By Gagandeep Ghuman
Published: June 8, 2015
ON APRIL 19, a massive rock slab fell off the North Wall of the Squamish Chief, rattling windows and shaking the earth. It was 1,200 to 1,600 cubic metres of granite that sheared off the forest below and slumped into a heap of debris. It made such heavy noise that a Valleycliff resident thought an aeroplane had smashed into the Chief.
The district commissioned a report by GeoPacific Consultants which estimated that events of similar magnitude have a return period in the range of 50 to 150 years along the North Walls area of the Chief. The rockfall had shaken the town—and the report lulled it back into its routines: It’s possible most of Squamish residents would not see another such rockfall in their entire lives, if one goes by the report.
However, a closer examination of the report and interviews with its author and other geologists of the area reveal contradictions, glaring omissions and sweeping generalizations that create an impression of minimal risk. At the heart of the report is a missing piece of data as glaring as the huge red scar the rockfall has left on the North Wall of the Chief.
“A return period of 50 years does not mean that the next rockfall of that particular size will happen 50 years from now, or that it cannot happen tomorrow, or even twice in 50 years. Rather, it is a statistical average of two events” Prof. John Clague, SFU.
According to John Clague, a professor at the Department of Earth Sciences at Simon Fraser University, a return period is the theoretical average time interval between events of a particular size, in this case rockfalls of a specified size.
Prof. Clague says a return period of 50 years does not mean that the next rockfall of that particular size will happen 50 years from now, or that it cannot happen tomorrow, or even twice in 50 years. Rather, it is a statistical average of two events. It means that a rockfall of the size that occurred earlier this month will, on average, happen once every 50 years.
First, it’s odd for GeoPacific to come to such a sweeping conclusion about the whole North Walls when they were doing only preliminary investigation and that too of its very small part. Second, they simply miscalculated.
The glaring omission of the district-commissioned report is the partial knowledge of events which led it to miscalculate the return period of a similar event. The report says: “It is believed that the magnitude of the April 19, 2015 rock fall was greater than any rockfall which has occurred in this area in at least the last 60 years. This belief is supported by the mature growth forest which extends to the base of The Chief along the North Walls area.”
The “belief” that led them to calculate the return period is, however, innocent of at least one vital piece of historical data.
In 1999, rock slabs, double the size of the recent one, fell off the North Walls of the Chief, obviously with much more drama. According to a January 19, 1999 report in The Squamish Chief newspaper, the rockfall “sounded like thunder, shook windows and rattled residents.”
It also caught the attention of the late Squamish geologist Frank Baumann, who estimated that two large slabs containing a total of about 2,500 cubic metres of rock—the size of a small house and twice the size of the recent rockfall—fell 400 metres vertically, crashing back into the wall and breaking into smaller pieces. By the time the rock hit the ground, the largest pieces were three metres in diameter, enough to destroy a hectare of forest. Two other rockfalls, a few hundred cubic meters each, followed 30 and 45 minutes after the major rockfall. The sound of the rockfalls rattled windows in Valleycliff and sent sound waves
into downtown offices, prompting people to call Baumann, wondering if their homes were in danger.
Valleycliff residents had nothing to worry as the rockfalls were outside the shadow zone, Baumann observed in the newspaper report. But he pointed out that these rockfall events could be expected to occur “every five years or so”.
Why does the district-commissioned report fail to reckon the 1999 event in its calculation of return period? Because the authors of the report were simply not aware of the magnitude of the 1999 rockfall. Steve Fofonoff, the report’s author, said he was aware of some report that Baumann had prepared but the, “accounts [that] we had indicated that it was much smaller than the recent rockfall”.
Fofonoff said GeoPacific had based its conclusions on information provided by the district and the province. “Based on information provided by the ministry and the district, this is what we have,” he said.
After first betraying lack of knowledge, then saying they were not told about it by the district and BC Parks so they did not take note of it, he went on to question the size of the rockfall—and the veracity of Baumann’s observations in 1999—saying that there was no official report and it was based on Baumann’s opinion and anecdotal accounts.
“Well, but that was Frank’s opinion. Is there a sealed report that says that? He can just call up the newspaper and tell them things but if there was a report that was made and it was verified and peer-reviewed, I’d like to see that,” Fofonoff said.
It’s odd that a geologist would choose to depend only on the district and province for the historical data of his own field. What’s even odder is that GeoPacific dismisses Baumann’s estimate as mere opinion when it repeatedly describes its own conclusions as nothing more than just opinions.
Oldrich Hungr, a professor of Engineering Geology at The University of British Columbia, says the return period in the report is exactly right because the last major rockfall that he heard from the Squamish Chief was in 1946 during the Van Island earthquake. When we tell him of the 1999 rockfall, he says, “Gosh, I didn’t hear of that. Although I live in Vancouver, I haven’t heard of that one.”
