South Fraser Perimeter Road – Delta and Surrey, British Columbia

south-fraser

The westerly 23 kilometres (km) of the South Fraser Perimeter Road (SFPR) passes through the low lands of the Corporation of Delta, crossing agricultural areas, and running along the northern boundary of the environmentally sensitive Burns Bog. SFPR’s drainage system needed to be an integral part of Delta’s drainage and irrigation system, which includes Burns Bog.

The performance objectives for the drainage system on Delta’s flat, near sea level low lands include: maintain critical flood elevations anywhere in the impacted watershed after SFPR construction equal to or less than the maximum water surface elevations before SFPR construction; treat highway runoff for water quality prior to discharging into agricultural ditches; incorporate spill control features to allow for quick response in case of a spill emergency; and prevent stormwater runoff from SFPR and from lands with mineral soils around it entering the Burns Bog.

The drainage design included features that accelerate the flow of stormwater runoff towards the system outfalls to the Fraser River to maximize discharge by gravity during low-tide periods and maximize system storage available for receiving runoff from subsequent periods of storm events. As a result, in spite of the increased runoff from the SFPR project, critical water levels and pumping needs will remain below pre-SFPR levels.

South-Fraser-Burns_Bog_ControlsHighway ditches include flow control devices that provide storage for runoff from water quality storms to allow settling of suspended solids, and provide for quick and efficient actions to isolate ditch segments in case of an accidental spill.

Adjustable weirs and flow control devices (flap gates) are installed on structures at the major outlets of Burns Bog, allowing only one-directional outward flow from the Bog, ensuring that neither surface water nor groundwater from the SFPR project and surrounding developed areas will enter the Bog.

The Delta Watershed Model, built on the XPSWMM platform, was used extensively in the performance assessment and design of the SFPR drainage system.

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