Backups & bypasses: what happens if a flood hits a Fraser Valley sewage plant?

If Abbotsford's wastewater treatment plant floods, sewage is expected to back up in Matsqui Prairie. Chilliwack has a bypass. And in Langley? No one will talk about the risk.

By Tyler Olsen | March 25, 2022 |5:00 am

Water flows downhill. As does poop. But where that poop goes if and when the Fraser River spills its banks will depend on your local sewage plant.

Five months ago, floodwaters inundated Merritt’s wastewater treatment plant, forcing the evacuation of the entire city—including those areas that hadn’t otherwise been damaged or threatened. That event showed the vulnerability of such plants, and the potential consequences when they are hit by floods. So we decided to investigate what would happen if floodwaters hit their wastewater plants—all of which are near the Fraser and often behind sub-par dikes.

What we found, and heard from municipalities, illustrates the differences between municipalities due each’s geography and wastewater system. And they reveal that there are few good options—other than preventing a flood in the first place.

In Chilliwack, for instance, staff would activate a bypass to allow sewage to directly enter the Fraser River. In Abbotsford, no bypass exists so sewage would back-up in Matsqui Prairie. And in Langley, the issue was so delicate that Metro Vancouver refused our initial requests to provide any information on its wastewater plant’s flood susceptibility or plans, except to say such plans exist. We continue to file freedom of information requests to seek more information about Metro’s freshet planning.

Merritt

First, to Merritt. The potential impact of a flood on wastewater treatment plants is worth considering because of what happened in that city last year. The entire community was evacuated after the Coldwater River burst its banks and flooded the city’s plant.

Sewage spilled across much of the town, and the plant was forced to stop operating. Two hours after telling people to not flush wastewater, the officials decided to evacuate the entire city.

“If anyone flushes a toilet or has a shower that does anything in Merritt, that water has nowhere to go,” the city’s public information officer told CBC. “We have no treatment capacity, it will simply back up in the system.”

Video showed the sewage lagoon overflowing.

The flooding of a wastewater treatment plant poses two related, but distinct, problems: what happens to the untreated sewage during a disaster, and what happens to the plant itself. Wastewater plants are the unsung heroes of local infrastructure. One of the fundamental tasks of a modern city is to provide water to citizens and carry waste away from their homes.

A wastewater plant is the last, most-important part of an extremely complex system. They are often one of a city’s most expensive, technologically complex pieces of infrastructure, and because they often sit along rivers, at low elevations, many are naturally susceptible to flooding.

That flooding can damage important and costly components—especially various electrical devices—that need to be fixed or replaced before the plant can be restarted. Flood erosion can also damage the land a plant itself sits on.

But also, vitally, a flooded treatment plant can’t operate and treat a city’s poop and other liquid waste. Where that waste flows—and where waste stored on site ends up going—depends heavily on a city’s specific wastewater system, and the river that floods it.

Even relatively clean floodwaters are extremely damaging—absent an inundated sewage plant, floodwater already carries an array of pollutants and contaminants. Sewage can significantly add to the hazards. Contaminated water can cause health problems for anyone forced to wade through waters, increasing the risk of E.coli and salmonella infections. It can also significantly complicate efforts to repair or rescue items swamped by floodwaters.

If there’s some solace, it’s that any Fraser River flood that inundates wastewater plants would involve an epic amount of water and dilute the concentration of effluent. And while dirty, that water isn’t pure filth: it includes water from sinks, showers, and runoff drains.

But it’s one thing if that water carries the sewage directly into the Pacific Ocean. It’s another if dikes break and water rushes into plants and then towards developed areas. So localized pollution levels will depend on the flow of currents, the location and scale of any dike breaches, and the wastewater system itself.

Langley, Abbotsford, and Chilliwack all have wastewater treatment plants along the Fraser River. 🗺 Bing Maps
Langley, Abbotsford, and Chilliwack all have wastewater treatment plants along the Fraser River. 🗺 Bing Maps

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Langley

A spokesperson for Metro Vancouver, which operates the Northwest Langley Wastewater Treatment Plant, would only tell The Current that it has “emergency response plans for all of our key infrastructure, including liquid waste facilities, to ensure continued operations.”

