recent earthquakes: implications for u.s. water utilities

Subject Area: Infrastructure

Recent Earthquakes: Implications for U.S. Water Utilities

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Web Report #4408

Recent Earthquakes: Implications for U.S. Water Utilities

Prepared by: John Eidinger G&E Engineering Systems Inc., 6315 Swainland Rd, Oakland, CA 94611 and Craig A. Davis Los Angeles Department of Water & Power, 111 North Hope St, Rm 1368, Los Angeles, CA 90012-2694 Sponsored by: Water Research Foundation 6666 W. Quincy Ave. Denver, CO 80235

Published by:

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.

Recent Earthquakes: Implications for US Water Utilities

Table of Contents

1.0 INTRODUCTION .................................................................................................................................. 1 1.1 PROJECT PURPOSE ................................................................................................................................ 1 1.2 APPROACH ............................................................................................................................................ 2 1.3 OUTLINE OF THIS REPORT .................................................................................................................... 3 1.4 SUMMARY FINDINGS ............................................................................................................................ 4

1.4.1 Chile Earthquake ......................................................................................................................... 4 1.4.2 Christchurch Earthquakes ........................................................................................................... 5 1.4.3 Tohoku Earthquake ...................................................................................................................... 6 1.4.4 Recommendations for US Water Utilities .................................................................................... 7

1.5 ACKNOWLEDGEMENTS ......................................................................................................................... 9 1.6 ABBREVIATIONS ................................................................................................................................... 9 1.7 UNITS ................................................................................................................................................. 10 1.8 LIMITATIONS ...................................................................................................................................... 10 1.9 ADDITIONAL INFORMATION ................................................................................................................ 10

2.0 RECOMMENDATIONS FOR WATER SYSTEMS IN THE USA ................................................. 12 2.1 PERFORMANCE GOALS ....................................................................................................................... 12 2.2 PIPELINE RENEWAL ............................................................................................................................ 14

2.2.1 Pipe Replacement – The Benefit Cost Ratio (BCR) Model ........................................................ 15 2.2.2 Recommendations ...................................................................................................................... 17

2.3 WATER TANK DESIGN ........................................................................................................................ 19 2.4 WATER WELL DESIGN ........................................................................................................................ 22 2.5 EMERGENCY RESPONSE ...................................................................................................................... 22

3.0 OBSERVATIONS ................................................................................................................................ 25

4.0 SEISMIC HAZARDS ........................................................................................................................... 28

5.0 REFERENCES ..................................................................................................................................... 31

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


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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 2010−2011, 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 "earthquake-proof" 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


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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.


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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.


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1.4 Summary Findings This report addresses the damage to water systems in three countries due to recent earthquakes in 2010 and 2011. Table 1-1 highlights damage categories in each earthquake.

Table 1-1. Summary of Damage (N.A. = not applicable. Unk. = unknown)

Asset Category Chile 2010

Christchurch 2010-2011

Japan 2011

Damage to large diameter transmission pipes Many n.a. Many Damage to small diameter distribution pipes and service laterals (CI, AC, PVC, etc.)

Thousands Thousands Thousands

Damage to HDPE distribution pipe None None None Damage to Kubota chain-jointed ductile iron pipe

N.A. N.A. None

Damage to at-grade wood, steel or pre-stressed concrete water storage tanks due to shaking

Minor Many Few

Damage to at-grade concrete water tanks due to ground failures

None Yes None

Damage to seismically-designed buried steel tanks due to liquefaction

N.A. N.A. Yes

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

Suspected due to salt water intrusion, but not verified

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

The key findings are as follows:

1.4.1 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


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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.

1.4.2 Christchurch Earthquakes

A series of three crustal earthquakes hit Christchurch in September 2010, February 2011, and June 2011. 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 roof-level 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.


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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


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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.

1.4.4 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 non-seismically-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


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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) over-predict the number of earthquake-caused fire ignitions in modern cities (Concepcion, Christchurch, Sendai, etc.). This may be in part due to the over-weight (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


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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 at-grade 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)


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PGD Permanent Ground Displacement (measured in inches)

PGV Peak Ground Velocity (measured in inches/second)

PVC Polyvinyl chloride pipe

psi pounds per square inch

TCLEE Technical Council on Lifeline Earthquake Engineering

WTP Water Treatment Plant

WWTP 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. 1000 mm = 1 m. 100 cm = 1 m. 1 kilometer (km) = 0.621371 miles. 1 kPa (kiloPascal) = 1 kN/m^2 = 0.145 psi (pounds per square inch). 1 pound (force) = 4.448 Newtons = 0.45 kilograms (force). 1 liter = 0.264 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 2012. 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


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earthquake performance of water systems. ASCE reports are available from www.ASCE.org.

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 www.geerassociation.org.

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 www.eeri.org.

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.


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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.


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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.


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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.


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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?

2.2.1 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

RepairCostPerYear1 r i

i1

n years

ReplacementCost

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: BCRTotal BCRseismic BCRaging.


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For the computation of BCRseismic, 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 BCRaging, 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 Rateaging k1k2k3 (generic, leaks per mile per year)

where k1 is the leak rate for the type of pipe (diameter, pipe barrel material), k2is the adjustment to consider pipe age, and k3 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 BCRaging is the higher of the generic leak rate or the pipe-specific leak rate.


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2.2.2 Recommendations For a water utility, a long term (20 years at the shortest, 100 years at the longest) pipe replacement strategy should look something like the following:

Seismic. Replacement pipes in areas zones with moderate to high or very high liquefaction / landslide threat, or traverse active faults, should be seismically designed per ALA 2005. This is true in high seismic risk California (San Francisco, Los Angeles), Kodiak (Alaska), La Malbaie (Quebec) or more moderate seismic risk areas like San Diego, Memphis, Salt Lake City, Portland, Seattle, Vancouver (British Columbia). In general, the decision of when to replace should be based on recent leak history, not on seismic risk alone. In the highest seismic hazard areas (faults that can produce M 6.5+ events with more than 5% chance in the next 50 years, and locally wide urbanized areas prone to liquefaction, landslide or surface faulting), the decision of when to replace pipe might be justified on seismic issues alone.

Aging. Pipes with a known leak history with more than 2 (or 3) leaks within the past 5 years should be high priority for early replacement (within the next ten years). This reflects a variety of benefit cost analyses, and a "willingness to pay" concept. There appears to be a fairly high correlation of the locations of on-going leaking pipes and the locations of high seismic pipeline vulnerability.

