Quesnel River Bridge Preliminary Hydrotechnical Design
The Quesnel River Bridge Preliminary Hydrotechnical Design Project began in 2019. Some of the main components of the project included replacing the Quesnel River Bridge and the Quesnel BC Railway Overpass. With the bridge being around 60 years old and at the end of its design life, it was time for a replacement. As it currently stands, the bridge route is regularly utilized by large vehicle traffic such as semi-trucks, and the existing bridge’s narrow properties make it highly challenging to accommodate multiple large vehicles.
As a result of this, in August 2020, commuters were stuck in congestion for several hours due to an out-of-town semi-truck that struck and damaged the rail on the Quesnel Bridge. Damage was estimated to be around $120,000, which included damage to the city’s water main.
The new proposed design would “increase safety and significantly reduce congestion as commercial vehicles travelling through the region.”
“The Quesnel River Bridge is “too narrow [and does] not meet height and width restrictions for overloaded trucks…. both the Quesnel River Bridge and the Quesnel Rail Crossing Bridge need replacement as they are both coming to the end of their service life,” as stated in a QA document prepared by MOTI.
As a part of this assignment, Binnie completed a hydrologic and hydraulic analysis to develop hydro-technical design criteria for the Quesnel River bridge replacement. Three potential bridge layouts were provided by CWMM (our structural sub-consultant) for consideration. The scope of the assignment included:
Estimating design flows with consideration of climate change.
Estimating maximum anticipated water levels for various design events.
Estimating design velocities.
Reporting on potential ice and debris loads.
Estimating the scour depth and the design of erosion protection to minimize future erosion.
One of the critical hydro technical components that we had to consider is the various forces acting upon the bridge piers and abutments. Piers located within the main river channel are subjected more frequently to ice and debris loads than those located within the floodplain, although ice and debris loading can still occur in the floodplain during peak flow events. Scour is another concern when designing bridge piers and abutments. High river velocities can scour out the riverbed from around a pier, and, if not calculated properly can compromise the structural stability of the bridge pier. In addition, piers in the main river channel are more difficult to construct, given that the final location of the pier is surrounded by water under normal conditions. In order to construct bridge piers in the main channel, more complicated and costly construction methods are required than those normally on dry land.
Additionally, the Ministry of Transportation and Infrastructure retained Binnie to complete the preliminary design for the Quesnel Interconnector project, which would provide a new route through the City of Quesnel and perform as an alternate route for traffic away from the downtown core. Currently, Highway 97 runs through Quesnel, with many signalized intersections. The new interconnector would allow for the highway to connect without the town commute. Once the interconnector is connected in the future, it will become Highway 97.
Overall, the project will improve highway mobility and safety for users travelling through and within the City of Quesnel by providing an alignment outside of the downtown core for commercial traffic with a reduced number of stoppage points and conflict locations.