Every spring and summer, Tony Morris worries about the roughly one-per-cent chance that this will be the year another massive flood will inundate downtown Calgary.

He's anxious for major upstream mitigation to be built on the Elbow River. Without it, he knows the city is left exposed to the possibility of a 1-in-100-year flood year after year, adding up to a cumulative risk that becomes far more daunting.

In the best-case scenario, he hopes that upstream mitigation will be complete by 2023. But he worries it could be longer. Left unprotected for another four or five years, the probability of Calgary being hit by another major flood is in the same ballpark as being dealt a blackjack at a casino table. With so much on the line, he doesn't love those odds.

When the Elbow spilled its banks six years ago, it poured into the heart of the city, forcing tens of thousands of people to flee their homes, including Morris and his family. Within the city's limits, one life was lost and the financial toll of the flood rung in at an estimated $6 billion, making it Canada's costliest natural disaster, to date.

As co-president of the Calgary River Communities Action Group, Morris also worries our collective memory of the 2013 disaster is fading, our sense of urgency to protect the city from another flood is receding and our understanding of how best to build that protection eroding. Resting his hands on binders full of documents detailing the finer points of various upstream mitigation plans proposed since 1986, he sighs.

"It's easy to have your eyes glaze over when you look at the stacks of studies that are done here, and to tease out the critical information," he says.

Tony Morris is a Roxboro resident and co-president of the Calgary River Communities Action Group, which advocates for upstream flood mitigation for the city. (Robson Fletcher/CBC)

Tony Morris is a Roxboro resident and co-president of the Calgary River Communities Action Group, which advocates for upstream flood mitigation for the city. (Robson Fletcher/CBC)

Those studies are dense. They span thousands upon thousands of pages and address everything from the impact of flood mitigation on migratory bats to the potential destruction of archeological sites to major engineering concerns like the risk of catastrophic dam failure. Three successive provincial governments — PC, NDP and UCP — have reviewed these reports and each has supported the construction of a reservoir in Springbank over the alternative — a dam near McLean Creek.

And yet, today, as the reservoir remains under review by federal regulators, debate continues over which project is best. While the provincial government has continued to express its commitment to Springbank, Banff-Kananaskis UCP MLA Miranda Rosin plans to present a petition in favour of McLean Creek to the legislature. And Premier Jason Kenney said recently he's "never been married" to one particular project, and would look at other options if federal regulations or First Nations objections become too high a hurdle for the reservoir.

So, at this juncture, it seems relevant to refresh our collective memory: Why was Springbank selected over McLean Creek, repeatedly? Those dense, technical documents underpin the answer. They're important to understand, but not easy to read. That's why we've been re-reading them — so you don't have to.

Let's review.

Dam safety

The most fundamental difference between the two proposals is that the Springbank reservoir is an off-stream project, built mainly adjacent to the Elbow River, while a dam near McLean Creek would involve construction directly in the river's path.

That makes construction of the McLean Creek project more complicated and presents greater risks if there were to be a flood event during the construction phase, which would span several years. These risks were highlighted as "serious" in some of the earlier reports on the project's feasibility.

"If a flood occurs at a late dam construction stage while flow divert/control measures are not in place or cannot handle the flow, then the project could cause catastrophic damage to properties downstream, and dam failure," reads a risk analysis from 2016.

(You can read that analysis on page 1,264 of the project's consolidated conceptual design report. Here's a PDF link, but be warned: the file is nearly 200 megabytes.)

A risk of a failure would persist even after the dam is completed, that same analysis warns, due to the potential for debris to clog up the conduits that allow river water to flow through the dam and out the other side.

Some steps would be required to guard against debris, including the creation of a permanent "pond" (some might say a lake) on the upstream side of the dam. Despite the project sometimes being described as a "dry dam," this permanent pond would be roughly 180 acres in size and 15 metres deep and would help keep floating debris from entering the conduit intakes, which would be located near the base of the dam.

The 'permanent pond' that would be created by the McLean Creek dam is indicated in pink on this map. (Alberta Government)

The 'permanent pond' that would be created by the McLean Creek dam is indicated in pink on this map. (Alberta Government)

The flow through those conduits would be controlled by gates that would need to be opened to varying degrees, depending on the river's flow rate. During a flood event, the gates would need to be managed carefully — and quickly.

If the conduits are plugged or the gates operated improperly, "the project functionality and its ability to achieve required level of protection could be compromised," the report warns.

