Capital Regional District parks staff are building a business case for a million-dollar-plus aerator system to reduce algae blooms in Elk/Beaver Lake.
The idea is to install a deep-water aerator on the bottom of Elk Lake at a capital cost of about $700,000 and an estimated operating cost of between $600,000 and $1.1 million over the next 10 years, for a total cost of $1.3 million to $1.8 million.
Elk/Beaver Lake is subject to seasonal blooms of cyanobacteria, commonly called blue-green algae; there is one at Beaver Lake now. The naturally occurring bacteria have the potential to release cyanotoxins that can be hazardous to people and pets that ingest the water.
The system, using a process known as high-efficiency hypolimnetic oxygenation, would pump in oxygen and improve water quality by reducing the release of sediment phosphorus, says a staff report.
It would also help ensure a healthy fishery and would not interfere with lake recreation, it says.
“The addition of pure oxygen to the lake bottom will immediately and significantly reduce the release of phosphorus from lake sediments, and thus reduce [blue-green algae] bloom frequency, duration and toxicity, and improve overall water quality.”
Blooms have become more frequent over the past few years and are lasting longer, staff say. They are primarily the result of the release of phosphorous from lake-bottom sediments during the summer, when the surface water layer is much warmer than the deep water layer.
“The difference in temperature creates a barrier between the two layers and, because the water at the bottom of the lake is low in oxygen, phosphorous is released into the water from the lake sediments,” the staff report says.
When the surface water cools in the fall, the two layers mix, and the phosphorous that had been in the lower layer becomes available as nutrients for the blue-green algae — resulting in a sudden population growth.
While Beaver Lake is also subject to occasional algae blooms, it is different from Elk Lake in that it is shallow and completely mixed, staff say. That means they can likely be managed through a simpler aeration system, at a capital cost of about $40,000.
CRD directors this week agreed to include the $40,000 in the 2018 budget and directed staff to build a business case for the more expensive Elk Lake system, including looking at possible grants and external funding sources.
Both CRD chairwoman Barb Desjardins and parks committee chairman Mike Hicks said something has to be done, especially given that Elk/Beaver Lake Regional Park is the most heavily used park in the region, with an estimated 1.46 million visits in 2016.
“We can’t do nothing,” Desjardins said.
“My feeling is the Beaver Lake system will show us how effective this might be. Certainly, it’s been effective in Langford Lake,” she said.
“It’s the most used park in the region, so it’s a huge part of the stakeholders in the region wanting use of it and being safe about it.”
Hicks agreed something has to be done and hopes that external funding sources can be found.
“I don’t personally think it should be borne totally by the Capital Regional District,” Hicks said, adding that the lakes are home to Rowing Canada, the national rowing and triathlon teams and should attract federal support.
He also pointed out the CRD recently spent about $300,000 on a weed harvester for the lakes.
“We’re contributing pretty hard to try to make the lake usable.”
