What Flows Off Banff’s Streets Is Raising New Concerns for the Bow River

For most people in Banff, stormwater is invisible.

It is the rain and snowmelt that runs off streets, parking lots, and rooftops, flows into drains, and disappears underground. Unlike sewage, it is not treated at a plant. In Banff, much of it is released directly into nearby creeks and, ultimately, the Bow River.

That system is now showing signs of strain.

According to a Dec. 9 environmental budget presentation and subsequent council discussion, stormwater runoff in Banff has been exceeding federal guidelines designed to protect aquatic life. Monitoring conducted in partnership with Parks Canada has identified recurring contaminants, while unpublished Parks Canada data points to declining aquatic ecosystem health downstream of the townsite.

As such, the Town of Banff unanimously approved funding for a stormwater treatment plan, marking its most comprehensive effort to date to understand what is flowing off local streets, where that runoff ends up, and how it could be managed differently in the future.

What stormwater is and why it matters

Stormwater is any water that does not soak into the ground. Instead, it flows across hard surfaces such as roads and sidewalks, picking up whatever it encounters along the way before entering drains and waterways.

In Banff, that runoff often carries road salt, vehicle residue, and other pollutants straight into the Bow River system.

“We operate a sewage system, and then we operate a stormwater system,” Darren Enns, Banff’s director of planning and development, told council. “The stormwater system, by far, is the… I don’t want to say neglected, but it’s not the favorite child.”

The difference, Enns explained, comes down to priorities and funding. Drinking water and sewage systems are critical to public health and have dedicated funding reserves. Stormwater, which affects environmental health, does not.

“You do not have a dedicated reserve for your stormwater system,” he said. “And so that makes it a really challenging service area to fund improvements to.”

The result is a system that does what it was originally designed to do, move water away to prevent flooding, but does very little to treat that water before it reaches the river.

“For the most part, our stormwater is delivered directly from our streets into the river,” Enns said. “There is no treatment at all.”

What the monitoring is showing

Since 2021, the town has worked with Parks Canada aquatic staff on a stormwater sampling program to assess how runoff from the townsite affects surrounding waterways, including the Bow River and smaller drainages.

One finding stood out.

“There were two critical paths for contaminants,” Enns said. “Heavy metals and chlorides, primarily coming off our road system.”

Chlorides, commonly associated with road salt, were most pronounced in winter. Heavy metals, typically linked to vehicle use, appeared throughout the year.

Much of that contamination is tied to impermeable surfaces such as roads, parking lots and sidewalks, which shed water quickly and funnel it into drains. Some runoff also comes from outside the townsite, flowing downhill into Banff’s stormwater system from surrounding slopes.

Banff has roughly 30 stormwater catchment areas, meaning defined sections of land where rain and snowmelt collect and drain through pipes and channels to a single outlet, most of which flow into the Bow River. One of the largest and most significant is the Wolfe Street catchment near the canoe docks, which Enns described as the “epicenter” of the system.

It covers roughly 756,000 square metres, includes residential areas and major roads, and contains several potential contamination sources, including gas stations.

“If you ever go to the canoe docks and you stand on the pipe, you know if something goes wrong,” Enns said. “It’s a very visible expression of contamination of the river.”

Limited treatment, isolated fixes

Banff does have a handful of stormwater treatment measures in place, but they are the exception rather than the rule.

At the Buffalo Street boat launch, runoff passes through a storm system, which functions like a sump to capture contaminants. On Bear Street, underground soil cells provide localized treatment before water is discharged.

New large developments are also required to submit stormwater management plans that focus on retaining water on site and reducing runoff volumes.

But these are isolated solutions, Enns said, not a coordinated system.

“What this would do is allow us to look at our stormwater system at large,” he said, “and come up with proposals that would be both end-of-pipe and source-based solutions over time.”

Questions about funding and accountability

Several councillors pressed administration on how any future upgrades would be paid for.

Councillor Pelham asked whether the proposed plan would identify potential funding sources, noting that stormwater lacks the user-fee model that funds water and sewer systems.

“Stormwater is… unaccountable in terms of funding,” Enns replied. “It is like the all-you-can-eat buffet of water.”

He added that Banff’s geography complicates the issue. The town sits at the valley bottom and receives runoff not only from within the community but also from surrounding mountains.

“We’re literally inheriting water from every mountain around us that at times will come into our stormwater system,” he said. “So accountability is a tough one.”

Councillors also asked about the town’s use of road salt. Operations staff confirmed Banff currently uses sodium chloride and typically keeps aggregate treated at three to five percent chloride, with higher applications permitted when necessary. Crews try to remove snow before chinook melts to reduce the first flush of salty runoff into waterways.

A requirement, even if late

The stormwater plan is not just a local initiative. It is explicitly required under the Banff National Park Management Plan (2022), which directs the town to submit to Parks Canada “an analysis and assessment of storm water systems to guide future storm water management policies,” originally due in 2025.

That requirement was cited by Mayor Corrie DiManno as council considered the funding request.

“This is a Banff National Park management plan requirement, so it’s essentially a non-negotiable,” she said. “We also want to be good stewards of the land and of the river.”

DiManno acknowledged the plan is a first step, not a solution in itself, and said administration would also pursue grant funding and explore potential support from Parks Canada once the analysis is complete.

“This is step one to ensuring that we are being good stewards,” she said.

Council approved $150,000 from the environment reserve to fund the stormwater treatment plan as part of the 2026 to 2028 operating budget. The motion passed unanimously.

For residents, the decision brings attention to a system that has long operated out of sight and, until recently, largely out of mind, even as its impacts have flowed downstream.