Canada Post will scale back its operations at its plant located at Industrial and Riverside in the fall.
CFRA has learned the Crown Corporation will be streamlining work at the plant starting in August.
"The plant will still be in operation, however, some of the mail processing is going to move to Montreal," John Hamilton, a spokesperson at Canada Post told CFRA. "The people at the plant in Ottawa will continue to do valuable work sorting some of the remaining mail: parcels, and packets and direct mail, which is part of the areas of our business that are growing."
Right now around 500 people work at the plant, but they plan to reduce the number of jobs by 100 full time and part time positions.
The jobs will be cut through attrition.
Canada Post will eventually sell off the plant at Industrial and Riverside and will move operations to a smaller, one-storey facility with newer equipment.
"Our plan is to continue for the next little while with that facility, but it no longer suits the needs of a modern processing operation," said Hamilton. "Eventually we will move to a new location and look to sell that building."
Similar initiatives are also taking part at plants in Hamilton and London.
The scale backs are part of Canada Post's 5-point plan introduced last December, which included a move to community mail boxes.
The Canadian Union of Postal Workers (CUPW) plans to fight the move to close the giant sorting plant.
"It's always, cutting, cutting, cutting jobs to make supposedly this corporation profitable, but you cut the service, you cut the jobs and now you will centralize all the mail in the larger facility in the country and leave Ottawa without that kind of services," said CUPW National President Denis Lemelin.
Lemelin told CFRA mail service could be affected in Ottawa as Canada Post scales back operations.
"There can be some impact around the delay of mail because the mail would be processed in Montreal, we'd be in the line, all the main coming from Quebec and part of Ontario," he said.
He insisted they have the same capability to process the mail in Ottawa as they do in Montreal and it's a shame to see jobs taken out of the community.
"It's always easy to say it's by attrition, but people are not replaced," said Lemelin. "When people are not replaced, it's a good job lost for the community."