Ontario Line

Potential effects and mitigation measures

Potential effects:

• Potential removal of/damage to street trees and urban wildlife habitat, including migratory breeding birds.
• Disturbance or displacement of urban wildlife within the study area.

Mitigation measures:

• Sensitive wildlife timing restrictions for early works activities (e.g., removal of vegetation outside of the breeding bird period).
• Prior to early works activities, a Common Nighthawk (Species of Conservation Concern) candidate nesting habitat survey and nest search for migratory breeding birds will be completed to confirm nesting habitat presence/absence on buildings within the project footprint and, if habitat is found to be present, appropriate mitigation measures will be implemented (e.g., conducting building demolition outside of the breeding bird period).
• Tree/vegetation removals will be kept to a minimum and limited to within the project 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 early works activities.
• Temporary increase in dust, silica and airborne particulates resulting from site preparation, earth works, demolition activities, heavy equipment travel over unpaved surfaces and uncovered soil storage piles.
• Potential release of contaminants due to disruption of contaminated soils.

Mitigation measures:

• Manage on-site construction vehicle activity to control emissions of odourous contaminants and diesel exhaust.
• If disruption of contaminated soils is anticipated, ensure that contaminants are not released.
• Develop an Air Quality Management Plan to ensure consistent attention to mitigation of dust and particulates, including silica, from the early works site, once early works activity means and methods have been confirmed.

Read more - Appendix A2 - Air Quality Report

Potential effects and mitigation measures

Construction noise

Potential Effects:

• Without mitigation, there is potential for daytime and nighttime noise criteria exceedances at representative receptors 302, 322, 361 and 393 King Street East, 2 Berkeley Street, 33 Hahn Place and 5 Mill 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.
• 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.
• 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 nighttime construction is necessary, activities with the highest noise levels should be conducted during daytime periods where possible.
  • 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.
• Limit the number of heavy trucks on site to the minimum required.
• Stage construction vehicles away from noise sensitive locations where possible.
• Coordinate with the Canadian Opera Company (at the Joey and Toby Tanenbaum Opera Centre at 227 Front Street East) and Canadian Stage (located on 26 Berkeley Street) to avoid disturbance during performances.
• Undertake noise monitoring throughout the construction phase. Where noise criteria are exceeded, additional noise mitigation measures shall be implemented.
• Develop a communications protocol for providing advance construction notices and addressing public complaints in a timely manner.

Construction vibration

Potential effects:

• Construction vibration may be perceptible at the following buildings near the Corktown Station early works project footprint: 300, 302, 310, 318-330, 361 and 191 King Street East, 2, 26, 53 and 54 Berkeley Street, 240 and 251 Front Street East, 5 Mill Street, and 45 and 51 Parliament Street.
• Exposure to vibration may result in public annoyance.

Mitigation measures:

• Use equipment with low vibration emissions where possible.
• Conduct off-site construction of components away from sensitive areas.
• Restrict construction house 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 where possible.
• Update vibration assessment based upon refined site staging, equipment, construction areas, and building locations prior to the commencement of construction.
• Use alternative means of construction within 5.8 metres of typical structures so that the City of Toronto’s prohibited vibration level limits are not exceeded.
• Use alternative means of construction within 11.1 metres of structures that are susceptible to vibration damage so that the vibration level limits for buildings susceptible to vibration damage are not exceeded where applicable.
• Review other applicable vibration limits that may apply, such as the City of Toronto Sepcification GN117SS.
• Conduct monitoring and pre-construction inspections in accordance with City of Toronto By-law 514-2008 as requited. Monitoring and pre-construction requirements can be determined by calculation of zone of influence (ZOI)* of construction equipment.
• Maximize distance between equipment and sensitive receivers where possible.
• Provide smooth surfaces for trucks to travel.
• Develop a communication protocol for providing advance construction notices and addressing public complaints in a timely manner.

Read more - Appendix A3 - Noise and Vibration Report

Potential effects and mitigation measures

Potential effects:

• Demolition of the contemporary buildings within the First Parliament Site at 265 and 271 Front Street East and 25 Berkeley Street, designated under Parts IV and V of the Ontario Heritage Act, to enable environmental due diligence studies, including archaeological assessment.
• Demolition of non-contributing buildings (buildings within the District that do not contribute to its cultural heritage value) within the St. Lawrence Neighbourhood HCD, causing physical impact to the District.

Mitigation measures:

• For 265 and 271 Front Street East and 25 Berkeley Street, implement the following:
  • As planning progresses, consult with City of Toronto’s Heritage Preservation Services regarding any physical impact to the property in order to determine and obtain any required approvals or permits.
  • As planning progresses, consult with Ontario Heritage Trust as current owners of part of the property and if required, obtain approval/consent.
  • Complete archaeological requirements where required, as early as possible and in advance of any ground disturbance.
• Metrolinx has sought consent of the Minister of Heritage, Sport, Tourism and Culture Industries for the First Parliament Site, and consent has been granted by the Minister. Metrolinx is committed to fulfilling all conditions outlined through the Minister of Heritage, Sport, Tourism and Culture Industries’ Consent for First Parliament Site.
• For the St. Lawrence Neighbourhood HCD, consult with City of Toronto’s Heritage Preservation Services as part of early works, prior to demolition of the buildings, regarding physical impact to the HCD in order to determine and obtain any approval or permits that may be required.

