Recent Earthquakes: Implications for U.S. Water Utilities

Transcription

1 Recent Earthquakes: Implications for U.S. Water Utilities Subject Area: Infrastructure

2 Recent Earthquakes: Implications for U.S. Water Utilities Prepared by: John Eidinger G&E Engineering Systems Inc., 6315 Swainland Rd, Oakland, CA and Craig A. Davis Los Angeles Department of Water & Power, 111 North Hope St, Rm 1368, Los Angeles, CA Sponsored by: Water Research Foundation 6666 W. Quincy Ave. Denver, CO Published by:

3 DISCLAIMER This study was funded by the Water Research Foundation (Foundation). The Foundation assumes no responsibility for the content of the research study reported in this publication or for the opinions or statements of fact expressed in the report. The mention of trade names for commercial products does not represent or imply the approval or endorsement of the Foundation. This report is presented solely for informational purposes. Copyright 2012 by Water Research Foundation ALL RIGHTS RESERVED. No part of this publication may be copied, reproduced or otherwise utilized without permission.

4 Table of Contents 1.0 INTRODUCTION PROJECT PURPOSE APPROACH OUTLINE OF THIS REPORT SUMMARY FINDINGS Chile Earthquake Christchurch Earthquakes Tohoku Earthquake Recommendations for US Water Utilities ACKNOWLEDGEMENTS ABBREVIATIONS UNITS LIMITATIONS ADDITIONAL INFORMATION RECOMMENDATIONS FOR WATER SYSTEMS IN THE USA PERFORMANCE GOALS PIPELINE RENEWAL Pipe Replacement The Benefit Cost Ratio (BCR) Model Recommendations WATER TANK DESIGN WATER WELL DESIGN EMERGENCY RESPONSE OBSERVATIONS SEISMIC HAZARDS REFERENCES APPENDIX A PERFORMANCE GOALS BY OTHER WATER AGENCIES... A-1 A.1 GENERAL ISSUES... A-1 A.2 AWWA GENERAL PERFORMANCE GOALS... A-2 A.3 EBMUD GENERAL PERFORMANCE GOALS... A-3 A.4 CCWD RELIABILITY AND SEISMIC CRITERIA... A-6 A.5 HBMWD SERVICE GOALS... A-8

5 1.0 Introduction 1.1 Project Purpose The purpose of this project is to provide water agencies information that highlights the following: Damage to water system infrastructure in three recent earthquakes (Chile 2010, Christchurch , Japan 2011). Response of the water agencies in repair and restoration of potable water service to customers Effectiveness of various earthquake-countermeasures that were previously implemented by these water agencies. This includes upgrades of tanks, buildings, equipment, and (selectively) replacement of old buried pipe with "earthquakeproof" pipe. In order to understand: The factors causing water system service outages. The strategies used and their effectiveness to restore water systems. Water system restoration times. The damaged infrastructure includes: Buried water pipes (PVC, Cast Iron, Asbestos Cement, welded steel, HDPE, etc.) This includes both distribution pipes (commonly 6" to 12" diameter), transmission pipes (commonly 24" to 96" or larger in diameter), and service laterals (commonly under 2" diameter) Water tanks. These include at-grade welded steel circular tanks, at-grade reinforced concrete and prestressed concrete circular tanks, and below grade reinforced concrete tanks. Wells. Water Treatment Plants/Pump Station Facilities. The damage is addressed with regards to the various seismic hazards: Ground shaking Page 1

