Vancouver Area Sewer Systems

Transcription

1 November 17, 2009 Vancouver Area Sewer Systems Brent Burton, M.A.Sc., P.Eng. Metro Vancouver Andrew Boyland, P.Eng. Kerr Wood Leidal Assoc. Ltd

2 Metro Vancouver case study Host: Metro Vancouver (Legal Name: Greater Vancouver Regional District) Partner: Engineers Canada Consultant: Kerr Wood Leidal Associates Sub: Associated Engineering (B.C.) Ltd. Treatment Plant

3 Metro Vancouver Population +/- two million, approx 280,000 ha Partnership of 21 municipalities and one electoral area

4 Metro Vancouver s climate Metro Vancouver s coastal location results in a moderate climate that is relatively warm year-round with little snow at lower, more populated elevations Relatively low-intensity, long-duration rain is common from November through to March High-intensity thunderstorms are not common, but can occur in spring, summer or autumn Metro Vancouver is a region of micro-climates, with significant variation BUT THIS CLIMATE IS CHANGING

5 Rising sea levels combined with storm surge Storm surge in Delta in February 2006 Photo: Corporation of Delta

6 Increasing extreme weather Windstorm in Stanley Park in December 2006

7 Changing precipitation patterns Flooding adjacent to Still Creek in Burnaby

8 Metro Vancouver sewerage system Maintains and operates major interceptor sewers and five treatment plants

9 VSA: Local geography North Shore Mountains Burrard Inlet Strait of Georgia Fraser River

10 Regional collection system

11 Iona Island WWTP

12 Time frame Study Horizons Liquid Waste Management Plan Upgrade to secondary treatment by 2020 Eliminate combined sewer overflows by 2050 Infrastructure age ~ 50 yrs+ Service life 50 to 100 yrs

13 Climate change factors Relevant climate factors rainfall (annual, seasonal, 24-hour) sea level storm surge rain on snow events extreme temperatures drought conditions snowfall wind speed (extremes, gusts) frost (freeze-thaw cycles) ice

14 Ouranos climate modelling

15 Climate change sources Ouranos PCIC Ministry of Environment Literature review

16 Climate factors 2050 Horizon *Intense rain (24 hr 73mm) 17% *Annual rain (1881mm) 14% *Sea level m (2080 Horizon) *Storm surge N/A, expected Temperature c Drought no change (20 days) Wind N/A, expected

17 Conclusions Key vulnerabilities Combined sewer overflows (CSO) Intense rain, annual rain WWTP Flooding - combined effects of storm surge, sea level rise and subsidence Saltwater intrusion Process unit redundancy Standby power Effluent disposal outfall/jetty structure Storm surge, wind/wave effects

18 Recommendations Next phase of treatment upgrading Design secondary treatment to accommodate sea level rise and storm surge Sewer Separation Confirm timelines and commitments Identify stand-by power requirements Assess potential for WWTP flooding

19 Recommendations Review and update the Liquid Waste Management Plan Review regional design standards Consider policies and commitments to set targets for climate change adaptation Reaffirm commitments to green infrastructure Review how to incorporate climate change into new designs (IDF curves)

20 Observations Vancouver is fortunately situated - limited extreme or catastrophic climate events Lots of rain

21 Cross cutting issues Climate change vulnerability study highlights ongoing management actions i.e. emergency response plan, review standby power availability Older/poorly maintained infrastructure systems may be most at risk due to the combined effects of infrastructure deficit and climate events

22 Cross Cutting Issues Infrastructure renewal cycles may address some climate change vulnerability Design assumptions for very old infrastructure often not readily available e.g. to determine basis of capacity Combined sewers may have built-in adaptive capacity. Designed to overflow in controlled manner Many built when sizing was empirical (i.e. big enough for a person to walk through)

23 Cross Cutting Issues Climate data uncertainty Regional models unable to account for local effects (wind speed & direction, storm surge) Expense/practicality limited the model runs to two initial conditions (same GHG scenario) Professional judgment required to bridge science and engineering worlds

24 Questions Brent Burton, Metro Vancouver Andrew Boyland, KWL