Cove Bay Water System Long Range Plan Update
Basics
Title
Cove Bay Water System Long Range Plan Update
Description
AI-generated: This engineering report, prepared by Dayton & Knight Ltd. for the Bowen Island Municipality's Cove Bay Water System Local Management Committee, updates the 1998 long range plan for the Cove Bay Water System (CBWS). The CBWS serves over 630 service connections in the Snug Cove, Millers Landing, Cates Hill, Queen Charlotte Heights, and Scarborough areas of Bowen Island, sourcing water exclusively from Grafton Lake. The report reviews historical population and water demand data, projects future demands to 2030, analyzes Grafton Lake hydrology and storage capacity under drought conditions, and assesses water quality issues. Key recommendations include raising the Grafton Lake control dam by 0.5 m to increase live storage from 222,000 m3 to 320,000 m3 (as permitted by MOE licence), installing a filtration system, improving water quality monitoring, and expanding the metering program. The report includes extensive appendices with precipitation regression analysis, monthly and summer frequency curves, and raw water quality test results.
Date
November 1, 2009
Creator Organization
Dayton & Knight Ltd.
Authors
Seamus Frain | Clive Leung
Document Type
report
Metadata
Keywords
Cove Bay Water System
|CBWS
|Grafton Lake
|Bowen Island
|water supply
|long range plan
|hydrology
|drought management
|storage capacity
|water quality
|population projections
|water demand
|equivalent residential units
|ERU
|chlorination
|filtration
|trihalomethanes
|THM
|Giardia
|Cryptosporidium
|turbidity
|evapotranspiration
|watershed yield
|Terminal Creek
|Josephine Ridge
|precipitation regression
|water licences
|Ministry of Environment
|metering
|water conservation
|per capita demand
|peak day demand
|average day demand
Time Period
1992-2009 (historical data); projections to 2030
Relationship - hasPart
Document ID
2605101956
Document ID
2605101956
Document ID
2605101956
Document ID
2605101956
Copyright holder
Dayton & Knight Ltd.
Document Filename
2009_cove_bay_water_system_long_range_plan_2605101956.pdf
Storage Location
analysis/bowen-municipality
Key Findings
The present Grafton Lake live storage capacity of 222,000 m3 can supply only about 66% of current CBWS demand during a 1 in 10 year drought. Raising the Grafton Lake control dam by 0.5 m to the MOE licence limit of 320,000 m3 would allow 127% of current demand to be met, enabling up to 395 additional equivalent residential units (ERUs) and potentially 540 ERUs with a 10% reduction in water demand. Water quality concerns include turbidity levels exceeding Health Canada guidelines, very soft water (hardness 16-30 mg/L CaCO3), pH ranging 6.1-7.5 (slightly corrosive), and 2008 trihalomethane levels of 150 ug/L exceeding the recommended limit of 100 ug/L. Beaver presence in Grafton Lake raises concern about Giardia risk, though no positive tests have been recorded. The report recommends installing a filtration system, raising the dam spillway, universal metering, and quarterly monitoring of disinfection by-products.
Methodology
Precipitation regression analysis using data from seven Environment Canada stations (Arbutus Bay, Sunset Park, Bowen Bay, Cates Hill, Millers Landing, Killarney, Josephine Ridge) for 1961-2008. Monthly evapotranspiration calculated using the Thornewaite equation. Watershed yield estimated from precipitation minus evapotranspiration over 709.2 ha watershed area assuming 100% runoff. Lake storage capacity analysis using bathometric survey data from 1983 Ministry of Environment survey. Frequency analysis of monthly and summer inflows over 41-year extended record to determine 1:10 year low flow scenario. Storage analysis modeled using idealized 2008 weekly demand curve against drought-year rainfall distributions (2002, 2004, 2006, 2008). Sensitivity analysis conducted for water demand variation (80-120% of 2008 demand) and drainage area estimation errors (-20% to +20%). Water quality data from British Columbia Analytical Technologies Ltd. enhanced potability tests 2004-2008.
Map Descriptions
Page 15 (document page 2-4): Table showing eleven Cove Bay Water System pressure zones and methods of supply across the distribution network.
|Page 16 (document page 2-5): Table showing seven Grafton Lake water licence details including licence numbers, licencees, purpose, maximum annual and daily withdrawal/storage amounts, and issue dates.
Graph Descriptions
Page 23 (document page 3-6): Line graph titled 'Historical Per Capita Demands' showing average day demand (ADD), peak day demand (PDD), and peak hour demand (PHD) in L/c/d from 1993 to 2008, with two data series for 1993-1996 and 2000-2008 periods. Shows demand peaked in 2000 and declined after water conservation measures.
|Page 78 (Appendix B): Table of Grafton Lake monthly and summer inflows in 1000 m3, ranked for frequency plotting, covering 41-year period 1961-2008 with Weibull position values.
|Pages 79-86 (Appendix B): Log-probability frequency curve charts for Grafton Lake monthly inflows (January, February, March, April, October, November, December) and summer total inflows, each covering the 1961-2008 41-year period, used to estimate 1:10 year return drought inflow volumes.
Image Descriptions
Page 1: Bowen Island Municipality logo with mountain silhouette graphic
|Page 2: Bowen Island Municipality logo with mountain silhouette graphic and Dayton & Knight Ltd. Consulting Engineers logo
|Pages 88-97 (Appendix C): Scanned laboratory certificates of analysis from British Columbia Analytical Technologies Ltd. (BCAT) showing raw water sample test results for Cove Bay Water System enhanced water potability analysis for multiple sampling dates from June 2004 through December 2008, including THM and HAA analysis tables.
Page Count
97
Publisher Location
Bowen Island, British Columbia
File Format
application/pdf
Geographic Locations
Bowen Island | Snug Cove | Millers Landing | Cates Hill | Queen Charlotte Heights | Scarborough | Grafton Lake | Terminal Creek | Josephine Ridge | Arbutus Bay | Bowen Bay | Queen Charlotte Channel | Apodaca Park | Crippen Regional Park | Mount Gardner | British Columbia | Canada