6 Ground failure due to liquefaction Landslide Surface faulting Inundation (flooding) due to tsunami Based on the observations from these recent earthquakes, this report provides guidance for the effectiveness of possible U.S. water system improvements that are cost-effective to address the following: Pipe replacement to address seismic weaknesses as well as pipe aging (leaks, corrosion, etc.) Water tank upgrades for seismic weaknesses Well head seismic upgrades Emergency Response preparedness and implementation (manpower, training, equipment, mapping, communication with the public) 1.2 Approach To develop this report, the following approach was taken: The principal investigators for this project visited with the water utilities in the affected countries: Mr. Eidinger visited Chile (April 2011), Christchurch (October 2010, April 2011, August 2011, December 2011), Japan (June 2010, October 2011, February 2012). Dr. Davis visited Christchurch (April 2011), Japan (July 2011, October 2011). Some of these visits were sponsored by the Water Research Foundation, and others by the American Society of Civil Engineers (ASCE), Technical Council on Lifeline Earthquake Engineering (TCLEE), and others separately. The researchers interviewed and collected information from the affected water utilities, and visited many of the sites with damaged water infrastructure. Some of the damage information presented in this report is based on tabulations developed by the affected water utilities. The researchers followed up with some of the water utilities to obtain additional maps, GIS information, reports, etc. Page 2

7 1.3 Outline of This Report This report is provided in four parts: Sections 1, 2, 3, 4, 5 and Appendix A. o Section 1: Project Purpose, Approach, Outline, Summary Findings (for each earthquake), Acknowledgements, Abbreviations, Units, Limitations, Additional Information sources. Summary Findings. This section provides the reader with a high-level summary of the key findings. o Section 2. Recommendations for Water Systems in the USA. Based on the accumulated observations in Appendices B, C, D, Section 2 summarizes the key recommendations, covering performance goals, pipeline renewal, water tank design, well design and emergency response. o Section 3. Observations. Section 3 provides additional commentary on the effectiveness of buried tanks (potable water) and cisterns (fire water); pipeline seismic design and renewal practices; and emergency response issues. o Section 4 provides a quick summary of earthquake hazards. o Section 5. References. o Appendix A. Performance Goals. Appendix A provides earthquake performance goals adopted by selected US water agencies. Page 3

8 1.4 Summary Findings This report addresses the damage to water systems in three countries due to recent earthquakes in 2010 and Table 1-1 highlights damage categories in each earthquake. Table 1-1. Summary of Damage (N.A. = not applicable. Unk. = unknown) Asset Category Chile Christchurch Japan Damage to large diameter transmission pipes Many n.a. Many Damage to small diameter distribution pipes Thousands Thousands Thousands and service laterals (CI, AC, PVC, etc.) Damage to HDPE distribution pipe None None None Damage to Kubota chain-jointed ductile iron N.A. N.A. None pipe Damage to at-grade wood, steel or pre-stressed Minor Many Few concrete water storage tanks due to shaking Damage to at-grade concrete water tanks due to None Yes None ground failures Damage to seismically-designed buried steel N.A. N.A. Yes tanks due to liquefaction Damage to water treatment plants Yes N.A. Yes Damage to pump stations Unk. Yes Unk. Damage to wells Not known to have occurred Widespread in liquefaction zones Damage to elevated steel tanks Widespread N.A. N.A. Fire ignitions due to earthquake 2 ~ 10 ~ 124 Fire ignitions due to tsunami None N.A. ~ 167 Suspected due to salt water intrusion, but not verified The key findings are as follows: Chile Earthquake This subduction zone earthquake seriously impacted the City of Concepcion, with a population over 1,300,000 people. The water system in this city had not been designed for earthquakes. Strong ground shaking and liquefaction damaged the city's only water treatment plant. Liquefaction damaged many of the larger diameter steel transmission pipelines. Liquefaction damaged many distribution water pipelines (about 3,000 total). Water outages to customers were lengthy, over a month to some customers. Even so, there was some good news: Essbio (the water system operator) had been installing HDPE Page 4

