The McNabb St./Pim St. Drainage Improvements
Location: Sault Ste. Marie, ON
Discipline: Environmental, Engineering, Contract Administration
Markets: Municipal Infrastructure
In 2016, the City of Sault Ste. Marie commissioned an Environmental Assessment to address flooding issues affecting public and private lands and infrastructure in the McNabb Street and Pim Street areas.
TULLOCH’s hydrological and hydraulic assessment of drainage systems identified the primary causes of flooding: the conveyance capacity of the minor piped storm sewer network and the lack of an overland flow route. Complicating the problem was that much of the City’s existing storm sewer infrastructure was placed very deep (~6-9m) on private property and the past topography of the area had undergone significant terraforming in the 1960’s, which filled a large existing ravine.
As common with many municipalities, development and urban sprawl has put pressure on existing downstream drainage systems. The subject sewer network drains much of the north central portion of the City of Sault Ste. Marie through the old downtown core. During the course of exploring options associated with increasing conveyance capacity within the storm sewer system, it was quickly identified that any increase in flows to the downtown core would simply result in moving the flooding problems from upstream to the downstream downtown core of the City.
The Class EA explored various options of reducing and managing runoff and/or flow rates from the watershed, both upstream and downstream of the proposed storm sewer replacement. The preferred alternative capitalized on the existing natural topography of the area by utilizing the existing ravine south of Bruce Street between Pim Street and Gladstone Avenue as a stormwater management pond. The reconstructed Gladstone Avenue roadway provided a man-made embankment/berm splitting the natural ravine in two.