In an email, a Metro Vancouver spokesperson wrote that “for safety and security reasons these plans are not made public.” The spokesperson refused to answer what would happen to waste if the plant flooded, or if there was a bypass system that allowed waste to continue to flow into the Fraser, rather than backing up around the plant.

The Current obtained the emergency response plan for the wastewater plant, but it contained no planning for a Fraser River flood event. The plan contains a half-page on localized flooding procedures. It then says: “This section applies only to localized flooding. Flooding potential due to a freshet is not covered in this ERP as a freshet can be anticipated and response planned well in advance.”

In response to further questions, the Metro Vancouver spokesperson said the regional district has a separate freshet response plan for liquid waste facilities. However, they have not provided that plan. The Current has filed another freedom of information request.

Metro’s spokesperson said officials have a “systematic staged plan” to monitor the Fraser, and that they regularly conducts emergency exercises. Metro Vancouver also has formed a new task force this year that, in part, will assess dikes and flood protection infrastructure in the region.

Other Metro Vancouver documents acknowledge the very real flood risk posed by the Fraser. The current plant serves around 30,000 people in the area and sits behind a dike too low to protect against a one-in-500-year flood.

“While the site is partially protected from flooding by an existing dike, it does not provide sufficient protection from flood events that consider increased peak river flows and sea level rise, driven by climate change,” a 2018 report says.

The existing North Langley Wastewater Treatment Plant sits behind a dike that is too low to protect against a one-in-500-year flood. 📷 Metro Vancouver
The existing North Langley Wastewater Treatment Plant sits behind a dike that is too low to protect against a one-in-500-year flood.

That will change relatively soon, though.

Later this year, construction is expected to start to expand the facility, which is located immediately west of the Golden Ears Bridge. That work will include raising the site by several metres, above the projected height of a one-in-500-year flood (factoring in the effects of climate change and sea level rise.)

The new plant will also serve many more people, including those in Maple Ridge and Pitt Meadows. It will be built atop elevated ground and is expected to be flood resistant over the long-term. Construction is expected to be completed in 2026, which means that unless a flood hits in the next few years, the new plant may be safe. When complete, it will be the first and only plant that could be expected to keep operating in the event of a historic flood.

Before it expands its wastewater treatment plant, Abbotsford plans to raise the ground considerably. But those upgrades won't happen for close to a decade. 📷 City of Abbotsford
Before it expands its wastewater treatment plant, Abbotsford plans to raise the ground considerably. But those upgrades won’t happen for close to a decade. 📷 City of Abbotsford

However, if a major flood hits sooner than that, it’s unclear where the waste from 30,000 residents will end up.

Before it expands its wastewater treatment plant, Abbotsford plans to raise the ground considerably. But those upgrades won’t happen for close to a decade. 📷 City of AbbotsfordContinues below

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Abbotsford

In Abbotsford, a flood of the JAMES wastewater plant—which also serves Mission—could leave surrounding homes and farmlands inundated not just with water, but with diluted human waste.

While Abbotsford refused The Current’s request for an interview on the subject, a spokesperson did provide some information about what would transpire in the event of a flood.

In an email, the spokesperson wrote that the city does not “anticipate” an emergency situation befalling the site.

If the JAMES plant did have to be shut down, the city “could control the flow and would ask residents to reduce their water usage and only flush when necessary,” the spokesperson wrote. Food processing plants and other industrial users would be asked to slow or stop their operations.

“Should the JAMES Plant shut down in a disaster, a city-wide action plan would be developed on a situational basis, in conjunction with Emergency Management BC and Public Health.”

But if the plant shuts down, the waste produced by more than 150,000 humans in Abbotsford and, across the river in Mission, will need to go somewhere. Flows might be reduced because of business shutdowns and evacuations, but most Abbotsford and Mission residents live above floodplains in areas that might escape direct flooding damage. Unless everyone is evacuated, those residents would have to use their toilets. And when they did, the waste would flow into pipes and towards the JAMES plant.

