Repairs ongoing to GRCA’s Wellesley and Baden Dams

The Grand River watershed experienced a mixed precipitation event from April 2 to April 3, 2025, including snow, freezing rain, thunderstorms and significant amounts of overall precipitation. Water levels in some river systems were already elevated at the time, due to previous rainfall and snow melt in late March 2025.

The extremely high water levels resulted in damage to the Grand River Conservation Authority’s (GRCA’s) Wellesley and Baden dams, both of which are former mill dams that do not serve a flood control or flow augmentation function as part of the GRCA’s water control infrastructure. In both cases, water either overtopped the dams’ embankment or seeped through the embankment, and the high water levels resulted in the loss of operation of gate discharge equipment at Wellesley Dam. GRCA were present at both locations during the weather event and were able to immediately identify the separate occurrences as dam safety incidents, which would impact the stability and safety of these structures. Emergency repairs were initiated, and both sites were stabilized within hours of the dam safety incidents being identified.

The GRCA operates 28 dams throughout the Grand River watershed. Of these, seven are large multipurpose dams and reservoirs, which play a vital vole in protecting the health and safety of downstream communities. These dams are used to manage flows and serve two principal functions – flood mitigation and flow augmentation. The GRCA’s other 21 dams are run-of-the river dams or earthen embankment dams with small head ponds. Although the smaller dams do not serve a flood control or flow augmentation function, they are important community features. As the owner of water control infrastructure, the GRCA is accountable for the safe operation and maintenance of all the dams it owns.

Wellesley Dam and Dam Safety Incident

The Wellesley Dam, located in Wellesley, Ontario, was built in the mid-1800s to provide power for the community’s sawmills, grist mills and flour mills. The watercourse is known as Firella Creek and is part of the Nith River watershed. The dam is an earth embankment dam with a concrete spillway and a single vertical lift gate. The dam and pond have undergone various maintenance works throughout the years. The dam and pond currently serve as a community recreation, aesthetic, and historical feature. As part of its regular maintenance program, the GRCA had already noted some deficiencies at the Wellesley Dam, and a project to complete a comprehensive conditions review and plan for rehabilitation at the dam site was to be initiated in 2025, as identified in the GRCA’s Water Control Structures Five Year Capital Forecast.

While operations of the gate were completed, the April 2 to 3 rainfall event exceeded Wellesley Dam’s gated discharge capacity. In the early morning hours of April 3, the water levels reached the overflow spillway. In addition, water began overtopping the east embankment. The east embankment is a portion of the dam that is not designed for overtopping.

These high water levels resulted in damage to the discharge gate equipment and erosion of the east embankment. Due to the loss of operation of the control gate, the decision was made to secure the gate in an open position until repairs to both the gate and the embankment could be made to protect dam safety and prevent overtopping. This resulted in the loss of the head pond; however, Firella Creek will continue to flow through the drained pond area in a low flow channel. While repairs to the discharge gate equipment have been completed, the GRCA has initiated an engineering assessment to provide designs and recommendations to address the safety and stability of the structure. These measures are required to be addressed prior to returning the dam to normal service and raising the water levels in the pond. These assessments will include a condition assessment of the concrete structure and geotechnical review and design to address the stability and seepage of the east embankment. Interim repairs will be completed to address immediate dam safety and public safety concerns identified in the engineering conditions assessment. Once the repairs have been completed the discharge gate will be returned to service and the pond will be filled to its normal water level. The anticipated timeline for these repairs to be completed is late spring 2025.

Baden Dam and Dam Safety Incident

Baden Dam is located on Baden Creek in Baden, Township of Wilmot. The watercourse is known as Baden Creek and is part of the Nith River watershed. The dam’s original construction date is unknown, although it is believed that it was constructed in the mid-1800s when the grist mill was constructed. The Baden Dam is an earthen dam with a concrete control structure. The dam was acquired by the GRCA in 1971, and the dam and pond currently serve as a community recreation feature.

During routine monthly inspections, GRCA staff identified a hole with active seepage traveling through the embankment from the upstream to downstream side of the embankment. The GRCA initiated engineering assessments of the embankment seepage, and in the fall of 2024 received an engineering report on remedial measures to provide seepage control and improve dam safety and stability of the Baden Dam. A project to complete construction at the dam site was already planned for 2025 as identified in the Water Control Structures Five Year Capital Forecast.

The Baden Dam was inspected by GRCA staff on the morning of April 3. It was observed that the seepage had increased significantly, and emergency measures were initiated to complete temporary repairs. The GRCA will be proceeding with the remedial measures as recommended in the late 2024 engineering report to address the current dam safety concern because of the seepage through the embankment. The 2024 engineering design has been updated to address additional repairs that are required following this event to return the dam to a safe and stable condition. Construction is anticipated to commence in early May.

Future Studies

For Wellesley Dam, the GRCA will be initiating a future study to complete a comprehensive conditions assessment of the structure and identify recommendations for future work. For Baden Dam, an additional study may be required.

In both cases, the studies would consider the long-term future of these structures that is cost-effective and mitigates risk to the public, the dam structure and the environment. Possible alternatives may include repair, modification or decommissioning of the dams. Any studies related to the long-term future of these structures will incorporate consultation with interest holders, including the municipalities, local community and First Nations.

Further details about these dams and dam safety incidents are available in the April 25, 2025 Board Report GM-04-25-46 April 2025 Flod Event Dam Safety Incidents – Wellesley and Baden Dams.

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Media Contacts:

Serena Catania, GRCA Supervisor of Communications and Marketing
Phone (519) 621-2763 x2240  |  Email scatania@grandriver.ca

Lisa Stocco, GRCA Director of Strategic Communications and Environmental Education
Phone 519-621-2763 x2316  |  Email lstocco@grandriver.ca