Water Quality

Water Quality

Treated Water

St. Mary Lake water is treated through pre-chlorination, pressure sand filtration and post-chlorination. Maxwell Lake water is treated by chlorine disinfection. Chlorination is an effective means of killing harmful bacteria and viruses and preventing their regrowth within the distribution systems.

Turbidity and free chlorine residual are monitored continuously in the treated water from both sources. Chlorine residuals are also monitored daily at select locations within the distribution system.

Samples from various locations in the distribution systems are regularly analyzed for E. coli, total coliforms and fecal coliforms as required by the BC Drinking Water Protection Regulation. In addition, treated water is tested for other microorganisms (algae and cyanobacteria), metals, pH and disinfection by-products at appropriate frequencies.


We do not fluoridate our water and there are no plans to do so in the future.

Raw Water

Both Maxwell and St. Mary Lake raw water are analyzed for a wide variety of water quality parameters as part of a comprehensive source monitoring program. Dissolved oxygen, temperature, secchi depth, and turbidity are measured in the field and samples are taken for laboratory analysis of pH, metals, and nutrient concentrations.

Collaborative Watershed Management

The District has a long history of working with a variety of agencies and community groups. The District has been involved with the Salt Spring Island Watershed Protection Authority (SSIWPA) since its inception in 2012. District Trustees and staff are active participants in both the SSIWPA Steering Committee and Technical Advisory Committee (TAC). By working collaboratively with Islands Trust, CRD, Island Health, Ministry of Health, Ministry of Environment, and the Highland and Fernwood water districts, SSIWPA has made significant progress towards the goal of developing effective remediation and management strategies for St. Mary Lake.

Annual Water Quality Reports

The following reports are available as downloadable pdf files.

2016 NSSWD Annual Drinking Water Quality Report

2016 Figures/Tables

St. Mary Lake System Water Quality Data

Figure 1 SML Treated POE inline chlorine and turbidity 2016

Figure 2 SML Treated Distribution system micro, turbidity and pH 2016

Figure 3 SML Treated DBPs 2016

Figure 4 SML raw and treated toxin 2016

Figure 5 SML raw and treated metals, pH, hardness 2016

Figure 6 SML raw bacteria, and turbidity 2016

Figure 7 SML raw Parasites 2016

Figure 8 SML raw water turbidity field tests 2016

Maxwell Lake System Water Quality Data

Figure 9 Maxwell treated water chlorine and turbidity 2016

Figure 10 Maxwell treated water micro turbidity and pH 2016

Figure 11 Maxwell raw water parasites 2016

Figure 12 Maxwell raw and treated water metals hardness and pH 2016

Figure 13 Maxwell distribution system DBPs 2016

Water Quality 2015 & Prior Reports

Swimming and Water Quality Advisories

Swimming and water advisories for St. Mary Lake and all of our island water bodies are issued and rescinded by the Island Health (formerly VIHA).  Please refer to their water infomation advisory site for the latest information on water quality and their Beach Reports for swimming advisories.

Maxwell Lake is a protected watershed.  No access is allowed for swimming or any other activities.

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