Construction of Autoroute 85 in the Bas-Saint-Laurent region

Large-scale project aimed at improving safety and enhancing traffic flow on the main highway link between Québec and New Brunswick.

This $1.7 B multidisciplinary project involves the conversion of 94 km of Route 185 into an Autoroute, to be carried out in three phases over a period of close to 25 years. The first two phases have been completed, and the third phase is expected to be completed in 2026.

The CIMA+ team has been involved in the design process and/or site supervision for the construction of 9 segments (55.2 km) of the new Autoroute in the Bas-Saint-Laurent region since 2002. The main aspects of the mandates in which our team has been involved are as follows:

  • Multidisciplinary projects (road engineering, transportation structures, lighting, environment, traffic management, hydraulics, landscaping, geotechnics)
  • Construction of divided highways and secondary roads
  • Construction of overpasses, river bridges and numerous related transportation structures
  • Deforestation along de entire length of Route 185 to facilitate construction of the divided highway
  • Relocation of public utilities (overhead, lateral and underground)
  • Stormwater management and road drainage
  • Traffic management and signage (work sequencing to ensure traffic control (major roadway with a high volume of heavy vehicle traffic))
  • Installation of electro-technical systems, overhead signage and traffic control devices
  • Integration of environmental protection measures for plant and animal life
  • Creation of wildlife management facilities

Difficult geotechnical conditions

Some segments of the project presented difficult geotechnical conditions, including the construction of new roadways on soils varying in nature from bedrock to liquefaction-prone silt. The team solved this problem through geodensification and surface sealing of the ditches. In addition, the presence of compressible soil made up of peat and sensitive clay within some sectors of the Autoroute was dealt with by designing a bog drainage system and using a method of soil consolidation involving overloading.

Sustainable development and environmental protection

A number of segments of Route 185 included asphalt overlays that contained asbestos. The team took an eco-friendly approach by reintegrating the waste into the backfill. In addition, given the presence of a number of watercourses within the right-of-way for the new Autoroute, hydraulic engineering was carried out to protect the habitat of various fish species.

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