Managing Distribution Integrity New Tools for Old Problems

Transcription

1 Managing Distribution Integrity New Tools for Old Problems David M. Hughes and Orren Schneider American Water November 3, 2009

2 American Water Utility Only O&M Only Both Largest investor-owned water services provider in North America Serves 16.2 million people Operations in 32 states and Canada 7,000 employees 308 individual service areas 71,500 km (45,000 miles) of distribution mains

3 Old Problems - Leaking Pipes & Backflow 0 Main breaks represent a loss of potable water with a cost involving chemicals, power, sludge handling and wear on the pumping and process equipment. 0 Main breaks have a cost for repair with excavation and restoration costs. (Main breaks do not occur on a set schedule and often surface in poor weather.) 0 Main breaks can damage other infrastructure and private property and draw unwanted public attention 0 Backflow can allow something outside the potable water piping to enter and compromise drinking water quality.

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5 Pipe Failure is Asset Management Information 0 Main breaks provide a definitive clue to pipe pp failure, signaling gstructural problems. 0 Efforts continue to quantify the deterioration rate of mains to predict failure - to a cohort of pipes and then specific pipe segments. 0 Search continues for economic condition assessment tools to evaluate when pipe is likely to fail in the future. 0 Ideally, utilities replace pipe just before y, p p p j the cost of failures exceeds the cost of replacement - the end of the life cycle.

6 Pipe Failure Happens 0 It is realistic to assume that for many pipes, some frequency of pipe breaks is both economical and tolerated by the customer. If this premise is realistic, minimizing the impact of expected pipe breaks would be a useful goal and might actually extend the life of assets. WARNING! This scenario is not appropriate for all pipes. There are critical pipes where pipe failures are catastrophic and unacceptable.

7 Low Consequence Water Main Leak Strategies 0 Conventional Leak Surveys Assisted by temporary dispatch of acoustic monitors 0 District Metering 0 Continuous Acoustic Monitoring Continuous Leak Correlation? 0 Other system alerts Pressure monitoring Backflow alerts Temperature monitoring

8 A New Tool for the Leak Management Continuous Acoustic Monitoring (CAM) 0 Devices placed permanently to listen for leak noise every night. By extending the monitoring time, distinguishing leak noise from background noise is more reliable. 0 American Water worked with two vendors to develop a monitoring program that sends vibration data on a daily basis directly to the field office.

9 Pilot Study Connellsville, PA 0 Connellsville is located along the steep Youghiogheny River valley 40 miles south of Pittsburgh. 0 System dates back to 1880 s s. Mostly cast iron and galvanized steel but also AC, ductile, & plastic. 80% of 57 miles of main are over 100 years old. 0 NRW was over 25% and the cost of water (purchased from an adjacent system) is $1,900 (US) per million gallons.

10 AMR Fixed Network and Acoustic Monitoring COMPUTER Acoustic (leak) Data Meter Reads, Meter Status Data Collector Units Billing Meter reads Meter Transmitter Units Acoustic (leak) Data Billing, and recent Meter reads Selected Reports Water Meter Water Meter Water Meter Acoustic Monitor American Water Computer Selected Meter reads Schematic courtesy of Aclara

11 How Does It Work? 0 Monitor identifies the minimum sound in short intervals during overnight hours. 0 The data points shows low, medium and high frequencies as well as a sum of the leak noise frequencies for ferrous and plastic. 0 The monitor also reports on the highest differential between the lowest noise and the highest. 0 The software interprets changes and magnitude of sounds to rate the location as a possible source of a leak

12 On Line WEB Snapshot of Leak Survey Data The acoustic monitor data is organized to highlight the most likely candidates for leak noise to check

13 Continuous Leak Survey Data There is a typical brief initial noise peak as leaking pipe smoothes and moves soil away from pipe The software displays a history showing the noise level at each day.

