TRACK 2, DAY 2
Unmaintained Stormwater Outfalls: Draining Water or Draining Resources?
Thursday, March 27, 2025 | 11:00 a.m. to 11:30 a.m. | Hall F
ABSTRACT
An increased number of drastically failed stormwater outfall structures causing widespread erosion concerns have been observed across Southern Ontario over the last 20 years.
The extreme failure of the stormwater outfall structures result in mass erosion of the surrounding areas, contributing to increased sediment loading within the downstream watercourses, leading to a decrease in the flow conveyance capacity, and an increase in operation and maintenance requirements.
In many instances of outfall failure, the infrastructure owner is unaware of the severity of the failure, and sometimes even the existence of the infrastructure itself. It is believed that these extreme cases of failure can be avoided through effective data base management, infrastructure monitoring, and preventive maintenance.
There are countless failure mechanisms across Ontario, including undermining of the stormwater headwall structure due to insufficient scour protection and the outflanking of the stormwater headwall structure through lateral channel erosion. However, one of the most devastating failure mechanisms is the corrosion and failure of upstream pipe segments, leading to the detachment of the headwall which in turn causes mass erosion that can rapidly propagate back up the upstream stormwater pipe, resulting in failure of the slope.
This form of outfall failure places property and infrastructure in close proximity to the failure, including buried utilities, multiuse trails and private dwellings, at an elevated level of risk.
The upcoming presentation will share examples of drastically failed outfall infrastructure, provide insight into the complex assortment of design factors, introduce the successfully implemented design solutions, and summarize the general design and construction best practices for future stormwater outfall projects.
One recently completed project of particular pertinence will be highlighted, in which a single stormwater outfall failure rapidly progressed over a 10-year timeframe, resulting in the loss of over 5,000 cubic metres of soil, ultimately requiring an eight-million-dollar design to be constructed in an environmentally sensitive and highly constrained urban area within Toronto, Ontario.
ABOUT THE PRESENTERS
Robert Amos, Aquafor Beech Ltd.
Robert Amos is a water resources engineer and fluvial geomorphologist specializing in the restoration of degraded natural channel systems within confined urban corridors to mitigate erosion and flooding related risks to infrastructure and private property. He has over 15 years of professional experience, has completed over 100 erosion control and stream restoration projects and currently serves as the CEO of Aquafor in Ontario, Canada.
Jacob Ursulak, Aquafor Beech Ltd.
Jacob Ursulak is a member of Aquafor’s water resources engineering team, contributing regularly to projects related to stream restoration, erosion control, slope stabilization, outfall rehabilitation, and culvert/bridge replacement. He has over 5 years of professional experience and has contributed to over 25 stream restoration and erosion control projects during his time at Aquafor Beech.