South Slocan Overhead

South Slocan, British Columbia

Project Details

Prime Consultant

BC Ministry of Transportation and Infrastructure

June 2015

December 2016


Structural | Transportation

Project Description


ISL was retained by the BC Ministry of Transportation and Infrastructure (MoTI) for functional design, detailed design, and tender and construction services, to replace a highway overpass structure (South Slocan Bridge) on Highway 3A between Castlegar and Nelson with a pedestrian culvert and embankment fill. The aging overpass structure spanned a decommissioned CP Rail spur line, and with the need to improve safety at the adjacent intersection by realigning the highway at the bridge, the overpass structure was removed.
The realignment of the highway was designed to improve sightlines at the intersection immediately north of the bridge. The ISL team’s design included upgrades to the two intersections on either side of the bridge, complete with improved turn bays, auxiliary lanes,
and upgraded lighting.

ISL developed the detailed contract language necessary for the contractor to dismantle and demolish the bridge. ISL also prepared the general arrangement and geometrics drawings for the pedestrian culvert, with close coordination and input from Ministry structural and geotechnical teams. The project was runner-up for the 2019 Deputy Ministers Award for Excellence in Design and Construction Preparation.



  • It was a requirement of the project to keep the highway open during the demolition of the bridge, given it is the primary route between Castlegar and Nelson.
  • The improvements to the highway and adjacent road network were immediately adjacent to several residences and business.


  • An adjacent frontage road which runs parallel to the highway was converted into a highway detour during construction. As the frontage road is a dead-end, it was temporarily extended to connect back to the highway at the north end of the project. The detour’s close proximity to the highway also required considerations for staging of the embankment fill and culvert.
  • The public open house had a high attendance from residents of the South Slocan Village. This allowed the design team to solicit input from the public on various items related to pedestrian connectivity, drainage, utilities, etc., and incorporate as many suggestions into the design as possible.