14 Initial Results MLOG leak detecting sensors were installed in Connellsville in Spring From June to December leaks were reported in Connellsville (18 in 2003, 12 in 2004) of the 46 leaks were identified by acoustic monitors and repaired without surfacing. Another 10 were MLOG identified before surfacing but appeared before repair made. The remaining 12 surfaced and were repaired. 0 With the reduction of blow-off flow and leaks system flow 0 With the reduction of blow off flow and leaks, system flow dropped about 255, ,000 gpd through 2006.

15 Piloting Results Connellsville Water Research Foundation Project# leaks occurred during period of which 131 (76%) were detectable. 33 leaks (19%) could not be detected because they surfaced and were repair before overnight monitoring. 0 Of the 131 leaks, 51 (39%) were detected and repaired before surfacing and 34 (26%) were detected acoustically but they surfaced before repairs were made. 0 The major cause for not detecting overnight leaks (35%) is believed to be the use of plastic and repair clamps for ferrous pipe main repairs that lessen leak noise transmission.

16 Piloting Results Connellsville Non surfacing leaks stopped leaks 690 gpm Non- surfacing leaks stopped 1392.gpm Stopped leaks 270 gpm

17 Leaks from all pipe types were detected PIPE/APPURTENANCE TOTAL COVERAGE EFFICIENCY 2 GALV. PIPE (86%) 38 (63%) 1-2 PVC PIPE 2 1 (50%) 1 (50%) 2 ½ - 4 CAST IRON PIPE 15 8 (53%) 5 (63%) 6-12 CAST IRON PIPE (54%) 9 (64%) 6 AC PIPE 5 2 (40%) 2 (100%) 12 DUCTILE IRON PIPE 3 1 (33%) 1 (100%) SERVICE LINES (90%) 21 (60%) HYDRANTS 5 5 (100%) 4 (80%) VALVES 4 2 (50%) 1 (50%)

18 All types of leaks were detected LEAK TYPE TOTAL COVERAGE EFFICIENCY CONNECTION FAILURE 2 2 (100%) 2 (100%) CLAMP FAILURE 3 2 (67%) 1 (50%) JOINT/BELL FAILURE 6 5 (83%) 3 (60%) BLOWOUT 5 2 (40%) 0 (0%) HOLES (CORROSION) (82%) 24 (60%) CIRCUMFERENTIAL (41%) 8 (73%) SPLIT (82%) 14 (67%)

19 Leak Trigger? The Stress from Changing Water Temperature 0 Definite higher noise in extremes of heat and cold. There are patterns that repeat annually. Optimum time for leak detection appears to be the fall. We can now anticipate leak starts occurring mostly after a water temperature drop in surface supply systems.

20 Water Research Foundation Project Evaluating the Leak Dynamic 0 There are potential implications in reducing liability 0 The value of water savings depends on the types of leaks and cost of water 0 The economic value of rapid repair is a reduction in repairs in non business hours and works sites where damage to pipe and subsurface is less. 0 There will be better information on leak locations and the ability to reduce the cost of water loss 0 Pipes that leak and do not indicate a sustained loss with acoustic monitoring move higher in the main replacement prioritization rankings.

21 Case Study Answers to Questions about the Continuous Acoustic Monitoring Process 0 The effective range of the acoustic monitors for is usually 250 feet for plastic and 400 feet for metallic pipes. 0 Leak noise does dissipate with distance. A mix of pipe types and repair clamps noise will mute sound. 0 About 20-30% of noisy locations are real leak suspects. Operator experience noise history helps analysis. 0 Noise patterns appear predictable for most noisy sites. Leaks still can be distinguished at such sites.

22 Case Study Answers to Questions about the Continuous Acoustic Monitoring Process 0 One to two weeks is an effective interval for monitoring but can be varied for changing temperatures or season. 0 Anywhere from 30-70% of surfacing breaks appear to start as small detectable leaks. Rapid breaks increase in cold weather 0 Some leaks run in excess of two months before surfacing. Isolated cases have been found running a year or more. 0 Confirmation in the field of a leak takes perhaps 30 minutes plus an hour to pinpoint. p

23 Continuous Monitoring Tools are expected to improve significantly in near future 0 Itron working on a monitor on every service to reduce missed leaks and decrease false positives 0 Gutermann working on a system stem that will allow for correlation from the office. 0 Echologics working on system to cross over from monitoring large mains leaks and have greater range 0 GL Industries use pressure monitoring and hydraulic models tested to find leak areas. 0 Smart meters are now alerting utility to customer 0 Smart meters are now alerting utility to customer issues: high reads, continuous flow and backflow.

