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Mactaquac Generating Station Alkali - Aggregate Reaction Mitigation Operations


Since the 1980s, concrete portions of the Mactaquac Generating Station located on the Saint John (Wolastoq) River have been affected by a chemical reaction called Alkali-Aggregate Reaction (AAR). AAR causes concrete to swell and crack, requiring annual maintenance and repairs. AAR concrete expansion at the station can result in movement of up to 5 mm/year. This movement affects embedded equipment such as turbines, generators, gates and pipes impacting the operation of critical equipment.

Since the 1990s NB Power has been employing slot-cutting, as well as drilling and grouting techniques to impacted concrete structures to mitigate AAR. These activities are essential to maintaining the on-going safe operation of critical equipment associated with the Mactaquac Generating Station. A by-product from the implementation of these mitigative strategies is the generation of wastewater effluent and sludge, which is currently being collected and transported off-site. 

As part of its commitment to sustainability, NB Power is working on a Long-term Treatment Suitability Study for the onsite treatment and disposal of the wastewater effluent and sludge. A pilot is currently underway to treat the wastewater effluent generated from the drilling grouting (Pilot Test). The results from the Pilot Test will be used to inform a Long-term Treatment Suitability Study. 

An Environmental Impact Assessment was registered in August 2021 for the project and is available for review at the following link: Mactaquac Generating Station Alkali-Aggregate Reaction Mitigation: Effluent and Sludge Treatment and Disposal. The report includes a complete description of the proposed project, an assessment of potential impacts and recommended mitigation measures to be incorporated into the project to ensure any environmental impacts are not significant.

Any questions, concerns or comments on the project can be submitted to:

Note: As of May 1, 2024, the Environmental Impact Assessment for this project has been withdrawn and information/results are being incorporated into the Mactaquac Life Achievement Project.