North American water supply systems : Past, present and future ...

Past …Machu Picchu, Peru

Urbanization begins …• 1692 – Boston incorporates water works (wood pipe)• …• 1664 – Versailles, France uses cast iron mains• …• 1804 – Philadelphia uses cast iron mains• …• 1841 – Toronto has first private water supply system• 1842 – NY completes Croton aqueduct for water supply

Wooden pipes …. Peel, Ontario 2004Source: Peel, 2004

Wooden pipes ….

Wooden pipes …. Hamilton, Ontario 2004Thick-walled, drillcored tree-trunk“Stave“ - five finelyjoined tongue andgroove strips ofwood joinedtogether by a 1/4"pre-stressed steelwire to strengthenthe jointsSource: Hamilton, 2004

Were problems any different in the past?

Time line for type of pipe materials ….

Time line for iron pipe wall thickness ….Wall thickness (inches)10.80.60.40.20Pressure rating 150 psi (10 bars)Pit castclass D -1908Pit castclass 1 -1957Spun castclass 22(18/40) -1957Spun castclass 21(21/57) -1957Ductileironthicknessclass 52 -1965150 mm300 mmDuctileironpressureclass 350 -199125181260Wall thickness (mm)Pipe standard

Growth in Toronto … like others in NACumulative Pipe installed (km)6,00035,0002.54,00023,0001.52,00011,0000.501850 1900 1950 2000 2050Year0Population (million)

Present …

Pipe Materials in North AmericaNortheastSoutheastMidwestSouth CentralWestNorthwestCast IronDuctile IronAsbestos CementSteelConcrete PressurePVCOtherTotal USTotal Canada0% 20% 40% 60% 80%100%

Pipe Materials in EuropeUKSwitzerlandSwedenLuxemburgGermanyIrelandDenmarkNorwayBelgiumAustriaSpainFinlandNetherlandsCast IronACPlasticSteelConcrete0% 20% 40% 60% 80% 100%Source: KIWA, 2004

Pipe mechanical and thermal propertiesCast ironpit spunDuctileironAsbestoscementPVCElastic modulus, GPa 120 137 165 20-25 2.25Ultimate tensilestrength, MPa 173 250 290 25 48Strain to failure, % 0.5 0.5 7 1 10Poisson’s ratio 0.3 0.3 0.28 0.3 0.42Thermal coefficient, x10 -6 / o C 12 12 11 8.5 79

New York January 1998

Failure types• Physical rupture– corrosion induced reduction in factor of safety,inadequate bedding, high pressures• Hydraulic failure– inability to meet demand, component failure,interior deterioration• Water quality failure– contaminant intrusion, bacterial regrowth,chemical leaching, permeation of organics

Asbestos cementCombined degradation /structural failure ofasbestos cement pipeSource: CSIRO, 2004

Cast ironAfter sand blastingBefore sand blasting125 year-old pipePit-cast pipe samplewith casting voidsSource: Toronto, 2004

Ductile ironSource: Toronto, 2004

Time line for iron pipe wall thickness ….Wall thickness (inches)10.80.60.40.20Pressure rating 150 psi (10 bars)Pit castclass D -1908Pit castclass 1 -1957Spun castclass 22(18/40) -1957Spun castclass 21(21/57) -1957Ductileironthicknessclass 52 -1965150 mm300 mmDuctileironpressureclass 350 -199125181260Wall thickness (mm)Pipe standard

PVC pipesBrittle fractureof PVC pipeSource: CSIRO, 2004

Polyethylene pipesRupture ofpolyethylene pipeSource: CSIRO, 2004

Large diameter cast iron mainsCleveland, 1926Source: Cleveland, 2002Hamilton, January 2003Source: Hamilton, 2003

Large diameter PCCPCalgary, AlbertaJanuary, 2004Temperature –31 o CPCCP 1200 mmRepair costs: $700 KSource: AWWA Opflow

Calgary, AlbertaJanuary, 2004No loss of lifeNo damageMajor arterial roadSource: AWWA Opflow

• Water quality problems• Maintain legislativerequirements• Reduce customercontact• Hydraulics• Reduced head loss• Reduced powerconsumption

Present …• Water main replacement value in North America US$ 400 B• Only 0.5% replaced annuallyFinancial needs …USASCEUS EPAAWWAWINCanadaFCMUS $11 B / yearUS $83 B over 20 yearsUS $250 B over next 30 yearsUS $460 B over next 20 yearsCan $ 12 B over next 15 years

Challenges to manage distribution systems• Large majority of mains subject to corrosion• Large systems – enormous ‘inertia’ – slow anddifficult to change course• Owners do not ‘depreciate’ assets• Pro-active vs. reactive maintenance• Distribution system self insuredDistribution system self insured• …

