East Don River Tributary Erosion Control Environmental Assessment

As a part of Markham’s Erosion Control Program, a Class Environmental Assessment was initiated for a tributary of the East Don River located in West Thornhill.


The East Don River Tributary is a 1,015 m long watercourse within the Don River watershed which spans from Proctor Avenue to Steeles Avenue East.

The watercourse is confined in a valley setting and has been historically modified by adjacent development.

Various private properties and City infrastructure in this area have been subjected to erosion and localized stretches of the watercourse demonstrate bank instability and deteriorated conditions.

The environmental assessment aims to:

  • Understand and define the causes of erosion and current conditions of the study area
  • Develop a range of alternative solutions to address and mitigate erosion, while minimizing risks to the environment, sanitary sewer system, private properties and public safety
  • Assess impacts of the proposed solutions and determine through the public consultation process which alternative is preferred
  • Identify property or easement acquisition opportunities to improve inspection and maintenance of the creek
  • Establish the funding, approvals and other activities needed to implement the recommended solution

East Don River Tributary Erosion Control Environmental Assessment Schedule

Winter/Spring 2019

  • Notice of study commencement;
  • Project initiation and background review;
  • Topographic and legal surveys;
  • Meeting with key stakeholders to review existing conditions;
  • Archaeologic, geotechnical, fish habitat, terrestrial resources and fluvial geomorphic assessments.

Summer 2019

  • Hydrologic and Hydraulic Assessment;
  • Public Information Meeting scheduled for August 7, 2019 at the Thornhill Community Centre. 
  • Development and evaluation of initial erosion mitigation alternatives;
  • Meetings with key stakeholders to review preliminary preferred alternatives and conceptual design.

Fall/Winter 2019

  • Confirmation or Refinement of Preferred Alternative;
  • Prepare environmental assessment report, detailed design next steps and implementation plan;
  • Notice of completion.

Municipal Class Environmental Assessment Process

Class EA Phase 1

Identify Problem or Opportunity

  • Identify Need
  • Initiate Consultation with the public and agencies
  • Notice of Commencement

Background Review

  • Obtain and review background documentation and initiate agency contact
  • Identify data gaps to be addressed during the site inventory/ investigation

Class EA Phase 2

Site Inventory / Investigation

  • Undertake natural heritage investigations
  • Aquatic habitat assessment
  • Incidental wildlife survey
  • Undertake hydrology/hydraulics investigation
  • Archaeological Investigations
  • Identify opportunities and constraints

Evaluation of Alternatives

  • Identify alternatives
  • Complete impact assessments
  • Evaluate alternatives
  • Select preferred alternative

Preliminary Design / Project File Report

  • Preliminary design of preferred alternative
  • Recommendation for further study, if required
  • PIC# 1
  • Develop a staging and implementation plan
  • Prepare Project File Report
  • Notice of Completion
  • 30-day Public Review
  • Implementation

Detailed Design / Implementation

  • Detailed design of the proposed works
  • Obtain permits and approvals
  • Prepare contract drawings and tender documents
  • Construction and operation of the works
  • Post-construction monitoring

View a detailed Class EA Process for municipal infrastructure projects