A Water Quality Snapshot of Grafton Lake, Bowen Island
Basics
Title
A Water Quality Snapshot of Grafton Lake, Bowen Island
Description
AI-generated: This report presents the results of a one-time water quality assessment of Grafton Lake on Bowen Island, British Columbia, conducted on October 8, 2024 by the Raincoast Conservation Foundation's Healthy Waters program. The study analysed a composite source water sample for 587 analytes spanning coliform bacteria, nutrients, physical parameters, 37 metals, 62 pesticides, 76 PAHs, 141 PPCPs, 209 PCBs, 4 alkylphenol ethoxylates, 6 bisphenols, 40 PFAS compounds, and sucralose. A total of 125 contaminants were detected. Grafton Lake ranked 8th most contaminated out of 21 source water samples from 12 BC watersheds, driven particularly by high sucralose (rank 1), PCBs (rank 3), PAHs (rank 3), PPCPs (rank 6), and PFAS (rank 6). Despite the overall contamination ranking, no exceedances of Health Canada Drinking Water Quality Guidelines or Environmental Quality Guidelines were recorded. The report identifies human waste infiltration via septic failures and atmospheric deposition as the primary contamination pathways, and recommends ongoing monitoring, watershed best practices, septic system maintenance, riparian zone protection, and public education. The lake supplies drinking water to approximately 48% of Bowen Island's 4,000 residents and supports coho salmon and cutthroat trout habitat.
Date
January 1, 2025
Creator Organization
Raincoast Conservation Foundation
Authors
Peter S. Ross | Samantha Scott | Marie Noel
Document Type
Report
Document URL
Full Text URL
Subject Area
Species Biodiversity > Aquatic animals | Policy & Governance > Environmental policy | Ecosystems > Freshwater ecology | Water Resources > Groundwater | Conservation & Protected Areas > Howe Sound Biosphere (B.C.) | Water Resources > Hydrology | Water Resources > Sewage | Water Resources > Water quality | Water Resources | Water Resources > Watershed management
Metadata
Keywords
Grafton Lake
|Bowen Island
|water quality
|drinking water
|contamination
|source water
|PAHs
|PCBs
|PFAS
|pharmaceuticals
|pesticides
|sucralose
|coliform
|metals
|septic systems
|Raincoast Healthy Waters
|Terminal Creek
|Cove Bay Water System
|coho salmon
|cutthroat trout
|6PPD-quinone
|trihalomethanes
|British Columbia
Time Period
2023-2025; sampling conducted October 8, 2024
Relationship - isPartOf
Document ID
2605072030
Document ID
2605072030
Copyright holder
Raincoast Conservation Foundation
Document Filename
water-quality-snapshot-grafton-lake_2605072030.pdf
Storage Location
analysis/other-sources/
Key Findings
Grafton Lake ranked 8th most contaminated out of 21 source water samples from 12 BC watersheds. No exceedances of Health Canada Drinking Water Quality Guidelines or Environmental Quality Guidelines were detected. Sucralose was detected at the highest concentration of all 21 BC source water samples, indicating human waste infiltration. PCBs ranked 3rd highest and PAHs ranked 3rd highest among BC source water samples. Six pharmaceuticals and personal care products were detected including caffeine, cotinine, metformin, cocaine, benzoylecgonine, and DEET. Arsenic, zinc and lead concentrations were the highest recorded among all 21 BC source water samples but remained within drinking water guidelines. Five legacy pesticides (no longer in use in Canada) were detected. Two PFAS compounds (PFOA and PFHpA) were detected. Grafton Lake is highly vulnerable due to its small, shallow nature and proximity to septic systems and recreational activity. The study recommends bi-annual water quality monitoring and watershed best practices including septic maintenance, riparian buffer protection, and public education.
Methodology
A single composite water sample (12L) was collected from Grafton Lake outflow on October 8, 2024 using a pre-cleaned stainless steel container. In situ water properties (temperature, pH, conductivity, dissolved oxygen, turbidity) were measured using a YSI-ProDSS portable meter. Samples were submitted to ALS Environmental (Burnaby, BC) for Tier 1 and 2 analyses (nutrients, metals, physical parameters, coliform) and SGS-AXYS (Sidney, BC) for Tier 3 analyses (APEs, bisphenols, pesticides, PFAS, PPCPs, PCBs, PAHs, sucralose). Results were blank-corrected and compared against 21 source water samples from 12 BC watersheds collected as part of the Raincoast Healthy Waters program. Contaminant concentrations were compared to Health Canada Drinking Water Quality Guidelines (n=35), BC Environmental Quality Guidelines (n=56), CCME Environmental Quality Guidelines (n=43), and Federal Environmental Quality Guidelines (n=7).
