Toxic algae blooms at Elk Lake and Beaver Lake could soon be a thing of the past.
This week, the Capital Regional District began building a business case for an expensive, but potentially revolutionary deep-water aerator system.
The aerator and its installation in Elk Lake would cost approximately $700,000. However, the system would rack up estimated operating costs of between $600,000 and $1.1 million during its decade of use. That would bring the total cost up between $1.3 million and $1.8 million.
The Toxic Culprit: Blue-Green Algae
Elk Lake and Beaver Lake have seen seasonal blooms of cyanobacteria (i.e. blue-green algae) become more frequent and long-lasting over the past few years. The current one at Beaver Lake even forced the CRD to temporarily prohibit swimming there.
The naturally-occurring bacteria can create hazardous cyanotoxins, making the water a health risk for any people or pets that ingest it.
Blooms usually occur after lake-bottom sediments release phosphorous. Those releases come from large differences in temperature between the surface water layer and the deep water layer. Often, such contrasts in temperature take place in the summer.
“The difference in temperature creates a barrier between the two layers,” says the CRD staff report. “Because the water at the bottom of the lake is low in oxygen, phosphorous is released into the water from the lake sediments.”
Surface water cooling causes the two layers to mix. That makes the phosphorous available for the blue-green algae. The abundance of nutrients causes massive population growth – a bloom.
According to a staff report, the system would use the process of high-efficiency hypolimnetic oxygenation to pump oxygen into the lake. That would reduce the release of sediment phosphorus, and thus improve water quality.
While the introduction of a system into Elk Lake would cost upward of a million dollars, Beaver Lake could be managed through a much cheaper and simpler system. In fact, the staff report estimates that project’s capital cost at about $40,000.
CRD directors will include the necessary $40,000 in the 2018 budget. However, the CRD have held off on the funds for the Elk Lake project. For the time being, staff have only been directed to build a business case for the larger system.
Possible external revenue sources, including grants, are being looked at.
