Ontario Line

Potential effects and mitigation measures

Potential effects

• Removal of/damage to trees, terrestrial vegetation and wildlife habitat.
• Erosion and/or sedimentation-related impacts to vegetation communities as a result of construction.
• Disturbance or displacement of wildlife species and reduced habitat connectivity.
• Risk of contamination to soil or waterbodies as a result of spills.
• Introduction or spread of invasive species.

Mitigation measures

• Identify opportunities to promote pollinator species and habitat in accordance with the Metrolinx Vegetation Guideline (2020) (e.g., this may include planting or seeding native flowering plants in temporarily disturbed areas).
• Tree and vegetation removals will be kept to a minimum and limited to within construction areas.
• Tree and vegetation removal compensation will be provided in accordance with the Metrolinx Vegetation Guideline (2020).
• Temporarily disturbed areas will be restored/re-vegetated.
• Erosion and sediment control measures will be installed prior to construction commencement.
• Prior to early works activities, species-specific surveys will be completed as required to avoid or reduce potential impacts to bat Species at Risk and meet all Species at Risk regulatory requirements.

Read more - Appendix A1 – Natural Environment Report

Potential effects and mitigation measures

Potential effects

• Temporary increase in air pollution and odour (e.g., diesel combustion products such as NO2) as a result of construction vehicle emissions and increased traffic due to congestion associated with early works activities.
• Temporary increase in dust, silica and airborne particulate matter resulting from earthworks, material handling and transfer, and other construction activities.

Mitigation measures

• Construction equipment will comply with all applicable regulatory emission standards.
• Contain (e.g., tarp) sources of dust such as soil stockpiles as required.
• Removal of accumulated mud, dirt and debris deposits, and regular truck washing.
• Reduction of activities during high wind conditions where feasible.
• Use dust suppressants such as water as required.
• Implement on-site air quality monitoring and apply threshold “Action Level” triggers for implementation of specific and increasing intensity mitigation activities linked to specific construction activities.

Read more - Appendix A2 – Air Quality Report

Potential effects and mitigation measures

Potential effects

Noise

• Without mitigation, potential for noise level criteria exceedances at 502 Front Street East, 68 Broadview Avenue, 9 Lewis Street, 20 Saulter Street and 2 McGee Street.

Vibration

• Without mitigation, there is potential for vibration criteria exceedances at 341 and 353 Eastern Avenue, 9/11 Lewis Street, 20 Saulter Street and 11 Sunlight Park Road.

Mitigation measures:

Noise

• Establish and apply project-specific construction noise criteria/exposure limits.
• Use construction equipment compliant with noise level specifications in the Ministry of the Environment, Conservation and Parks’ NPC-115 and NPC-118 guidelines.
• Keep equipment in good working order and operate with effective muffling devices.
• Evaluate acoustic equipment enclosures for equipment such as compressors and generators.
• Use upgraded construction hoarding (considering requirements from CSA Z107.9 for noise barriers) between construction equipment and noise sensitive receivers.
• Use localized noise barriers for specific equipment and operations, including on corridor construction works.

• Reduce simultaneous operation of equipment where possible.
• Implement a no idling policy on site (unless necessary for equipment operation).
• Restrict construction hours where possible:
  
  • perform construction during daytime hours where possible; and
  • if nighttime construction is necessary, activities with the highest noise levels should be conducted during daytime periods. If construction will occur outside of normal daytime hours, inform local residents of type of construction and expected duration prior to commencing work.
• Undertake noise monitoring and regular reporting throughout the construction phase as required.
• Develop a communications protocol for providing advance construction and vibration impact notices and addressing public complaints in a timely manner.

