Building a Defensible Framework for Prioritizing Water Main Rehabilitation and Replacement

March 21, 2012

James Carolan

The Challenge

Challenge - How do you effectively balance infrastructure growth, upgrades and replacement, within your available budget?

Solution - Identify, then upgrade and/or replace highest “risk” assets first, right?

…but it’s not that easy

– How do you know if your strategy is keeping up with the degradation of your assets? • How much is enough?

– How do you assign and prioritize asset risk? • Which pipes are a your riskiest?

– How do you manage the plan long term? • How to integrate capital planning with your enterprise?

Past Solutions

• Target leaking or obviously failing assets

• Line or replace the “old stuff”

• Look at past breaks and try to identify “bad areas”

• Keep your ear to the ground – advanced leak detection

The New Approach

• Use hydraulic criticality from a hydraulic model

• Use GIS for consequence analysis

• Use statistical tools for failure forecasting

– Age and break analysis

– Corrosion & soils analysis (GIS)

– Stray current analysis

• Manage the data and the plan in capital planning software

– Integrated with GIS and other systems (CMMs, etc)

The New Approach is a Continuous Process

Capital Plans

(Care-W & Care-S)

LEYP/GompitZ

KANEW

GIS Data

Hydraulic Model

O&M Data

Field Samples

Anecdotal Data

CapPlan®

ARP – Annual

Renewal Planning

Riva Modeling

Defensible &

Sustainable

Capital

Planning

Spreadsheets

Management

Strategies

The New Approach – Basic Toolkit

• GIS – Can help assemble data from multiple sources and do spatial analysis, but no

hydraulics

• Hydraulic Modeling Software – Useful for seeing the consequences of a hydraulics failures, but unable to build

models that encompass non-hydraulic data (breaks, condition, etc.)

• Computerized Maintenance Management Software (CMMS) – Source of failure and performance data, but not able to do modeling using multiple

factors

• Capital Planning and Management Software – Pull all these data together then develop and manage your plan long term

– Better integrated with the organization than past paper reports or long term studies

• Statistical Analysis Tools - LEYP

– Advanced review of historic pipe failure data

– What types of pipe are failing and why

– Provides better estimate of pipe condition – system wide

• Macro Modeling Tools - KANEW

– How do we know how much to do each year and of what type?

– Use pipe life spans and pipe inventory to develop long range plans

The New Approach – Advanced Toolkit

Leverage GIS and Hydraulic Model

Historic Shorelines Fluid Age/Chemistry Economic Zones

Critical Users Roads and Tunnels Hydraulic Criticality

GIS - Automated Service Generation

• Automated service placement to nearest main

• Determined demands for water model

• Not 100% perfect, but significantly improves accuracy of demand allocation

• Used in water outage analysis

• Link your customers to your model/GIS

GIS - Soil Data

• Overlay main breaks on

– Fill areas

– Soil types

• Corrosive soils vs Break Locations

GIS - Flood Risk Analysis

• Locate sensitive locations

– Hospitals

– Schools

– High use roadways

– Critical facilities

• Use topographical data to develop “flow sheds”

– What areas will “drain” to the sensitive location?

• Overlay sheds with mains and sensitive locations

• Determine which mains breaks may flood a sensitive location

HM - Hydraulic Criticality

• Hydraulic model based on GIS can identify problem areas

– Pipes where failure results in loss of service

– Areas that are only served by one pipe

– Extent of outage area resulting from pipe failure

HM - Automated Valve Isolation Tracing

• Valve shutoff for single main failure affects multiple pipes and buildings

• Analyze and rank each main feature

• Identify mains that would effect sensitive customers

HM - Water Age

• Hydraulic model analysis

– Identify areas of

• low flow

• high residency time

– Of those identify

• older pipes

• non-lined pipes

• Query water quality complaints from work orders

• Correlate complaints with hydraulic model results

• Determine if model accurately predicts water age

Example: CapPlan – Bringing it All Together

• Uses existing hydraulic model and GIS

– Innovyze hydraulic models – Esri GIS

• Performs spatial analysis “on the fly”

– Easily builds spatial tests for consequence

• Use hydraulic modeling results

– Pressure

– Water Age

– Hydraulic Criticality

• Manages the plan long term

CapPlan - Past Break Analysis

• Proxy for condition

• Use past breaks to rank assets

• Each pipe is assigned a value based on number of past breaks

• Allows each pipe to be compared for break risk against each other

• But it only ranks pipes with breaks… what about the others?

