TRACK 2, DAY 2
Adaptive Scope Management to Respond to Rapidly Changing Site Conditions – A Case Study in the Design and Implementation of Two Emergency Slopes Failures Along the Rouge River
Timothy Ng and Vithusan Jeyakanth, City of Markham; Jacob Ursulak, Aquafor Beech Ltd.
Wednesday, April 1, 2026 | 11:30 a.m. to 12:00 a.m. | Hall F
ABSTRACT
Over the last few years the City of Markham has experienced a series of mass slope failures along their watercourses resulting in imminent risks to private property, municipal infrastructure and public health and safety. Two of these slope failures occurred in quick succession along the banks of the Rouge River in late 2023 / early 2024 necessitating the undertaking of emergency works projects.
The first slope failure occurred along a City road, Mill Street, creating immediate risks to public safety and buried municipal infrastructure within the road right of way. As a direct result of the slope failure a street light feel into the watercourse creating a debris jam and the roadside guide rail was fully undermined.
In response to the slope failure, the road was closed and placed under a monitoring program. Emergency works were then implemented to temporarily stabilize the slope and mitigate erosion, while a long-term design solution was developed to address the localized failure area.
Later on, as the long-term design was about to be issued for tender, a second larger slope failure occurred further downstream highlighting the overall instability of the road embankment and necessitating that a second emergency works project be undertaken to stabilize the second failure area while the long-term design was rescoped to address the broader instabilities of the slope system.
Following the rescoping of the design, construction was completed in 2025 to stabilize the full 100-meter length of the road embankment using a combination of hardscaping (i.e., eight-tier armourstone wall) and bioengineering features.
The second slope failure occurred on a private residential property, creating risks to the residential dwelling and residents’ safety. In contrast to the Mill Street project, temporary erosion control works were not implemented at this site. Instead, a monitoring program was enacted with safety controls put in place to track the emerging conditions of the slope failure while a long-term design was developed and implemented under an expedited timeframe and emergency works permitting framework.
The design solution included a multi-tier armourstone retaining wall buried beneath a vegetated buttress for toe erosion protection.
The completion of these two projects act as a case study into how adaptive scope management is needed to respond to rapidly changing site conditions. The rapid evolution of the two slope failures onsite necessitated rescoping to expand the restoration area and ensure that immediate risks to public safety and infrastructure were addressed while also giving due consideration to the long-term stability of the overall slope systems.
ABOUT THE PRESENTERS
Timothy Ng, City of Markham
Timothy Ng is a project engineer working in the City of Markham’s Environmental Services Department where he manages projects related to storm water management and erosion control. Timothy acted as the City’s project manager for the Mill Street Slope Stabilization Project.
Vithusan Jeyakanth, City of Markham
Vithusan Jeyakanth is an environmental engineer working in the City of Markham’s Environmental Services Department where he manages projects related to storm water management and erosion control. Vithusan acted as the City’s project manager for the 8202 McCowan Road Local Slope Stabilization Project.
Jacob Ursulak, Aquafor Beech Ltd.
Jacob Ursulak is a water resources engineer at Aquafor Beech Limited, contributing regularly to projects related to stream restoration, erosion control, slope stabilization, outfall rehabilitation, and culvert/bridge replacement.
He has over 8 years of professional experience and has contributed to over 40 stream restoration and erosion control projects during his time at Aquafor Beech. Jacob acted as the project engineer and contract administrator for both the Mill Street Slope Stabilization and the 8202 McCowan Road Local Slope Stabilization projects in the City of Markham.