Vibration

• Use equipment with low vibration emissions where possible.
• Operate construction equipment on lower vibration settings where available.
• Provide smooth surfaces for trucks to travel.
• Maximize distance between equipment and sensitive receivers where possible.
• Restrict construction hours where possible:
  
  • perform construction during daytime hours where possible. If nighttime construction is necessary, the activities with the highest vibration levels should be conducted during daytime periods; and
  • if construction will occur outside of normal daytime hours, inform local residents in advance, describing type of construction and expected duration.
• Use alternative construction methods and/or equipment with lower vibration emissions or power settings where possible.
• Review and refine the construction activities to avoid potential impacts to 341 and 353 Eastern Avenue, 9/11 Lewis Street, 20 Saulter Street and 11 Sunlight Park Road.
• Conduct monitoring and pre-construction inspections in accordance with City of Toronto Bylaw 514 as required.
• Develop a communications protocol for providing advance construction noise and vibration impact notices and addressing public complaints in a timely manner.

Read more - Appendix A3 – Noise and Vibration Report

Potential effects and mitigation measures

Potential effects

• Temporary lane restriction/closures and construction vehicle traffic causing impacts to traffic flow of nearby roads such as Eastern Avenue and Broadview Avenue.
• Travel time delays for existing transit services (i.e., TTC bus route #143 Downtown/Beach Express) due to potential lane restrictions and construction vehicle traffic.
• Potential realignment of the existing sidewalks along Eastern Avenue, Lewis Street, Broadview Avenue, and Sunlight Park Road could lead to increased walking distances.
• Temporary full or partial closure of existing rail tracks may cause temporary reductions or delays of typical rail services.

Mitigation measures

• Develop and implement a transit and traffic management plan as planning progresses.
• Consider scheduling early works activities during off-peak periods and weekends to minimize disruptions to traffic during the critical peak hours.
• Issue notifications and advisory signage to alert traffic and transit users of any upcoming road closures and disruptions as required.
• Coordinate with the City of Toronto to provide pedestrians and cyclists with safe, accessible, and continuous routes during early works activities.
• Consult and coordinate with the City of Toronto to ensure any modifications to pedestrian crossing distances at signalized intersections are reflected in revised pedestrian clearance timing.
• Consult with rail companies (i.e., Canadian National Railway, Canadian Pacific Railway, and VIA Rail) that operate along the rail corridor to assess how track closures would impact their service and coordinate temporary schedules to accommodate all rail services on the open tracks.

Read more - Appendix A4 – Traffic and Transportation Report

Potential effects and mitigation measures

Potential effects

• Potential for disturbance of deeply buried archaeological resources due to East Harbour Station early works activities.

Mitigation measures

• Complete additional archaeological assessment(s) where required, as early as possible and in advance of any ground disturbance.
• If archaeological materials are encountered (or suspected) during construction, all work will stop. The site will be protected from impact and additional assessment will be undertaken.

Potential effects and mitigation measures

Potential effects

• No known, previously identified or potential built heritage resources/cultural heritage landscapes (BHR/CHL) were identified in the East Harbour Station study area.
• No impacts to BHR/CHL are anticipated as a result of East Harbour Station early works.

Potential effects and mitigation measures

Potential effects

• Potential impact on flooding conditions in the Don River floodplain.
• Potential flooding impacts on site during construction.
• Potential change in stormwater quantity and quality which may impact receiving waterbodies and/or municipal stormwater drainage systems.

Mitigation measures

• Floodplain impact assessment will be conducted during detailed design following Toronto and Region Conservation Authority (TRCA) guidelines once relevant design information is available.
• Develop a flood contingency plan with specific measures for any proposed work or temporary laydown and staging areas in the Don River floodplain, as project planning progresses.
• Develop the overall stormwater quality and quantity control strategy in accordance with all relevant municipal, provincial, and federal requirements.
• Develop a stormwater management plan and an erosion and sediment control plan, as project planning progresses.
• The following stormwater management best practices will be considered and implemented as required:
  
  • reduce amount of exposed soil;
  • install sediment control measures before grading/land alterations begin;
  • sequence early works activities;
  • protect storm drain inlets to filter out debris; and
  • stabilize all exposed soil areas as soon as land alterations are complete.
• If required, obtain a Municipal Discharge Permit (City of Toronto Private Water Discharge Permit/Agreement) to manage excess surface water/stormwater.
• TRCA, Waterfront Toronto, and City of Toronto will be consulted to avoid potential infrastructure conflicts and impacts to adjacent flood protection measures/ initiatives.
• East Harbour Station early works will be aligned with the Lower Don Special Policy Area requirements, in consultation with TRCA.

