Improved Management of Water Infrastructure Assets with Non-Invasive Acoustics

Agenda

• Background

• Condition Assessment Methods

• Non-Invasive, Non-Destructive Assessment Technologies

• Implementing Non-Invasive Non-Destructive Assessment Technologies (Case Studies)

• Serviceable Lifetime Prediction

BACKGROUND: Water Infrastructure Asset Management Challenges

• The age of pipe that currently exists in water systems often dictates how water utilities prioritize their rehabilitation and replacement programs.

• Prioritization is rarely based on actual measurements of the structural condition of pipe.

• Traditional methodologies are typically costly and invasive:

• Inaccurate • Disrupt service • Disturb surrounding infrastructure • Introduce foreign organisms into the water system • Lose tools in the pipe • Disturb existing sediment in the pipe • Negatively affect water quality

BACKGROUND: Water Infrastructure Asset Management Challenges

• Recent developments in non-invasive acoustics provide more accurate and cost-effective methods for pipe condition assessment and leak detection.

• Implementing an advanced acoustic pipe condition

assessment and leak detection program will help utilities: ▸ Reduce non-revenue water

• Lowers operational and energy costs • Supports water conservation

▸ Effectively prioritize capital spending ▸ Identify intrusions of potentially harmful material to water stream ▸ Reduce the risk of catastrophic failure

Condition Assessment Methods

Condition Assessment Methods

• Internal Environment ▸ Water quality, aggressivity Index ▸ Calcium carbonate saturation

testing • Soil Environment

▸ Soil/geological mapping ▸ Soil corrosivity (pH, sulphate

content) ▸ Soil testing

• Statistical/Criticality Models ▸ Review break rate, soil type ▸ Includes consequence of failure

Current Indirect Assessment Methods • Pipe Sampling / Destructive Method

▸ Hardness testing ▸ Phenolphthalein Dye test ▸ Strength (crush) testing

• Ground Penetrating Radar (GPR) Based Method ▸ Modified GPR unit looks at the

density changes in concrete matrix of pipe

▸ Requires direct access to pipe through a pit, and 360 degree access

• Acoustic Assessment Methods ▸ Provides average minimum

structural thickness assessment ▸ Leak detection often performed

at the same time

Current Direct Assessment Methods

Advantages and Disadvantages of Indirect Inspection Methods

Water Aggressivity Testing • Advantages: • Provides general idea on whether

pipes are at risk • Disadvantages: • Does not account for pipe

environment

Criticality Models • Advantages: • Necessary to understand overall

system requirements • Disadvantages: • Often based on statistically

inadequate model

Soil Testing/Geological Mapping • Advantages: • Provides general idea on whether pipes

are at risk • Disadvantages: • Aggressive soils do not necessarily

correlate to degraded pipe • Time consuming, expensive • Need good GIS system to make sense of

the data

Condition Assessment Methods

Condition Assessment Methods

Pipe Sampling • Advantages: • Direct test of structural condition of

pipe • Very accurate assessment of sample

possible • Disadvantages: • Not statistically significant • Cost • Issue of handling and disposal

GPR • Advantages: • Direct test of structural condition of

pipe • Do not need to cut pipe to obtain

results • Disadvantages: • Not statistically significant • Cost • Still need to dig

Advantages and Disadvantages of Direct Inspection Methods

Condition Assessment Methods

Advantages:

• Provides minimum structural wall integrity • Non-destructive, Non-disruptive • Cost effective • Good survey accuracy • Leak detection is performed at same time • Can be included in engineering criticality models to prioritize pipes for

replacement/rehab

Disadvantages:

• Average wall thickness is obtained

Advantages and Disadvantages of Acoustic Testing

Condition Assessment Methods Advantages of Non-Invasive Acoustic Testing

• No need for specialized ports; we can often use existing appurtenances • 0% probability of:

• foreign organisms being introduced into the pipe • loss of components in the pipe • disturbance of sediment in the pipe

• No requirement to dewater, alter the flow in the pipe or have minimum flow • No requirement to close service take-offs, which can require other technologies and increases cost • Can identify large leaks many miles away on transmission mains • Low cost of implementation compared to other available methods • No post cleaning or flushing

Non-Invasive, Non-Destructive Acoustic Assessment Technologies

Non-Invasive Non-Destructive Assessment Technologies - Velocity Measurement

Wave propagation velocity (v) = D/ΔT, where ΔT is time delay between signals 1 and 2

Noise Source

Measure the sound velocity

Non-Invasive Non-Destructive Assessment Technologies - Background • Low frequency acoustic pressure wave is induced in pipe • Dominated by a non-dispersive axi-symmetric (S1,n=0) • Pressure wave causes pipe wall

to “flex” on microscopic level • Thicker (stiffer) pipe walls are more resistant to “breathing,” causing

wave to travel faster • Measuring this phenomenon

allows calculation of remaining wall thickness

Velocity Equation

Where: v = propagation velocity of leak noise in pipe vo = propagation velocity of sound in an infinite body of water D = internal diameter of pipe e = thickness of pipe wall Kwater = bulk modulus of elasticity of water Epipe = Young’s modulus of elasticity of pipe material