The report not only falters in its basic calculation, but is also riddled with contradictions and rank generalisations. Consider this: The report states that the authors have limited their review to the portion of the Chief where the rockfall occurred. “We have limited our review to the portion of The Chief where the rockfall occurred on April 19, 2015 and the immediately surrounding rock,” the report says.
And yet, they have extended their conclusions on the return period to the entire North Walls of the Chief—an area they haven’t studied and about which they lack sufficient historical data.
The conclusions about return period in a preliminary report seem out of place and also misleading.
And this when Fofonoff himself says, “We weren’t hired to assess the risks…that wasn’t part of the report. This was an initial review of the rockfall. This report isn’t the end of it. This doesn’t include a probability-based risk assessment.”
Even when it comes to the cause of the rockfall, the report does not convince many geologists who think it’s premature, speculative and hypothetical.
The report says the rockfall occurred because of root-jacking, a process in which the roots grow in cracks in the rock and then start jacking the rock outward. “I guess in a lot of ways that would be the root cause, if there were not roots growing in the cracks, it likely won’t have fallen,” said Fofonoff. He compared root-jacking to putting a flat tire at the back of the rock. As the roots grow, they pump out the rock. “There are quite tall trees on that block, probably 8-10 metres high, and they would have a big root system and they will be going into the cracks and with all the water they can get they get bigger and bigger and start pushing the rock outwards.”
“It’s just a guess, it’s hypothetical, that’s all. They had to come up with something. Well, it’s because they want to give a reason, so they give a reason. Because everyone thinks of a trigger.” Pierre Friele, Geologist
While some geologists such as Glenn Woodworth support this theory, others such as local geologist Pierre Friele and Prof Clague of SFU doubt if root-jacking was the only cause as the report claims.
“It’s just a guess, it’s hypothetical, that’s all,” says Friele. “They just had to come up with something.” But why would professional geologists do that? “Well, it’s because they want to give a reason, so they give a reason. Because everyone thinks of a trigger. When I write a hazard report, the first thing I do, I examine weather condition and look for a trigger. If you can pinpoint something, that allows you to manage the risk. We try to associate an event with a triggering mechanism, because if you can pinpoint something, then may be that gives us a reason to manage the event. In this case, there is no obvious triggering mechanism, there was no frost, no extreme rainfall, there was no extreme temperature so there was no obvious trigger, so they invent one…the trees grew root.” But Friele also adds if there is no way to prove that the rockfall happened because of tree-jacking, their is no way to disprove it either. He thinks the cause could be just natural weathering. “There are time and gravity. With time, you have slow weathering, and at some point, slow weathering and gravity meet a threshold and the thing breaks free. It doesn’t necessarily has to be this trigger, like an agent back there that pulls the lever.”
But Prof. Hungr somewhat agrees with the findings of the report. “The root activity will put pressure inside the open joint. It doesn’t require too much pressure to fall off the edge. It’s like a book that is on the edge. The roots do open up cracks. This was on the verge of failure. It doesn’t take very much force but it’s a little premature to say that it was only root-jacking.” But he agrees that root-jacking could be the last straw that pushed it out.
“One thing is that joint behind the slab of rock was open. You can see it for the discoloration. It’s a process called exfoliation where several agents work in the joints, water pressure, freeze thaw, root-jacking. In this case, it was aggravated by the fact that it was a very heavy slab and rested on a narrow ledge, and that rock may have been a little bit less massive than the other rock. It seems there was some crushing in the foundation, in the little shelf that the rock was standing on,” he says. The report too mentions the crushing in the foundation that contributed to the fall of the rock.
Woodsworth doesn’t find it so difficult to believe. “You will see the whole area is stained, and that is the result of weathering of the rock. It’s been loose for a long time, and if there is any place, the water will get down there and the roots will go down there. You can see that tree roots even push the sidewalks and they can do a lot of damage,” he says.
Prof. Clague says there were probably roots in the fracture, but it leaves open the question of how significant it was as the cause. “Roots don’t normally exert strong enough pressure on the rock to significantly displace it,” he says. “Well, it’s one cause. It’s not the total explanation for it. Clearly, there are trees on that slope. The roots do get into the joints and they can cause the rock to expand but fundamentally that is not the cause. The cause is the fact that there are fractures in the rock. The Chief has a lot of fractures. It’s a very strong granite rock but the weak links are the fracture points. A block of that rock mass failed along an already established joint.”
Fofonoff said it was really hard to get geologists to come to the same conclusion and that root-jacking was his opinion which he shared with the co-authors of the report. He said it needed to be stressed that this is a preliminary report based on observation and that they were not asked to carry a comprehensive probability-based risk assessment for future users. “I’d like to focus that it’s preliminary and further review may be carried out,” he said.