Read more - Appendix A4 - Heritage Report

Potential effects and mitigation measures

Potential effects:

• Temporary increase in traffic delays, especially at intersections, due to construction vehicle traffic.
• Increase in pedestrians’ and cyclists’ exposure to traffic due to traffic congestion along Front Street and other adjacent roads, as a result of the increase in construction vehicle traffic.
• Temporary impacts to the transportation network and its road users due to potential overlapping construction timelines with other nearby planned projects (e.g., local developments).
• Closure of Green P municipal parking lot located within the Corktown Station early works project footprint.

Mitigation measures:

• Develop and implement a Transit and Traffic Management Plan(s) as planning progresses. Consult with the City of Toronto and local school boards to include safety precautions for nearby schools in the Management Plan(s).
• Consult and coordinate with the City of Toronto and Toronto Parking Authority during early works planning, including consideration of public parking, route detours and road closures to maintain the mobility of road users (i.e., drivers, cyclists and pedestrians).
• Ensure all safety protocols are followed as construction vehicles enter and exit the Corktown Station early works project footprint.

Read more - Appendix A5 - Traffic and Transportation Report

Potential effects and mitigation measures

Potential effects:

• Potential for disturbance of registered archaeological sites (i.e., First Parliament Site, Lime Kiln Site) and/or archaeological resources not previously identified due to early works activities.
• Potential for recovery of unexpected archaeological resources (e.g., Indigenous artifacts) during early works.

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 early works activities, all work will stop. The site will be protected from impact and additional assessment will be undertaken.
• The Mississaugas of the Credit First Nation and other Indigenous Nations will be invited to participate in archaeological fieldwork.

Potential effects and mitigation measures

Potential effects:

• Potential change in stormwater quality and quantity, including erosion of exposed soil and increased sediment loading, which may impact receiving waterbodies and/or municipal stormwater drainage systems, and increased surface water/stormwater runoff.

Mitigation measures:

• 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.
• Consider and implement the following stormwater management best practices as required:
  • Minimize amount of exposed soil;
  • Install sediment controls before grading/land alterations begin;
  • Sequence early works 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 possible.

Potential effects and mitigation measures

Potential effects:

• Access disruption to adjacent lands to accommodate early works activities.
• Nuisance effects (i.e., dust, noise, and vibration) to adjacent lands from early works activities.
• Visual effects from early works activities.
• Permanent and temporary property acquisition (property requirements will be confirmed as project planning progresses).
• Light pollution effects.
• Temporary relocation or removal of streetscaping materials, furniture and landscaping in the public realm.

Mitigation measures:

• Minimize property requirements associated with early works activities to the extent possible.
• Maintain access to businesses during working hours.
• Develop an Air Quality Management Plan to mitigate potential impacts of dust during early works activities (see Air Quality for further detail and more mitigation measures).
• Use equipment with low vibration emissions where possible, provide smooth surfaces for trucks to travel to reduce noise and restrict construction hours where possible to minimize activities that generate the highest noise and vibration levels overnight (see Noise & Vibration for further detail and more mitigation measures).
• Consider providing temporary landscaping and/or screened enclosures along the borders of the early works site, where space allows and necessary.
• Temporary lighting and wayfinding signage around early works sites.
• Clearly marked pedestrian and cyclist detours where required.

Potential effects and mitigation measures

Groundwater

Potential effects:

• Although no significant dewatering is anticipated to be required, construction dewatering may include impacts to private groundwater supply wells (if present) caused by a reduction in local groundwater levels.
• Potential release of minor contaminants and/or contaminated groundwater due to early works activities (e.g., excavation and dewatering).

Mitigation measures:

• As project planning progresses, if dewatering is required for early works activities, determine water taking quantities, groundwater quality, resultant dewatering ZOI* and dewatering impact assessment through a site-specific Hydrogeological Investigation, Construction Dewatering Assessment and Groundwater Management Plan.
• Complete monitoring activities such as groundwater and dewatering effluent sample collection and measurement of groundwater parameters (e.g., pH). If dewatering is required, conduct regular groundwater quality testing of discharge water as required.
• Develop a Spill Prevention and Response Plan which outlines the steps required to prevent and contain any contaminant releases and/or to avoid impacts to groundwater/surface water and includes a requirement for a spill kit to be maintained on-site at all times, as planning progresses.

Soil

Potential effects:

• Displacement of soil as a result of early works activities may result in ground movement and settlement.
• Though no significant dewatering is anticipated to be required, soil settlement and impacts on surface and/ or subsurface structures within the Zone of Influence (ZOI)* due to dewatering activities.
• Early works activities (e.g., excavation) could expose contaminated materials 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:

• Complete detailed soil investigations, including soil settlement analysis, as planning progresses.
• Conduct pre-construction inspections of structures within the dewatering/construction ZOI* and develop a ground settlement monitoring program as required in advance of the early works.
• Stabilize and prevent migration of soil off-site due to wind/water action.
• Develop remedial action plans and risk assessment and mitigation plans for encountering contamination, as necessary.
• Develop a Soil and Excavated Materials Management Plan for the handling, management and disposal of all excavated material (i.e., soil and waste).