Reducing I&I is always beneficial when considering wastewater treatment expansion needs, as it takes up treatment plant capacity that could otherwise serve growth. As part of the overall solution, the Region of Waterloo (Region) is working with the Township of Woolwich (Township) to implement system improvements, since the collection system is owned by the Township. The Township is actively identifying and addressing I&I sources in the current collection system, and these efforts are expected to continue reducing I&I over time.

A detailed breakdown of the amount of total wastewater flows attributed to I&I is not currently available, as the Townships' investigations are ongoing. The higher per capita wastewater flows recorded at the wastewater treatment plant are assumed to be largely attributed to I&I. While new developments typically generate lower per capita flows, the St. Jacobs collection system has historically experienced higher than average I&I.

Therefore, for the purpose of this Class EA expansion study, future I&I reductions were not assumed in the projected flow, instead historical data was used. The impact of I&I reduction efforts will continue to be monitored throughout the Class EA process and into the implementation phase, and adjustments to the recommended alternative may be made, as appropriate.

Yes. Both three-year and five-year average flows have been reviewed, and the results indicate relatively high values. There have been I&I reductions to the St. Jacobs collection system through the Township’s capital investment within the last 18 months. Additionally, further I&I remediation and capital investment into the St. Jacobs collection system are planned for 2026. Therefore, as mentioned above, the Region and the Township will continue to reevaluate these flows in the coming years as the I&I reduction initiatives progress, to potentially reduce the per capita flows to a more typical value.

This option will be evaluated further in Phase 3 of the Class EA, which would assess aspects such as operational efficiencies. The Region currently operates 13 wastewater treatment plants, many of which are relatively small, and consolidation can be an effective strategy in some cases. The Waterloo WWTP is significantly larger than the St. Jacobs facility, and can accommodate these flows in the near-term. Therefore, there are no capacity concerns at this time.

As part of the Region’s upcoming Wastewater Treatment Strategy Update, all wastewater treatment plants and long‑term growth needs will be reviewed. Through this process we will identify the time horizon for any expansion needs.

The optimal operating capacity depends on the specific plant. Operating too close to maximum capacity can be challenging, while significant oversizing also presents operational issues. Generally, plants are not operated at 100% capacity in order to maintain redundancy and operational flexibility.

Typically, expansion planning begins when a plant reaches approximately 80% of its rated capacity, as design, approvals, and construction can take many years. Ministry guidance generally recommends operating facilities within the 70–80% range, with 80% often serving as the trigger for expansion planning.

The plant is currently operating at approximately 70% of its rated capacity and can accommodate an additional population as indicated in the Region’s annual monitoring report. That said, expansion would need to be implemented before the plant reaches 100% capacity to ensure continued reliable operation.

Future flow projections incorporate a conservative assumption for I&I. The proposed designs therefore account for higher per capita flows, providing additional capacity to manage peak conditions. Based on historic peak flow and wet‑weather event data, surge capacity and peak flow management strategies will be examined in greater detail during Phase 3 of the Class EA.

Past sewer backups typically occurred during extreme weather events when inflow and infiltration (I&I) levels were elevated. The Township has a multi-year program to address the I&I into the Township’s collection system. The Region will continue to monitor the flows and work with the Township, and assist where possible, to reduce the I&I.

Additionally, the Region and Township have been working together on a separate but related study to this MCEA to better understand the cause of basement flooding. Separate meetings with impacted residents are planned to discuss findings of the joint study and discuss potential mitigation options.