Three Mile Lake Causation Study

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Muskoka's residents and District Council care about water quality. This important topic impacts the environment, economy, and desirability of the District as both a place to call home and a destination. In an effort to enhance water quality and resident/visitor experience in Muskoka, the District is undertaking causation studies on lakes considered as vulnerable from a water quality perspective. One of these causation studies will be on Three Mile Lake.

Three Mile Lake is 8.66 km2 in size and is located in the Township of Muskoka Lakes. Most recently, Three Mile Lake experienced two blue-green algae blooms in 2020, the first located at the east end of the main basin and the second in the north-western end of the lake. These blooms were confirmed by the Ministry of environment, Conservation and Parks (MECP) on August 13, 2020 and August 27th, 2020, respectively. Three Mile lake also experienced a blue-green algae bloom in 2019 which was confirmed on August 27, 2019. This led to the lake being classified as vulnerable in Schedule E2 of the Muskoka Official Plan (MOP). As outlined in the MOP, when a lake is listed as vulnerable, a waterbody-wide causation study should be initiated to determine the causes and relative contributing factors which lead to the identified water quality indicator, as well as to produce recommendations and mitigative actions that can be taken by stakeholders, the District, and others to ensure water quality may be enhanced in the long-term.

To receive project updates and to stay informed of the outcomes of the Three Mile Lake Causation Study Project, enter your email address in the "Stay Informed" tool (located at the top right-hand corner of this page on your desktop or scroll down on your mobile device) and click the subscribe button.

Muskoka's residents and District Council care about water quality. This important topic impacts the environment, economy, and desirability of the District as both a place to call home and a destination. In an effort to enhance water quality and resident/visitor experience in Muskoka, the District is undertaking causation studies on lakes considered as vulnerable from a water quality perspective. One of these causation studies will be on Three Mile Lake.

Three Mile Lake is 8.66 km2 in size and is located in the Township of Muskoka Lakes. Most recently, Three Mile Lake experienced two blue-green algae blooms in 2020, the first located at the east end of the main basin and the second in the north-western end of the lake. These blooms were confirmed by the Ministry of environment, Conservation and Parks (MECP) on August 13, 2020 and August 27th, 2020, respectively. Three Mile lake also experienced a blue-green algae bloom in 2019 which was confirmed on August 27, 2019. This led to the lake being classified as vulnerable in Schedule E2 of the Muskoka Official Plan (MOP). As outlined in the MOP, when a lake is listed as vulnerable, a waterbody-wide causation study should be initiated to determine the causes and relative contributing factors which lead to the identified water quality indicator, as well as to produce recommendations and mitigative actions that can be taken by stakeholders, the District, and others to ensure water quality may be enhanced in the long-term.

To receive project updates and to stay informed of the outcomes of the Three Mile Lake Causation Study Project, enter your email address in the "Stay Informed" tool (located at the top right-hand corner of this page on your desktop or scroll down on your mobile device) and click the subscribe button.

  • Public Survey Results Now Posted

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    Thank you to all who participated in the Three Mile Lake Causation Study Survey this spring. A summary of the survey results is now available and posted to this page at the following link: Three Mile Lake Survey Results.

    Other key aspects of the public consultation process will be summarized in the study’s final report.


    Next steps in the study:

    • The Terms of Reference (TOR) for the study will be shared with stakeholders by August 2021. We will post the TOR to this page and send a newsletter to advise that this document has been posted.
    • Data collection and field work will continue into the fall, after which, the consultant will analyze the data and prepare the draft report for the study.
    • Once the draft report is ready, a stakeholder meeting will be scheduled where you can ask questions to better understand the report findings and recommendations and provide feedback.
    • The timing of the draft report may be affected by late fall blooms but is expected to be prepared for early 2022.
    • After the stakeholder meeting, the report will be revised (if needed), finalized, and presented to the District’s Community and Planning Services Committee.


    Please continue to be our eyes on the lake over the summer and fall seasons and report any sightings of potential blue-green algae blooms to the Ministry of the Environment, Conservation, and Parks’ Spills Action Centre at 1-866-663-8477.

    If you have any additional data or information you would like to share with the consulting team, please send it to jacquie.evans@muskoka.on.ca. We will be accepting submissions from lake stakeholders until October 31, 2021.

  • Three Mile Lake Public Survey

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    Three Mile Lake Causation Study Survey Now Open!

    The goal of the survey is to gather information on lake use and observations of water quality, and how it has changed over time. We are seeking input from members of the lake association, those who live or work on or near the lake, those who use the lake for recreational purposes, and others with knowledge about the lake to help inform the causation study. We know that these stakeholders have data, information, and observations to share which is critical to our current and historical understand of the lake.

    Anyone with specific knowledge about Three Mile lake, factors that could contribute to algae blooms, and overall water quality on the lake is asked to complete the survey to share this information with us. The survey can be accessed at the link below and will be available until May 27th, 2021.

    Take the survey now!

  • April 20th Public Meeting - Video Recording

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    The first public meeting for the Three Mile Lake causation study took place on Tuesday, April 20, 2021 via Zoom - thank you to those who were able to participate in the live meeting!

    If you were not able to participate with us, we have made a video recording of the meeting available below. If you have any questions or comments about the presentation or the study process, or if you have information or data to contribute to the study, please contact Jacquie Evans, Planning Policy and Programs Coordinator, at jacquie.evans@muskoka.on.ca or 705-645-2100 ext 4114.

    Thanks again for your interest in the Three Mile Lake Causation Study!


  • Upcoming Public Meeting

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    A public meeting for the Three Mile Lake Causation Study is scheduled for Tuesday, April 20, 2021 from 10:00 am – 11:30 am via the virtual platform Zoom.

    Please RSVP to Jacquie Evans at jacquie.evans@muskoka.on.ca to receive the details for this meeting. Please note that the consultant’s presentation from this meeting will be recorded and posted to this project page at a later date.

    The purpose of this meeting is to provide stakeholders with the opportunity to understand the consultant’s approach to the study, to ask questions of the consulting team, and to provide any information or insights that may be helpful to the project. Please help us spread the word!

    For those unable to attend in person or wishing to provide additional details, an online survey will be conducted and will be posted to the this project page when available.

    Stay tuned for more project updates in the coming weeks!


  • Consultant Selected

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    Through the Request for Proposal (RFP) process, the District Municipality of Muskoka has selected Hutchinson Environmental Sciences Ltd. (HESL) as the successful proponent for the Three Mile Lake Causation Study. Using a multi-disciplinary approach, HESL has partnered with Eco-Vue Consulting, a firm which specializes in public consultation, to ensure both the scientific and engagement components of the project are thoroughly performed.

    A start-up meeting between the District and the consultants have recently taken place and the consultation plan is currently underway.

    Please be sure to subscribe to the Three Mile Lake project page to receive information regarding upcoming meeting dates, consultation opportunities and important project updates.

    Thank you for your interest in the Three Mile Lake Causation Study!