General Motors Canada says it will cease operation of another assembly line at its Oshawa, ON, Canada vehicle plant in 2013, removing an estimated 115,000 units of capacity from a facility that once churned out more than 1 million cars and trucks annually.

The auto maker first announced its intention in 2005 to shutter Oshawa’s “consolidated” assembly line in 2008, which builds the current-generation Chevrolet Impala large sedan and some Equinox cross/utility vehicles.

However, the auto maker gave the line a reprieve due to sustained demand for the Impala. In 2010, GM started a shuttle program to meet demand for the Equinox, shipping unfinished units started at the company’s Ingersoll, ON, facility for completion at Oshawa.

GM last year said extra Equinox production would shift to the U.S. and its Spring Hill, TN, assembly plant, which has been idle for three years.

Oshawa will maintain production on its “flex” line, which builds the Chevy Camaro sports car, Buick Regal sports sedan and all-new Cadillac XTS large sedan. In 2013, the facility will serve as one of two sites for assembly of the ’13 Impala.

GM says the cadence for winding down the consolidated line will start with the removal of the third shift in the fourth quarter, followed by the take-down of the second shift in the first quarter of next year. June 2013 will see the line stop operations entirely.

Faye Roberts, a spokeswoman for GM Canada, says it’s unclear how many jobs will be affected by today’s announcement.

“It is too early to predict accurately the job impacts related to these scheduling actions, which will unfold over the next year, as some employees may elect to retire and others will be on indefinite layoff,” she tells WardsAuto.

Closure of Oshawa’s consolidated line comes ahead of national contract talks this summer with the Canadian Auto Workers union and marks another blow to GM’s operations in Southern Ontario.

As recently as 2008, the region accounted for 1.2 million units of GM car and truck output. But the severe downturn in truck sales that year ended their production as the worldwide recession took hold, removing some 310,000 units, according to WardsAuto data.

The consolidated line produced 365,000 units in 2011 while the flex line accounted for 200,000 builds. The flex line will boost production to 450,000 vehicles annually in 2013, a WardsAuto forecast shows.

The Ingersoll plant, located 120 miles (200 km) north of Oshawa, will contribute another 240,000 units annually going forward.

jamend@wardsauto.com