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Soil & Groundwater - Corktown Station

← Return to Early Works: Corktown Station

Key Findings

  • Glacial till deposits (i.e., sediments deposited below a glacier) are the main near surface soil type and are mostly made up of sand and silt.
  • The study area is serviced by municipal water supply from Lake Ontario.
  • Depending on groundwater conditions at the time of the early works, dewatering may be required to support early works activities.
  • Without mitigation, there is potential for impacts to groundwater (e.g., contaminant releases) and soil (e.g., ground movement and settlement as a result of excavation/dewatering). The completion of hydrogeological and geotechnical investigations and a construction dewatering assessment during detailed design, completion of Groundwater and Soil Management Plans as planning progresses, and the implementation of appropriate mitigation measures during early works activities are anticipated to minimize potential impacts (see Potential Effects & Mitigation Measures).

Asphalt removal on a construction site, revealing<br />
 groundwater. Source: AECOM, 2016

Asphalt removal on a construction site, revealing groundwater.
Source: AECOM, 2016

Existing unopened tunnel entrance building - view from the east

Asphalt removal on a construction site.
Source: AECOM, 2016.

Potential Effects & Mitigation Measures

Potential Effects:

Groundwater

  • 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).

Soil

  • 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:

Groundwater

  • 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

  • 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).

← Return to Early Works: Corktown Station

Submissions are closed.