Description

In 2021, a consultant (ARCADIS Canada Inc.) was retained to design an in-lake remediation system to address the water quality problem, and a direct oxygen diffuser system was recommended for the Elk Lake. The main components of this system and related capital project include:

• an underwater diffuser line to deliver oxygen to the deepest part of Elk Lake;
• an oxygen-generating system;
• a building to house the oxygenation system equipment;
• electrical power to the building to run the system equipment.

Project Timeline

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Completed:

• The oxygen-generation system was purchased in July 2022.
• The contract for the Supply and Installation of In-Lake Air Diffusion Line was awarded in September 2022.
• Development of building design documents was completed for the system building in late 2022.
• A Fisheries and Oceans Canada (DFO) permit for in-water project was secured and a geotechnical assessment at the building site was completed in late 2022.
• A building permit from the District of Saanich was secured in March 2023.
• Construction of the Elk Lake oxygenation system building was completed in August 2023.
• The in-lake diffusion line system was deployed in mid-August 2023.
• Initial testing to confirm system operation was conducted in mid-August 2023.
• BC Hydro completed on-site electrical service in fall 2023.
• The system was initiated in late fall 2023.

Future:

• Water quality monitoring and system calibration will continue through 2024 and beyond.
  

Background

The Elk/Beaver Lake Initiative is a multi-pronged, holistic approach to address high nutrient levels in Elk/Beaver Lake and surrounding ecosystem. This approach aims to improve water quality, reduce frequency of blue-green algae and improve fish habitat through the implementation of two plans:

• a watershed management plan;
• and an in-lake remediation plan.

Watershed Management Plan

On October 14, 2020, the CRD Board received the Elk/Beaver Lake Watershed Management Plan and directed staff to implement actions within the Plan as opportunities allow. The Watershed Management Plan outlines a series of actions and long-term monitoring efforts to address external nutrient sources.

In-lake Remediation Plan
The in-lake remediation plan is designed to address internal sources of nutrients in Elk/Beaver Lake. These nutrients have accumulated over decades in the lake and bottom sediments and are continually recycled back into the water column under low-oxygen conditions.

The in-lake remediation process is guided by expert consultants and an intergovernmental working group. On September 11, 2019 staff brought forward a Staff Report and Business Case to the CRD Board outlining the environmental, recreational, community and economic values of the lake (over $10 million annually) and a recommendation to remediate the lake. The CRD Board approved the recommendation to move ahead with the in-lake remediation of Elk/Beaver Lake, subject to receiving at least 50% capital grant funds for the project.

This recommendation included the installation of oxygenation systems in Elk/Beaver Lake to improve water quality at a capital cost of $1.4 million and ongoing operational costs of $100,000 -$150,000 annually. For more details on the CRD Board discussion and decision, watch the video online (Section 8.9 19-755 Elk/Beaver Lake Remediation).

The Province contributed $750,000 to help buy an oxygenator for the In-Lake Remediation Plan. The CRD is responsible for the system and ongoing maintenance costs.

The design team considered the potential impacts of the operation of the system on the ecological, cultural, recreational and operational values in Elk/Beaver Lake Regional Park and surrounding lands. Following an assessment of all of those values, a site near Hamsterly Road was selected as most appropriate because it was the most operationally feasible and environmentally responsible. For more information on the site selection for the system building, see the detailed Options Analysis Memo.

Future Phases - Beaver Lake

An oxygenation system was prioritized for Elk Lake to improve water quality and reduce toxic blue-green algal blooms. For Beaver Lake, a de-stratification system to promote mixing and turnover in the smaller water body is recommended. It is not the recommended approach to install treatment systems in both lakes simultaneously. As Elk Lake and Beaver Lake are connected water bodies, it is anticipated that an oxygenation system installed in Elk Lake may also have a positive impact on Beaver Lake. Successful implementation of the Elk Lake system will provide the information required to properly size the system for Beaver Lake, which may be delivered as a second future phase.