9 pipe in its water distribution system for about a decade prior to the earthquake; while the rest of the water system suffered thousands of damaged pipes, no HDPE pipe was damaged. This earthquake also shook a wide area of Chile, much of it rural/farming. Over the prior decade, the central government of Chile had installed 2,000 small wells water tank systems for these small farming communities (typical population of 100 people or fewer). A standardized type elevated steel tank design was used throughout the country. Unfortunately, the design was insufficient for strong ground shaking, and at least 73 of these elevated steel tanks collapsed, sometimes causing fatalities. The restoration of water service after the earthquake was seriously slowed down by the failure of the regional power supply and communication networks (cell phones). The water companies had learned to use cell phones as their primary method for voice communication. Primarily because of the failure of the widespread cell phone system, restoration efforts were delayed by a few days. There were two fire ignitions requiring fire department response after the earthquake; there was no fire spread. The damage to the water system had no impact on the outcomes of these fires Christchurch Earthquakes A series of three crustal earthquakes hit Christchurch in September 2010, February 2011, and June The earthquake affected an urban population of about 400,000 people. Each earthquake damaged the water system. Between the three earthquakes, many thousands of repairs to water pipe mains and sub-mains were required. The water pipes and wells in this city had not been designed for earthquakes; a few of the potable water tanks had been seismically upgraded prior to the earthquakes. Strong ground shaking and liquefaction damaged many of the city's wells. Liquefaction damaged many distribution water pipelines. Some of the water tanks performed well (some rooflevel damage still occurred), a few very small unanchored wood and steel tanks slid, and several larger pre-stressed concrete tanks had serious damage (ongoing leaks) or failed completely (lost all water contents). The city's largest concrete reservoir failed completely due to ground deformations. Water outage durations to customers were moderate, mostly restored within 10 days after each earthquake. Even so, there were some good lessons learned: The Christchurch City Council (the water system operator) had installed some HDPE pipe in its water distribution system after the first earthquake; in the subsequent earthquakes, no HDPE pipe was damaged, while nearby older pipes were damaged. There were a few fire ignitions requiring fire department response after the first and second earthquakes; there was no fire spread. The damage to the water system had no impact on the outcomes of these fires. Page 5

10 1.4.3 Tohoku Earthquake A magnitude 9 earthquake hit the northeastern part of Japan on March 11, 2011, commonly called the Tohoku region of Japan. The earthquake affected an urban and rural population of about 35,000,000 people. The largest city close to the epicentral area is Sendai, with greater metropolitan population of about 1,500,000 people. The great magnitude of the earthquake also resulted in some earthquake damage to water systems in more distance large prefectures, including Chiba, Tokyo, Kanagawa, and others. The earthquake also triggered a major tsunami event. The tsunami event caused the vast majority (likely over 95%) of all damage and fatalities in Japan, affecting just the first few hundred meters (distances vary along the coastline) inland from the shore. Just outside the tsunami inundation zone, damage to the regular building stock was nearly zero. The tsunami seriously damaged many wastewater treatment plants located at the low elevations near the coastline. The tsunami event had nearly zero impact on potable water systems outside the inundation area. In part due to the many large earthquakes in Japan's history over the past 100 years or so, and in particular the 1923 Great Kanto earthquake (affecting Tokyo) and the 1995 Great Hanshin earthquake (affecting Kobe), many (not all) of the larger water utilities in Japan have undertaken extensive (and expensive) seismic countermeasures over the past 20 years or so. These countermeasures include seismic upgrade of tanks and water treatment plant buildings/facilities; installation of underground emergency storage tanks; and most importantly (and most expensively), wholesale replacement of older (more than 50+ years old) pipelines with new "seismic resistant" water pipes, mostly ductile iron with chained joints (as manufactured by Kubota) and electro-fusion welded HDPE. Two water treatment plants suffered major damage due to liquefaction. A large diameter water transmission pipeline in the epicentral area suffered major damage at more than 50 locations, mostly due to pulled slip joints. A few large diameter water transmission pipelines suffered some slip joint damage in low-shaken areas, very distant from the earthquake. There was no known major damage to at-grade water tanks. Below-grade emergency storage tanks, installed for purposes of providing potable drinking water to local residents, in the event of damaged pipeline distribution networks, mostly performed well (undamaged), but one performed poorly (liquefaction damage). It seems that in areas where the emergency buried tanks performed well had no other major damage, so they were mostly unneeded; in one area where the emergency buried tank performed poorly, there was also a lot of damage to the buried pipeline network and water outages were widespread and lengthy in duration. At the time of the earthquake in March 2011, between 5% to 15% (some water utilities have higher percentages of seismic-resistant pipe, others have none) of the water Page 6