Potential effects and mitigation measures

Potential effects

• Potential for land use and access disruption to adjacent lands to accommodate early works activities.
• Nuisance effects (i.e., dust, noise and vibration) and potential for light trespass from early works activities.
• Visual effects from permanent public-facing structures and early works activities.
• Permanent and temporary property acquisition (property requirements will be confirmed as project planning progresses).
• Permanent or temporary relocation or removal of streetscaping materials, furniture and landscaping in the public realm.

Mitigation measures

• Maintain regular (existing) access to businesses during working hours, where feasible. Where regular access cannot be maintained, alternative access and signage will be provided.
• Develop a plan to manage air quality to mitigate potential impacts of dust during early works activities (see Air Quality for further detail and additional mitigation measures).
• Comply with all local applicable municipal by-laws and Ministry of Transportation practices for lighting in areas near or adjacent to highways and roadways regarding outdoor lighting for both permanent and temporary construction activities.
• Specific permanent property requirements associated with the early works infrastructure components and temporary property requirements associated with construction staging/laydown and access will be minimized to the extent feasible as planning and design progress.
• Where possible, use equipment with low vibration emissions, provide smooth surfaces for trucks, and restrict construction hours (see Noise & Vibration for further detail and additional mitigation measures).
• Reduce the visual effects of the station structures and the Eastern Avenue bridge by selecting appropriate building materials and architectural design.
• Provide screened enclosures along early works site boundaries where necessary.
• Provide temporary lighting and wayfinding signage around early works sites as required.
• Provide clearly marked pedestrian and cyclist detours where required.
• Following completion of early works, impacted lands will be restored to current City of Toronto standards wherever feasible. Temporary relocation or removal of streetscaping materials, furniture and landscaping in the public realm will be minimized to the extent feasible.

Potential effects and mitigation measures

Potential effects

Groundwater

• Subsidence/settlement of structures in the Zone of Influence* (ZOI) due to construction dewatering if dewatering is required.
• Encounter previously contaminated groundwater during early works activities (e.g., dewatering).
• Construction dewatering may impact groundwater-dependent natural features (i.e., Don River) as a result of decreases in groundwater discharge.

Soil

• Potential displacement of soils as a result of early works activities may result in ground movement and settlement.
• Early works activities (e.g., excavation) could expose and/or result in the spreading of contaminated materials.

*The Zone of Influence refers to the area where groundwater levels will be lowered due to dewatering.

Mitigation measures

Groundwater

• As project planning progresses, determine water taking quantities, quality, and resultant dewatering ZOI through a site-specific hydrogeological investigation, construction dewatering assessment and groundwater management plan as required.
• If anticipated, potential subsidence/settlement impacts to existing structures can be mitigated with measures such as the completion of pre-construction inspections of structures in the dewatering ZOI and implementation of a detailed settlement monitoring program, complete with settlement triggers that result in changes to the dewatering program if surpassed.
• Adhere to source water protection best management practices where necessary, including the development of a salt management plan and a plan for handling and storage of chemicals.
• Develop remedial action plans, risk assessment and risk mitigation plans for encountering contaminated groundwater.

Soil

• Complete detailed soil investigations, as project planning progresses.
• Employ excavation support systems if required and/or implement appropriate ground treatment such as jet grouting to reduce the risk of ground loss during early works activities.
• Develop management plan(s) for handling, management and disposal of excavated material as required.
• Develop and implement remedial action plans, risk assessment and risk mitigation plans for encountering contamination.