Yet another risk is upstream erosion and the resulting sediment carried downstream, which could collect at the base of the pond and also potentially clog the conduits.

One report suggested roughly 11,200 tonnes of sediment should be expected per year, but a subsequent report cautions that there is a huge amount of uncertainty in that estimate and the actual amounts could vary widely. During the 2013 flood, it notes, an estimated 715,000 tonnes of sediment was "delivered in a single day."

"If the baseload sediment transport is underestimated, then the designed storage capacity could be inadequate and the low level pond will be filled with sediments," the 2016 risk-analysis warns.

The design of the dam was revised in 2017, however, with changes that engineers believe would reduce those risks.

One of the biggest design changes was to the conduits, themselves. Initially, the thought was that steel pipes or reinforced concrete tubes could be buried in the earthen part of the dam. But the latest design instead calls for a pair of tunnels to be built through existing rock, instead. These tunnels would be less susceptible to leakage and erosion. They could also divert water during the construction process, reducing the risk of a failure if there were to be a high-water event while the dam was being built.

These and other design changes helped reduce the estimated risk of dam failure from a severity rating of "serious" in the 2016 analysis down to "important" in the most recent analysis from 2017. This rating is based on a combination of the consequences of a dam failure (which are high) and the likelihood of it happening (which is low).

So, how does that compare to risks of failure with the Springbank reservoir?

Diverting instead of damming

Unlike the McLean Creek project, which would be built right in the existing path of the Elbow River and constantly hold back water, the Springbank project would not interfere with the normal flow of the river — most of the time. Only when the river's flow rate reaches a certain threshold (160 cubic metres per second, to be precise) would the protection mechanism kick in.

That mechanism is a diversion structure that would be built on one of the riverbanks. Opening the structure's gates would allow some of the river water to flow into a secondary channel and then the reservoir itself, where it would be held back by a storage dam until the Elbow returns to normal levels and the downstream flood risk has passed. At that point, an outlet in the dam would open and the water would be slowly returned to the river via an existing, unnamed creek.

Construction of the diversion structure would require the river to be temporarily diverted to allow the work to proceed "in the dry." But compared to the McLean Creek dam, which would take years of in-stream work to construct, Springbank's diversion structure could be built much more quickly. The plan is to get it all done in one summer, according to the project's environmental impact assessment report.

An annotated aerial photograph showing where the diversion structure would be built to allow water to flow from the Elbow River into the Springbank reservoir during periods of high flow. (Alberta Government)

An annotated aerial photograph showing where the diversion structure would be built to allow water to flow from the Elbow River into the Springbank reservoir during periods of high flow. (Alberta Government)

Even if there were to be a flood event during this period, the report says it "will have minimal consequence downstream of the project site" because no water would be held back during construction. Any damage would be limited to the construction site, itself.

This was one of the key reasons the Alberta NDP — which supported the McLean Creek option prior to winning the 2015 election — cited for its change of position once it formed government. Former NDP transportation minister Brian Mason said in 2018 it was "a risk of a catastrophic failure that was flagged for us when we were looking at McLean Creek" that helped sway the party to support the Springbank reservoir instead.

Operational failures are also possible with the Springbank reservoir, especially with respect to the diversion structure. Problems due to mechanical breakdowns, debris, or human error are all possible and, if the diversion isn't opened properly during a flood event, the protective effect would obviously be compromised. The project's assessment says these risks can be reduced through routine inspection and maintenance, along with communication protocols and backup safety protocols for operators.

Not everyone is convinced the remote chance of a dam failure, alone, should sink the McLean Creek project, however.

'Exaggeration' of risks?

Dave Klepacki is a retired geophysicist who lives in Bragg Creek and was also directly affected by the 2013 flood, which devastated both homes and businesses in the small hamlet at the edge of Kananaskis Country. He's also an avid outdoorsman who spends a lot of time on the Elbow River, fishing, canoeing and rafting.

He, too, has delved into the guts of more than a dozen reports produced on the Springbank reservoir and McLean Creek dam projects. Unlike Morris, however, he believes the weight of the evidence leans toward the latter.

Of course a dam failure would come with severe consequences, he says, but it's unlikely to happen.

Dave Klepacki, seen here in a file photo, is a retired geophysicist who lives in Bragg Creek and an avid outdoorsman who spends a lot of time on and around the Elbow River. (Anis Heydari/CBC)

Dave Klepacki, seen here in a file photo, is a retired geophysicist who lives in Bragg Creek and an avid outdoorsman who spends a lot of time on and around the Elbow River. (Anis Heydari/CBC)

"I felt when I read that report that there was an exaggeration of those risks," Klepacki says.

