After encountering a series of hurdles and setbacks, Niagara Region’s four-year, first-phase $62-million project to significantly upgrade the Niagara Falls Wastewater Treatment Plant to bring it into compliance with federal and provincial treated effluent limits is nearing the finishing line.
Designed by Environmental Infrastructure Solutions Inc. and overseen by Maple Reinders Contracting Limited, the project has encompassed a thick catalogue of work.
It includes construction of a new chemical and blower building, adding a new a new chlorine contact tank, and, notably, the removal of the plant’s aging 35 rotating biological contractors and their replacement with a Moving Bed Biofilm Reactor (MMBR), which is a process for reducing soluble organics and nutrients.
As part of the commissioning process and to ensure there would be no disruption to the plant’s operation, both the old and new systems kept operating for a period, says Niagara Region’s Water-Wastewater Engineering capital projects manager, Michelle Miller.
“But the MMBR will be fully commissioned by the end of this month (August).”
Still to be completed is the demolition of the old rotating biological contractors and the construction of the new chlorine contact tank, says Miller.
The upgrades are aimed at improving the plant’s performance and effluent quality. Earlier this year the plant was cited for violations of federal rules after toxic discharges were found in lab testing.
Multiple failures of the end-of-the service life biological contractors and their poor treatment performance were the catalyst for the project, the need of which was first identified in 2018.
Construction by Maple Reinders got underway in April 2022. But almost from the outset the project was beset with several significant challenges, says Miller.
Near the end of May of that year work had to be installed when the contractor encountered soil stability problems during the installation of a new storm sewer on the east side of the plant property.
While reviewing a number of options to remedy the soil stability issues, foreign materials were discovered in the exposed excavation area. A third-party consultant confirmed those materials contained ACM or asbestos containing material, she says.
Maple Environmental Inc., the specialty environmental consultant hired by the region, worked with the contractor, a team of other consultants, and regional and provincial staff to mitigate the environmental impact and the health and safety of workers, she says.
Maple Reinders and civil subcontractor Peters Excavation were kept busy loading, hauling, and trucking the excavated soil to a landfill site for six months. After that work was completed, the issue of the unstable soil had to be addressed. “That was a challenge in itself.”
The concrete foundation for the new standalone Moving Bed Biofilm Reactor is set on more than 120 steel piles that had to be driven into bedrock approximately 15 metres below the ground surface. (A total of 400 are needed for all the new structures.) Because of pile heaving and pile settlement that was not a straight-forward procedure, says Miller.
“Pile heaving and pile settlement can be caused by the vibration generated when a when a new pile is driven into the bedrock, causing surrounding piles to bounce back up from their final positions.”
Pile settlement can occur when piles appear to sink deeper than intended post installation. For piles experiencing settlement, it was identified that—although it appeared they reached bedrock—the actually only reached a dense layer located on top of the bedrock, she says.
Both challenges were mitigated by a surveying and monitoring plan and additional re-tapping of the piles in cases where heaving or settlements were found.
“Although these issues required more time and effort to properly complete the foundations pile installation, they were well managed and successfully mitigated.”
Once the piles were in place the concrete foundation poured, the contractor was able to devote its full attention to the plant upgrades. Still, construction with an active operating wastewater plant is a complex undertaking, she says.
“It requires meticulous planning and collaboration between the contractor and regional staff.”
Although this phase will be wrapped up in about four months, that will not mark the end of work at the plant. Detailed design of a Phase Two primary treatment upgrades is currently underway. In 2026 a third phase design of upgrades to the raw sewage pumps and screens is anticipated to commence, she says.
Serving more than 107,000 residents and visitors year-round, the Niagara Falls Wastewater Treatment Plant is designed to treat 68,300 m³/day (cubic metres) on average of waste water, up to 136,400 m³/day during dry-weather peaks, and as much as much as 205,000 m³/day during wet weather, says Miller.
