Ontario Line

Potential effects and mitigation measures

Potential effects

• Disturbance or displacement of wildlife.
• Removal of/damage to trees, terrestrial vegetation and wildlife habitat, including migratory breeding bird habitat.

Mitigation measures

• Sensitive wildlife timing restrictions for construction activities (e.g., removal of vegetation outside of the breeding bird season).
• Prior to construction, a Common Nighthawk (Species of Conservation Concern) candidate nesting habitat survey will be completed to confirm nesting habitat presence/absence at 1 Atlantic Avenue and, if habitat is found to be present, appropriate mitigation measures will be implemented (e.g., conducting building demolition outside of breeding bird window).
• Tree/vegetation removals will be kept to a minimum and limited to within the construction footprint.
• Tree removal compensation will be provided in accordance with the Metrolinx Vegetation Guideline (2020).

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 construction activities.
• Temporary increase in dust, silica and airborne particulate matter resulting from earthworks, excavation, material handling and transfer, demolition and 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.
• Full or partial enclosure of demolition and other activities, where possible and necessary.
• Reduction of activities during high wind conditions.
• 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

Construction noise 

Potential effects: 

• Without mitigation, potential for noise level criteria exceedances at 5 Hanna Avenue and the complex located at 6 Pirandello Street and 65 to 85 East Liberty Street.

Mitigation measures:

• 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.
• Acoustic equipment enclosures for equipment such as compressors and generators.
• Evaluate acoustic enclosures for power generators.
• Additional equipment silencers/mufflers.
• Use of upgraded construction hoarding (considering requirements from CSA Z107.9 for noise barriers) between construction equipment and noise sensitive receivers.
• Use of localized noise barriers for specific equipment and operations, including rail corridor construction works.
• Minimize 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.  If night time construction is necessary, activities with the highest noise levels should be conducted during day time periods.
  • If construction will occur outside of normal daytime hours, inform local residents of type of construction and expected duration outside of daytime hours prior to commencing work.
  • Consider operational duration limits for construction on the portion of the Exhibition Station Early Works Project Footprint near 5 Hanna Avenue and the complex located at 6 Pirandello Street and 65 to 85 East Liberty Street.
• Undertake noise monitoring and regular reporting throughout the construction phase. Where noise criteria are exceeded, additional noise mitigation measures shall be implemented.
• Develop a communications protocol for providing advance construction noise and vibration impact notices and addressing public complaints in a timely manner.

Construction vibration

Potential effects:

• Without mitigation, potential for perceptible vibration levels at the commercial buildings located at 15, 2/28 Atlantic Avenue, 1 Fraser Avenue, and 3 Mowat Avenue/2-20 Fraser Avenue.
• Without mitigation, potential for City Bylaw vibration level exceedance at the footings of the Gardiner Expressway and 15 Atlantic Avenue.

Mitigation measures:

• Use equipment with low vibration emissions where possible.
• Restrict construction hours where possible:
  • Perform construction during daytime hours where possible. If night time construction is necessary, the activities with the highest vibration levels should be conducted during day time periods.
  • If construction will occur outside of normal daytime hours, inform local residents before construction of type of construction and expected duration outside of daytime hours.
  • Consider operational duration limits for construction near the commercial buildings located at 15, 2/28 Atlantic Avenue, 1 Fraser Avenue, and 3 Mowat Avenue/2-20 Fraser Avenue.
• Update impact assessment based upon refined site staging, construction areas, and building locations prior to the commencement of construction.
• Use alternative means of construction within 11.1 metres of structures extremely susceptible to vibration damage.
• Review and refine construction activities in proximity to the Gardiner Expressway and, if required, conduct a more detailed analysis with respect to
• the Gardiner Expressway footings and review other applicable vibration limits such as the City of Toronto Specification GN117SS.
• Conduct monitoring and pre-construction inspections in accordance with City of Toronto Bylaw 514, as required.
• Provide smooth surfaces for trucks to travel.
• Operate construction equipment on lower vibration settings where available.
• Maximize distance between equipment and sensitive receivers.
• 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

Effects:

• Demolition of the main building at 1 Atlantic Avenue, a potential built heritage resource/cultural heritage landscape (BHR/CHL).
• Potential vibration impacts to the chimney and accessory building at 1 Atlantic Avenue.

