Ontario Line

Potential effects and mitigation measures

Potential effects

Construction

• Disturbance or displacement of wildlife.
• Removal of/damage to trees, terrestrial vegetation and wildlife habitat.
• Potential impacts to aquatic/riparian vegetation.
• Potential erosion and sedimentation.

Operation

• Maintenance activities may result in disturbance/loss of vegetation and habitat.

Mitigation measures

Construction

• Sensitive-wildlife timing restrictions for construction activities (e.g., removal of vegetation outside of the breeding bird season).
• Wildlife exclusion measures will be implemented as required to avoid destruction, injury or interference with wildlife species and their habitat.
• Tree/vegetation removals will be kept to a minimum and limited to within the construction footprint.
• Temporarily disturbed areas will be restored/re-vegetated using non-invasive, preferably native plantings and/or seed mixes.
• Construction activities will maintain buffers established during the design phase to minimize potential impacts to wetlands and waterbodies.
• Erosion and sediment control measures will be implemented.

Operation

• Vegetation removal and habitat disturbance will be kept to a minimum and limited to within the Metrolinx right-of-way.

Read more - Appendix B1 – Natural Environment Report

Potential effects and mitigation measures

Potential effects

Construction

• Air pollution as a result of construction vehicle emissions.
• Dust resulting from earthworks, demolition and construction.

Operation

• No impacts to air quality are anticipated as a result of operations

Mitigation measures

Construction

• Contain (e.g., tarp) sources of dust such as soil stockpiles, as required.
• Use dust suppressants such as water, as required.
• Use equipment with low emissions, to the extent possible.

Read more - Appendix B2 – Air Quality Qualitative Assessment Report

Potential effects and mitigation measures

Potential effects

Construction

• Annoyance.
• Sleep disturbance.
• Interference with activities.

Operation

• Annoyance.
• Sleep disturbance.
• Interference with activities.

Mitigation measures

Construction

• Use equipment with low vibration levels, enclosures and silencers, where possible.
• Use construction equipment compliant with noise level specifications in Ministry of the Environment, Conservation and Parks (MECP) guidelines.
• Implement temporary construction site noise barriers.
• Off-site construction of components, where possible.
• Restricting construction hours, where possible.

Operation

• Noise and vibration reduction at the source (e.g., rail dampers, continuously welded rail, and quieter heating and ventilation).
• Noise walls.
• Resiliently supported rail ties and high resilient fasteners.
• Ballast mats or floating slabs.

Read more - Appendix B3 – Noise and Vibration Report

Potential effects and mitigation measures

Potential effects

Construction

• Access disruption to adjacent lands during construction.
• Visual effects from construction areas/activities.

Operation

• Visual effects from permanent public-facing structures and/or operations activities.

Mitigation measures

Construction

• Clearly marked pedestrian and cyclist detours, where required.
• Temporary lighting and wayfinding signage around construction sites.
• Maintained access to businesses during working hours.
• Temporary walkways with a pedestrian clearway of 2.1 metres in accordance with city guidelines.
• Screened enclosures and temporary landscaping along construction site boundaries, where necessary.

Operation

• Minimize the visual effects of project structures (e.g., elevated guideways, support structures, retaining walls) by considering their location, building materials, architectural design and surrounding landscape treatments.

Read more - Appendix B4 – Socio-Economic and Land Use Characteristics Report

Potential effects and mitigation measures

Potential effects

Construction

• For each property, the report presents a range of potential impacts and alternative mitigation options ordered from most to least preferred, from avoidance to demolition or removal. Avoidance is the preferred option. Demolition or removal is to be considered as a last resort and only when no other options are viable.

Operation

• No impacts to built heritage resources and cultural heritage landscapes are anticipated as a result of operations.

Mitigation measures

Construction

• Potential mitigation measures will vary based on the potential impact. Examples of potential mitigation measures include:
• Review of the project design to avoid impacts to property.

• Limit encroachment as close to the property line as possible to minimize impacts to the building and/or heritage attributes.
• For retention and reuse of the building, complete an Adaptive Reuse Study to document the heritage attributes and plans for minimizing impacts.
• For relocation/demolition, complete a structural engineering assessment, complete detailed documentation of the property including salvageable materials and/or heritage attributes, and during design, incorporate commemoration signage in consultation with the City of Toronto Heritage Preservation Services.

Read more - Appendix B5 – Cultural Heritage Report: Existing Conditions and Preliminary Impact Assessment

Potential effects and mitigation measures

Potential effects

Construction

• Potential for disturbance of archaeological resources.

Operation

• No impacts to archaeological resources are anticipated as a result of operations.

Mitigation measures

Construction

• If unexpected archaeological materials are encountered (or suspected), all work will stop. The site will be protected from impact until assessed by a licensed archaeologist as required.

Read more - Appendix B6 – Stage 1 Archaeological Assessment Reports

Potential effects and mitigation measures

Potential effects

Construction

• Temporary road/lane closures.
• Access restrictions to local bus routes.

Operation

• Modifications to local transit routes.

Mitigation measures

Construction

• Traffic control and management plans will be developed prior to construction.
• Access to nearby land uses will be maintained to the extent possible.
• Potential effects to pedestrians and cyclists will be mitigated through installation of appropriate wayfinding, regulatory and warning signage.
• Notifying the public in advance of potential disruptions.

Operation

• Notifying the public in advance of potential transit modifications.

Read more - Appendix B7 – Traffic and Transportation Report

Potential effects and mitigation measures

Potential effects

Construction

• There is a potential for structures to have foundations built below the local water table which may be affected by dewatering.
• Construction activities (e.g., excavation) could expose contaminated materials.

Operation

• No impacts to soil and groundwater are anticipated as a result of operations.

Mitigation measures

Construction

• Site-specific mitigation measures for impacts to groundwater quantity (e.g., avoiding or minimizing dewatering requirements).
• Remedial action plans, risk assessment and risk mitigation plans for encountering contamination, as necessary.
• Regular site inspection and associated monitoring activities.