The Champlain Bridge reopened on Saturday after a delay of more than nine hours as workers secured a "superbeam" to the span's underside.

The Champlain Bridge is about to get superbeamed -- workers and cranes are moving the superbeam into place. (Bridge Corporation/Twitter)

The bridge was supposed to be closed overnight from 2 a.m. to 7 a.m. ET, but the reopening has been delayed because of the time it has taken workers to first cut a median on the bridge, then to secure the superbeam.

It was originally rescheduled to open at noon, but it was just before 4 p.m. ET Saturday when the Jacques-Cartier and Champlain Bridges Corporation said it would slowly start the reopening process of one lane in either direction.

The beam that is being installed this morning is meant to reinforce a cracked girder. The crack was first discovered three weeks ago and has since doubled in length.

The Champlain Bridge is the main lifeline for hundreds of thousands of commuters travelling between Montreal and the South Shore.

It's also the main bridge used for trips from Montreal to the Eastern Townships, New England and elsewhere on the Eastern Seaboard, making it Canada's busiest span.

The federal government says that approximately $20 billion in international trade crosses the Champlain Bridge every year.

The Champlain Bridge... Was built between 1957 and 1962 and cost $35-million.

It opened in 1962 and was named for French explorer Samuel de Champlain.

Is a steel truss cantilever bridge.

Is three kilometres long; its approaches make it six.

Carries the most trucks, cars and people than any other bridge in Canada.

Bridge with a troubled past

The bridge has been a source of Montrealers' consternation for years. Opened in 1962, it has had multiple repairs and reinforcement measures applied in recent years, resulting in closures.

A hole in the Champlain Bridge developed last May, and before that, in 2011, the Montreal Catholic Church took out a billboard ad overlooking the bridge that read, "Say Your Prayers."

The federal government announced a plan two years ago to replace the bridge by 2021, at a cost of between $3 billion and $5 billion.

When the bridge does reopen, a lane in either direction will be what commuters have to contend with until Monday at 5 a.m.

At that point, traffic is expected to return to normal.