The variety of views on the cause of the rockfall indicates the report’s findings are, at best, opinions—preliminary opinions based on basic observation. And to be fair to Fofonoff, he admitted he was willing to re-evaluate his opinions in the light of a new opinion—even though this stance makes his return-event prediction even more incredible, and quite superfluous.
When it comes to the limited analysis of the rockfall area, the report makes clear recommendations of scaling in the area, closing of the Angel’s Crest access trail until the hazard is determined to be acceptable, and a geotechnical assessment of the source area by a rock mechanics expert. According to the Ministry of Environment, rockscalers were out last week following the report’s recommendations and geo-scientists were studying the stability of two remaining areas of concern.
Perhaps, no one publically challenged the report for diluting a major risk because there is a general perception that the rockfall risk is acceptable and little can be done about it beyond local and immediate measures such as rock scaling. That’s why the Ministry of Environment has never had any hazard study done on the Chief. Nor do they plan any after this rockfall. “We are not planning any further assessment beyond that being conducted by the geotechnical engineer this week,” it said in response to a question.
Geologist and climber Friele says a further study of the climbing areas isn’t needed because the risk is acceptable. “There has been climbing on the Chief since 1968 and there has never been a rockfall fatality. Risk of fatality is infinitesimally small,” he says.
Friele also thinks a hazard study on the Chief is not advisable. “You’d be spending hundreds of thousands of dollars if you were to do a study on the Chief. They’d have to have people clambering around, documenting every loose block.” When asked if the risk was ever quantified by anyone, he says,“I’m speaking both as a climber and a geologist. The rockfall is so infrequent, and the evidence of fatality is non-existent. There is no demonstrated risk. There has been no death. There is low risk, and it’s well below what we would consider unacceptable. It’s very acceptable.”
Prof. Hungr shares Friele’s view. He says rockfall is a natural process and climbers are aware of the risks associated with climbing on the Chief. “This has been going on with this intensity for the last several decades and no one was ever hurt, even the climbers were not hurt. So, it’s a natural process, if you have a cliff like that, things are going to fall off it,” he says.
Indeed, climbers embrace risk, even if it’s the extra risk of rockfall. Ramey Newell, a blogger, recounts a near-death experience on her blog Ramey on the Road: “Two months ago [July 2013] I found myself pondering death in a more immediate way than usual. In fact, I was pretty certain I would be dead less than thirty seconds from the time this thought first arose. Aside from my blood-curdling scream and subsequent adrenaline-induced hyperventilation, I was pretty calm about the prospect of impending death. We were in Squamish, British Columbia, on a climbing trip (part of my Pacific Northwest road trip). Ben and I had decided to climb one of our favorite routes at the base of the Stawamus Chief, a 2,300-foot granite monolith overlooking the sparkling turquoise fjords of the Sea to Sky Highway. The weather had cleared after a day of heavy rain, and we were about a hundred feet of the ground when we heard it.
“A thunderous crack. A crashing, rumbling, echoing roar interspersed with the screams of other climbing parties higher up on the wall ahead of us. As I looked up, I realized that everyone was yelling, “ROCK!” As a climber, this is never something you want to hear.
“And there it was. Or, more accurately, there they were. A portion of the wall had broken away from a ledge about 1,000 feet above us, and came crashing down the cliff face in pieces. Some of these chunks were fist-sized, and others were proper boulders. Any one of them would have either killed or seriously maimed us.
“I screamed as I watched the huge granite projectiles hurtle toward us. A few of them bounced off the low-angle cliff face less than a hundred feet above us, separating into yet more deadly missiles…
“Later, someone asked me if this experience would make me more nervous about climbing as recreation. I didn’t really even have to think about it. No. Absolutely not. Fact: We all engage in dangerous activities every day, and some of us will die while doing them.”
On an Internet forum, Baumann probably wrote about the same rockfall: “A strange little rockfall occurred on July 1 just below the crux move on the 3rd pitch of Sickle. There is still some potentially unstable rock hanging there, so be cautious. B.C. Parks decided to scale the rock in this case because of the potential threat to climbers below, Highway 99, and the B.C. Hydro power lines, but it is certainly not possible for them to scale all areas of loose rock; everyone must accept the fact that there is a certain amount of inherent risk when you climb on the Chief.”
However, not all rockfall risk on the Chief is acceptable. And it rarely gets the attention it deserves. Once in 2012, Baumann came across a rockfall risk he would call totally unacceptable.
Above: Nearly 20 tonnes of rock hit the Stawamus Chief trail, crushing one of the staircases on the lower part of the popular hiking trail, about 200 metres up from the trailhead.
