BC Hydro submitted its application to the Environmental Assessment Office for an environmental certificate to install a sixth turbine at the Revelstoke Dam.
The Crown utility says the energy produced by the turbine will be needed by 2026, but that it hopes to have it installed by 2021 in case more capacity is needed sooner.
The turbine is expected to boost the capacity of the dam by 500 megawatts to 3,000 megawatts total.
A news release says the turbine will be needed earlier than expected because of major maintenance scheduled for the Mica Dam starting in 2026. The work at Mica will mean one turbine at a time will be out of commission for periods of 12-18 months.
Revelstoke Six is expected to cost $582 million and will create 436 person years of employment, says BC Hydro.
The Environmental Certificate process has been criticized for only looking at the incremental impacts of adding a sixth turbine, and not seeking to address the unforeseen impacts of the fifth turbine, which was installed in 2010.
At an open house about the project last June, concern was expressed about what the increased flows resulting from a sixth turbine could mean for downstream ecosystems.
Revelstoke Dam was completed in 1984 with four turbines, but room was made for two more to be added in the future.