11 pipelines in the strong-shaken area had been upgraded with seismic-resistant pipe. By "seismic resistant pipe", it is meant pipe that can sustain a modest amount of ground deformation without failure. In Japan, the most common types of ground failures are due to liquefaction or landslide; given the nature of the earthquake hazard in Japan, fault offset is not generally a concern (and there was none in the March 2011 earthquake). None of the seismic-resistant pipelines is known to have been damaged in the March 2011 earthquake. The observed good performance of the seismic-resistant pipe cannot be extended to say it would perform equally as well under highly concentrated ground deformations due to fault offset. As of the time of writing this report (mid-2012), the tabulated count of fire ignitions is 287, of which 124 were due to the tsunami; 167 due to ground shaking; and 24 due to uncertain cause. In one coastal town impacted by the tsunami, some initial ignitions spread and burned several neighborhoods. In all but one instance, the self-evacuation of people from the low lying area resulted in apparently no fire department response to any of the tsunami-caused fires Recommendations for U.S. Water Utilities Over the past 20 years or so, many U.S. water utilities in high seismic regions have adopted seismic retrofit practices for buildings, water treatment plans, and tanks. The lessons learned in these three earthquakes confirm that these practices remain sound practice. Even so, a major weakness remains for nearly all U.S. water agencies in high seismic zones, namely that the existing buried pipe infrastructure remains highly susceptible to damage due to earthquake-caused ground failures (liquefaction, landslide, surface faulting, and other effects). Today, most U.S. water utilities continue to install nonseismically-designed distribution pipes, even in zones prone to ground failure effects. A few U.S. utilities have seismically retrofitted (or replaced) the most critical large diameter transmission pipes across known active earthquake faults, mostly using welded steel pipe, and in a few cases, HDPE pipe. These three recent earthquakes continue to show that the bulk of the total earthquake damage to water systems, and the resulting water outages to customers, is due to failure of hundreds to thousands of smaller diameter distribution pipes in zones of infirm ground. Until water utilities install seismically-resistant pipes in these areas, this problem will continue to re-occur in future earthquakes in the United States. New technology in water pipeline joinery has been in place in Japan for nearly 20 years, and today (2012), it is estimated that more than 75% of new water pipes installed in Japan use seismic-resistant design; in California, less than 1% of new water pipes use seismic resistant design. For common distribution pipes and service laterals (from under 1" to 8" diameter), HDPE pipe (either fusion butt welded or electro-welded with clamped joints) appear to have excellent earthquake performance, as evidenced in all three recent earthquakes. For distribution and transmission pipes (from 3" to greater than 100" diameter), ductile iron Page 7

12 pipe with "chained" joints, as manufactured by Kubota of Japan, have had excellent performance in the March 2011 and many other Japanese earthquakes. Several areas for further applied research by the Water Research Foundation are recommended: Develop a cost effective pipe replacement strategy for U.S. water utilities that factors in the ongoing issues of aging pipeline replacements, as well as earthquakes. A seismic design guideline for water pipes (ALA 2005) is currently available in the United States, but it addresses only seismic issues. This guideline, coupled with addition issues for pipe aging/corrosion, plus the ongoing lessons learned, should be updated for practical implementation by U.S. water utilities. Research into the failure of larger diameter water transmission pipelines at slip joint locations. While ALA (2005) provides some guidance, the failed large diameter pipe observations in Japan as well as other earthquakes shows that the current mandatory design standards (such as AWWA M11 and others) are completely lacking in requirements for seismically-designed slip joints (or bellows or similar). As part of this research, a better understanding of the multiple failures of large diameter girth-welded steel pipes in liquefaction zones in Concepcion should be done to reveal the root causes of these failures. Review and update the Performance Goal targets that are suitable for U.S. water utilities. As of 2012, different water utilities have adopted widely varying goals (ranging from bulk water restoration in 1 day to as much as 30 days or longer after major earthquakes), resulting in widely varying earthquake preparedness and mitigation strategies, and capital costs. Nothing the researchers observed suggests that Performance Goals should be legal mandates. Even so, if a water utility adopts overly aggressive Performance Goals, the resulting cost impacts to ratepayers may seriously outweigh the future benefits. With these considerations in mind, a review of the various strategies recently adopted, addressing forecast benefits, and actual costs, would be a useful document to utilities to help them select their own utility-specific strategies. Review and update the available fire following ignition models in ASCE (2005). These models are also used by FEMA in HAZUS. In all three earthquakes, the evidence appears to clearly indicate that the older models (ASCE, HAZUS) overpredict the number of earthquake-caused fire ignitions in modern cities (Concepcion, Christchurch, Sendai, etc.). This may be in part due to the overweight (ASCE, HAZUS) of fire ignition data from the 1906 San Francisco earthquake, the 1933 Long Beach earthquake, and other earthquakes where the widespread collapse of unreinforced masonry buildings occurred; the use of modern electrical wiring; and other factors. While fire ignitions are still occurring, they seem to be occurring at a much lower rate (perhaps a 75% reduction) than from older earthquakes, like the 1906 San Francisco earthquake. If true, then the Page 8