Old Pipes. Pipes without a recent leak history should be "left in place" without a specific schedule for replacement. Only in extremely high seismic risk areas, or for critical non-redundant pipes, should pipe replacement be done primarily for seismic reasons.

Other Issues. Pipes that require replacement due to inadequate fire flows, tuberculation, taste or odor, or other reasons, should be replaced with suitable pipe materials per ALA 2005 or similar seismic guidelines. In a nutshell, if the pipe to be replaced is not exposed to potential ground failures, then "push on joint" pipes (lower cost) are acceptable, while important pipes exposed to liquefaction or road-fill slumps should have seismically-designed "restrained" or "chained" joints, while important pipes subject to fault offset should be designed to accommodate the fault offset. For pipes in landslide zones, avoidance is the primary solution (zone the area as not fit for permanent or important facilities); but for existing landslide zones one solution is generally "buyer beware" and the water utility should not have to design to accommodate landslide other than to prescribe restrained joints; and customers in landslide zones must accept the higher risk for damage to water pipes and relatively poor post-earthquake performance. For critical pipes passing through potential landslide zones, the ductile iron “chained” joint structure previously presented could be used to protect the pipe under some landslide movements, but re-route to avoid the landslide is preferred for truly critical pipes. All new pipes should be designed with suitable corrosion protection. The seismic performance of aged (over 40-years) thin-walled ductile iron pipe, with or without "external baggies", located in corrosive environments, is currently unknown.


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Simple replacement rules like: "replace all Cast Iron pipe installed prior to 1935" are not supported by the facts. Local corrosion cells or weak soils or locally high pressure, or local installation practices, may have much more influence on pipe vulnerability and leakage than the type and age of pipe in general.

Seismic Design for Pipes. If both Aging and Seismic issues are considered in a long term (20 to 50 year) asset replacement program, then a water utility can develop a sound and cost effective long term capital program for pipe replacement. As a quick guideline, the following approach could be adopted:

Distribution pipes. Pipes (diameter 12" and smaller) that have leaked and been repaired more than 2 times (3 times in residential areas) over the past 7 years, per 1 km length, deserve replacement in the next 5 to 10 years. The replaced pipe, if located in soils that are prone to liquefaction, should be designed to accommodate up to 6" of movement; plus all other requirements, with suitable corrosion protection. The replaced pipe, if located in soils not prone to permanent ground deformations, does not need any special seismic design.

Transmission pipes. Pipes (diameter 30" and larger) that have leaked and been repaired more than 2 times over the past 7 years, per 1 km length, and are in soils prone to liquefaction, landslide or faulting, deserve replacement in the next 5 years. The replaced pipe, if located in soils that are prone to liquefaction, landslide or surface faulting, should be designed to accommodate the expected permanent ground deformations associated with earthquakes that occur once every 1,000 to 2,500 years or so; plus all other requirements, with suitable corrosion protection. The replaced pipe, if located in soils not prone to permanent ground deformations, still requires proper design of any slip joints in order to accommodate seismic ground shaking effects; or avoid the use of slip joints. (Note: the unit length used for considering the repair rates should be shorter in zones with very high economic activity, and longer in zones with low economic activity).

Emergency response plans need to be developed to reflect the likely vulnerabilities of the water agency, and the needs of the local community. A balance of emergency response and pre-earthquake mitigation will need to be considered.

It is beyond the scope of this report to recommend the specific type of pipe that should be used for seismic design. The authors believe that there is no one solution that will be equally cost effective for all US water utilities. The three case studies show that HDPE and chain-jointed ductile iron pipe have performed well in earthquakes, even where they are in located in infirm ground; non-seismically designed welded steel transmission pipes have failed in many places in the Japan and Chile earthquakes (there were no steel transmission pipes in Christchurch).


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However, if seismic design issues are not factored into pipeline material and joinery selection, and if one only adopts existing AWWA pipeline design standards, then US water utilities should continue to expect widespread water pipeline failures in future earthquakes, whenever the pipelines traverse infirm ground. At the present time, ALA (2005) provides guidelines (non-mandatory) for seismic design of buried water pipelines for the USA.

Over time, it is hoped that US-based and Canada-based pipe manufacturers will be able to supply a variety of suitable pipes for use in water distribution systems; these might be chain-jointed ductile iron pipe and HDPE pipe in zones subjected to liquefaction and moderate landslides; heavy-walled and high quality welded steel pipelines through fault offset zones; and hopefully new products (ductile PVC, ductile clamp-jointed HDPE, etc.) not yet commonly available. Import of overseas-made seismic-designed pipes (such as Kubota products) might be an alternative for US and Canadian water utilities, until such time that suitable products are available locally.

It is well understood that water utilities have long-established pipeline installation practices, and any change in pipeline design will be met with a lot of questions. But, until these questions are answered, and suitable practices adopted, new non-seismically-designed pipeline infrastructure now being installed through infirm soil zones might prove to have been a major waste of money after the next large earthquake.

2.3 Water Tank Design

Each of the earthquakes resulted in some damage to water tanks. Non-seismically designed elevated tanks in Chile collapsed at an alarmingly high rate. Several concrete and prestressed concrete tanks failed in Christchurch (lost their contents). Empty (or near-empty) steel tanks floated in the tsunami inundation zones in Japan. New buried steel tanks floated in liquefaction zones in Japan. Roof damage occurred to some tanks in New Zealand, although these tanks were kept in service.

Water tanks in the USA are commonly designed to AWWA D100 (steel tanks) or D110 (prestressed concrete tanks) or ACI 350 (concrete structures for liquid storage service). Each of these standards includes seismic provisions. However, these standards have evolved over time, and the seismic provisions in older standards (including AWWA D100) have not always resulted in good performance, even for tanks designed to these standards.