24 Continuous Acoustic Monitoring and the District Metering Approach 0 District Metering normally waits for metered nighttime flow to reach an economic threshold of leakage before performing a DMA leak survey. The DMA method does track leakage flow. 0 Continuous Acoustic Monitoring does not track flow but does enable any leak to be investigated as soon as it appears acoustically. This would tend to reduce water loss over the DMA approach. 0 The best solution is a combination of CAM and DMA. With CAM, the size of the DMA normally ( customers) as it serves to quantify leakage and verify that t a system that t is quiet is not experiencing i leaks not detected by CAM.

25 Implications for Leakage Management 0 Conventional wisdom is that the reactive approach to asset management is not as effective as proactive. 0 We can speed reaction time so that the consequences of some breaks and many minor leaks are mitigated. The cost of repair is reduced by fixing break before subsurface is heavily disturbed. Repairs are made at scheduled hours instead of under emergency conditions. Loss of water is minimized. Damage to other infrastructure and private property reduced. 0 Finding more leaks in a tighter system adds confidence to condition assessment process using pipe leaks as the criteria.

26 Backflow Risk every leak is a failure of system integrity Backsiphonage U.S., 1986 Blistered hands ph 13 water Burned in the Shower ossconnection/chapter02.pdf

27 Cross Connection and Backflow Vulnerability: Monitoring and Detection Orren D. Schneider, Ph.D., P.E. American Water David M. Hughes, P.E. American Water Zia Bukhari, Ph.D. American Water Mark LeChevallier, Ph.D. American Water Paul Schwartz, P.E. USC FCCCHR Patrick Sylvester USC FCCCHR J.J. J Lee, Ph.D., P.E. USC FCCCHR

28 Acknowledgements 0 This work is part of Water Research Foundation Project 3022, funded by the Water Research Foundation and USEPA. 0 We would like to thank the Project Manager, Maureen Hodgins, PAC members, and utility volunteers American Water Operating Companies (NJ, PA) Neptune Technology Group

29 Project Overview 0 Vulnerability Assessments Risk Matrix Surge Models 0 Technology Screening Direct Hydraulic Monitors Indirect Hydraulic Monitors Indirect Water Quality Monitors 0 Monitor Evaluations Direct Hydraulic Monitors Indirect Water Quality Monitors 0 Site Selection 0 Response Protocols 0 Conclusions

30 Vulnerability Assessments Risk Matrix 0 Developed based on data extracted t from documented backflow events between 1930 and 2000 (600 alone from 1970 to 2000). 0 Analysis focused on several physical, environmental, and human factors to establish relative levels of backflow risks for distribution systems (or pressure zones).

31 Vulnerability Assessments Risk Matrix Physical Factor Data Weight of Risk Score Nominal working pressure in the system Maximum elevation difference in system Typical pressure fluctuation in a day Environmental Factors Month of the year Human Error Factors Training/Education TOTAL SCORE psi psi psi psi 1 > 125 psi 0 > 500 ft ft ft ft 2 <50 ft 1 > 40 psi psi psi psi psi 1 < 5 psi 0 June - October 2 November - May 0 Agency does not have training and/or education in cross-connection control Agency has training i and/or education in cross-connection Water Research Foundation. ALL RIGHTS RESERVED

32 Vulnerability Assessments Risk Matrix Score Risk Level 0-5 Moderate 6-8 High 9 Greatest 0 Based on the analysis of the past events, the highest correlation to backflow was the lack of adequate backflow prevention education/training. 0 Other important factors included low nominal working pressure (<40 psi), high elevation differences, and high pressure fluctuations (>40 psi) Water Research Foundation. ALL RIGHTS RESERVED