"If you look at the database for dam risks, especially in North America but worldwide as well, the risk is very small, given the many tens of thousands of dams in the world."

When it comes to in-stream dams, he says "the technology is there" and has been proven in our own backyard. Just look at the various dams on both the Bow and Elbow rivers right now, which have been operating safely for decades, such as the Barrier Dam (built in 1947), the Bearspaw Dam (built in 1954), the Ghost Dam (built in 1929) and the Glenmore Dam (built in 1932).

It's actually the Springbank project that has less precedent, Klepacki says, as fewer off-stream reservoirs of that size have been built worldwide and they are often used for different purposes, such as drinking-water supplies or hydroelectric generation.

Water quality concerns

The proposed use for the Springbank reservoir — the temporary storage of excess water during the late-spring and early-summer flood season — is what worries Klepacki, as someone who cares about the health of the Elbow River and its ecosystems downstream.

He's concerned the large and relatively shallow body of water will bake in the high-intensity sun of June and July, leading to the growth of algae and cyanobacteria, also known as blue-green algae.

"At least the top couple of metres will get warm and you'll likely get algal blooms and cyanobacteria," he says.

A bloom of blue-green algae, which is actually a form of bacteria that grows through photosynthesis, is shown by a researcher near Edmonton in this file photo. (University of Alberta)

A bloom of blue-green algae, which is actually a form of bacteria that grows through photosynthesis, is shown by a researcher near Edmonton in this file photo. (University of Alberta)

He fears that warmed water will then damage the ecosystems downstream — threatening cutthroat trout and bull trout, in particular — when the reservoir is emptied back into the Elbow. It could also pollute the drinking water supply for the City of Calgary once it enters the Glenmore Reservoir, he says, requiring additional water treatment at "significantly increased cost."

"It can be easily two times the normal cost of water treatment to get rid of the toxins and to remove that kind of musty taste that comes along with cyanobacteria," he says.

In response to questions from federal regulators, the province says the "the risk for cyanobacteria to bloom is low" given the nutrient levels it expects will be found in the reservoir water. If blooms were to occur, "it is expected that they would only be in small, localized areas and not in an abundance."

Klepacki believes a dam on the Elbow River at McLean Creek would have fewer downstream water-quality concerns. With a low-level intake on the relatively deep permanent pond, he says colder and cleaner water would flow through to the other side.

As for the pond itself, he also believes it would create new recreational opportunities and could also serve as a firefighting resource, providing a pickup point for water-carrying helicopters to combat wildfires in the area.

Others, however, aren't so thrilled by the idea of a large dam and artificial lake at the entrance to Kananaskis Country.

Environment, recreation and archeology

Permanently flooding this section of the Elbow River valley would have an impact on not just the natural environment but also a host of recreational activities and infrastructure in the area.

The Elbow Valley Ranger Station would have to be relocated, as would a section of the McLean Creek Campground, along with the sewage treatment plant that currently services both of those facilities, as well as the nearby Easter Seals Camp Horizon. Approximately 10 kilometres of Highway 66 would have to be rerouted, including an existing bridge over the Elbow River, along with numerous power and communication lines.

In total, the relocations would cost more than $57 million, according to the latest estimates. The project's latest risk analysis also warns of "potential resistance from stakeholders and land users" who might be upset by the "irreversible negative impact on the traditional land use." The risk of public resistance is rated as "serious," as it could delay the project's "overall schedule."

Of course, there has been plenty of resistance to the Springbank project from landowners who would be directly affected, from the broader Springbank community, from the Tsuut'ina First Nation and from rural municipalities. But Morris, with the Calgary River Communities Action Group, believes there would be even more pushback from affected land users if the province were to go ahead with the McLean Creek project.

"In our view, the opposition that would be lining up against a McLean Creek project, where you're building in heavily used recreational areas, in Crown land and an environmentally sensitive area ... would be much more substantial, to the point, I think, of not even having that project completed," Morris says.

Another aspect that hasn't been raised too often in public discussion but is identified as an "important" risk in the McLean Creek project's risk analysis is the potential presence of archeological or paleontological artifacts in the area.