For steel tanks, the basic seismic flaw in AWWA D100 is that the tanks, being made of steel, are "ductile" and capable of resisting seismic overloads beyond the elastic limits of the steel. In actual observation in past earthquakes, a high percentage of unanchored AWWA D100-designed tanks (pre-2004), if 80% to 100% full of water at the time of the earthquake, have suffered serious damage and/or loss of all water contents, when exposed to earthquakes with local PGA much over 0.3g; whereas anchored tanks have performed much better. ALA (2001) documents the actual seismic performance of more than 500


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such steel tanks. Another simplification in AWWA D100 is that the vertical wall stress in unanchored tanks due to the seismic overturning moment is computed assuming "plane-sections-remain-plane"; this assumption is often not valid for commonly-sized tanks (diameter to height ratios much higher than 1), and can lead to significantly underestimating the actual wall stress, and hence underestimating the potential for wall buckling.

For new steel tank design, we recommend that unanchored tanks can be safely used when no tank wall uplift is forecast assuming the design-basis earthquake and elastic limits; all attached pipes should include flexible connections to accommodate tank wall uplift1. For anchored or unanchored tanks, response modification coefficient (R) of no more than 2 can be used for purpose of checking against tank shell stresses. For anchored tanks designed with R more than 1, tank wall uplift should be checked assuming R = 1, and all attached pipes designed accordingly.

For prestressed concrete tanks, the seismic performance has been good, to date, as long as the tank is anchored (seismic cables), as long as the hoop-direction prestress wires are not corroded, as long as the hoop-direction pre-stressed wires do not yield under elastically-computed seismic forces (for both horizontal and vertical earthquake directions) and as long as the site does not experience settlements (compaction or landslide). Prestressed concrete tanks have failed due to hoop-stress overload (rapid wall rupture with rapid loss of all contents; or hoop-direction yielding with uncontrollable leaks through the concrete walls) as well as due to differential settlements (so far, observed to have only modest rate of water release). Under non-seismic conditions, failure rates of bonded non-galvanized wire (strand, cable) systems have been about 1 tank in 50 tanks per year, once the tanks reach 50 years of age; but perhaps this rate will be reduced for tanks with newer and better corrosion protection systems. An open issue remains about the correct quantity of hoop force needed to resist hydrodynamic forces due to vertical accelerations, as yielding of the hoop steel will allow the concrete tank to crack vertically.

The unrestricted water slosh heights computed using AWWA D100 or D110 are reasonably computed (when using R=1). There is, however, no absolute need to provide unrestricted space above the maximum water level for this wave height, if the roof system is designed to accommodate the sloshing loads; or if the damage is acceptable. The observed damage to roof rafters in steel tanks (many such instances, see ALA (2001 for a list) can be caused either by wave sloshing forces (can be readily resisted with suitable design) or due to tank wall uplift. In most cases where the roof has been

1 Except for very small tanks of common diameter-to-height ratios (much under 150,000 gallons),

large-scale tank sliding has not been observed in past earthquakes. Common design provisions (soil-tank coefficeints of friction, etc.) would suggest that a lot of tanks should slide at PGA much over 0.3g or so; yet the empirical evidence is lacking for this failure mode for larger tanks. The reasons for this might include the small displacements involved with sliding (under ¼ inch or so) for high frequency (impulsive) loading. Anchorage of steel tanks can largely eliminate the sliding issue, protect attached pipes (bottom entry for sliding, side entry for uplift and sliding), and reduce damage to roof-wall connections.


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damaged by one (or both) of these issues, the tank remains serviceable (retains water), and repairs can be scheduled after the earthquake.

Reinforced concrete tanks have performed well in earthquakes, except when exposed to settlements.

For tank sites exposed to permanent ground deformations in the design basis earthquake, we recommend the following:

Avoid using the site. If this is not feasible, then consider:

Attached pipes must be able to absorb all estimated ground settlements or lateral spreads. A variety of flexible pipe hardware can be used, which will be most effective if the pipe is above ground (or in an underground vault) to allow the pipe to move without soil resistance.

Steel tanks might be able to take as much as a few inches of ground settlements, without rupture of the tank.

Concrete tanks (prestressed or reinforced) appear to be more fragile than steel tanks, and ground settlements of 2 to 3 inches appear to be enough to crack the tank.

For new tank installations in high seismic zones, we recommend site-specific subsurface investigations to establish the potential for permanent ground movements. If the site is thought to have potential movements, use steel tanks (not concrete tanks) unless the hazard is mitigated. If the tank site requires pile foundations (for example, a site atop young bay muds, etc.), then the pile-pile cap detail must be designed to accommodate the design basis earthquake, inclusive of soil-structure interaction effects, with ductility demands low enough to assure no leakage in the tank.

Avoid placing tanks at sites prone to surface fault offset from normal or reverse faulting movements, as it will be hard to design for these movements. A steel tank could be placed atop a fault that has only (or almost only) horizontal fault movements, by using a sliding-type foundation system (might be a gravel layer).

If other mitigation schemes are impractical or not cost effective, and if a suitable water drainage system is included to as to avoid life-threatening inundation impacts to nearby residents, and if the tank is sacrificial (not needed) post-earthquake, then a tank can be placed in faulting, landslide or liquefaction zones.


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2.4 Water Well Design

There are currently no national-level seismic design standards for water wells, either in Christchurch or in the USA. Most wells in stable soils have performed well in past earthquakes (once power is restored), so the lack of seismic standards has not yet been a great issue in the USA.

However, the well performance in Christchurch, in zones prone to liquefaction, was less than stellar. Soil settlements due to liquefaction resulted in broken well casing pipes.

Where possible, wells should be located outside zones that may be subjected to seismically induced permanent ground deformations; this includes liquefaction prone areas, landslides, fault crossings, etc.

For wells located in zones prone to liquefaction, a prudent design approach would be to design the casing pipe (top 40 feet) to be able to resist all imposed loads due to liquefaction. The geotechnical parameters needed for this type of design can be adopted from ALA (2005), but specific geotechnical site investigations are recommended. If the well casing can survive the effects of liquefaction (including seismically induced settlements), and if the attached discharge pipes are provided with suitable flexible connections, most such wells should remain functional once power is restored. Backup power generators with sufficient fuel supplies for critical well supplies will eliminate the need for electric power restoration.

The lower portions of wells can collapse in an earthquake if the materials deteriorate; stainless steel screens are good to use. Use screens instead of slots for the well casing. Submersible pumps can eliminate problems that may result in long pump shafts when casings deform.

Ground water wells in subduction zone areas that are near the sea may be impacted from salt water intrusion where large tectonic subsidence can occur.

