The City of Montreal’s drinking water department must repair the building envelopes of its drinking water plants in western island. The Dorval, Lachine and Pointe Claire plants are affected. The City contracts Macogep to manage the project. Objective: to analyze existing conditions and plan required work on the building envelope and site safety. The project has some sizeable challenges: construction work must be carried out without affecting plant production and must adhere to very high hygiene requirements to prevent drinking water contamination. Furthermore, Macogep must plan work taking into account the many projects that must be carried out simultaneously. Another success, as the program is respected and is allowing the City to achieve its objectives without affecting drinking water production.