• Statistical Analysis Tools – Casses/LEYP – Allows failure and GIS data to be assessed simultaneously using advanced

statistics

– Great for determining how different variables (material, age, soil type, etc.) impact each other

– Used to determine failure probability of each pipe

• Not just previously failed pipes

• Macro Modeling Tools - KANEW – Looks at pipe renewal rate as a collection over time

– Relies on user setting service lives for each type of pipe

– Budget impacts shown over time

– Does not help decide which specific pipe segments need to be replaced or when

The Advanced Tools – Taking it the Next Step

Statistical Analysis

• Advanced regression analysis used to identify contributing factors

• Identifies strong and weak correlations

• Provides a predicted break rate for ranking the pipes

– All pipes in the system get ranked, not just those that have broken

• Provides an overall guide to pipe life spans

Asset type Predicted Break Rate

[breaks per mile/ year]

CI1 0.038

CI2 0.02

CI2R 0.02

CICL 0.11

DICL1 0.025

DICL2 0.004

DICL2R 0.004

PCI1 0.09

PCI2 0.02

PCI2R 0.02

LEYP - Example

Asset Type PCI

Break stats (1976-2007)

Length [ft]: 1,865,451 ft # Breaks, all pipes: 553 breaks

Length [%]: 37 % Break rate, all pipes: 4.89 #/100mi.year

Average age 106 years # Breaks, active pipes: 344 Schäden

100%-Age: 82 years Break rate, active pipes: 3.04 #/100mi.year

50%-Age: 102 years

10%-Age: 127 years Trend:

Replacement stats (1978-2007)

From To not representative

100% 70 100 Replaced length [ft]: 0 ft

50% 115 135 Cumulative replacement rate (x years): 0 %

10% 140 160 Average replacement rate (x years): 0 %

Ageing factor a 48.556 18.361 Average age at time of replacement: 0 years

Renewal factor b 0.087 0.086 Required age at time of replacement: 0 years

Resistance time c 70 100

Inventory (2009)

Ageing parameter

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 20 40 60 80 100 120 140 160 180 200

Age

Survival function

0

10

20

30

40

50

60

70

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160

Bre

ak r

ate

(bre

aks/

100m

i/ye

ar)

# b

reak

s

Age (years)

PCI - Breaks and break rate per age

# breaks Break rate (breaks/100mi/year)

• Use past break history to develop survival curves

• Curves provide a guide to when and what percentage of assets will fail over the short and long term

• Important for macro analysis – system wide long term analysis

KANEW – Macro Analysis

• How much should we work on to keep up?

• Which types of pipe will fail first?

• What should our mix of rehabilitation vs replacement be?

• Will rehabilitation help extend our system life?

• Run scenarios and develop long term approaches

The Tools Need Data

• Data quantity can be an issue

– Material and age information

– Joint type and lining information

– How many previous break records exist?

– Is there soils data?

• Data quality can be an issue

– Accurate GIS data – age, material, etc.

– Are the breaks as points on the pipes?

– How spatially accurate and well defined are the soil records?

Developing a System for Your Agency

• Build on a good GIS base

– Good material & age data

• Add asset management & historical data

– Type and number of breaks and leak

– Link between work activity and affected assets

• Identify risk and performance factors

– Where failure will impact service?

– What do you and your customers worry most about?

• Feed back data to asset database (GIS)

– Internal procedures

– Leverage existing and new computer technology

Questions??

James Carolan

Associate – CDM Smith

carolanjr@CDMSmith.com