Mitigation measures:

• For 1 Atlantic Avenue, implement the following:
  • Consult with City of Toronto’s Heritage Preservation Services as part of the detailed design phase and prior to the Environmental Impact Assessment Report, regarding any required physical impact to the property in order to determine and obtain any approval or permits.
  • Complete detailed documentation of the property that includes the identification of salvageable materials and/or heritage attributes, prior to demolition. Documentation should include a photographic record, drawings and floor plans, where appropriate. Heritage attributes of the property that are within the boundaries of the study area should be retained/conserved where possible.
  • The final development plan for the site should incorporate commemorative signage, in consultation with City of Toronto Heritage Preservation Services, to communicate the cultural heritage value or interest of the demolished structure.
  • Documentation of the structural condition of the chimney and accessory building. Establish vibration limits including the type of construction.

Read more - Appendix A4 - Heritage

Potential effects and mitigation measures

Potential effects:

• Temporary lane restrictions/closures and construction vehicle traffic causing impacts to traffic flow of nearby roads such as Manitoba Drive, Atlantic Avenue, and Jefferson Avenue.
• Detour routes lead to increased walking distances.
• Relocation/removal of existing bicycle amenities (e.g., bicycle parking racks).
• Disruption to existing rail operations if short-term track closures are implemented.

Mitigation measures:

• Develop a Construction Traffic Management Plan prior to construction.
• Issue notifications and advisory signage to alert traffic and transit users of any upcoming road closures and disruptions, as required.
• Consult and coordinate with the City of Toronto during construction planning, including consideration of route detours.
• 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 A5 - Traffic and Transportation Report

Potential effects and mitigation measures

Potential effects:

• Potential for disturbance of deeply buried archaeological resources (e.g., historical structure remnants) due to construction activities at Exhibition Station.

Mitigation measures:

• Complete additional archaeological assessments, 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 potential effects to hydrology and surface water are anticipated.
• Change in stormwater quantity and quality, including erosion of exposed soil and increased sediment loading which may impact receiving waterbodies and/or municipal stormwater drainage system.

Mitigation measures:

• The overall stormwater quality and quantity control strategy will be developed in accordance with all relevant municipal, provincial, and federal requirements.
• Prior to construction, a Stormwater Management Plan and an Erosion and Sediment Control Plan will be developed.
• The following stormwater management best practices will be considered and implemented, as required:
  • Minimize clearing and amount of exposed soil;
  • Install sediment controls before grading/land alterations begin;
  • Sequence construction activities so that soil is not exposed for long periods of time;
  • Protect storm drain inlets to filter out debris; and
  • Stabilize all exposed soil areas as soon as land alterations have been completed.

Potential effects and mitigation measures

Potential effects:

• Access disruption to adjacent lands to accommodate construction activities.
• Nuisance effects (i.e., dust, noise, and vibration) from construction areas/activities.
• Visual effects from permanent public-facing structures and construction areas/activities.
• Permanent and temporary property acquisition (property requirements will be confirmed during detailed design).
• Temporary relocation or removal of streetscaping materials, furniture and landscaping in the public realm.

Mitigation measures:

• Maintained access to businesses during working hours.
• See air quality and noise and vibration for mitigation measures related to these potential nuisance effects.
• Minimize the visual effects of structures by selecting appropriate building materials and architectural design.
• Screened enclosures and temporary landscaping along construction site boundaries, where necessary.
• Temporary lighting and wayfinding signage around construction sites.
• Clearly marked pedestrian and cyclist detours, where required.
• Following completion of construction, restore impacted lands to existing conditions, to the greatest extent possible.
• Ongoing consultation with affected property owners and provision of fair market value compensation in accordance with applicable laws.

Potential effects and mitigation measures

Groundwater

Potential effects:

• Subsidence/settlement of structures within the Zone of Influence (ZOI*) due to construction dewatering.
• Encounter previously contaminated groundwater during construction excavation and/or dewatering activities.

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

Mitigation measures:

• As part of detailed design, determine water taking quantities, quality, and resultant dewatering ZOI through a site-specific Hydrogeological Investigation, Construction Dewatering Assessment and Groundwater Management Plan.
• Subsidence/settlement impacts to existing structures can be mitigated with measures such as completion of pre-construction inspections of structures within 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.
• Remedial action plans, risk assessment, and risk mitigation plans for encountering contaminated groundwater.

Soil

Potential effects: 

• Displacement of soils as a result of construction may result in ground movement and settlement.

Mitigation measures:

• Complete a detailed settlement analysis during the detailed design phase.
• During construction, employ excavation support systems, as required, and/or implement appropriate ground treatment.
• Develop a Soil and Excavated Materials Management Plan for the handling, management and disposal of excavated material.