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Freeze-thaw and the long-term climate impacts on Calgary infrastructure

As Calgarians manage yet another, albeit brief, freeze-thaw cycle, there’s an underlying impact the temperature swings have on Calgary’s major infrastructure.

If freeze-thaw frequency projections hold true, changes to Calgary’s climate could only make matters worse.

Back in October 2022, Calgary’s auditor highlighted the City’s 2022 Corporate Asset Management Plan (CAMP), which reported that 15 per cent of the city’s buildings were in poor and critical condition, and 20 per cent of building to in medium-high to high-risk exposure.

The Corporate Asset Management Plan report states in the introduction that Calgary’s infrastructure overall is low risk – 5.6 out of 25.

“The overall condition of City assets has declined compared to the 2017 CAMP,” the report read. It’s to be expected; everything deteriorates over time.

The 109-page CAMP report dedicates a section to acknowledging climate risks to city assets. It mentions climate further as it breaks each area of infrastructure down. The report outlines eight primary hazards: Extreme heat, drought, wildfire, shifting seasons, heavy rainfall, heavy snowfall, severe storms and river flooding.

“These impacts have the potential to significantly affect many City of Calgary assets,” it reads under the climate-related risk heading.

It does mention the risks related to extreme temperatures but doesn’t single out potential freeze-thaw cycles.  The City of Calgary’s Climate Projections report (January 2022), however, does.

“The shifts in seasonality also affect freeze–thaw cycles, which have significant effects on construction and road design,” it reads.

It shows that historically Calgary has 16.2 freeze-thaw cycles in winter (Dec., Jan, Feb.). A freeze-thaw cycle is defined as any number of consecutive days where the temperature is above zero Celsius, followed by (or preceded by) consecutive days below zero.

By 2050, a median projection shows an increase of 2.3 freeze-thaw cycles in that period alone. By 2080 that drops back down to 17.6 annually. 

Freeze-thaw in Calgary is largely driven by Chinook activity in the city. Other models show over the course of a year, annual freeze-thaw cycle numbers may decline due to an overall increase in mean temperature in the shoulder months (Sept.-Nov., and March-May). Though, it’s presumed that overall snow removal and application of salt-sand mixtures would happen in the winter months.

Focus on road, bridges and concrete

In 2019, the City of Calgary announced the closure of the Jaipur Bridge connecting Eau Claire and Prince’s Island Park.  An inspection done a month prior to the closure showed accelerated deterioration from water and salt.

Climate impacts are not specifically mentioned. It should be noted that the bridge was 52 years old and past its 50-year design life.  It’s clear from the photos that both the concrete and the reinforcing rebar are significantly impacted by wear and corrosion.

This is where the focus of this story begins.

City of Calgary reports acknowledge climate impacts on all infrastructure, including natural.

Of the City’s $100.4 billion in assets, roads, bridges and tunnels account for 22.3 per cent. This also includes things like streetlights or their bases. Many of these have an element of concrete in their structure.

For that matter, many of the buildings in the city’s inventory have concrete but represent a much smaller portion of the asset mix (2.7 per cent).

(It was actually the crumbling of the Saddledome exterior that prompted inquiries leading to this story. In that piece, the City’s GM of Infrastructure Services, Michael Thompson said, “We see that on many of our buildings, structures like bridges, that concrete, it starts to weather as it gets older.”)

The concrete factor could also impact parks, pathways, trails and park infrastructure, which makes up $5.8 billion, or 5.8 per cent of the city’s asset portfolio.


Concrete and climate change

In 2019, British Columbia Institute of Technology civil engineering coordinator Sudip Talukdar dug into research on climate change and the deterioration of concrete infrastructure.

His review of research showed what many such studies reveal: Increased risk of chloride-induced corrosion of steel reinforcement (via road salt) and carbonation-induced corrosion from increased temperatures and CO2 concentrations in the air.

Talukdar said climate change would have little impact on concrete structures built today, but a greater impact on infrastructure built in the near future.

Dr. Muntasir Billah, P.Eng, Member of the American Society of Civil Engineers, and assistant professor in the University of Calgary’s Department of Civil Engineering said there’s still a significant climate impact on existing infrastructure.  Dr. Billah said they weren’t thinking about climate impact when concrete structures were built 30-40 years ago.

“We did not have any concern about climate change and not many people were talking about those climate change effects,” he told LiveWire Calgary.

Chloride corrosion is one of the big concerns. Particularly in Calgary.

Dr. Billah said most concrete structures are reinforced with carbon steel. It’s prone to degradation with water contact. That’s compounded with the chloride compound often used in road salts.

It enters through cracks in the concrete or the pavement. The cracks appear over time but are also created, expanded and contracted by rapid freeze-thaw cycles. Even the smallest crack, unseen by the naked eye, can carry salted water into a structure, Dr. Billah said.

“The saltwater is getting in there and it is reacting with the chemicals that are in concrete and also in the reinforcement,” Dr. Billah said.

