City to apply for flood mitigation grant

·3 min read

At Tuesday night’s regular council meeting, council voted to direct staff to apply for a Community Emergency Preparedness Fund (CEPF) Flood Mitigation Planning Grant in order to create a Masterplan for the Wastewater Treatment Plant (WWTP).

The City had previously received funding from CEPF for flood hazard mapping, which included a Light Detection and Ranging (LIDAR) project.

“In this instance what we’re looking at is to put forward an application regarding a plan to upgrade our wastewater treatment plant to better accommodate flood level flows through the City of Merritt,” said City CAO Sean Smith.

Merritt has battled extensive flooding in previous years, with the associated groundwater levels wreaking havoc on the Wastewater Treatment Plant’s ability to safely process and discharge wastewater.

“One of the things that we’ve experienced… is in 2017 and 2018, and even in 2020 even though we didn’t see so much overland flooding, the higher groundwater levels during freshet create greater groundwater infiltration on our system,” said Smith.

“When it comes down to it our system, as a whole, is capable of accommodating up to about 5,400 cubic metres of wastewater each day. Our average is around 2,400 cubic metres and even during peak times when groundwater levels are lower, we creep into the 3,000s. We have plenty of capacity for ordinary, day to day demands on our system, even peak demands. It is the groundwater infiltration that causes the greatest issue.”

When groundwater levels increase, it becomes necessary to run what is known as an ‘overland bypass’ to prevent raw sewage overflow into the wastewater treatment plant, this needs to be implemented around the 5,400 cubic metre level.

“I don’t want to oversell the degree of that problem, but it’s not a good long-term solution to need to regularly go to overland bypasses in order to be able to process an amount of water that we end up seeing during most freshets now,” said Smith.

Perhaps a greater technical issue for the process of wastewater is the fact that the gravity fed siphon which runs from the Wastewater Treatment Plant to the Rapid Infiltration (RI) basins in Collettville, can only handle roughly 233 cubic metres per hour, which is roughly the 5,400 cubic metre per day maximum.

“What we end up seeing is when we have greater flows coming from the wastewater system, we end up taking, admittedly processed sewage, but it goes into the river in accordance with our operating permits,” explained Smith.

“It’s not illegal doing it, but it’s not an ideal case scenario.”

Smith also noted there was an unfortunate incident in 2017 in which raw sewage ended up being discharged directly into the river, as the system was simply too overloaded to effectively prevent the situation.

In 2018, extreme amounts of groundwater, nearly 9,000 cubic metres per day, created a sewer backup and the City was forced to put out a bulletin asking residents to reduce wastewater creation as there was a “real risk” of once again overrunning the system.

Merritt’s current WWTP was built in 1960 and faces the issue of aging infrastructure. It is the hope of City staff that should the grant from the Flood Mitigation Planning Stream of CEPF be approved, a new WWTP Master Plan could be created.

“The processing capacity of the Waste Water Treatment Plant is currently a weak link in mitigating flood waters within the City of Merritt,” reads the report brought before Mayor and council.

Council voted unanimously to direct staff to apply for the grant.

Morgan Hampton, Local Journalism Initiative Reporter, Merritt Herald