2.5 Emergency Response

Water systems consist of large and diverse networks made up of many different components, over long periods of time, crossing diverse geologic conditions and as a result can expect to have damage after large earthquakes. The level of damage can be controlled using seismic design principles, but an operator should never expect to be damage free after a significant earthquake. This will require the water utility to "manage the damage" in a fashion so as to restore water service as rapidly as practical.

Assuming the water system is located in areas with wide areas prone to permanent ground deformations (liquefaction, landslide, road-fill slump, fault offset), then lacking seismically-designed pipes, a lot of pipe damage will occur. This will require a large work force to repair, with labor and equipment usually being the limiting factors. It will not be cost effective for a water utility to keep a large pipe repair crew on staff, just for a


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"one in one hundred year" type earthquake. Therefore, the need for supplementing day-to-day pipe repair crews is essential.

Any emergency response plan should provide for a major increase in work crews, via outside contractors and/or mutual aid. The faster the crews are available, the shorter the water outage times. For practical purposes, assume no more than about a 100% increase in normal work crew size, unless the water utility has the ability to manage a much larger crew size.

While the buried pipe network is out of service, there will still be need to distribute potable water to customers, some of whom will be displaced. Pre-made manifolds with hose bibs, cable to be attached to working hydrants / pipe outlets, will expedite the process.

A fleet of small water tanker trucks and small distribution tanks, and the people (fuel, etc.) needed to operate them, will be needed to serve residential zones with liquefaction and/or landslide issues. In the USA, these trucks and tanks (and fuel) have traditionally been provided by emergency response agencies (not the water utility itself). Most likely, this practice will continue in the future. The water agency should factor in coordination with outside agencies in the effort to provide potable water for delivery to end-users for drinking and sanitation purposes.

The quantity of small tanks / trucks needed can be as little as nearly zero (for water systems with seismically-designed infrastructure and good emergency response, and communities with seismically-built buildings) to perhaps as much as 1 gallon per day per capita, times the expected outage times.

In communities with fire conflagrations and/or many collapsed poorly-built buildings, there will be emergency shelters set up at suitable unaffected community centers. Mostly, these shelters will be selected based on their ability to have good utility service (including piped water, electricity, etc.). Even so, there will be "tent cities" for people displaced from their damaged homes, and these sites will still need access to nearby water supply, likely via distribution points (taps off fire hydrants) or portable water tanks.

For especially high hazard zones (like coastal areas subject to tsunami inundation in Oregon, Washington, Alaska, Hawaii, northern California, and even perhaps places like South Carolina and other east coast seafront), the need for post-earthquake tanked water supply for emergency potable service might be nearly zero, as the tsunami will wipe out much of the built environment. Even so, in these hard hit areas, there will likely still be pockets of buildings that survive, so it would remain prudent to be able to provide potable tanked water supply at about the 1 gallon per capita per day rate.


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In the USA, the CalWARN organization provides support and promotes earthquake emergency disaster response for water and wastewater utilities. For more information, see www.CalWarn.org.

In the USA, the USGS provides near-real time earthquake ground shaking maps, called ShakeMaps and ShakeCast (earthquake.usgs.gov/earthquakes/shakemap/). These maps can be a useful first indicator of the level of ground shaking after actual earthquakes. For larger earthquakes (M 6 or larger), Shakemaps can sometimes be available from the USGS web site within 15 minutes, but often take 30 minutes to 2 hours (or more) to appear. Shakemaps, and its related software Shakecast, provide no indication as to liquefaction, landslide or surface faulting, and as such, are not very useful for rapid prediction of damage to water system buried pipelines. While many people think that ShakeMaps represent "ground truth" levels of shaking, in reality, ShakeMaps are not very accurate at locations away from actual recording instruments, and even the ShakeMaps values at recording instruments are filtered by making non-site-specific assumptions about local soil affects, and the merging of the three directions of earthquake motions into a single value. ShakeMaps that show "MMI" results are especially unrevealing with regards to performance of water system infrastructure. Even with these caveats, the underlying data collected by the ShakeMap software, from actual ground motion instruments, when correctly calibrated, can be used in software like SERA (www.geEngineeringSystems.com) to factor in site specific knowledge about liquefaction, landslide and surface faulting, and buried water system inventories, to make near real time forecasts for water system (electric system, train networks, etc.) performance. Pacific Gas and Electric, Bay Area Rapid Transit, Bonneville Power, EBMUD, SFPUC, SCVWD, San Diego, Pasadena, Burbank, and many water agencies are amongst the agencies using SERA. Caltrans and EBMUD agencies are among the agencies used ShakeMaps and ShakeCast.


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3.0 Observations The following is a commentary on some specific topics.

Since 1995, Japan has installed some buried water tanks to be used to provide drinking water to residents while the normal buried pipe system is broken. How well did this work?

In Chiba Prefecture, as well as in Sendai City, we understand that about 42 such tanks had been installed in the years between 1995 – 2010. The tanks commonly held 10,000 to 40,000 gallons. Essentially, these tanks were built as very large diameter (2 meters or larger) pipes, laid in parallel to existing pipes; each tank would have isolation inlet and outlet valves; normally open so that the water within is constantly "turned over" to maintain quality; the valves are designed to close in the event of strong ground shaking, thereby keeping the water in reserve to be obtained by local residents.

We understand that 39 of these tanks functioned as planned: i.e., the valves closed and the tanks were available for local residents. 1 tank failed outright due to liquefaction. 2 tanks were located in tsunami inundation zones, and they were not used after the earthquake (all nearby residential structures destroyed).

The 39 remaining water tanks did not seem to have much overall effect. We observed many water distribution points, being re-supplied by small tanker truck, and then using small local above ground tanks (200 gallons to 1,000 gallons) for local storage. We do not have specific statistics, but of the 39 tanks that were functional, likely many were in locations where the buried pipe network was not damaged, and thus were not needed. Whether the initial capital cost of installing these tanks was better than the emergency response (small tanker truck and local tanks), remains speculative; but we would guess that the emergency response approach is less costly and more flexible, when considered over a long period of time (say 100 years).

The failure of the one tank due to liquefaction reveals that the small buried tank approach, if adopted, must factor in liquefaction effects. "Standardized" design of such tanks would initially seem to make sense (lower overall capital cost), but in reality makes little sense: the tanks in liquefaction zones will be the ones that are most needed, and need to be designed differently than those in stable ground. Since most pipes do not fail in stable ground, it is questionable whether a buried tank approach for residences in stable ground make much sense anyways.