Future …• Take care of high risk assets – transmissionmains• Promote the use of technology• Condition assessment and monitoring• Rehabilitation technology, e.g., cathodicprotection, , trenchless technology• Leakage audits• Leak detection programs

Future …(cont’d)• Promote the use of technology (cont’d)• Implementation of Geographical Informationsystems (GIS)• Collect data but must be good data!• Use models to foresee possible problems• Use decision-making models to arguefinancial needs• Use benchmarking• Conduct ‘acturial’ analysis of mains …

Distribution mains (small) – failure managementFailure frequency (#/km)Cost(presentvalue)min.cost1 2 3 4Total expectedcostt*Failure riskCost ofrenewalTime of renewal

Transmission mains (large) – failure preventionCost(presentvalue)Failure frequency (#/km)1 2 3 4Total expected costmin.costFailure riskt*Cost of renewalTime of renewal

Modelling risk of large mains – “fuzzy approach”Why fuzzy set theory?• Scarcity of pipe condition data – not enough forcredible probability analysis• Fuzzy mathematics explores possibility rather thanprobability (avoid false precision). Formalisesexpert opinion• Interpretation of distress indicators (inspection/NDE) into condition state often involves subjectivejudgment – well accommodated by fuzzy sets

What are fuzzy logic, fuzzy sets?Crisp setFuzzy setY: UniverseBY: UniverseBElement not in Bµ B = 0Element in B, µ B = 1Element hasdegree ofmembershipbetween 0 and 1,0 < µ B < 1The set B is characterized by µ B: → {0, 1}

Failure likelihood as a fuzzy (TFN) valueDegree of membershipµVery low Low Medium High Very high10.80.40X = 0.35Probability of failure1

Markovian-based fuzzy deterioration modelMembership value10.9Excellent0.8 Good Adequate Fair0.70.60.50.40.30.2PoorBadFailed0.101 21 41 61 81 101Year

Renewal of small diameter mains• Multi-covariate breakage frequency model –background ageing AND time-dependent factors• Cathodic protection a time-dependant factor• Retrofit cathodic protection - systematicinstallation of CP anodes on existing or newwater mains• Hotspot cathodic protection - opportunisticinstallation of CP anodes at breakage repair• Effect of CP on life-cycle cost and on lifeexpectancy

Hotspot CP modelling0.350.30Observed breakage ratesBackground ageing curve0.25Breaks/km0.200.150.10Multi-variate modelr a2= 0.680.050.001970 1975 1980 1985 1990 1995 2000 2005Year

Retrofit CP modelling0.800.700.60Breaks/km0.500.400.300.200.10r a2= 0.630.001970 1975 1980 1985 1990 1995 2000Year

Pipe life - economic outcome of life-cycle costsCost(presentvalue)total expected costcost ofbreakage repairmin.costt* t* t*Time of renewalcost of renewal

Hotspot CP economicsTotal discounted life-cycle costs ($K/km)$120$80$40No HS CPT * T o*20 40 60 80 100 120 140Age (years) at replacementStart HS CP at age100 years80 years60 years40 yearsStart HS CPon installation

Possibilities and challenges …Houston, I have detecteda leak, odour, , DBP, etc

Analyze data,assess condition(hydraulics andwater quality)Breaks,repairs,pressure,CISConditionsand performancereportsAssetRegisterReplacement ITSystem forTeromanMaintenance StrategyStandardising AssetMaintenancePart ofSTampSWhatisMainMan?FieldWorkingTrialSurfaceAssets (heterogeneous)Compliance ModuleBestPracticeCommonAssetDefinitionsValidatedDataCoModstuleSurfaceAssetsInvestmentModelDemandModuleAssetRegisterPerformanceInventory& ConditionConditionOutlinInvestmeProgramentmeWork ordermanagementsystemUndergroundAssets(homogeneous)StatistInvesticalmentModelsKANEWCARE-WWARPInformationManagementTools (GIS)consequence/risk assessmentNew assetsPrioritizationof renewals(based oneconomic andfinancial criteria)Source: Deb, 2004

Holistic view …Pipe deteriorationWater qualityin pipesPipebreakageNetwork hydrauliccapacity / reliabilityDecision - makingrisk vs. renewalFailure frequencyFailure riskRenewal,mitigation costsFailureconsequence (costof failure)

Quantifying probability of failure• Physical rupture– mechanistic and/or empirical models• Hydraulic failure– network simulation, demand forecast,component failure (empirical)• Water quality failure– physico-chemical chemical models, qualitative -quantitative approach (complex interactions)Challenge: Spatial and temporal variations, no data

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