Significant geotechnical considerations for this project included long-term stability and erosion protection of the embankment slopes; bearing capacity and settlement considerations for the new arch culvert foundations; and/or, temporary excavation and temporary control of surface/ground water at the site.

This waterway is classified as a red-coded watercourse and is considered to be year-round salmonid habitat. In addition to corrosion and deformation, the culvert was determined to be undersized for existing and future land use flows as per the Upper Nicomekl River Integrated Stormwater Management Plan.

Geotechnical input was required to identify and address potential consolidation settlement, slope stability, foundation, retaining wall, and general constructability considerations. Kontur conducted a site reconnaissance/review, shallow hand-augered testholes, a desktop study, and provided a geotechnical memorandum outlining subsurface soil and groundwater conditions, considerations for slope stability, erosion, settlement, and for foundation design for design of reinforced concrete headwalls, wingwalls and culvert footings, engineered slope design, pavement restoration, excavation, temporary ground water or surface water control, site preparation, and engineered fills.

Replacement of the culvert was timed to coincide with the instream works window (Aug. 1 to Sept. 15). The existing arch culvert was replaced with twin-box pre-cast culverts (ea. 3.05m wide x 2.130m high x 19.86m long) and a redi-rock wall with a lock-block/Sierra slope system.

The $760,000 project also included creek bed improvements; tie-in of existing storm infrastructure into the new box culvert; removal and re-instatement of 35.3m of 200mm dia. PVC watermain; and road restoration. The new crossing will have increased hydraulic capacity.

As the crossing is approximately 6m wider than existing conditions, the road embankment was reconstructed on both sides with a Sierra slope (with living green wall face treatment) and concrete lock-block wall. The roadway was widened to current municipal design standards in anticipation of future road upgrades. Construction field reviews involving subgrade reviews, general construction reviews, documenting materials used (soils, geotextile fabric, geogrid), visual compaction verification, and lock-block wall installation were provided.

Significant geotechnical considerations for this project included long-term stability and erosion protection of the embankment slopes; bearing capacity and settlement considerations for the new arch culvert foundations; and/or, temporary excavation and temporary control of surface/ground water at the site. Kontur provided recommendations to address and mitigate the impacts.