In the past 10 days in Calgary, it went from 10 Celsius to -30 Celsius with heavy snowfall in between. It will go back up above zero in the next couple of days.  During the snowfall, the City of Calgary would have applied a salt and sand mixture to many road surfaces. That slushy combination ends up somewhere.

If there are more freeze-thaw cycles as the City projects, the deterioration problem worsens.

Solutions to slow the infrastructure decline

There are two primary avenues to fix the concrete infrastructure issue short and long-term, Dr. Billah said. One is adaptation, the other is design, he said.

“I think more focus should be on the adaptation side: How we can make our existing infrastructure more resilient against climate change?” he said.

“If we can reduce the rate of degradation, if we can apply some preventive measures, we can definitely prolong their service life.”

According to Talukdar’s research, concrete covering or sealing to reduce permeability will help inhibit the penetration of degrading substances into the concrete.

The City of Calgary said they’re always evaluating standard details and materials to come up with longer-lasting designs that require less maintenance. They said design and construction standards for bridges and pavement have been updated to increase resilience to changing climatic conditions.

“New specifications for pavement and concrete have been presented to the builders committee and the plan is to implement these specifications starting January 1, 2023,” read an emailed response.

“These new specifications aim at improving infrastructure resilience but are not specifically focused on the impacts created from climate change.”

Dr. Billah said design changes like building with corrosion-resistant, fiber-reinforced polymer rebar, paired with high-performance concrete mixtures would help the service life of structures.

Initially, the cost may be higher, but when accounting for the service life and maintenance over an entire life cycle, the cost of the structure would be significantly lower, he said. Further, the costs for many of these materials have come down in recent years.

The cost of doing nothing about climate

A 2021 Canadian Construction Association report mentions that infrastructure failures linked to climate change could cost Canada $300 billion over the next 10 years if no further changes are made to existing practices.

(Their report also happens to mention waterproofing concrete used in cement mixtures to reduce the porosity – and therefore potential rebar corrosion and degradation.)

Calgary’s $22.3 billion in roads, bridges and tunnels (plus $5B for parks, pathways and park infrastructure) is just a tiny portion of the trillions in Canadian infrastructure. The reality is most of it’s in good condition.

Roughly 17 per cent is in poor or critical condition. Much of that amount is related to the typical life cycle of the asset. Aging, if you will.

From the City of Calgary Corporate Asset Management Plan

The City of Calgary said they’re currently reviewing costs and the impact of climate on the city’s infrastructure. LWC asked if there was an estimated impact in terms of upgrades or outright replacement of city capital assets due to climate-induced deterioration.

“We do not have a dollar amount at this time as this is something we are currently working on,” read an email response.

The CAMP report shows that while $1.6 billion will be spent on roads, bridges, and tunnels infrastructure over the next 10 years, there’s a funding gap of $1.832 billion, based on the needs outlined in the infrastructure status.

Calgary’s audit committee chair, Coun. Richard Pootmans said that the City needs to get a detailed handle on the existing conditions of infrastructure. A total replacement cost of $100 billion on a total annual city budget of $4.5 billion is math that just doesn’t work.

“We haven’t even defined the problem,” he said.

“We’re aware of the problem. It hasn’t been cohesively, coherently, comprehensively put together into one study.”

The freeze-thaw is here to stay

The City said, and rightfully so, that flooding is a leading concern when considering the impact of climate change. We’re coming up on the 10th anniversary of the multi-billion-dollar 2013 Southern Alberta floods.

But it’s not the only one.

Calgary, due to its proximity to the Rocky Mountains, the wonderful southwesterly flow from the Pacific that comes with our geography, plus being north of the 49th parallel, therefore subject to polar vortices, means freeze-thaw is going to happen no matter what.

Frequency is another matter. Should the City of Calgary’s projections bear out, it means another 2.3 freeze-thaws during winter. It’s difficult today to assess what that impact would be on how infrastructure in this city degrades as a result.

Calgary’s roads, bridges and tunnels were the focus. There’s currently a $1.8 billion funding shortfall – just there. Exacerbating that amount with climate-induced impacts could result in heavier taxpayer responsibility.

Now cascade that to buildings, parks and pathways, and even the stormwater system. The funding gap grows exponentially.

Dr. Billah said while most infrastructure is in fair to good condition, the amount that’s in poor to critical is not inconsequential. He said it impacts the entire city’s resiliency.

Many European cities are examining their existing infrastructure to ensure it’s climate resilient, he said. They’re adopting climate adaptation policies to combat the impacts today.

“It is time that we look into different adaptation policies and adaptation techniques so that we can make our existing infrastructure more adaptable against climate change,” Dr. Billah said.

“If your infrastructure is not functioning, then you cannot hold your city to be resilient enough.”

FURTHER READING: Climate Change Impact and Risks of Concrete Infrastructure Deterioration