Two excavators that entered Georgian Bay after a temporary stone berm became unstable during construction of the Thornbury Wastewater Treatment Plant outfall have been recovered, with no injuries or spills reported.
Just before 10 p.m. on September 23, personnel working for the project’s marine contractor were repositioning equipment on the berm when a section became unstable, causing the excavator to enter the water, according to the Town of The Blue Mountains, Ontario.
During the initial recovery effort, another section of the berm became unstable and a second excavator entered the water.
Clearway Construction, the town’s primary contractor for the project, deployed spill-containment measures around both excavators following the incident. The town said no releases of fuel, oil or other fluids were observed.
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Recovery was delayed while the contractor assessed the stability of the berm and the access route to the equipment.
The first excavator was recovered at approximately noon on September 25, while the second was removed from the water at approximately mid-afternoon the following day. The extrications were at no additional costs to the town, according to Allison Kershaw, manager of water and wastewater services for the Town of The Blue Mountains.
Spill kits and other containment measures remain at the site as a precaution, Kershaw added.
The incident was reported to the Canadian Coast Guard, Fisheries and Oceans Canada, Ontario Ministry of the Environment, Conservation and Parks, Ministry of Natural Resources and Grey Sauble Conservation Authority.
Clearway Construction has advised the town that it remains committed to completing the outfall work during the 2026 construction season. Approximately 310 metres of the trench has been excavated to full depth. The final 100 metres of the trenched portion requires minimal digging.
The outfall pipes will allow the plant to meet its full capacity, and will run 1.5 kilometres into Georgian Bay. The pipes will be assembled in 200-metre lengths on the shore, and then floated until final assembly can be completed.
The project team is now determining which work must be completed before October 14 to avoid impacts on fish-spawning areas, as well as what work could continue after the permit period, subject to regulatory approval and without adversely affecting those areas.
According to the town, its contract requires the contractor to deliver the outfall according to its design for the tendered amount, barring any contract change orders. No additional municipal budget approval is required for the excavator recovery or work extending beyond the project’s original schedule.
The town, its engineering consultant and the contractor will continue meeting to monitor construction progress and address issues as work proceeds.
