The Wainman Line culvert replacement project involved replacing a deep-fill concrete culvert buried beneath more than 10 metres of embankment while maintaining uninterrupted flow of the North River. The existing structure, originally constructed as a cast-in-place concrete box culvert and later extended with precast sections, presented significant design and construction challenges including high-velocity river flows, a nearby Hydro One transmission corridor, and multiple utilities within the roadway corridor.

Tatham developed an innovative solution featuring an open-bottom culvert supported on footings that spanned beyond the footprint of the existing structure. This approach allowed the river to continue flowing through the original culvert throughout construction, eliminating the need for in-water work, reducing environmental impacts, and simplifying construction staging. Hydro and natural gas utilities were successfully relocated using directional drilling beneath the culvert foundation.

Construction included cast-in-place footings, installation of precast culvert units, up to 4-metre high retaining walls, and full roadway reconstruction. By preserving the natural creek bed and maintaining aquatic habitat throughout the project, the design balanced constructability, environmental stewardship, and long-term infrastructure resilience.