Drivers trying to get to the West Island on Highway 20 west will be in for traffic headaches this week.

Transports Québec has temporarily closed the left lane of Highway 138 east, off the Mercier Bridge, on the approach to Highway 20 west at the St-Pierre interchange.

The ministry said the closures are necessary because workers discovered more serious damage than anticipated during the repair of a pillar of the bridge crossing the Lachine Canal.

The repairs could take all week, according to Transports Québec.

The Réseau de Transport Métropolitain says it will offer free train service on the Candiac train line until the repairs are complete.

The hours of the reserved bus lane on the Champlain Bridge will also be extended.

Hwy 20 W from the Champlain Bridge off limits for 2 months

Motorists trying to get to Highway 20 from the Champlain Bridge will also have a tough go starting Monday night.

Access to Highway 20 west from Highway 15 north will be off-limits for the next eight weeks, as of 10:30 p.m.

Motorists will have to choose between two different detours. Exit 62 at de la Vérendrye Boulevard will be modified to allow drivers easier access to Saint-Patrick Street.

Click on this map for a closer look at the detour options:

From there, they will be able to reach Highway 20 via Notre-Dame Street West and the Monk Bridge.

The other option would see drivers continue on Highway 15 northbound to Côte-St-Luc Rd., and then backtrack on Highway 15 southbound to Highway 20 westbound ramp. Officials stressed the latter option should be a last resort, as Côte-St-Luc is already seeing dense traffic.