There, the waste would begin to accumulate.

“If we needed to shut the plant down,” the city spokesperson wrote, “the flow would back up and then spill into the Matsqui Prairie flood plain and not into the river.”

It’s unclear just how flood-resilient the current facility is. And while it is protected by a dike, the stability of the dike is unclear. Just two years ago, a sinkhole developed adjacent to the wastewater plant. Fixing it cost more than $1 million. Abbotsford refused to make any staff available for an interview on the subject.

The city’s long-term wastewater plans show Abbotsford is looking to flood-proof its wastewater infrastructure over the long-term. And the large cost to do so reflects the threat the Fraser poses to Abbotsford’s infrastructure. As it looks to expand the facility in the future, the city intends to spend upwards of $50 million to raise the ground for future expansions nine feet higher than the dike currently protecting the plant.

Chiliwack's waste water treatment plant is just to the west of the city's downtown core. 📷 Tyler Olsen
Chiliwack’s waste water treatment plant is just to the west of the city’s downtown core. 📷 Tyler Olsen

Chilliwack

Chilliwack’s waste water plant also sits on a floodplain behind a dike that probably wouldn’t protect it or the northern part of the city in the event of a 500-year flood.

But what would happen to the city’s poop is clearer: it would go straight into the Fraser River.

The city’s wastewater plant has a bypass that allows waste water to be routed past the treatment plant and into the river just to the north.

If Chilliwack’s sewage plant is flooded and needs to be shut down and evacuated, staff would first activate that bypass. Doing so would take only about 15 minutes, the city’s director of planning and engineering, David Blain, told The Current in an interview.

“It’s something you don’t ever want to use, but it exists,” he said. “That’s step one.”

Such a bypass would stop wastewater from accumulating in the facility, damaging precious infrastructure, and the surrounding area. That, Blain said, would make it easier to bring the plant back online after it was shut down.

Chilliwack has more residents living on the floodplain than any other Fraser Valley city. That puts the city at an elevated risk when it comes to a flood, and means tens of thousands would need to evacuate if floodwaters breached the substandard dikes protecting the city. The only positive is that would dramatically reduce the city’s sewage output if floodwaters ever inundate its wastewater plant.

“Keep in mind, an event that would flood the wastewater treatment plant would also pack most of downtown, or most of Chilliwack north of the highway, so a sizable amount of people would have to be evacuated.”

That will decrease the amount of sewage flowing towards the plant and, from there, into the river. But residents remaining in the south end of town would still need to use their toilets, especially since the flooding could close any roads out of the city. During a flood, staff would leave the site.

“It could be under a meter of water, a meter and a half of water,” Blain said. “No one can stay there and all the roads will be cut off. It’s not until the water recedes that we can re-access the site and start reactivating it as quickly as possible.”

Long-term, Blain says the city is constantly looking for ways to increase the resiliency of its wastewater plant. Much of that has involved ensuring that expensive technical equipment is located above the base flood level, so that it can stay out of the waters, if and when they come.

Agassiz (Kent)

The Fraser valley’s other communities also have wastewater treatment plants, though their size and location decreases their significance in the case of a flood. The District of Kent noted that any flood to its plant would likely take place concurrently with a mass evacuation of residents. Hope’s plant, meanwhile, lies downriver of the community.

Still, in its response, Kent noted that even properties not flooded would have to be evacuated in the event of a closure of the wastewater treatment plant “as public health would be at risk.”

But that assumption, may be less applicable downriver. Because of our inability to secure an interview with officials in Langley or Abbotsford, it’s unclear whether those two communities would be prepared or able to evacuate more than 100,000 upland residents if their wastewater treatment plants went down.

The cities have plans to floodproof their treatment plants by raising the land they sit on. But only Mother Nature will decide what comes first: higher ground or higher water.

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Tyler Olsen

Managing Editor at Fraser Valley Current

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