Non-Invasive Non-Destructive Assessment Technologies - Implementation • Average distance 300 to 500’ is optimal, can measure

from 100’ to 1000’ • Typically measure between two valves or hydrants • Can measure ¾ to 1 mile per day • For transmission mains, can vacuum excavate to the

crown of the pipe to obtain proper distance • Average structural integrity between the two locations

is obtained • Pipe sampling may be done to confirm results

Implementing Non-Invasive Non-Destructive Assessment Technologies (Case Studies)

Southern Nevada Water Purveyor • Two sections of 6” AC pipe tested • 0.73” remaining structural thickness measured by Echologics • Results indicated that pipe met requirements of PC200 • Excavated pipe to confirm results • Testing confirmed that results accurately represented the

pipe’s remaining structural thickness

Southern Nevada Water Purveyor: Velocity Measurement & Results

Southern Nevada Water Purveyor: Excavated Pipe

Southern Nevada Water Purveyor: 14” Pipe Degradation Project

Southern Nevada Water Purveyor: Asset Management Plan

• Utility has standardized non-invasive, non-destructive acoustical methods to test for AC pipe based on confidence and repeatability

• To date: ~30 miles of AC pipe tested successfully

• Most AC pipe was found to be in excellent condition ▸ Avoided unnecessary replacement

• Several areas of degraded AC pipe identified and replaced

Case Study: Medium-sized BC Utility

Location Pipe Distance Nominal thickness

Measured Structural Integrity

Stiffness Loss

16th to Spring 6” AC 178.5 m 16.75 mm 8.43 mm -50%

• Both ‘hard’ and ‘soft’ AC pipe; no discernable geographical/age patterns

• Several sections tested; identified one pipe as ~50% degraded

• Lab testing confirmed results

Newark, NJ: Pilot

Confidential – Use pursuant to Company instructions

• Condition assessment performed on section of 1890’s era 6” cast iron pipe

• Service leak discovered

• 3 coupon samples extracted along street to confirm

• Pipes in area selected for concrete mortar relining

Serviceable Lifetime Prediction

Serviceable Lifetime Prediction: What is it? • Models developed to predict remaining serviceable life based

on condition assessment measurements

• Based on the measurement results and current loading conditions of the pipe (pressure and depth), an estimate will be provided on how many more years the pipe can be used

• Provides an accurate idea of when pipe will need to be rehabilitated/replaced in the future

Serviceable Lifetime Prediction: How does it work?

• Current thickness of the pipe is measured using PIT method

• Linear extrapolation is performed by using the measured thickness, the nominal thickness and the installation date

Installation Date

Measurement Date

Serviceable Lifetime Prediction: How does it work?

• Failure thickness is predicted by calculating the minimum required thickness to carry the given loads

• Loads include: internal pressure from the water column and external pressure from the soil and traffic loads

Failure Thickness

Serviceable Lifetime Prediction: How does it work?

• Asbestos Cement degrades in a mostly uniform fashion • The Schlick Failure Criterion is used to predict the failure

thickness

Serviceable Lifetime Prediction: Example

High Pressure Zone • 90 psi • t* = 0.09 mm/yr • tf = 11.9mm • 5 years remaining service

life

Low Pressure Zone • 43 psi • t* = 0.11 mm/yr • tf = 11.3mm • 3 years remaining service

life

• The degradation rate was higher in the low pressure zone and its life expectancy is lower

• Counterintuitive!

Summary

Summary • Utilities need to understand condition of their AC pipe • Condition assessment enables utilities to:

▸ Reduce costs ▸ Prioritize capital ▸ Ensure access to safe, clean drinking water

• AC pipe

▸ Significant portion in acceptable condition ▸ Degraded pipe needs to be replaced for costs savings and water quality ▸ Condition assessment program can distinguish between the two

• Utilities have options for condition assessment

• Non-invasive non-destructive condition assessment has distinct advantages

Summary: Benefits of Non-Invasive Non-Destructive Acoustic Condition Assessment

Scalability

• Cover larger areas with one crew (~0.7 miles/day)

Ease of use

• No need for specialized access, road repairs or service disruptions

Reduction of NRW

• Leak detection is performed • On average, find 1 leak per mile of pipe

surveyed

Top-down approach

• Large areas covered for lower costs than intrusive in-pipe technologies

• Screening performed on large areas to identify problems and avoid rehabbing or replacing pipes in good condition

Prioritize capital spending

• Rehab costs of $50 - $200/foot vs. replacement costs of $150 - $300/foot

• Identifies mains NOT needing rehab or replacement

• Protects water quality by not inserting tools into the system • Simultaneously performs condition assessment and leak

detection • Can provide extensive, well-documented case studies and

references • Utilizes well-trained, highly qualified field and analysis

personnel • Can identify “quiet” leaks that are common on AC pipe

Summary: Selecting An Acoustic Condition Assessment Partner

Q & A

For comments or additional information, please contact Carl Sharkey at (415) 819-7270, csharkey@echologics.com . Or, please visit www.echologics.com.