This map shows the estimated potential of archeological resources in the vicinity of the proposed site for the McLean Creek dam. Areas in red are listed as having high potential, while yellow areas are considered to have moderate potential. (Alberta Government)

This map shows the estimated potential of archeological resources in the vicinity of the proposed site for the McLean Creek dam. Areas in red are listed as having high potential, while yellow areas are considered to have moderate potential. (Alberta Government)

During a field visit in 2014, a new archeological site was discovered when "a quartzite chopping tool ... was observed eroding out of the bank of a terrace overlooking an intermittent tributary of the Elbow River," according to a report on the McLean Creek project from 2015.

The discovery supports the belief that the area is "of high archeological potential," the report adds, "confirming that previously unrecorded archeological resources are likely in the study area."

If the dam were to proceed, the report notes archeological sites could be damaged during both the construction and operation, and further evaluation would be needed, as such sites are "finite and non-renewable" and protected under Alberta's Historical Resources Act. The risk analysis cautions the discovery of additional archeological or paleontological sites could lead to potential delays in the project's timeline, cost overruns and the need for further First Nations consultations.

Known archeological sites also exist where the Springbank project's diversion structure would be built along the Elbow River, but not in the reservoir area, itself. There have already been consultations with the Tsuut'ina Nation (in 2016) and the Piikani, Siksika and Kainai nations (in 2017) with respect to these sites.

Finally, let's look at the project costs.

Each $400M+, but comparison not apples to apples

There have been numerous revisions and updates to the cost estimates for both the Springbank reservoir and McLean Creek dam projects over the years.

But the province cautions that comparing the latest price tags for each proposal is difficult, because the Springbank reservoir (SR1) project has been updated with more refined estimates than the McLean Creek dam (MC1) project.

"What we know regarding costs and timing for SR1 has increased greatly while the MC1 option remains conceptual," reads an updated cost-benefit analysis from April 2019.

That makes direct cost comparisons "questionable," the analysis adds.

Emergency vehicles stop at the edge of floodwater covering the intersection of Macleod Trail and Ninth Avenue in downtown Calgary during the 2013 flood. (Robson Fletcher)

Emergency vehicles stop at the edge of floodwater covering the intersection of Macleod Trail and Ninth Avenue in downtown Calgary during the 2013 flood. (Robson Fletcher)

With that in mind, the latest estimate for the Springbank project's total cost is $432 million.

The province has already spent more than 10 per cent of that — an estimated $47 million — on work related to design, assessment, engagement and regulatory approval.

The total price tag includes $140 million earmarked for land acquisition. For any parcel of land that is touched by the reservoir footprint, the government plans to acquire that entire parcel, but believes it could later sell the portions of those parcels that are outside the reservoir footprint. The province has said in the past it expects it could recoup as much as $60 million by selling surplus land after the project is built.

In March, the federal government also pledged $168.5 million to the project through its Disaster Mitigation and Adaptation Fund.

The total cost for the McLean Creek dam, meanwhile, is slightly lower. It's pegged at roughly $407 million in the latest estimate.

In terms of benefit, the April 2019 report found "benefits for both projects are nearly the same" but again cautioned that direct comparisons are tricky, since the Springbank project is at a "preliminary design phase" while McLean Creek is still "at a conceptual stage."

One of the biggest question marks around either project is how long it would take to start — and finish — construction.

What's next

For now, the Springbank reservoir project remains tied up in the federal regulatory process. There is no firm date as to when that process will wrap up, but there are some educated guesses.

"Construction is now expected to begin in 2021," the latest cost-benefit analysis says. But it cautions that is an assumption, not a certainty. If that indeed happens, the reservoir could be partially operational by 2022, then capable of providing full flood protection the following year.

Morris, too, hopes the project will be complete by 2023. But some of the mixed messages coming from the UCP caucus — including the premier's recent comment about not being "married" to a particular project — have raised new concerns among those who want to the see the reservoir built as quickly as possible.

The provincial government made a technical expert available to CBC News for this story, to confirm details of the various reports that have been produced over the years and, in a statement, Transportation Minister Ric McIver said the government remains committed to the Springbank project.

"We ran on a commitment to get Calgary flood mitigation built as quickly as possible, and we remain committed to moving SR1 through the regulatory review process without delay," the statement reads.



"Following regulatory approval, SR1 would take two years to build to a functional, one-in-100-year capacity, and three years to build to full completion."

Even if everything proceeds as quickly as possible, Morris says Calgarians have several more springs and summers of worry ahead of them, until that major upstream mitigation is in place.

"It's never soon enough, considering that what happened in 2013 — or worse — could happen in any year," he says.

"That's just the way these things work."