Chester Creek Hydrologic Analysis and Culvert Design
From 2016 to 2019, The Ministry of Transportation and Infrastructure retained Binnie to prepare the detailed design for a 3 km stretch of Highway 7, located between Silverdale Avenue and Nelson Street, in Mission, BC.
The project was part of a multi-phased project to upgrade the highway from two lanes to four lanes through Mission. Upgrading the last remaining two-lane segment of the highway was crucial to improve capacity and safety. In addition, the two intersections along this stretch of the highway have higher collision rates than the provincial average. This project was intended to improve the safety at these intersections and decrease the collision rates.
The project included widening the highway to four lanes, upgrading highway drainage infrastructure, and improving the overall hydrology and hydraulics of Chester Creek and associated tributaries to minimize flooding risks in the area. Binnie was the prime consultant responsible for the overall design. As the prime consultant, we completed a detailed drainage study for the project including a hydrologic model using the AutoCAD Storm and Sanitary Analysis Modeling Program.
The hydrological model was used to determine the peak design flows and maximum water levels along Chester Creek during various storm events. Culverts along Chester Creek and its associated tributaries were designed to meet Water Sustainability Act regulations, including fish passage criteria for both free outfall and pumping scenarios. Extensive coordination was required with the City of Mission, adjacent property owners, utility owners, and the Department of Fisheries and Oceans. The drainage assessment also considered the potential risk of flooding the adjacent farm fields.
Chester Creek is located immediately upstream of the Fraser River, with water levels within Chester Creek partially controlled by water levels within the Fraser River. This created a particularly challenging design constraint for the project. The capacity of Chester Creek was further constrained by an existing pump station located between the Highway and the Fraser River. Chester Creek outfalls to the Fraser River through a pump station located within the project limits. The hydraulic performance of the Chester Creek pump station was modelled using survey data, as-built records, and input from the City of Mission operations staff to determine input parameters. The existing pump station was under capacity, causing unwanted flooding upstream. This pump station was scheduled for an upgrade after the completion of the project with the project relying on future upgrades to help reduce upstream flooding.
Upon completion of the project, benefits included improved road safety along this stretch of highway, improved hydraulic capacity that will reduce flooding, and fish habitat improvements along the new four-lane corridor.
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