Update On Our Three Mile Lake Water Sample Results

September 15, 2020


On August 10, 2020 the Ministry of Environment, Conservation and Parks (MECP) took water samples on the eastern end of the main basin of Three Mile to determine the presence of a blue-green algae bloom. This presence was confirmed by the South Muskoka District Health Unit (SMDHU) on August 13,2020 and a warning was sent by Email to all of our members, along with posting this notice on both our website and Facebook page. On August 18, 2020 the MECP took additional water samples at the west end of our main basin and at the entry into Hamell’s Bay. Once again these water samples confirmed the presence of an algae bloom, and we notified our members and the general public on August 27, 2020 of these additional findings. Both sets of samples were sent to the MECP laboratory on August 27, 2020 to conduct toxicity tests.

On September 14, 2020 I was advised by the MECP that these toxicity tests came back negative “results below detection level” which means that there were less than .2 micrograms per litre. As a reference, the safe drinking level is less than 1.5 micrograms/litre, while recreational use has a level of 20 micrograms/litre.  That was the good news! These results were forwarded to the SMDHU for their review.


Today the SMDHU advised me that they were going to request new water samples.These samples will be taken on September 16, 2020, at all of the original sites. The reason for the need for new samples is that when blue-green algae “dies off”, it releases toxins, which is a natural process. The SMDHU is concerned about this and has required new water samples to be taken, to be on the safe side. We are also concerned, as the health of our members, their families and their pets is OUR primary concern.


We will wait for the preliminary results to see if there is still a presence of blue-green algae, which I think is likely due to the greenness of the water. The results of these tests should be available within 4-5 days. We will of course communicate these results to you. If the samples require additional toxicity testing, as we have seen, this could take up to another month. In the interim, the health warnings remain in force and we certainly recommend that everyone use their common sense when swimming or if drinking the lake water or using it for household chores. Please be safe!

I realize that everyone has been frustrated with this whole process. Certainty we as your Board Of Directors have been! We are in discussions with both the SMDHU and MECP to try and find ways to streamline these processes and speed up the timelines. We will provide updates as soon as we receive them.

John Roberts

President-Three Mile Lake Association