The extension, which will be announced on Thursday, is designed to take pressure off north-south road routes where congestion is a serious problem.
As well the new line is expected to be funded by about $30 million in development charges.
The money is being added to the procurement of Phase 2 light rail, now in early planning stages.
This extension will be accompanied by a new park-and-ride and a shuttle is expected to be created to ferry Barrhaven residents to the new Riverside South station.
The Trillium Line was originally begun as the O-Train that was designed as a temporary demonstration project for light rail in Ottawa but surprisingly is still the only operating LRT line in Ottawa.
Phase 1 of light rail, the Confederation Line under construction now at $2.1 billion, has been dogged by massive sinkholes and, under City of Ottawa stewardship, is late. It was expected to be operating this month but that deadline has been pushed back to November and some analysts believe Phase 1 won’t be completed then.
The November target extends the completion of Phase 1 past the Oct. 22 municipal election date.