UIM, Dec 9, 2008

Criticality and Prioritization of

Pipe Rehab Projects

Annie Vanrenterghem Raven, Ph.D.Research Associate ProfessorPolytechnic Institute of NYU

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Assignment

Choose best pipes candidates for rehab for the next year (short term) given a certain budget.

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Constraints

Several thousands of miles of pipes

Limited budget

Many criteria to take into account

Choices will have to be justified

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Water and Waste Water Rehabilitation Planning

BuriedNetwork

BuriedNonNetwork

Above groundNetwork

Above GroundNon network

Water Pipes Valves; fittings

Hydrants;Manholes

Plant; Pumping Station

WasteWater Sewer

Storm Water

Storm

Drains

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Points of View

Points of view:Time: long term and next year/short term

Space: whole system; zone; cohort of pipes; pipe level

Prioritize or optimize

Problems to address:StructuralWater qualityHydraulic (adequate pressure)

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Other Points of View

Points of view:Time: long term and next year/short term

Space: whole system; zone; cohort of pipes; pipe level

Prioritize or optimize

Problems to address:StructuralWater qualityHydraulic (adequate pressure)

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Performance

Indicators=

Prioritize problems

Zonescohorts

Long-Term Rehabilitati

on Planning

= Design CIPBased on stock and

degradation

HydraulicCriticality

and Vulnerability

Failure Forecastin

g=

Calculate the

probability of failure for each year and each pipe

Annual Rehabilitation

Planning

Macro analysisInput and output data at system, zone or cohort

level

Micro analysisInput and output data at

pipe level

The suite of tools

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Overall Context

Legal GASB 34; no federal mandate; state or local incentives

PhysicalAssets are ageing; in need of rehab (ASCE report card: D-)Water quality problems, decrease of hydraulic capacitySystems need to grow or shrink

NaturalDrought situations make leaks and breaks unacceptable

FinancialCapital needs ( to maintain and replace existing waterinfrastructure between 2003 and 2023) expected to be $277 billion; up to 2/3 for buried assets. (U.S. EPA, 2005) Gap between projected revenues and expensesLess public funding Full cost pricing rate increasesLess demand/revenues due to conservation technologies, change in public behavior, current financial crisis.

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Rehab planning: challenges

BuriedA lot to replace (US: 1M+ mi; LV: 4K mi; NYC: 6K mi)

Networks are scattered and ubiquitous;

even at most sensitive areas

Inspection, repair, replacement expensive and disruptiveDegradation/failure/impact unknown or very spectacular…

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Spectacular failure…

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Rehab planning: challenges

Multi-problems; multi-disciplinary, complex tasks involving multiple criteria.In the past, rehabilitation decisions have been pragmatic, opportunistic, and difficult to justify. In house DSS attempts; could be quite simplistic (matrix) and erroneous. No comprehensive research in the US.Lack of trust for advanced models (“black boxes”.) Funds are limited but business case of AM is still difficult to make.

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Rehab planning: Challenges with dataIf data does not exist, it has to be collected. Even simple solutions need data.Data is needed to populate the GIS and the HM, CMMS and AM system.Data collection is expensive. Data should be used for more than having a snap shot of the system at a given time, to set priorities.Prioritization should use the kind of advanced tools (used in other industries) that provide more answers and deal with uncertainty.This can be done at a rather low marginal cost. Added value and function to high price tools such as GIS, HM, CMMS. However the data must meet certain needs.

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Assignment

Choose best pipes candidates for rehab for the next year (short term) given a certain budget.

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Annual Rehab Planning

Multi-Criteria Decision Making Model (Electre) uses reference profiles to mitigate uncertainty.Criteria express risk (probability x consequences of failure) as well as other relevant points of view.Data is collected at different levels of refining.

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Criterion name Code Definition

Coordination with Other Infrastructure Co-ordination Score COS Score [-1,1]

Repair CostsAnnual Repair Cost

ARC ARC(i) = PFR(i) x UCRp(i)

Water Loss Water Losses Index WLI Index [0,1]

Water Interruptions

Predicted Water Interruptions PWI PWI(i) = PFR(i) x EDI(i) x NPS(i)

Predicted Critical Water Interruptions PCWI PCWI(i) = PFR(i) x EDI(i) x SC(i)

Predicted Frequency of Water Interruptions PFWI

PFWI(i) = L (i)/100 x PFR(i) x EDI(i)

Damages and Disruptions

Damages due to Flooding in Housing areas DFH

DFH(i) = PFR(i) x DI^2(i) x P(i) x SFH(i)

Damages due to Flooding in Industrial or commercial areas DFI

DFI(i) = PFR(i) x DI^2(i) x P(i) x SFI(i)

Damages due to Soil Movement DSM

DSM(i) = PFR(i) x DI^2(i) x P(i) x LS(i)

Traffic Disruption DT DT (i) = PFR(i) x SR(i)

Damages and/or Disruption on other Infrastructure DDI

DDI(i) = PFR(i) x DI^2(i) x P(i) x SI(i)

Water Quality Water Quality Deficiencies WQD Index [0,1]

Hydraulic Criticality

Hydraulic Criticality Index HCI Index [0,1]

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Criterion nameCode Definition

Coordination with Other Infrastructure Co-ordination Score COS Score [-1,1]

