North Cowichan’s senior environment specialist Dr. Dave Preikshot told council at its last meeting that core samples from Quamichan Lake will be taken this summer to better determine the lake’s chemistry as solutions to its toxic blue-green algae blooms are sought. (File photo)

North Cowichan’s senior environment specialist Dr. Dave Preikshot told council at its last meeting that core samples from Quamichan Lake will be taken this summer to better determine the lake’s chemistry as solutions to its toxic blue-green algae blooms are sought. (File photo)

North Cowichan to determine best means to deal with Quamichan Lake’s algae problem

Core samples of lake bed to be taken this summer

North Cowichan’s environmental staff plan to collect sediment core samples from Quamichan Lake this summer to establish the lake bed’s chemistry as part of the ongoing efforts to deal with its blue-green algae blooms.

In a presentation to council on Feb. 17, the municipality’s senior environment specialist Dr. Dave Preikshot said the information will help determine whether treatment options like oxygenation, in which air is used to oxidize and dissolve organic materials like algae blooms, and the use of Phoslock, which removes phosphate, one of the essential nutrients for algae growth, from the water, are viable for Quamichan Lake.

Secondarily, Preikshot said if the lake bed chemistry is favourable to a treatment option, it would also have to be determined the scale at which that treatment should be implemented.


“We need to get a baseline [of the lake bed’s chemistry] so we can set attainable targets,” he said.

“We have to understand the physics of the lake, including its temperatures and oxygen levels. The sediment core samples will provide us with detailed answers so we can begin to select the management options to best control the algae blooms.”

There had been at least three reported dog deaths around Quamichan Lake in 2016, and all are suspected to be caused by ingesting toxic blue-green algae from the lake.

North Cowichan decided at the time to set up the Quamichan Lake Water Quality Task Force, consisting of staff and council members, along with water specialists, to study and seek solutions to the ongoing health issues related to the algae.

The task force concluded the nutrients that are causing the algae outbreak in the lake are coming mainly from a number of sources, including urban runoff, and runoff from nearby agricultural lands, construction areas and logging sites.


Preikshot was contracted by the municipality in 2018 to design a water quality sampling program and conduct monitoring activities in order to establish baseline conditions for several water quality parameters in the lake.

Preikshot said at the time the control of phosphorous in Quamichan Lake is most likely to be best achieved using one, or a combination of, a number of options.

They included oxidization, chemical treatments, flushing the lake with stored and/or diverted water, and dredging the bottom of the lake.


Preikshot said at last week’s meeting that monitoring equipment has been put in place in and around the lake that regularly checks and records nutrient levels and other chemical and physical information on changes in the lake.

“The monitoring program now in place will allow North Cowichan to make an informed decision on which of these options is most likely to succeed in mitigating blue-green algae blooms in Quamichan Lake,” Preikshot said last week.

“Significant progress has also been made in controlling phosphorus entering the lake by working with stewardship groups to enhance riparian vegetation, managing stormwater through wetlands and detention ponds, and the establishment of zeolite/limestone nutrient traps around Quamichan Lake on a pilot basis.”

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