According an STM news release, groundwater has seeped through the tunnel roof, requiring major repairs to both the structure and electrical system.
"These repairs are needed to keep our infrastructure in good working condition and ensure the reliability of our network. Although the safety of transit users is not at all at issue, if we want to act responsibly, we must carry out this work in 2014," said Carl Desrosiers, STM's chief executive officer in the statement.
Work will be be carried out at night in January, which will have not impact on customers.
However, there will be no metro service between Montreal and Longueiul for a total of 25 weekends from March to May and from September to December.
During these construction periods, the yellow line will close Friday evenings and reopen Monday mornings.
Service will operate as usual during the summer months.
The STM said it will provide a shuttle bus service between Longueuil, Papineau and Berri-UQAM during the metro interruptions.
"The success of the work depends largely on the quality of the mitigation measures that will be implemented and information to customers. That is why nothing will be spared to ensure travel efficiently, despite the inconvenience created by the repair work," said Philippe Schnobb, the newly appointed chairman of the STM's board of directors.