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TransAlta Corporation – Keephills Power Plant Repowering, AUC Decision 25240-D01-2020

Link to Decision Summarized

Coal Plant Conversion

In this decision, the AUC considered whether to approve an application from TransAlta Corporation (“TransAlta”) for the alteration of a power plant, designated as the Keephills Power Plant, by constructing and operating a new combined-cycle power plant to repower Keephills Unit 1 (the “Project”). The AUC approved the application.


TransAlta applied to the AUC for approval under sections 11 and 19 of the Hydro and Electric Energy Act to alter Keephills by installing a new combined-cycle power plant to repower Keephills Unit 1.

Keephills units 1 and 2 are in the process of being converted from coal-fuelled to natural gas-fuelled. They have been approved to operate as coal-fuelled until alterations have been completed.

The AUC noted that TransAlta is seeking approval to alter Keephills by constructing and operating one combustion turbine generator and one heat recovery steam turbine generator to repower Keephills Unit 1. The newly installed turbine would be integrated with the existing facility to produce electricity and steam. The produced steam would drive the existing Keephills Unit 1 steam turbine generators.

Separately, TransAlta registered a similar application, Application 25239-A001, to alter the Sundance Power Plant by installing a new combined-cycle power plant to repower Sundance Unit 5. The Sundance Power Plant is also located in the Wabamun Lake area, approximately five kilometres from Keephills.


The AUC determined that the technical, siting, environmental and noise aspects of the application were met. The AUC was satisfied that TransAlta conducted its participant involvement program in accordance with Rule 007.

The AUC found that the Project complies with Rule 012. It was satisfied with TransAlta’s use of conservative assumptions in its modelling, and expects that if non-compliances are discovered, TransAlta would mitigate them appropriately.

The AUC noted that TransAlta submitted the application with generic equipment assessed, which it indicated would be representative of the equipment that would eventually be installed. The AUC requires confirmation that the final equipment selection would not materially change the impacts of the Project from what was detailed in the application. Therefore, any approval granted by the AUC is conditional upon the following:

a. Once TransAlta has made its final selection of equipment for the Keephills Unit 1 project, it must file a letter with the Commission that identifies the make and model of the generating units. In this letter, TransAlta must also confirm that the project will not increase the land, noise, or environmental impacts beyond those reflected in the materials submitted by TransAlta in its application and approved by the Commission. The letter is to be filed no later than 30 days before construction of the project would commence.

Based on the foregoing, the AUC found that the approval of the Project is in the public interest.

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