With regards to buried tanks used as cisterns (i.e., they are completely isolated from the water system, and the water stored is for fire fighting purposes). Some cities in Japan use buried cisterns to supplement water via the buried pipe network (for example, Tokyo and Kobe). In the 2011 earthquake, according to the responses from the City of Sendai and Chiba Prefecture, none of these cisterns were used as water sources for fire fighting. One cistern failed due to liquefaction. We also asked if the cisterns had been used in the 1995


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Kobe earthquake: in that event, there were many fires in Kobe; we were told that no water was used from the cisterns for a variety of reasons: most fires were located where there were no nearby cisterns; at one location near the waterfront, the fire department did attempt to use the water in one cistern, but the manhole was "stuck" (possibly due to liquefaction-induced distortions).

How well did emergency response work?

In Japan, we observed that the water utilities with earthquake damage, outside of the tsunami zones, did call in mutual aid from other water utilities that were not affected by the earthquake. The Japanese have adopted the need to bring in large crews of people to help rapidly restore water service. This would seem a marked improvement in willingness and speed to bring in outside help, as compared to the 1995 Kobe earthquake.

For communities located within the tsunami zones, even after 6 months after the earthquake, there was essentially no attempt to repair damaged buried water pipes. For the few small pockets of residential buildings that remained occupied, water was being delivered by small tanker truck to distribution points.

There were a great number of fires caused by the tsunami. In smaller communities along the Iwate and Miyagi coastline that were inundated, a few of these fires spread and resulted in additional damage. Given the tsunami conditions, we asked if there had been any fire department response; no Japanese utility we talked with knew of any fire department response to try to control these fires; possibly there was.

In Japan, the two largest affected water utilities, Chiba Prefecture (serving a population 5,900,000 people) and the City of Sendai (serving population 1,040,000 people), reported no fires in their service areas (at least none that spread or relied on water from fire hydrants).

In Japan, about 78% of all new water pipe now being installed are seismically designed. There is still a large inventory of older water pipe that remains seismically-weak. Many Japanese water utilities have adopted a 40-year to 65-year pipe renewal strategy. While in Japan, a 50-year old pipe is considered "very old, should be replaced", in the USA, a 50-year old pipe is commonly thought to be not old at all.

In Christchurch, the CCC had previously prepared for earthquakes, beginning with a seismic vulnerability assessment done in 1997 (Risk and Realities, 1997). In the intervening years, CCC had seismically upgraded some of their water tanks; this effort may have reduced the number of failed tanks in the February 2011 event. However, in CCC, while the risk to damage pipes was made apparent in the 1997 study, CCC did not change its pipeline design practices; so more pipes were damaged in the 2010-2011 events that would have otherwise have occurred. After the second earthquake in 2011, CCC has adopted that all new pipes in poor soil areas be seismically designed.


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In Christchurch, there were less than a dozen fire ignitions requiring fire department response in the three earthquakes. The concurrent damage to the water system never resulted in any lack of water needed to control these ignitions. There was no fire spread.

In Concepcion, there were two fire ignitions requiring fire department response. There was no fire spread beyond the initial structures. The concurrent damage to the water system never resulted in any lack of water needed to control these ignitions. There was no fire spread. Water pipes that had been installed using seismic design suffered no damage.


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4.0 Seismic Hazards In this report, we address five types of seismic hazards:

Ground shaking

Liquefaction and lateral spreading

Landslide

Surface faulting

Tsunami

As some readers may be unfamiliar with these terms, the following short summaries provide highlights of these hazards. Further information is available in ALA (2001, ALA (2005).

Ground Shaking

Given that an earthquake occurs in or near a water system, there will be some level of ground shaking hazard at all locations. The ground shaking levels at locations near the fault will usually be higher than ground shaking at locations far from the fault, but uncertainty in ground motions and local soil conditions can sometimes negate this trend.

Ground shaking is usually characterized by peak ground acceleration (PGA), peak ground velocity (PGV), or response spectra (RS) at the site location of the component. PGA or RS are usually used for above ground components. PGV is usually used for below ground pipelines. Once the source location of the earthquake in known, PGAs, RSs and PGVs can be calculated using attenuation models. Attenuation models have been developed to account for various types of earthquakes (subduction, strike slip), types of shaking (acceleration, velocity, response spectral values for varying levels of damping), type of soil (rock, firm, soft) and other special factors (near field directivity effects, vertical motions, upthrust locations).

Liquefaction and Lateral Spreading

Liquefaction is a phenomenon that occurs in loose, saturated, granular soils when subjected to long duration, strong ground shaking. Silts and sands tend to compact and settle under such conditions. If these soils are saturated as they compact and settle, they displace pore water, which is forced upwards. This increased pore water pressure causes two effects. First, it creates a quick condition in which the bearing pressure of the soils is temporarily reduced. Second, if the generated pressures become large enough, material


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can actually be ejected from the ground to form characteristic sand boils on the surface. This displaced material in turn results in further settlement of the site.

Lateral spreading is a phenomenon which can accompany liquefaction. At many sites, the layers of liquefiable materials are located some distance below the ground surface. If the site has significant slope, or is adjacent to an open cut, such as a depressed stream or road bed, liquefaction can cause the surficial soils to flow downslope or towards the cut. Lateral spreading can be highly disruptive of buried structures and pipelines, as well as structures supported on the site.

Landslide

Landslide hazards encompass several distinct types of hazard. These are deep seated and rotational landslides; debris flows; and avalanche / rock falls. These different types of landslides can affect water system components in different ways:

Buried pipelines, valves and vaults. Deep seated rotational and translational landslides pose a significant threat to causing damage to buried pipelines, valves and vaults. Most past efforts in estimating landslide-induced damage to water pipelines has been for deep seated landslides. Debris flows and avalanches are usually not credible threats to buried structures.

Water storage tanks. Deep seated rotational and translational landslides pose a significant threat to causing damage to at-grade storage tanks. Even a few inches of landslide-induced settlement can distort a tank enough to fail it (particularly concrete tanks). Debris flows can also damage tanks if the flow is large enough and hits the tank at high enough velocity. Avalanches and rock falls might, in some circumstances, impact sufficiently on above ground structures to cause damage.

