The City of Markham will be treating Swan Lake with a coagulation product to reduce phosphorus levels in the lake. This will reduce the incidence of algal blooms and increase the oxygen level in the water.

The treatment is scheduled to begin in late July 2021 and is expected to take about two weeks to complete. During the operation, roadways will be open; however, access to some of the park pathways will be temporarily closed.

The treatment involves the application of polyaluminum chloride over several days from a motorized barge. The application will make the water appear slightly cloudy while the chemical settles through the water column. Testing will be completed following each day of application and operations will be adjusted to ensure minimal impact on aquatic organisms. The contractor for this project is Ground Force Environmental Inc.

While there will be some inconvenience to the area residents and park visitors, the contractor and the City staff will work together to complete the project as efficiently as possible. All areas disturbed during construction will be restored to their original conditions.

If you have any questions, please contact the City of Markham at (905) 477-7000 x2867. Should a problem arise after regular working hours or on the weekend, please call the City’s after-hours line at (905) 477-7000.

Location Map
Swan Lake - Ward 5
Project Scope and Methodology

Chemical treatment of Swan Lake will be completed through the following activities:

a) Preparation and Staging

  • Prior to chemical application, the work area will be established and fenced off
  • Ground protection mats will be laid on the staging area and any other area which could be impacted by the movement of heavy equipment or placement of material
  • Appropriate site safety signage will be erected. The City will also install construction signage and mail notifications to the area residents
  • The Swan Park trail will be open throughout the construction period. Any access to the trail during the work will involve pedestrian management to ensure public safety

 b) Product Supply and Application

  • Approximately 13 tonnes of Poly Aluminum Chloride (PAC) will be applied to Swan Lake. The project consultant recommended this material after the supplier of Phoslock informed the City that Phoslock is not available for application in Swan Lake this year
  • PAC products are highly effective and relatively inexpensive. In addition, studies have shown no significant risk of toxicity if the product is applied correctly. There may be transient changes in water chemistry during the application. Therefore, the application will proceed in stages to minimize such temporary changes and will be closely monitored, with water quality tests completed following each treatment event
  • The product will be stored in a warehouse and brought to the site for use daily
  • The Contractor will use a boat/vessel equipped with a product injection system to inject undiluted liquid product just below the surface of the Lake
  • The application will be staged into at least three (3) application events with a wait time between the events
  • Two (2) to four (4) days are required between application events to allow floc settling and provide sufficient time for the consultant to receive and review the test results
  • The application may be postponed, stopped, or otherwise delayed if concerns are identified from the monitoring work until such time that the concerns can be resolved
  • The application will avoid the shoreline, maintaining a distance of approximately two (2) meters from the banks to prevent the direct deposit of the product on the shoreline
  • The application will occur under dry weather conditions. It will not proceed if there is significant wind causing the floc to drift from the intended treatment area or pose a health and safety issue.

c) Site Restoration

  • The site will be cleaned of mud and any waste generated due to this operation
  • Staging area and any other disturbed areas will be restored to the original condition
  • For any other planting needs, only native, locally present trees, shrubs, and grasses will be used to restore the site

Project Contact:

Zahra Parhizgari, M.Sc., P.Eng.
Environmental Engineer, Stormwater, Environmental Services
T: 905.477.7000 Ext. 2867
M: 416-550-6936
zparhizgari@markham.ca