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Feature Garibaldi's demise

Does an unstable geological formation continue to pose a threat? Did it ever?

Doug McDonald, the owner of Alpine Lodge, has forgotten exactly where he was when he learned that the residents of Garibaldi were going to be expropriated because of the threat of the Barrier collapsing. But, he remembers the day.

"It was on May 18, 1980, the Saturday morning that Mount St. Helens blew," he says.

A B.C. Hydro employee had approached him.

"He indicated that, he had seen on somebody's desk a paper that turned out to be word for word what was in an Order in Council," McDonald recounts.

The Order in Council, passed by the provincial government, meant an end to the small community of Garibaldi, which was situated on the banks of the Cheakamus River just south of the Daisy Lake dam. It was determined that the Barrier, a headwall above Rubble Creek that holds back three lakes, was unstable. If the Barrier ever collapsed the results would be catastrophic for Garibaldi.

McDonald had spent his summer months working on the construction of the Daisy Lake dam before moving with his family to Garibaldi in October, 1966, with the intention of settling there. In addition to Alpine Lodge, McDonald built up a general bulldozing business. With the anticipated growth of Whistler, he had envisioned a secure future for the tiny community of Garibaldi. And by 1980 there were more than 100 residents there.

"We had over 400 acres," McDonald says. "I was gradually building up an equipment base so that come somewhere in the late '80s, I was planning to retire from active outside work and start doing work on our property towards a phased development of a subdivision into affordable-type housing. I figured Garibaldi would be the bedroom for Whistler."

McDonald wasn't the only person interested in the potential of Garibaldi. A developer had built water and sewer services for a subdivision he proposed for the area. But the Department of Highways started getting calls from people worried about the collapse of the Barrier and the project was turned down. A judge in the ensuing court case ruled that the expected frequency of landslides in the area was too high, which put an end to any development plans for Garibaldi.

Frank Patton was one of three co-authors of the Report of the Garibaldi Study Group, which was struck to determine the stability of the Barrier. Patton and co-author Alan Williams, MLA for West Vancouver Howe Sound, were concerned with digging up all the relevant facts and interpreting them as best they could.

"Our objective was to make the report understandable to the residents," Patton recalls.

The threat of the Barrier collapsing and sending a rock avalanche down Rubble Creek seemed star crossed with the eruption of Mount St. Helens and the massive debris torrent that followed.

"The government reacted to Mount St. Helens and made an offer to allow people to get out of Garibaldi," Patton says.

The study group's findings were presented by Patton and Williams at a meeting at Alpine Lodge.

Patton thought that the response from the residents at the meeting on that beautiful spring morning was good. McDonald remembers the day differently.

"It was a jolt," McDonald says, "because most of the residents were aware of what Rubble Creek had been doing for the last 70 years. There were old timers still living telling us tales of what had occurred over the years in that creek. And those tales explained virtually everything about that area."

At first the residents of Garibaldi refused to accept that they were going to have to move.

"Fur's gonna' fly!" Diane McDonald exclaimed outside the lodge the day after the meeting.

Then the reality of the threat of the Barrier collapsing began to set in.

"They're so scared they can't sleep at night," one resident said referring to his children.

Most of the residents grudgingly accepted the expropriation. Many moved to Black Tusk Village. For others the news was devastating.

"They're not paying anything for vacant land!" a voice echoed from inside the lodge at the end of a telephone conversation.

Geological origins

There's an eerie kind of silence when one steps onto the debris slope below the Barrier. Stunted, bent-over evergreen trees seem like old men frozen in time in the boulder fields and clutches of willows. Supposedly born 10,000 years ago when a volcano eruption spilled lava down the slopes of Clinker Peak onto a glacier that filled the Squamish Valley, the river of lava cooled and solidified against the ice near Rubble Creek, forming the Barrier.

"The Barrier is such a peculiar place," Patton says mystically. "It's effectively the highest earth- and rock-filled dam in the world. It has these large springs coming out of the base that no other dam in the world has."

Shear cliffs rise 500 metres above the headwaters of Rubble Creek, 5 km from the Sea to Sky Highway and the banks of the Cheakamus River. The silence is broken only by the sound of falling rock, that you can't see, and rushing water. This water is one of the factors that could trigger a major landslide of the Barrier, like the one that occurred in 1855.

The surface water in the boulder field below the Barrier comes from the large springs at the foot of the Barrier, where water leaks from Barrier Lake, Garibaldi Lake and Lesser Garibaldi Lake. All three lakes lie along the margin of lava flow from Clinker Peak, at the contact between the lava and much older rock that is virtually watertight. The leaky part of the lava flow is on the surface where gaps and passages between loose blocks of lava easily provide an escape for water. And the volume of water leaking from these lakes during some months of the year is formidable.