Canals. Debris flows can be significant threats to canals, and can be activated by heavy rainfalls and/or earthquakes, particularly when the ground is saturated.

Tunnels. Landslides pose a serious threat to tunnels at the tunnel portal locations.


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Surface Faulting

Surface faulting (also called fault offset) often occurs for M 6 or larger earthquakes on crustal faults, when the rupture plane reaches the surface. For example, many faults in California (like the San Andreas, Hayward, Calaveras, San Jacinto, Elsinore, etc.) will likely rupture the ground surface in future earthquakes with magnitude 6 or larger.

Not all crustal faults will produce surface faulting, such as some deeply buried faults near Los Angeles.

Subduction zone earthquakes usually do not involve surface faulting on land, as the breakage of the fault is often under the ocean, and the top of the broken fault usually ends about 5 to 15 km beneath the ocean surface.

Tsunami

Earthquakes that result in a rapid up-movement or down-movement of the land mass under an ocean will generate tsunamis. Most subduction zone earthquakes with magnitude 8 or larger will generate significant tsunamis. If the movement of land occurs under a lake, it is called a seiche. Underwater landslides (earthquake triggered or otherwise) can also create tsunamis.

The height of the tsunami water in open ocean is usually small, on the order of a few inches. As the wave approaches shallow water, the effects of the bathymetry will slow the wave, increasing its height. One common term to measure tsunami height is the height of the wave, when the wave is located at a water depth of 10 meters near a shoreline. Another common term is to measure the tsunami run-up height, meaning the highest ground elevation which becomes wet from the tsunami waves as they roll onto shore. A very large tsunami, such as in Japan 2011, had water heights of 7 to 8 meters (at 10 meters water depth offshore), with local run-up heights as much as 25 meters or more (run-up heights in narrow canyons can be much higher).


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5.0 References ALA, "Seismic Fragility Formulations for Water Systems," American Lifelines Alliance, FEMA, March 2001.

ALA, Seismic Guidelines for Water Pipelines, American Lifelines Alliance, March 2005.

ASCE, 2005, Fire Following Earthquake, Scawthorn, Eidinger and Schiff, Editors, ASCE, March, 2005.

AWWARF-EPA, Customer Acceptance of Water main Structural Reliability, AWWA Research Foundation, 2005.

AWWA. Water Infrastructure at a Turning Point: the Road to Sustainable Asset Management, AWWA May 2006.

Ballantyne, D., Minimizing Earthquake Damage, A Guide for Water Utilities, American Water Works Association, 6666 West Quincy Ave., Denver CO 80235, 1994.

Boroschek, R., Soto, P., Leon, R., Maule Region Earthquake, February 27, 2010 Mw = 8.8, University of Chile, Faculty of Mathematics and Physical Sciences, Civil Engineering Department, Report 10/08, August, 2010.

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Eidinger, J., Avila, E., Eds., Guidelines for the Seismic Evaluation and Upgrade of Water Transmission Facilities, ASCE Technical Council on Lifeline Earthquake Engineering, Monograph No. 15, January, 1999.

Eidinger, J, Water Pipe Replacement: Seismic and Aging, in Proceedings, 7th Taiwan-US-Japan Workshop on Water System Seismic Practices, Niigata, Japan, October 2011.

Eidinger, J., and Tang, A., eds., Christchurch, New Zealand Earthquake Sequence of M 7.1 September 2010, M 6.3 February 22 2011, M 6.0 June 13 2011: Lifeline Performance, http://www.geEngineeringSystems.com, ASCE, Technical Council on Lifeline Earthquake Engineering, Monograph No. 40, February 2012.

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Si, H., and Midorikawa, S., New attenuation relations for peak ground acceleration and velocity considering effects of fault type and site condition, in Proceedings of the 12th World Conference on Earthquake Engineering, paper No. 0532.


Page A-1

Appendix A Performance Goals by Other Water Agencies Appendix A is adopted from: Guidelines for the Seismic Evaluation and Upgrade of Water Transmission Facilities, ASCE Technical Council on Lifeline Earthquake Engineering, Monograph No. 15, January, 1999 (Eidinger and Avila, 1999), AWWA (Ballantyne 1994), and other utility-specific source materials.

A.1 General Issues

One of the first tasks of a seismic assessment of a water or wastewater transmission system is to develop a suitable set of earthquake performance goals. A performance goal reflects the desire to provide some level of adequate service following an earthquake, which reflects upon the balance of needs to provide service at a reasonable level of cost.

This "balance" between service and cost will vary on a case-by-case basis. For example, if the only function of the aqueduct is to move raw water between a distant large reservoir and another smaller reservoir located close to the population center served by the transmission system, an earthquake-induced temporary closure of that aqueduct may be completely adequate, because the end user customer may still be able to get water from alternate supplies, at least for some time. On the other hand, if damage to this same aqueduct causes leakages that would inflict a significant life-safety impact to people located near the leak, damage may not be tolerable.

Although performance goals are often highly case-specific, it is useful to present a "baseline" set of performance goals that might provide a starting point in establishing the case-specific goals.

The utility operator will want to assess the system for at least the maximum earthquake. In some instances, it may benefit the utility operator to also assess its system for a probable earthquake.

Under both the maximum earthquake and probable earthquake, the utility operator should develop a set of performance goals that are consistent with the desired level of post-earthquake service to its customers. Issues to be considered include:

Life Safety Fire Service Water Quality Critical Facility Service Customer Service Direct and Indirect Economic Losses to the Community Private Property Loss


Page A-2

A.2 AWWA – General Performance Goals

Table A-1 provides "baseline" performance goals for the probable and maximum earthquakes for potable water systems that also provide fire flows (ref. Ballantyne). These should be adjusted to meet the particular needs of a utility, including provision of raw water, or if the utility only provides transmission.

The definitions of "probable earthquake" and "maximum earthquake" used in Table A-1 are suggestive of the following recurrence intervals:

Probable Earthquake. Is likely to occur within the design lifetime of regularly constructed facilities. Could be defined as a 50% chance of occurrence within a 50 year time frame, or about a 72 year recurrence interval. Sometimes called a "Moderate Earthquake" or "Operating Basis Earthquake", but this nomenclature is not meant to guarantee that a water system will experience no damage or service outages given that the earthquake occurs.