Nearly 20 tonnes of rock hit the Stawamus Chief trail, crushing one of the staircases on the lower part of the popular hiking trail, about 200 metres up from the trailhead. The rock slab started a few metres above the trail, and then broke up as it hit the trail. The rockfall occurred a minute or two after four hikers had passed by the area. One among those lucky hikers was Baumann’s daughter, Julia Baumann. He wrote on another Internet forum: “We are Christians, and my wife had specifically prayed that morning to keep our daughter safe; for some reason, she had an uncomfortable feeling that something wasn’t right. Needless to say, when we heard what happened, we thanked God for an answer to prayer. Imagine, if she had been delayed by one traffic light driving to get there, she might have been killed!”
Julia Baumann still remembers the day as if it’s etched in her memory: It was a Monday and every Monday she would drive from Vancouver to hike the Chief. On June 18, she and few of her friends came around 5 pm for their regular Monday hikes. A few minutes after they had passed the staircase, they heard a loud thudding crash. Julia recalls they kept walking thinking a tree had fallen on the trail. They were told later by other hikers that a rock had fallen on the staircase. It’s only when they saw the rock, they knew they had been lucky.
“When we walked down, we were shocked at how big this piece of rock actually was. “It was a massive slab of rock and it was blocking the trail so it was exactly where any hikers were going up would have been. It literally took out the staircase and blocked part of the trail.” Julia Baumann.
“When we walked down, we were shocked at how big this piece of rock actually was,” said Julia. “It was a massive slab of rock and it was blocking the trail so it was exactly where any hikers were going up would have been. It literally took out the staircase and blocked part of the trail.”
Julia says if they hadn’t been five minutes early, they would have been crushed immediately. It was a huge rock, probably 10 by 5 feet across, she says. “It was a massive boulder that would have crushed hikers immediately had they been there. You breathe a sigh of relief when you see how close that could have been,” she said.
Julia says she knows hikers are aware that there is a certain risk attached in exploring the wilderness but feels the government can take up some measures such as putting up warning signs along the trail.
“It was a really close call and there could have been some really serious repercussions,” she says.
Prof. Clague says he’s surprised BC didn’t order a study after the event. By comparison, US Geological Survey has conducted a detailed rockfall hazard risk studies for Yosemite Park where there are lots of people in the rockfall shadow areas. “In Yosemite Valley, you have near-vertical granite faces and there have been rockfalls that have killed people. It’s a very user-intensive area. You get tens of thousands people in the valley. And they did a wonderful geological study to document the risk. It was done by the US Geological Survey and it wasn’t triggered by or the consequence of one particular event.”
While it is understandable that climbers will accept whatever risk comes their way, the thousands of people who use the trail are not trained to handle risk. Nor are they out looking for near-death experience. So, even the North Walls may not need a study, the hiking trail certainly does.
Friele agrees that a study of the trail would do no harm since the trail is so popular and there are thousands of people walking every year. “The trail is used by hikers who are not aware. There are lots of people going up and down, so the exposure is very high. The climbers, because they are climbers, they should be more attuned to the environment. The tourist are not attuned. They think they are participating in a safe activity since it’s a trail,” he says. Prof. Hungr says they conduct studies in Yosemite because they do have roads and campsites in the rockfall shadow area unlike the Chief. “But if they have had an event at the Chief trail, I think it may be a good idea for some kind of inspection.”
Prof. Clague also says since lots of people utilise the Chief for recreation, the area requires study. “We are a little blasé about it,” he says. “The individual risk when they climb on the Chief is low, but when you look at more societally with thousands of people who come to climb, then it’s a different game. Then you have to worry about the group risk. In other places, where there is such activity, there would already have been a study, and that is why I’m interested. This event has raised my curiosity as to how serious the risk is. We normally think of these things occurring in bad weather. I don’t think they only occur in the winter but can occur anytime.”
This summer, Prof. Clague and his SFU colleague Prof. Doug Stead will be studying the Chief along with two summer students. They plan to do laser and photographic scans to generate 3-D images of the Chief. Such a study, Prof. Clague says, is manageable with remote-sensing tools that provide 3-D distribution of the rock fractures. “You are looking for a needle in the haystack but that analysis is feasible and we do it all the time,” he says.
Even a little investigation into the matter will show that rockfalls, big and small, keep happening everywhere on the Chief, and the lack of sufficient historical data should discourage anyone from terming them rare. The lack of fatality shouldn’t be the basis to measure acceptability of the risk. Should we wait for a death to occur to take the risk seriously? Not in case of the Chief, since it is more than just a mountain—it’s an economic asset. Anyone can well imagine what it would do to tourism if ever there is a rockfall fatality on the hiking trails.