TBT Engineering News

Agimak River Culvert – Replacement And Stream Rehabilitation


The 2018 Agimak River Culvert Replacement and Stream Rehabilitation on Highway 599, north of Ignace, ON, involved the removal of an aging creosote timber box culvert and replacing it with an open bottom sheet pile structure. This culvert replacement was required to improve highway safety, hydraulic capacity, and enhance existing fish spawning habitat for walleye and white sucker.

TBT Engineering’s Role

TBTE was retained by LH North Ltd. (LHN) to provide Fisheries Contract Specialist (FCS) Services during construction activities. FCS services during construction included:

  • Provide environmental input into dewatering and isolation plans, including Erosion and Sediment Control (ESC) planning;
  • Provide fish rescue services prior to removal of the old culvert;
  • Monitoring of erosion and sediment controls (ESC) during construction;
  • Assist with implementation of the new natural stream channel, which included a cobble substrate with a low-flow channel and large boulders to provide resting spots for fish.
  • Provide overall environmental monitoring to ensure serious harm to fish and fish habitat did not occur.


The Agimak River culvert was replaced with minimal disturbance to the aquatic environment. The combined efforts of TBTE’s FCS and the LH North construction crew resulted in a new watercrossing that is stable with a stream channel that provides enhanced spawning habitat and improved fish passage which should result in a significant benefit to the fishery.