Maximum Earthquake. Is possible to occur within the design lifetime of regularly constructed facilities. Could be defined as a 10% chance of occurrence within a 50 year time frame, or about a 475 year recurrence interval. Sometimes called a "Large Earthquake" or "Design Basis Earthquake", but does not necessarily represent the maximum possible level of shaking from a Maximum Credible Earthquake.

Table A-1. Water System Performance Goals

Service Category Probable Earthquake Maximum Earthquake Life Safety Minimal life-safety risk Minimal life-safety risk Fire Suppression Available in all areas Available from 70 percent of

sources or reservoirs after valving off limited areas of damage.

Critical Service Drinking water and public health Domestic, commercial and industrial supply Property damage

Continuous full service to all areas at winter demand rates. Maintain good water quality.

Service to 70% of service area at 70% of winter flows; potable water made available at centralized locations, both within 72 hours. Boil-water order may be required. No outside use of water. Full service to all but a few areas within 7 days at winter demand rates. Full service to all within 1 month at winter demand rates.

Irrigation Full service to all areas at summer demand rates within 7 days.

Full service to all areas within 6 months at summer demand rates.


Page A-3

A.3 EBMUD – General Performance Goals

Tables A-2 and A-3 provide the performance goals adopted by the East Bay Municipal Utility District, EBMUD.

Within EBMUD's context, a "Probable" earthquake was considered to be a Magnitude 6 earthquake on the Hayward fault occurring somewhere within the EBMUD's service area; or similar sized earthquakes on the Concord, Calaveras and other faults within the service area, or even larger magnitude earthquakes on faults located further away from the District's service area.

Within EBMUD's context, a "Maximum" earthquake was considered to be a characteristic earthquake on the Hayward fault rupturing through the entire length of the service area, or characteristic earthquakes on the Concord or Calaveras faults, rupturing within or very near the service area.


Page A-4

Table A-2. Water System Service Goals - Probable Earthquake (EBMUD)

Service Category Probable Earthquake

General 1 Minimal secondary damage and risk to the public

2 Limit extensive damage to system facilities

3 All water introduced into the distribution system minimally disinfected

4 All water introduced into the distribution system fully treated

Fire Service 5 Sufficient portable pumps and hose to provide limited fire service in all areas

6 All areas have minimal fire service (one reliable pumping plant and reservoir)

7 High risk areas have improved fire service (all facilities reliable, minimum fire reserves)

8 Normal service to all hydrants within 20 days

Hospitals and Disaster Centers

9 Minimum service to affected area within 1 day (water available via distribution system near each facility)

10 Impaired service to affected area within 3 days (water available via distribution system to each facility, possibly at reduced pressures)

Domestic Users 11 Potable water via distribution system or truck within 1 day

12 Impaired service to affected area within 3 days (water available via distribution system to each domestic user, possibly at reduced pressures)

Commercial, Industrial and Other Users

13 Impaired service to affected area within 3 days (water available via distribution system to each commercial or industrial user, possibly at reduced pressures)


Page A-5

Table A-3. Water System Service Goals - Maximum Earthquake (EBMUD)

Service Category Maximum Earthquake

General 1 Minimal secondary damage and risk to the public

2 Limit extensive damage to system facilities

3 All water introduced into the distribution system minimally disinfected

4 All water introduced into the distribution system fully treated

Fire Service 5 Sufficient portable pumps and hose to provide limited fire service in all areas

6 All areas have minimal fire service (one reliable pumping plant and reservoir)

7 High risk areas have improved fire service (all facilities reliable, minimum fire reserves)

8 Normal service to all hydrants within 100 days

Hospitals and Disaster

9 Minimum service via distribution system or truck within 3 days

Centers 10 Minimum service within 10 days (water available via distribution system near each facility)

11 Impaired service within 30 days (water available via distribution system to each facility, possibly at reduced pressures)

Domestic Users 12 Potable water at central locations for pickup within 3 days

13 Minimum service to 70% of customers within 10 days

Commercial, Industrial and

14 Potable water at central locations for pickup within 1 week

Other Users 15 Minimum service to 70% of customers within 10 days

16 Impaired service to 90% of customers within 30 days (water available via distribution system to 90% of commercial or industrial users, possibly at reduced pressures)


Page A-6

A.4 CCWD – Reliability and Seismic Criteria

Tables A-4 and A-5 provide the "reliability criteria" adopted by the Contra Costa Water District (CCWD).

The reliability criteria set goals for the post-earthquake restoration of different types of service, as defined in Table A-4, beginning with emergency fire service within 2-8 hours and ending with permanent repair (as opposed to temporary fixes often used to quickly restore service) of all damaged facilities within 2 years.

Table A-4 - Reliability Criteria - Raw Water System (CCWD)

Service Category Reliability Criteria - Raw Water

General RW-1: No primary damage to District facilities that endangers the general public and CCWD staff.

RW-2: No direct secondary damage to non-District facilities due to catastrophic failure of District facilities.

RW-3: Temporary repairs to achieve emergency fire service and essential service as soon as possible.

RW-4: Temporary repairs to achieve full service within 30 days.

RW-5: Permanent repairs to all raw water facilities completed within 2 years.

Wholesale

Municipal

RW-6: Emergency and normal fire service needs at user point of delivery within 2 days after earthquake. Customers utilizing storage or other services to fight fires in the interim.

RW-7: Partial service within 10 days at user point of delivery after earthquake with periodic 3 day interruptions for repairs.

RW-8: Full service within 30 days after earthquake.

Industrial Users

RW-9: Emergency and normal fire service needs at user point of delivery within 2 days after earthquake. Standby customers utilizing storage or other services to fight fires in the interim.

RW-10: Restoration priority based on minimizing economic loss.



Standby Users

Agricultural Users

Landscape Users

RW-13: Emergency and normal fire service needs at user point of delivery within 2 days after earthquake. Standby customers utilizing storage or other services to fight fires in the interim.

RW-14: Restoration priority based on minimizing economic loss.




Page A-7

Seismic criteria were developed in order to set forth a consistent and prioritized set of standards for the earthquake resistant evaluation and design of CCWD facilities, such as the Contra Costa Canal, necessary to meet reliability criteria. The seismic criteria establishes a four level facility classification system (Class I to Class IV) based on the importance of the facility remaining functional to meet post-earthquake fire service demands. Table A-5 illustrates these classifications and their relationship to the type of service and reliability criteria.

