Case Study Whistler Water Distribution System Corrosion Study

Transcription

1 Case Study Whistler Water Distribution System Corrosion Study

2 The Eureka Moment 2

3 Corrosion Consequences 3 Pipe and fitting failures Water loss Increased pumping Customer complaints Water quality Photo Photo credit: credit: Photo credit:

4 Background 4 Linear water system: 128 km of water mains AC, Cast Iron, DI, PE, PVC, Steel 3,175 service connections Replacement value $51.7M years = $130,000/year

5 What is a Hot Soil? 5 External Corrosion Hot soils? Measure: Soil Resistivity ph Redox Potential Sulphide Concentration Moisture Content Proactive or reactive monitoring? Opportunistic data collection SOIL & GROUNDWATER CONDITIONS

6 External Corrosion Validation and Mitigation 6 Lower cost More samples Timely

7 Evidence of Internal Corrosion 7 Green Staining Indicative of copper corrosion Photo credit:

8 Determining Internal Corrosion Risk 8 Corrosion Index Langelier Saturation Index (LSI) Ryznar Index (RI) Larson Index (LI) Aggressiveness Index (AI) Calcium Carbonate Precipitation Potential (CCPP) Basis Based on theoretical tendency of water to deposit or dissolve calcium carbonate. It is a logarithm of the ratio of the hydrogen ion concentration that the water must have if saturated with calcium carbonate to the actual hydrogen ion concentration. Also based on theoretical tendency of water to deposit or dissolve calcium carbonate. Based on conductivity effects of specific ions rather than calcium carbonate precipitation. Developed to determine what water can be transported in asbestos cement (AC) pipe without adverse structural effects. Based on theoretical quantity of CaCO 3 that can be precipitated from oversaturated waters or dissolved by under saturated waters. Comment on Use Inaccurate outside ph range of Inaccurate in soft or saline waters. Inaccurate in soft or low total dissolved solids (TDS) waters. Does not incorporate temperature or TDS effects. Accurate for all waters, but computationally cumbersome. Source: USEPA Corrosion in Potable Water Systems Final Report

9 Mitigating Internal Corrosion 9 Mitigation Strategy ph and Alkalinity Control Corrosion Inhibitors Pipe Linings Cathodic Protection Pipe Replacement Pros Least capital intensive corrosion mitigation option Protects all infrastructure fed by controlled water source CaCO 3 corrosion inhibition can be implemented as part of a ph and alkalinity control strategy Can be implemented gradually as part of an asset management program Can be combined with other mitigation strategies Effective for large water containing vessels, straight pipes, and fittings Can be implemented gradually as part of an asset management program Can be combined with other mitigation strategies Cons Ongoing chemical costs Health and safety concerns associated with chemical use and storage Less effective in an old system Potential health implications of chemical addition (with the exception of CaCO 3 ) Ongoing chemical costs Protective film can degrade if the supply of chemical is stopped Linings can be compromised by extreme temperatures and/or physical stress Linings reduce carrying capacity of pipe Lining effectiveness is dependent on quality of installation Expensive Ineffective for distribution systems Expensive to replace materials all at once Metal fittings are still susceptible to corrosion Source: USEPA Corrosion Manual for Internal Corrosion of Water Distribution Systems

10 Water Sampling and Analysis 10 Source 21-Mile Creek (Surface) Emerald Estates (#1, #2) Alpine (#1, #2, #3) Function Junction (#1, #2) Community (#1, #2, #3, #4) Combined Community Wells 21 Mile Creek Well Cheakamus Crossing Well Rainbow Park Well Parameter Total dissolved solids (TDS) Temperature ph Alkalinity (as CaCO 3 ) Calcium (as CaCO 3 ) Chloride (Cl-) Sulfate (SO -2 4 ) Units mg/l o C s.u. mg/l mg/l mg/l mg/l

11 Results 11 Ranked Source CCPP Value Legend Function Well #2-130 Corrosion State CCPP Value Colour Combined Community Wells -110 Scaling (protective) > 0 Emerald Estates Well #1-100 Passive 0 to -5 Function Well #1-99 Mildly Corrosive -5 to -10 Rainbow Park Well -60 Corrosive -10 to -50 Emerald Estates Well #2-49 (aggressive) - 50 to -100 Emerald Estates Well #3-46 < -100 Cheakamus Crossing Well -46 Alpine Well # Mile Creek Well -38 Alpine Well # Mile Creek -9.7 All sources highly aggressive to AC pipe based on Aggressiveness Index (AI)

12 Chemical Dosing System 12 Capital Cost for Largest System Estimated at $300,000

13 Chemical Dosing Pilot 13 Confirm raw water corrosivity Validate corrosion model Confirm chemical dosing is effective Determine best chemical(s) Optimize dosing concentration Predict service life implications

14 Pilot Location Cheakamus Crossing 14

15 Pilot System Setup 15 Install dosing pumps Connect dosing lines to existing port Install ph analyzer Install sample collection port Relocate Ventilation Equipment Install dosing lines Place chemical drums on spill containment Install new hot water tank safety shower and tempering valve Capital Cost for Containerized System Estimated at $100,000

16 Baseline Testing 16 Mild Steel Corrosion Coupon 212 days 2.4 g (22%) lost New 1 month 4 months

17 Baseline Testing 17 Copper Corrosion Coupons Cu 2 O (Copper I)? CuO (Copper II)? Cu 2 O 3 (Copper III)? CuSO 4 (OH) nh 2 O? Cu 2 Cl(OH) 2? New 1 month 4 months 212 days 0.01 g (0.08%) lost What is happening on the surface? Stable or unstable? Installation?

18 Next Steps Research Project 18 STATEMENT OF COOPERATION

19 Research Objectives 19 Benefit municipalities across the country Expand field of corrosion science Improve understanding of corrosion impact on municipal systems Validate/calibrate Build business case

20 Questions? 20