13 lower fire ignition rate would somewhat lower (but certainly not eliminate) the need to seismically mitigate existing water systems. Review and update AWWA and other standards for steel and pre-stressed atgrade concrete tanks to reflect ongoing poor performance of these tanks when exposed to high levels of ground shaking. The unanchored steel tank provisions should be carefully reviewed, especially for smaller steel tanks in high seismic hazard areas (PGA 0.3g or higher). The combination of vertical earthquake and hydrostatic forces for prestressed concrete tanks needs to be reviewed to ensure that yielding of hoop-direction prestress steel does not occur under high levels of ground shaking. The acceptable ductility limits in current ASCE 7, IBC, ACI, and AWWA codes (ranging from 2 to 4.5 or so) need to be reviewed and revised as suitable in order to provide suitable reliability for a leak-tight tank under high levels of ground shaking. 1.5 Acknowledgements This report was prepared by G&E Engineering Systems Inc. (G&E) under subcontract to the Water Research Foundation. John Eidinger (G&E) was the principal investigator, supported by Craig Davis. 1.6 Abbreviations AC Asbestos Cement ASCE American Society of Civil Engineers AWWA American Water Works Association CCC Christchurch City Council CI Cast Iron pipe DI Ductile Iron pipe g acceleration; 32.2 feet/sec/sec = 9.81 m/sec/sec = 1 g G&E G&E Engineering Systems Inc. GIS Geographical Information System GS Galvanized steel pipe HDPE High Density Polyethylene km kilometer M Magnitude (moment magnitude unless otherwise noted) MDPE Medium Density Polyethylene MG Million Gallons MGD Million Gallons per Day PGA Peak Ground Acceleration (measured in g) Page 9

14 PGD PGV PVC psi TCLEE WTP WWTP Permanent Ground Displacement (measured in inches) Peak Ground Velocity (measured in inches/second) Polyvinyl chloride pipe pounds per square inch Technical Council on Lifeline Earthquake Engineering Water Treatment Plant Wastewater Treatment Plant 1.7 Units This report makes use of both common English and SI units of measure. Common and metric units used in this report include: inches, feet, millimeters (mm), meters (m). The conversion is 12 inches = 1 foot. 1 inch = 25.4 mm mm = 1 m. 100 cm = 1 m. 1 kilometer (km) = miles. 1 kpa (kilopascal) = 1 kn/m^2 = psi (pounds per square inch). 1 pound (force) = Newtons = 0.45 kilograms (force). 1 liter = gallons (US liquid measure). MGD = million gallons (US liquid measure) per day. 1.8 Limitations As is not uncommon in post-earthquake reconnaissance, incomplete information in the weeks and months after the event can lead to omissions and misunderstandings. Hidden damage might become known only some time after the earthquake. We apologize if the findings in this report are incomplete, and the reader is cautioned that it may take months to years of post-earthquake evaluations before a comprehensive understanding of damage to water systems is available. Neither the Water Research Foundation, G&E Engineering Systems Inc., or the authors of this report assume any responsibility for any such omissions or oversights. 1.9 Additional Information This report was written and edited between late 2011 to mid Over the next decade or so, additional research into specific aspects of the water system performance will be developed. The interested reader should be aware that there are three organizations in the United States that also have done reconnaissance into the effects of these three earthquakes: ASCE TCLEE sent out a number of investigation teams to Chile, New Zealand, and Japan to document the performance of all types of lifelines, including water, power, communications, gas and liquid fuels, ports and harbors, railroads, highways, debris management, wastewater, etc. The authors of this report participated as part of those teams. ASCE TCLEE plans to publish comprehensive reports on each earthquake, including detailed discussions on the Page 10