Table A-5 Relationship Between Reliability and Seismic Criteria (CCWD)

Seismic Criteria Facility Class

Class Description

Type of Service

Related Reliability Criteria

Criteria for Max. Duration of Loss

Example District Facilities

Facility Reli- ability

System Reli- ability

I Critical Emergency Firefighting

RW-6 1 -2 days Contra Costa Canal Milepost 0.0 to 26.0; Raw Water Storage Reservoirs

99.5% 90%

II Essential Emergency and Critical Care

RW-3, RW-6, RW-9, RW-13

2 - 5 days

Secondary Municipal and Industrial Laterals

95.0% 80%

III Important Partial and Sanitary

RW-4, RW-7, RW-11, RW-15

5 - 15 days

Contra Costa Canal Turnouts

90.0% 50%

IV Standard Full RW-1, RW-2, RW-8. RW-12, RW-16

15 -60 days

All Contra Costa Canal Facilities

80.0% 0-30%


Page A-8

A.5 HBMWD Service Goals

The Humboldt Bay Municipal Water District (HBMWD) is a water wholesaler serving the cities of Eureka, Arcata, Mckinleyville and several other smaller communities around Humboldt Bay, California. HBMWD operates water treatment facilities, and large diameter raw water and treated water pipelines. HBMWD delivers water to various retail water agencies. Tables A-6 and A-7 provide the performance goals adopted by that utility. The following paragraphs explain the goals in more detail.

Goal

1. Minimal Secondary Damage and Risk to the Public

Damage to the infrastructure should pose minimal risk to the public. For example, chlorine releases should not occur, and occupied buildings should not collapse.

2. Limit Extensive Damage to System Facilities

Undue amounts of damage to HBMWD's own facilities could result in the inability for the HBMWD to respond after an earthquake. Damage to critical facilities should be avoided (such as the designated areas for emergency operations coordination). Damage posing life safety threat to HBMWD's own personnel should be avoided.

3. All Water Introduced into the Potable Water Transmission System Minimally Disinfected

All water from the HBMWD raw water source should be at least minimally disinfected prior to introduction into the treated water transmission system, immediately after the earthquake. This means that no "untreated" water should be introduced. Minimal disinfection would include chlorination.

4. Provide 50% of Average Winter Level Flows to Domestic Customer Meters within 4 Hours After the Earthquake

This service goal reflects that after an earthquake, there may be multiple fires in HBMWD's customers' service areas. This will be compounded by damage within the customer's distribution systems, which will rapidly deplete storage in local storage tanks and reservoirs. If no water can be re-supplied to the customer's distribution systems, there can be an unacceptable high risk of fire spread, especially if it is windy at the time of the earthquake.

The target restoration time for HBMWD to restore water service of 4 hours should be adequate for McKinleyville. This service goal may vary for other distribution system customers based on their own system needs.


Page A-9

5. Provide 100% of Average Winter Level Flows to Domestic Customer Meters within 3 Days After the Earthquake

This service goal reflects that HBMWD should be able to restore its normal wintertime capacity to deliver water to major customer's turnouts at normal pressures and flows, within 3 days after any earthquake.

6. Potable Water via truck or Accessible Locations within 1 Day to Meet Minimum Consumption Needs.

It is likely that many Humboldt Bay area residents will be unable to get potable water via their normal water distribution system following large earthquakes. This will include people who are forced out of their homes because of damage to those structures; and due to damage to the underground water distribution networks. In coordination with HBMWD's distribution customers, suitable delivery points for distribution of potable water should be identified as part of an emergency response plan. Suitable facilities should be available to allow water tanker trucks to be filled from reliable sources of potable water.

7. Impaired Service to all Domestic Water Customers within 7 Days.

Impaired service is defined as the delivery of some amount of water (enough to meet winter time demands, allowing for mandatory curtailment of irrigation if necessary) via the transmission system. Occasional pressure fluctuations or brief outages are possible.

8. Normal Service to all Domestic Water Customers within 60 Days

Normal service is defined as the delivery of water at the same level of reliability as under "normal" pre-earthquake conditions.

9. Impaired Service to Industrial Water Customers within 7 Days

Impaired service is defined as the delivery of non-potable water to meet low level to average level operations via the transmission system. Occasional pressure fluctuations or brief outages are possible. This level of water should be sufficient for industrial customers to restore operations, albeit at somewhat less than maximum operating day capability.

10. Normal Service to Industrial Water Customers within 60 Days

Normal service is defined as the delivery of water at the same level of service as provided prior to the earthquake.


Page A-10

Table A-6. HBMWD Water System Service Goals - Maximum Earthquake

Service Category Maximum Earthquake General 1 Minimal secondary damage and risk to the public

2 Limit extensive damage to system facilities 3 All water introduced into the distribution system minimally disinfected

Fire Service 4 Provide 50% of average winter level flows to customer meters within 4 hours after earthquake. (Tentative goal for large customers)

5 Provide 100% of average winter level flows to all customer meters within 3 days after earthquake. (Tentative goal for large customers)

Domestic Water Service 6 Potable water via truck or accessible locations within 1 day to meet minimum consumption needs (1 gallon per person per day)

7 Impaired service within 7 days 8 Normal service within 60 days

Raw Water Service 9 Impaired service within 7 days

10 Normal service within 60 days

Table A-7. HBMWD Water System Service Goals - Probable Earthquake

Service Category Probable Earthquake General 1 Minimal secondary damage and risk to the public

2 Limit extensive damage to system facilities 3 All water introduced into the distribution system minimally disinfected

Fire Service 4 Provide 100% of average winter level flows to customer meters within 4 hours after earthquake. (Tentative goal for large customers)

5 Provide 100% of average winter level flows to all customer meters within 3 days after earthquake. (Tentative goal for large customers)

Domestic Water Service 6 Potable water via truck or accessible locations within 1 day to meet minimum consumption needs (1 gallon per person per day)

7 Impaired service within 3 days 8 Normal service within 20 days

Raw Water Service 9 Impaired service within 3 days

10 Normal service within 20 days

Minimally Disinfected Chlorination or better. Impaired Service Provide water (adequate to meet winter time demands), possibly at lower

pressure than normal. Normal service Provide water at the same level of reliability as under "normal" pre-earthquake co nditions.

recent earthquakes: implications for u.s. water utilities

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