Repair CostsAnnual Repair Cost

ARC ARC(i) = PFR(i) x UCRp(i)

Water Loss Water Losses Index WLI Index [0,1]

Water Interruptions

Predicted Water Interruptions PWI PWI(i) = PFR(i) x EDI(i) x NPS(i)

Predicted Critical Water Interruptions PCWI PCWI(i) = PFR(i) x EDI(i) x SC(i)

Predicted Frequency of Water Interruptions PFWI

PFWI(i) = L (i)/100 x PFR(i) x EDI(i)

Damages and Disruptions

Damages due to Flooding in Housing areas DFH

DFH(i) = PFR(i) x DI^2(i) x P(i) x SFH(i)

Damages due to Flooding in Industrial or commercial areas DFI

DFI(i) = PFR(i) x DI^2(i) x P(i) x SFI(i)

Damages due to Soil Movement DSM

DSM(i) = PFR(i) x DI^2(i) x P(i) x LS(i)

Traffic Disruption DT DT (i) = PFR(i) x SR(i)

Damages and/or Disruption on other Infrastructure DDI

DDI(i) = PFR(i) x DI^2(i) x P(i) x SI(i)

Water Quality Water Quality Deficiencies WQD Index [0,1]

Hydraulic Criticality

Hydraulic Criticality Index HCI Index [0,1]

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Criterion name Code Definition

Coordination with Other Infrastructure Co-ordination Score COS Score [-1,1]

Repair CostsAnnual Repair Cost

ARC ARC(i) = PFR(i) x UCRp(i)

Water Loss Water Losses Index WLI Index [0,1]

Water Interruptions

Predicted Water Interruptions PWI PWI(i) = PFR(i) x EDI(i) x NPS(i)

Predicted Critical Water Interruptions PCWI PCWI(i) = PFR(i) x EDI(i) x SC(i)

Predicted Frequency of Water Interruptions PFWI

PFWI(i) = L (i)/100 x PFR(i) x EDI(i)

Damages and Disruptions

Damages due to Flooding in Housing areas DFH

DFH(i) = PFR(i) x DI^2(i) x P(i) x SFH(i)

Damages due to Flooding in Industrial or commercial areas DFI

DFI(i) = PFR(i) x DI^2(i) x P(i) x SFI(i)

Damages due to Soil Movement DSM

DSM(i) = PFR(i) x DI^2(i) x P(i) x LS(i)

Traffic Disruption DT DT (i) = PFR(i) x SR(i)

Damages and/or Disruption on other Infrastructure DDI

DDI(i) = PFR(i) x DI^2(i) x P(i) x SI(i)

Water Quality Water Quality Deficiencies WQD Index [0,1]

Hydraulic Criticality

Hydraulic Criticality Index

HCI Index [0,1]

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Criteria, example PWI

PWI(i) = PFR(i) x EDI(i) x NPS(i)Units: (No./mile/year) x (hours) x (persons)

With:PFR (i) Predicted Failure Rate for pipe i (No./mile/year)EDI (i) Expected Duration of Interruption (hours) NPS (i) Number of Customers Supplied by pipe (i) (or by all pipes that will be affected by the interruption of service; using hydraulic criticality results )

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Criteria, example ARC

ARC (i) = PFR (i) x UCRp(i)

Units: (No./100m/year) x ($)

With :

PFR (i) Predicted Failure Rate for pipe i (No./mile/year)UCRp (i) is the Unit Cost of Repair ($)

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Knowledge base, example UCR

Code Cost Description

1 3000 Unknow

2 1900 Diam <12” & easy context

3 3100 Diam <12” & normal context orDiam >12” & easy context

4 4700 Diam >12” & normal context orDiam <12” & difficult context

5 6200 Diam >12” difficult context

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Weights, example

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The reference profiles (electre)

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Dealing with uncertainty (electre)

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The categories

C33: Pipes with highest priority level. Pipes have been assigned to C3 according to both OP and PP.C32 (or C31): No consensus among criteria may be due to incomparability.C31, C22, C21, C11: low and moderate performance deficiencies.

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Annual Rehab Planning Categories

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Annual Rehab Planning results on GIS

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Performance

Indicators=

Prioritize problems

Zonescohorts

Long-Term Rehabilitati

on Planning

= Design CIPBased on stock and

degradation

HydraulicCriticality

and Vulnerability

Failure Forecastin

g=

Calculate the

probability of failure for each year and each pipe

Annual Rehabilitation

Planning

Macro analysisInput and output data at system, zone or cohort

level

Micro analysisInput and output data at

pipe level

The suite of tools

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Failure ForecastingHydraulic criticality

FF = Calculate Probability of each pipe for each year (PHM, LEYP)Hydraulic criticality and vulnerability

Effect of one pipe being out of service on delivery of service in rest of systemEffect of each pipe being out of service on one specific pipe2 pipes being out of service

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Performance

Indicators

Long-Term Rehabilitati

on Planning

HydraulicCriticality

and Vulnerability

Failure Forecastin

g

Annual Rehabilitation

Planning

Macro analysisInput and output data at system, zone or cohort

level

Micro analysisInput and output data at

pipe level

Implication of Polytechnic University

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Thank you for your attention!

avanraven@poly.edu