15 earthquake performance of water systems. ASCE reports are available from GEER Association (Geotechnical Extreme Events Reconnaissance) teams have developed reports on the seismic hazards portion of these earthquakes. GEER reports on all three earthquakes are available from EERI (Earthquake Engineering Research Institute) teams are developing reports on performance of structures and societal response on all three earthquakes. A special issue dedicated to the Chile 2010 earthquake, to be published in 2012, will include a detailed discussion of the performance of the earthquake performance of the water systems. EERI reports on all three earthquakes are available from The interested reader should also be aware that some additional information from three case studies of earthquake impacts to water systems is also available. These case studies cover the experience in recent earthquakes in Chile, New Zealand (Christchurch), and Japan (Tohoko earthquake), and are available to Water Research Foundation subscribers, for information purposes only, upon request to the Water Research Foundation. Page 11

16 2.0 Recommendations for Water Systems in the USA In Section 2, we present recommendations for application to US water utilities. 2.1 Performance Goals In order to provide a "yardstick" as to what constitutes acceptable water system performance after earthquakes, a water utility should adopt earthquake Performance Goals. As of 2011, there are no Federal or State mandated Performance Goals for US water agencies as to what constitutes adequate preparedness for problems after an earthquake or most other types of emergencies. In Chile, no water utility had stated performance goals. In Christchurch, the CCC water utility had done some prior seismic upgrades of water storage tanks; but had no stated performance goals. In Japan, the common assumption is that Japanese people will suffer for up to 28 days without piped water, before becoming too angry with the water utility (as observed in Kobe, 1995). Some US water utilities are now striving to upgrade their water systems to have considerably shorter restoration times. One large US water utility has adopted a goal of restoring bulk water transmission to most customers within 24 hours after a major earthquake. By adopting such a short restoration target, the utility is now incurring significant seismic upgrade costs. It might be cost effective and fiscally prudent to avoid committing to a very short restoration target (like 24 hours), and instead rely partially on a "manage the damage" strategy. The "right" balance between mitigation and preparedness will be different for different water utilities, facing different earthquake hazards and risks, with different types of economic impacts. It is impractical for both financial and technical reasons to upgrade all parts of a water systems to withstand all levels of future earthquakes (or other hazards) with no damage. Therefore, post-earthquake (post-emergency) service levels will be below normal for some period of time following future events. For example, some buried water pipes are vulnerable to earthquake effects. The cost to replace, parallel or upgrade all of these pipes and facilities to be seismically rugged is very high. It may be more prudent to plan for a certain level of damage and to have adequate spare parts, personnel and other resources on hand to rapidly fix the damage after the earthquake (emergency), as long as the interim water service outages do not cause undue hardships. Page 12