33 Vulnerability Assessments Surge Modeling 0 Used to determine nodes in distribution system that are vulnerable to low or negative pressure transients 0 Short time scales to determine vulnerability to pressure transients 2009 Water Research Foundation. ALL RIGHTS RESERVED

34 Main Break/Backflow Simulation Locations modeled d with low/negative pressure pressure < 30 psi pressure < 20 psi pressure < 0 psi

35 Technology Screening Direct Hydraulic Monitors 0 Commercially available standard d water meters that t can sense backflow Electronic comparison of consecutive readings (Neptune, Master Meter) Magnet rotation/paddle wheel (Actaris) Alarm setpoints dependent on model (1 gal to 30 gal) Communication through touchpad AMR (fixed network or Communication through touchpad, AMR (fixed network or drive-by), or AMI

36 Smart Metering Backflow Monitoring Alerts utility if backflow occurred in last 35 days anytime meter is read Backflow checked every 15 minutes Level 1-1 gallon Level 2-10 gallons Looks at worst case Updated d E-coder will add time stamp and provide interval data Graphics courtesy of Neptune Technology Group

37 Monitor Evaluations Direct Hydraulic Monitors 0 Set up monitors in four systems (NJ, WV, 2 in PA) 0 System coverage 1% % 0 For systems with <100% coverage targeted areas based on suspected of backflow vulnerability or random scattering 0 Used one fixed network AMR, three drive-by AMR systems

38 Field Test Results PA1 0 Installed >3,300 meters 0 Found 51 instances of backflow in one month 13 instances of >10 gal 38 instances of 1-10 gal 0 Pattern indicative of main breaks and confirmed by operators 0 Several isolated spots have warranted further investigation for possible meter tampering Main break low level backflow high level backflo Water main Main Isolated break high leve break & repair backflow 2009 Water Research Foundation. ALL RIGHTS RESERVED

39 Field Test Results PA2 0 Installed 60 backflow meters out of 5000 meters locations strategically selected 0 Found 13 instances of backflow in one year from six locations 24 instances, 11 locations in 2 years 0 Some patterns indicative of main breaks and confirmed by operators 0 Several locations suggest pump surge issues and warrant further investigation 2009 Water Research Foundation. ALL RIGHTS RESERVED

40 Field Test Results NJ1 0 Approximately 200 meters placed in both vulnerable and non- vulnerable locations 0 Eight unique meters (4%) registered backflows with 21 alerts over 10 monthly reads 0 No alerts in vulnerable locations 2009 Water Research Foundation. ALL RIGHTS RESERVED

41 Monitor Evaluations Direct Hydraulic Monitors 0 Collected reads from over 10, meters System # Monthly Total % Reads % Unique reads meters with homes with read backflow positive reads NJ , WV , PA PA , Total , Water Research Foundation. ALL RIGHTS RESERVED

42 Site Selection 0 Marginal cost ($10-20) is low enough to place on all connections as part of routine meter change out program 0 For systems with history of leaks and/or main breaks, a vulnerability assessment can help prioritize initial placement, 0 Managers must be aware that backflows can and do occur in areas that may not appear to be vulnerable 0 Due to financial and administrative issues, it is not practical to require backflow preventers on all residential services. 0 Backflow preventers should be limited to commercial and high-risk residential services that can be tested on a regular basis

43 Conclusions 0 Low levels of residential backflow occur on a regular basis (1-2% of houses per month) 0 Up to 4-5% of houses may have a backflow in each year 0 Pressure e monitoring can help determine e areas of distribution systems vulnerable to backflow 0 The health impacts of these backflows are not yet known 0 Reverse signals from water meters may signify issues other than backflow 0 Reverse signals could indicate serious issues. Utilities should have protocols in place to identify and investigate these occurrences 2009 Water Research Foundation. ALL RIGHTS RESERVED

44 Thank You Questions