A transportation route

The route that Highway 99 takes through the Sea to Sky corridor has always been plagued with uncertainty. Up until the early 1800s the corridor from Burrard Inlet to Pemberton was well travelled by First Nations people who traded highly valued oolichan oil with Interior native bands.

But it was the discovery of gold in the Cariboo in the 1850s that attracted more attention to the route as an alternative to travelling up the Fraser Canyon or Harrison Lake.

In 1858 John Mackay, an employee of the Hudson's Bay Company, and William Downie, a British Major, made a survey to investigate a possible route from Howe Sound to Lillooet. Travelling from Pemberton and crossing the Alta Lake watershed, Mackay and Downie came upon what appeared to be a large landslide at Rubble Creek. Downie wrote about crossing a broad tract of land where not a trace of timber was left.

James Douglas was the governor of the Crown Colony of Vancouver Island when Mackay and Downie went through on their survey. Douglas had been alarmed by the onslaught of American prospectors heading for the Cariboo gold fields. And by 1858, the year New Caledonia was declared to be a Crown colony called British Columbia, Douglas was committed to curbing American territorial ambitions.

Governor Douglas did not act on Mackay's recommendation that a route from Pemberton to the Pacific be adopted. The Rubble Creek landslide and the threat of the Barrier collapsing may have been a catalyst for Douglas's decision, but the governor may also have been guided by a determination to halt American ambitions and not make access to the Cariboo any easier.

Disputed history

Almost a century and a half after Douglas's decision, rock dislodges daily from the Barrier. But rock falls today pale in comparison to the slide that most people believe came down in 1855 when a giant slab - 610 metres from one end to the other and 244 metres high - broke away from the cliffs. Snaking from one side of the Rubble Creek valley to the other, rising up one slope then falling back and crossing at an angle to the other slope, the slide is estimated to have travelled at 96 km/h before finally coming to rest at the Cheakamus River.

Doug McDonald has other ideas about the rock debris.

"One thing that you need to know about the Barrier," McDonald continues, "was that never was it ever proven that there was ever a landslide. The whole speculation was on the basis of a British army major who was doing some survey work for the Pemberton Trail. He came upon immense devastation and he said 'landslide'. Now, he was not a geologist. He was not even a good surveyor, I don't believe. But, he was doing that kind of work and it's on the basis of what Major Downie had to say that all of the landslide theory was put forth."

The information that McDonald has gleamed in the last 40 years from digging and excavating and watching Rubble Creek flood indicates to him that the means of transport for the rock debris was other than straight gravity.

"Water and ice," he says assuredly. "Clues are there for both. You just have to be smart enough to read them."

"Interesting," I add, "given that the volcano came up through the top of a glacier."

"We don't know that!" McDonald retorts. "Who was here to see it?

"When you look at the Barrier, the southerly end of it has got quite a heavy coating of ground cobbles and fine sands and silt. This did not get there on its own. And nobody has ever explained how it got there."

"What we know about the formation of the Barrier is that it's pervious," Oldrich Hungr, a professor of Geology with the department of Earth and Oceans at the University of British Columbia, explains. "Rubble Creek flows right under the lava flow and not on the surface."

The Barrier is made up of layers of lava and rubble.

"Lava came off the mountain and ponded behind the ice," Oldrich continues. "It formed a thick layer. Underneath it's rubble that may consist of some pre-existing volcanic rocks and maybe some glacial deposits."

Something that was formed in such a strange environment, with hot lava ponding up behind a wall of ice would create a pretty unstable structure.

"With this drainage there would be high pressure underneath it," Hungr says. "An earthquake could have been the final trigger."

Geologists know that the ground water was an important factor in triggering the 40 million cubic metres of material that came down in the 1855 slide.

"It would not have been a single rainstorm," Hungr says. "These deep-seated slides react to other things, like an especially wet year, a wet month or a seismic event."

But not everyone sees it that way.

To this day, McDonald gets very worked up whenever the subject of the Barrier and whether it was a threat to the residents of Garibaldi comes up.

"I'm afraid that never will anybody convince me that it was ever a landslide," he says. "When you look at the Barrier, the material that came down, if it came down all in one chunk it would have had to make a 90 degree turn as soon as it hit the bottom of the Barrier. It would have gone half a mile and would have had to make a 70-degree turn. Now both of these turns would have to destroy the energy in that system if it were to have collapsed as they claim it happened."

The findings of a panel, though, indicated that the slide that occurred in 1855 actually played a role in forming Daisy Lake, where the water is 50 metres deep in places.

"It was clear," Patton continues. "We had pictures of the original Daisy Lake that was formed by the 1855 slide. There were trees that had been flooded by the water."

The Report of the Garibaldi Study Group concluded that the probability of another slide occurring from the collapse of the Barrier is one in several thousand. But even that low a probability was enough to preclude allowing a new community to ever be established at Garibaldi. Looking back, McDonald thinks it was probably the right thing to move people - off the Rubble Creek fan.

