Hydro-Québec carries out the La Romaine hydroelectric station development. This facility produces annually 1550 MW, and 8 TWh on average. It is located on the Romaine River to the north of Havre-Saint-Pierre – on the north coast. Macogep executes class A cost estimates as part of various construction projects. It must identify and analyze the risks, and determine construction methods, master schedule, detailed work schedule, direct costs, and overhead. This complex project presents many challenges: number of involved stakeholders that require a close coordination, and a project multidisciplinarity that requires an expertise in various fields. Concurrently, Macogep contributes to Hydro-Québec pilot project. The goal is to implement BIM (Building Information Modeling) design, and develop a 3D modelling software-oriented approach in estimation. This approach optimizes and increases the accuracy of quantity calculation. Macogep’s contribution optimizes the proposed design within budget and gets an objective perspective on the costs of the projects to carry out.