Some are noted in the AMEC Report:
Dr. Bernander’s PhD thesis confirms the effect of a build-up of pressure in the slope due to extreme precipitation and adds others like down-slope undercutting by
erosion, seismic tremors, as well as man-made influences like road construction, embankment supports, excavation,
rock-blasting, soil compaction, and interference with drainage. All have the capacity to cause quick clay to
AMEC suggests that the most probable cause was meteorological — a winter period when the temperature was 8 degrees above the norm, causing excessive snow melt and saturation of the river bank.
The North Spur Quick Clay Instability And Landslide Problem: The Weak Link In Nalcor’s Muskrat Falls project By Cabot Martin
The sheer number of causal factors for a landslide within valleys containing quick clay only heightens the risks for a catastrophic event at the North Spur.
|James L. Gordon, P. Eng. (Ret’d)|
James L. Gordon also wrote of the unpredictability of such landslides.
He made specific reference to a slide that occurred in Surte, Sweden:
“The slope in Surte had remained stable ever since it emerged from the sea some
thousands of years ago. Yet, only driving of a few pre-cast piles for the
foundation of a family house in a steep part of the slope was sufficient to
trigger this catastrophic event. Quick Clay was proven the cause. A slope of this kind”, he stated, “may be
regarded as ‘a time-set bomb ticking through the millennia.’”
warning, and one worth noting, Gordon wrote with respect to the North Spur: “It
is essential to ensure that the safety of the natural dam is determined with
precision by geotechnical engineers with “quick clay” experience.”
photographs of the Edward’s Island landslide constitute proof that the demands
of Dr. Bernander, Jim Gordon, Cabot Martin, and the Grand River Keepers of
Labrador (among others) for an independent review of the North Spur design are both reasonable and long overdue.
The landslide at Edward’s Island was measured by AMEC having a volume of 2.2 million
m³. The area of the slide is approximately one square kilometre.
|From Cabot Martin’s PowerPoint Presentation “Field Trip Report” to Central Labrador with Dr. Stig Bernander, October 2014|
|This is a view of the landslide area from across the Churchill River at Edward’s Island|
The photos from our kayaking trip were all taken at grade. Standing on the landslide site at this elevation, several photos are needed to capture the entire area.
In the photo below, the slide carried all surface vegetation to the river. This dead sentry had its roots torn away in the avalanche of sand, clay and mud.
The next two images capture a river flowing not over the hilltop but through it. Sub-surface water flows pose a huge risk to quick clay impacted slopes because they cause erosion and soil saturation. Nalcor has installed a bentonite cut-off wall along the toe of the river at the North Spur to prevent water migration. But test results were never reported as to whether this work was properly completed. Workers performing the installation and hydro engineer James L. Gordon have spoken to the need for such testing.
However, there is a larger issue which Cabot Martin reported on in 2014 — explained in the next slide:
|Excerpt from a Presentation by Cabot Martin, 2014|
Indeed, Dr. Bernander’s concern about the forces acting downhill, and the special character of the clay along the Churchill River, was reinforced just days ago, in technical correspondence with the Grand River Keepers.
The next series of photos depicts specific features inside the landslide area. One can’t help feeling the sense of devastation. The magnitude of the slide simply bewilders. Imposed upon the North Spur, the implications are staggering. Even a landslide farther upstream would likely cause a massive wave to topple the dam.
Nalcor’s proposition is that such an event couldn’t happen at the North Spur. The next photograph, taken during the portage around the Spur is one more piece of proof, if any were needed, that the North Spur contains the sensitive clay called quick clay. It was taken by a third member of the group of paddlers on our 2015 kayak trip down the Churchill River.
|Physical evidence of quick clay at North Spur caught on camera — displaying the same plastic-like property evident in several places at the Edward’s Island site|
The Edward’s Island quick clay induced landslide is only one — and not the largest — to have occurred in the area of the Lower Churchill Valley.
For a mere few thousand dollars, a three–member panel of geotechnical experts could be assembled to perform a review of the North Spur design that Nalcor has, so far, adamantly refused to undertake. The essential issue today is exactly as Cabot Martin described it, following Dr. Stig Bernander’s visit and field work in 2014.
“Even Hatch (Nalcor’s Consultant) recommends a review board with their comment in the conclusions — “Further analysis on the sensitive marine clays with regards to potential loss in strength when subjected to seismic loading is required. This should be coupled with engaging two eminent consultants with specific expertise on sensitive marine clays”.
Perhaps, the Premier’s newly–reconstituted “Muskrat Falls Oversight Committee” can test Nalcor’s resolve to countermand any challenge to its authority. If the Committee has assumed the status of “real” as distinguished from “fake” — the status of the Committee set up under Premier Tom Marshall — it has much to prove. A measure of its resolve is whether it will insist that the review is conducted — with or without Nalcor’s co-operation.
Of course, unless the people of Happy Valley-Goose Bay and Mud Lake realize their predicament — and get angry — the issue will continue to get lost among the one thousand moving parts that make this project a catastrophe.
If nothing else, the Edward’s Island example confirms that a landslide at the North Spur or along the slope of the Lower Churchill Valley goes well beyond a mere theoretical proposition.
And if you have read the entirety of this piece, which has turned out to be far more lengthy than planned, you deserve the reward of seeing two of the many magnificent photographs contained in Mark Dykeman’s collection, taken somewhere on the Churchill River…
See also: Captured By A River Damned (A Photo Essay)