Motorists travelling between Montreal and South Shore may experience significant slowdowns this weekend as workers install a “superbeam” to support the deteriorating Champlain Bridge.

Traffic will be reduced to one lane in either direction on the bridge from 9 p.m. Friday to 5 a.m. Monday.

The bridge will also be closed completely for a five-hour period early Saturday morning, 2 a.m. to 7 a.m., while engineers and workers place the 75-tonne steel girder.

They’ll need the entire width of the bridge to place the superbeam, which is meant to reinforce the bridge’s supports after a crack with a two-millimetre opening developed in mid-November. The crack doubled in length in one week. 

The superbeam installation is a temporary measure to help ensure the bridge is secure. It will be removed in the spring and replaced with another, lighter girder that will support the cracked concrete.

According to the Jacques-Cartier and Champlain Bridges Corporation — which is responsible for the management and upkeep of the structure — weather conditions should be favourable enough to allow the work to proceed this weekend.

Environment Canada is predicting clouds overnight, sun on Saturday and intermittent rain and snow on Sunday.

Bridge circulation, including bus lanes, should return to normal on Monday afternoon.