17 Reflecting these limitations, Performance Goals for individual water utilities should be developed to identify and prioritize those facilities most prone to suffering damage resulting in an unacceptable level of service, life safety hazard and/or cost to the water utility's customers as a result of an earthquake. To develop suitable Performance Goals for a specific water utility, the following steps should be taken: First, the utility establishes "target" performance goals. This should be done as one of the first tasks of the overall utility-wide seismic vulnerability assessment. Second, these tentative goals should be discussed with senior utility management, and perhaps in some cases, with elected officials. The term "target" is stressed, in that the cost of achieving the goals is not initially known, and that the "final" goals should reflect that the cost of achieving certain goals should be reasonable in some fashion to the costs to be borne by rate payers, as well as other factors. Third, a vulnerability analysis should be performed for earthquake hazards, to establish the performance of the "as-is" water system should various types of earthquakes occur. In some cases, the analyses might be done on a probabilistic basis (annualized, given the annual chance of occurrence of a particular earthquake), while in other cases the analyses might be performed on a deterministic basis (scenario-based, assuming the earthquake actually occurs). Fourth, a series of possible mitigation and response activities should be developed (a "capital improvement plan, CIP") and costs estimated to implement the CIP. Given that different CIPs could be adopted, the reduction in outage times (or water quality or life safety, etc.) impacts should be estimated. o Any CIP should include both earthquake preparedness and mitigation strategies. Preparedness covers items like: "manage the damage", "mutual aid", "training", "spare parts", "procedures", etc. Mitigation covers items like seismically-designed pipes, tanks, pump stations, wells, water treatment plants, equipment anchorage, network redundancies, reliable water supply, redundant water supply should landslide-induced turbidity be at issue (or ash fall, radioactive fallout, etc.), building upgrades, etc. o The effectiveness of the water utility's existing emergency response capability should be carefully considered. A "thick binder on the wall" may not be of much use in an actual emergency without ongoing training. Fifth, the performance goals should be ranked in terms of whether or not each CIP or mitigation measures would meet the target goals. In some cases, economic analyses (benefit cost analyses) can be used to help establish the suitability of the goals. Page 13

18 Sixth. After appropriate review by senior management, stakeholders and elected officials, the "target" performance goals should be adopted by the water agency, along with a suitable multi-year capital program and emergency response capability needed to reach these goals. Appendix A provides some Performance Goals that have been published in various industry documents, or adopted by some water agencies. In reviewing the Performance Goals in Appendix A, a water utility should recognize that the goals adopted by other water utilities do not necessarily have to be adopted by the their own agency. There are many reasons for this, including: Some water utilities are wholesalers, some are retailers, and some are both. In context of this report, a "wholesaler" is a water utility that sells treated water to other water utilities, but not to end-user customers; and a "retailer" is a water utility that sells water to end user customers. The Performance Goals for a wholesaler can be very different from those of a retailer. Some water utilities also sell raw water (untreated water) to agricultural or certain types of industrial users. Some water utilities sell reclaimed water for irrigation or gray water purposes. Some end users can accept limited duration water outages without serious economic impacts; others require water on a nearly-continual basis. For example, an agricultural customer might not be too worried if water being used for irrigation is lost for a few hours or even a few days; whereas a computer chip manufacturer might have to close down certain fabrication processes should there be even a temporary loss of treated water. Some communities are highly susceptible to fire ignitions and possible fire spread, whereas others are not. For example, communities built largely of wood frame construction with limited setbacks in wildland-urban interface zones and often subject to high wind are much more susceptible to fire spread than communities built largely of masonry construction with large setbacks (wide streets). 2.2 Pipeline Renewal Each of the three earthquakes showed substantial damage to non-seismically designed buried water pipelines. Seismically-designed pipes showed no damage in each earthquake. The long term solution is to replace non-seismically designed pipes with suitably seismically-designed pipes. Over the past decade or so, the concept of "Asset Management" has gained some traction at water utilities in the USA. These concepts are described in AWWA (2006) and AWWARF-EPA (2005). Neither of these documents formally addresses seismic issues as one of the factors to be addressed in pipe replacement. We clearly need better guidance on how to address seismic issues within the overall asset management effort. Page 14