Map Descriptions
Page 9: Map of the Grafton Lake watershed on Bowen Island, BC. Shows the watershed boundary (green shaded polygon) and Terminal Creek (blue line). Labels geographic features including Mt Gardner, Snug Cove, Killarney Lake, Millers Landing, Dorman Bay, Apodaca Cove, Seymour Bay, Fairweather Bay, Tunstall Bay, King Edward Bay, Bowen Bay, Grafton Bay, Smugglers Cove, Enchanta Bay, and Cates Bay. North arrow and 2 km scale bar included. Map credit: Brooke Gerle / Raincoast Conservation Foundation.
|Page 12: Regional map of southern British Columbia showing all Raincoast Healthy Waters program watershed partnership locations. Labeled watersheds include Grafton Lake, Louis Creek, Nicola River, Green River, Cheakamus River, Harrison Lake, Sliammon Creek, Anderson Creek, False Creek, Sqwa:la, Chemainus River, Little Campbell River, Fulford Creek, Cowichan River, and Tod Creek. Scale bar 80 km. Map credit: Brooke Gerle / Raincoast Conservation Foundation.
Graph Descriptions
Page 23: Bar chart (Figure 2) showing total PAH concentrations (pg/L) in Grafton Lake source water compared to 21 other BC source water samples. Samples ordered highest to lowest. Grafton Lake (red bar) ranked 3rd at 35.9 pg/L. Y-axis range approximately 0-55 pg/L. Badge shows #3 out of 21.
|Page 25: Bar chart (Figure 3) showing total pesticide concentrations (ng/L). Grafton Lake (red bar) ranked 17th at 0.197 ng/L. Y-axis range 0-3 ng/L. Badge shows #17 out of 21.
|Page 29: Bar chart (Figure 4) showing total PPCP concentrations (ng/L). Grafton Lake (red bar) ranked 6th at 18.7 ng/L. Y-axis range 0-100+ ng/L. Badge shows #6 out of 21.
|Page 33: Bar chart (Figure 5) showing total PCB concentrations (pg/L). Grafton Lake (red bar) ranked 3rd at 81.7 pg/L. Y-axis range 0-175+ pg/L. Badge shows #3 out of 21.
|Page 40: Bubble chart showing relative ranking of Grafton Lake for each contaminant class. Sucralose shown as largest dark red circle (poorest ranking). PCBs and PAHs shown as large orange circles. PPCPs and PFAS as medium yellow circles. Metals, BPA, Nutrients, Coliform, APEs, and MRES as smaller circles.
|Page 51: Bar chart (Table 1F) showing number of PAHs detected in Grafton Lake and 20 other source water samples (dry season). Grafton Lake (red bar) at 20 PAHs detected, ranked 4th. Y-axis shows number of PAHs detected (out of 76). Badge shows #4 out of 21.
|Page 52: Bar chart (Table 1G) showing number of pesticides detected in Grafton Lake and 20 other source water samples (dry season). Grafton Lake (red bar) at 5 pesticides detected, ranked 8th. Y-axis shows number of pesticides detected (out of 62). Badge shows #8 out of 21.
|Page 53: Bar chart (Table 1H) showing total number of PPCPs detected in Grafton Lake and 20 other source water samples (dry season). Grafton Lake (red bar) at 6 PPCPs detected, ranked 3rd. Y-axis shows total number of PPCPs detected. Badge shows #3 out of 21.
|Page 57: Bar chart (Figure 1J) showing number of PCB detections in Grafton Lake and 20 other source water samples (dry season). Grafton Lake (red bar) at 72 PCBs detected, ranked 4th. Y-axis shows number of PCBs detected (out of 159). Badge shows #4 out of 21.
Image Descriptions
Page 10: Photograph of a Bowen Island Municipality sign reading "Drinking Water Protection Area -- Grafton Lake is our drinking water. Stay on trails and do not pollute." with a cartoon frog graphic. Sign is mounted on a wooden post surrounded by trees. Photo credit: Peter S. Ross.
Page Count
68
Publisher Location
Sidney, BC, Canada
File Size
2.5 MB
File Format
application/pdf
Geographic Locations
Grafton Lake | Bowen Island | Nexwlelexwm | Bowen Island Municipality | British Columbia | Terminal Creek | Cove Bay Water System | Kwilakm (Deep Bay/Mannion Bay) | Howe Sound