"The Rubble Creek fan is in itself indefensible," he says. "When that creek goes wild and decides to move around it moves, and there's almost no stopping it."

The conclusion of the Report of the Garibaldi Study Group was that another slide could occur. The concern is the Fourth Lobe, an almost pristine cliff on the south section of the Barrier. There's an opinion that the Fourth Lobe could come down, but the cost to find out for sure would be astronomical.

"To evaluate the stability of that Fourth Lobe you're looking at easily $100 million," Patton says.

"The failed cliff was the Third Lobe," Hungr continues. "The Fourth Lobe has a similar structure and it's an unstable cliff just waiting for an opportunity to go."

Hungr believes that if the Fourth Lobe collapsed debris could be deposited in Daisy Lake, causing a displacement of water that would breech the dam. He has some doubts about whether another large rock avalanche would run as far down the Rubble Creek valley as the slide that occurred in 1855 because the valley is filled with debris and there's a different kind of substrate condition. But these doubts are tinged with uncertainty.

"A new slide might actually not run that far," Hungr says, "but it would take a very difficult study to prove that."

Re-routing?

Flooding on Boxing Day in 1980 left an old cabin near Alpine Lodge hanging precariously over the Cheakamus River. An A-frame was swept away.

The October, 2003 flood was worse. Whole sections of railway track were torn out by raging floodwaters below the dam. A section of the Sea to Sky Highway 150 metres long and eight metres deep was washed out just north of the Cheakamus canyon.

So what are the risks for the highway and railway in this corridor?

The boundaries of the Civil Defense Zone denoted by the May, 1980 Order in Council covered the area from the Barrier down the Rubble Creek Valley then followed around the 400 metre contour, up to Brandywine Falls Provincial Park on the north and the 400 metre contour south past the Forestry bridge that spans the Cheakamus River at Garibaldi.

At one time the Ministry of Highways looked at the feasibility of re-routing the highway north of the Cheakamus Canyon to a place beyond the Civil Defense Zone.

"We had an original design that showed a bypass of the area next to Daisy Lake," Peter Milbourne, director for the Sea to Sky project for the Ministry of Highways, says. "We had a potential bypass area of the Civil Defense Zone that was done under preliminary alignment. We ran that through a multiple count evaluation in terms of looking at what would be the environmental values that would be impacted in terms of alternatives. We also looked at the costs and what is the impact of the Civil Defense Zone given all the information."

The costs have always been too high. Howard Hunter, provincial approving officer for the Ministry of Transportation, says that the current highway upgrade will improve the existing highway all the way through what was the Civil Defense Zone, and is now called the Rubble Creek Slide Hazard Area.

"We're leaning towards upgrading the existing alignment where it is," Hunter says.

Risk assessment

Although the Report of the Garibaldi Study Group indicated that a complete assessment on the stability of the Barrier was not done because of the prohibitive costs, the opinions of the panel were that the same conditions that existed at the time of the 1855 slide prevail today. These conditions include a disintegrating large, steeply inclined mass of rock, water pressure from the springs at the base of the slide that are thought to be greater now than in 1855, and high stress levels at the base of the Barrier that are also worse now than in 1855.

Earthquakes, erosion at the base of the Barrier and groundwater fluctuations were the most important of six triggering mechanisms identified by the panel. A closer look at these mechanisms gives pause for reflection.

In 1932 a study was done to establish the hydroelectric power potential behind the Barrier. The study demonstrated that in March and April the level of Garibaldi Lake fell at a rate of 75 cubic feet per second. To put this in perspective consider the analogy put forth by Dr. William H. Mathews in "Garibaldi Geology." A mountain stream running at five cubic feet per second can be crossed by stepping on boulders or jumping from bank to bank. A mountain stream running at 100 cubic feet per second can be crossed by wading with great difficulty, if it can be crossed at all.

There are no known active fault lines in the Garibaldi region and no evidence linking the 1855 slide to an earthquake. But the Barrier is susceptible to moderate to high seismic activity. A report on the 1995 earthquake that destroyed railways, highways and bridges in Kobe, Japan concluded that a lack of recent seismic activity may only be a sing of accumulating seismic stress.

The question still looms: If the Fourth Lobe came down could enough debris be deposited in Daisy Lake to cause the dam to fail?

"If there were another slide like the one in 1855 that could happen," Hungr says.

The dam at Daisy Lake is one of many earth dams in the world. The dam has a buttressed central section and supporting walls built up with rock and gravel from Rubble Creek. If the dam overflowed the central concrete section would not fail, but Hungr believes that the earth filled section of the dam could be washed out. If that happened the amount of water coming down the Cheakamus River would be almost unimaginable.

"It would exceed any hydrological flood," Hungr says.

And there would be no warning.



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