19 Over the past 25 years, some US water utilities have been replacing existing pipes at a rate of about 0.1% to 0.3% per year; a few replace at rates as high as 1% per year. This translates to about a 100 to 1,000 year replacement cycle. For example, EBMUD replaces about 5 miles of pipe per year (when capital funds are tight), to 10 miles of pipe per year (when capital funds are readily available) out of its 4,000 mile pipe inventory, which suggests a 400-year to 800-year replacement cycle. The big worry is that at some time, pipe leakage due to age-related issues will suddenly rapidly increase, overwhelming the owner's ability to repair, and resulting in many water outages and customer dissatisfaction. Unless seismic issues are addressed, common US practice is to replace old pipes with new non-seismically-designed pipes. For example, it would be common to replace a 6" leaking 1920-vintage cast iron pipe with push-on caulked joints, with a 2012-vintage 8" PVC or Ductile Iron pipe with push-on rubber joints. In high seismic areas prone to soil failure, this practice is seriously deficient. If one simply assumes that there is truly a "100-year" lifetime for pipes, then most US water utilities are facing a huge increase in pipe replacement requirements over the next few decades. Some policy documents are saying that the pipe aging issue is a pending "crisis" or "catastrophe". ASCE issues annual proclamations that the nation's infrastructure is in gross disrepair, and gives scores like "C-" and "D-" for water and wastewater buried pipe systems. Perhaps these are "scare" tactics? or, are these economically sound observations? Pipe Replacement The Benefit Cost Ratio (BCR) Model It is not economically sound to make annual pipe replacement investments without a rational engineering basis. It might be reasonable for water agency A to replace pipes at a 1% per year rate (say with corrosive soils and high risk of earthquake-induced ground failures); whereas it might also be reasonable for water agency B to replace pipes at a 0.3% rate (say with non-corrosive soils and low risk of earthquake-induced ground failures). The question is how do we compute the "right" amount of pipe replacement per year, given the actual pipe inventory and the local corrosion and earthquake conditions? The basic computation is to sum up the expected future benefits (= reduction in future repair costs should the pipe be replaced) divided by the replacement costs. BCR n years i1 RepairCostPerYear ReplacementCost 1 r i where r = discount rate, and n = number of years assumed in the discount calculation. A good Asset Management program should use this type of model to include both aging and seismic issues by summing up the BCRs for each pipe: BCR Total BCR seismic BCR aging. Page 15

20 For the computation of BCR seismic, most of the details are outlined in FEMA (2001). The following paragraph highlights some of the key seismic assumptions: For seismic mitigation, the long term replacement strategy is to plan to replace all seismically-weak pipes crossing zones subject to permanent ground displacements (PGDs), such as those from liquefaction or landslide or fault offset. The replaced pipes should be designed to be able to withstand settlements due to PGDs (such as using ductile iron pipe with chained joints, fusion-butt welded or clamped electric-resistance welded HDPE pipe, or heavy-walled butt-welded steel pipe. Once these upgrades are in place, the annualized seismic losses will typically be reduced by about 90% (this realizes that there will remain some pipes that will still fail in future earthquakes). ALA (2005) gives specific recommendations for selection of new pipes in seismic areas. For the computation of BCR aging, most of the details are outlined in Eidinger (2011). The following describes the key steps: Examine the last 10 to 40 years of pipe leaks in the actual pipe system. Sort the leaks by type of pipe, diameter of pipe, age of pipe, and by local soil corrosivity. If one does not have test data to establish the local soil corrosivity, then collect it. A relatively straight forward process is to conduct city-wide soil resistance tests (R, ohm-cm). This can be done rapidly using the Wenner 4-pin test, at locations roughly spaced equally throughout the water system. About 100 tests per 25 square miles can be readily done in a few days of field work. Depending on the styles of construction, it would be expected that the leak rate in soils with R much over 10,000 ohm-cm (mildly corrosive) will be on the order of 50% lower than in R values of 5,000 ohm-cm, or 80% to 90% lower than for comparable types of pipe in soils with R under 1,500 ohm-cm (highly corrosive). Given the leak history and test data, develop a water utility-specific pipe aging model (Leak rate per mile per year) as follows: Leak Rate aging k 1 k 2 k 3 (generic, leaks per mile per year) where k 1 is the leak rate for the type of pipe (diameter, pipe barrel material), k 2 is the adjustment to consider pipe age, and k 3 is the adjustment to considered local soil resistivity. For pipes with known leak history, the leak rate is taken as either its average over the entire history of documented leaks, or the system-wide rate, whichever is higher. The leak rate for any individual pipe that is used in the computation of BCR aging is the higher of the generic leak rate or the pipe-specific leak rate. Page 16