Scientist says city must plan for an escarpment that will always be falling down
Dave Beatty | CBC News | Posted: April 5, 2017 9:45 AM | Last Updated: April 5, 2017
Recent closures of escarpment access roads portend a future that looks the same, unless Hamilton adapts
The Niagara escarpment, at its own geologic pace, is falling down, and a McMaster University geologist says the prudent course for the city is to be proactive in dealing with that reality.
It's trying.
Over the past year, at varying times, the city has closed parts of the East and West legs of the Sherman Access, the Claremont Access, Kenilworth Accee, New Mountain Road, and James Mountain Road for maintenance, slope repairs or rock scaling. Sometimes that maintenance has been "urgent."
We have to respect that the geological processes are going to continue. - Dr. Carolyn Eyles
It's bumped up its maintenance budget and is developing a long term plan to try to address the safety at the escarpment roads.
But it won't be able to stop what is an inevitable geological process. And waiting too long can be expensive. The Claremont closure was originally an "urgent" one-day job that turned into an eight week, $1 million effort.
In the last few years, there have been a number of rock falling incidents on escarpment access routes. Rock falling incidents usually cost the city, on average, anywhere between $25,000 and $500,000 annually, and that's on top of the normal yearly budget of $300,000 allocated to preventative maintenance.
But in the last year those numbers have been higher: the preventative maintenance budget was beefed up to $450,000.
"We put additional money in this year so we could upgrade some of our barriers at a number of our crossings," said Brian Hughes, the city's manager of capital rehabilitation. "That may be a temporary thing. We can hopefully go back to $300,000 a year."
Hughes also said that recent winters with fluctuating freezes and thaws have exacerbated rock movement on the escarpment.
Despite that, he said the increased preventative maintenance budget "wasn't a deliberate response to changes in weather patterns." However, now that the budget is higher, it could stay that way if next winter looks like this one.
"We never know what's going to happen," he said.
While it may seem like there have been an unusual number of mountain access closures in the past year, Hughes said the only work from that time that exceeded the (newly increased) preventative maintenance budget was the emergency work on the Claremont Access in November.
That work has a price tag of "about a million dollars, give or take," said Hughes.
In 2016, the city also hired a consultant to help predict likely sites of future rock falls. Hughes said the city is adjusting its maintenance plans and budget accordingly.
"There's a long term strategy as well that's being developed by Engineering for presentation in May," said Hughes.
Redrawing the map
But Dr. Carolyn Eyles, a professor in the school of interdisciplinary science at McMaster University, says no matter what the weather is doing, Hamilton had better get used to falling rocks.
"When we drive up the escarpment, we are actually driving up a geological feature that's still forming," she said. Elyes is glacial sedimentologist, which makes her knowledgeable about formations, like the Niagara escarpment, that are formed by glaciers over millions of years.
We have to think in terms of planning, and where it's going to be most effective to create geologically stable access routes. - Dr. Carolyn Eyles, McMaster University
"The whole length of the Niagara escarpment is a very active land feature," Eyles said.
She said the process of rock falling down isn't going to end any time soon. It's an immutable geologic process, millions of years into its process of solid cap rocks on top of less-hardy shale rock, slowly tumbling backward over the ages, with millions of years still to go.
"We have to respect that the geological processes are going to continue."
When asked if the city's efforts to deal with the escarpment are adequate, Eyles said a proactive approach it appears to be moving toward is better than scrambling after rock falls and collapsing retaining walls.
"We have to use our engineers and our geologists to design better roads. A lot of them were built as tracks originally. We have to think in terms of planning, and where it's going to be most effective to create geologically stable access routes."
"The city leverages the expertise and knowledge of our in-house engineers," said City of Hamilton's director of engineering services Gary Moore, "with that of consultants who are well-established and experienced in rock mechanics and slope stabilities to maintain the performance and safety of all our escarpment crossings."
"Given the realities of scarce resources and the infrastructure deficit facing all municipalities," said Moore, "safety is still our paramount focus."
The escarpment is moving to London
"The rocks are being eroded backwards," Eyles explained.
The escarpment, she says, has a hard upper layer they call the cap rocks. Normally, the cap rocks would be resistant to erosion. "It's quite strong. That's why we have the escarpment," Eyles said.
But in this 150 million year-old formation, the cap rocks are sitting atop a layer of shale rock called mudstone, and that's weaker. It erodes. The eroding mudstone base affects the integrity of the cap rocks. "It causes the cap rocks to fail," said Eyles.
"The fractures on top fill with rain water," she said, and when that freezes, the cap rocks become further compromised, eventually breaking apart.
"It's a unique geological feature because we have this particular layering. The rocks are slightly tilted down, to the southwest."
"So in past glaciations," said Eyles, "the ice has been able to erode parts of the edge and start the erosion process backwards."
"The escarpment is moving down toward London," she said.
But for now, the Hamilton mountain is keeping its home in Hamilton.
"I think Hamilton's very lucky to have such a unique geological feature in its back yard," Eyles said.