MAINTAINING AND RESTORING WATER LIFELINE SYSTEMS

AFTER AN EARTHQUAKE

Donald Ballantyne; EQE International; Seattle, Washington, USA, and Tokyo, Japan

ABSTRACT

This paper presents an overview of the impact of the January 17, 1994 Northridge Earthquake on

the Los Angeles Department of Water and Power and the Metropolitan Water District of Southern

California water systems. These systems, as they are impacted by the earthquake, are used as

basis to discuss five questions:

1. Why is water important following earthquakes?

2. What is acceptable reliability of a water system in terms of adverse consequence levels?

3. How can we determine the reliability of existing lifeline systems?

4. What system component failure have had the greatest impact on “system” performance in

historic earthquakes?

5. What approaches can be used to enhance reliability?

It is the hope that the discussion of these questions will be useful for water system professionals

considering earthquake mitigation.

MAINTAINING AND RESTORING WATER LIFELINE SYSTEMS

AFTER AN EARTHQUAKE

Donald Ballantyne; EQE International; Seattle, Washington, USA, and Tokyo, Japan

INTRODUCTION

On January 17, 1994 Northridge Earthquake damaged lifeline system serving the Los

Angeles area. The Northridge Earthquake impact on the Los Angeles Department of Water and

Power (LADWP), and the Metropolitan Water District of Southern California (MWDSC) water

systems provides a basis to examine five questions.

1. Why is water important following earthquakes?

2. What is acceptable reliability of a water system in terms of adverse consequence levels?

3. How can we determine the reliability of existing lifeline systems?

4. What system component failure have had the greatest impact on “system” performance in

historic earthquakes?

5. What approaches can be used to enhance reliability?

The discussion focuses on the two water systems, and does not address the impact on other

smaller water systems north and west of the San Fernando Valley.

NORTHRIDGE EARTHQUAKE

Introduction

The Mw 6.7 Northridge Earthquake occurred on January 17, 1994 at 4:31 AM, with the

epicenter in the central San Fernando Valley. A maximum Modified Mercalli Intensity of X was

experienced. Water supply was lost to over 60 percent of the San Fernando Valley, or about

100,000 customers (Figure 1). Ninety percent of the lost service was restored within four days.

Over 100 fires ignited, but were all controlled within five hours. Electrical power went out city-

wide when the earthquake occurred with restoration occurring as follows: 50 % in 6 hours, 65%

in 12 hours, 93% in 24 hours, and nearly 100% in 48 hours.

Two major water suppliers, Metropolitan Water District of Southern California

(MWDSC) and Los Angeles Department of Water and Power (LADWP) serve the area.

MWDSC, the largest water provider in the U.S., serving 16 million people in Southern California,

gets water from the California State Water Project from the north, and from the Colorado River,

to the east. One of LADWP’s two primary supply comes from the Owens Valley, again from the

north. In all cases, the water comes from over 250 kilometers away, so the supplies were not

impacted by the earthquake. MWDSC delivers water directly and indirectly to over 200

wholesale customers throughout Southern California, including LADWP (LADWP’s second

primary supply). LADWP delivers water to 3.5 million people in Los Angeles.

Aqueducts

MWDSC has multiple branch feeds and five water treatment plants. Only the Valley

Branch was impacted in the Northridge event. The Foothill Feeder (Valley Branch), a welded

steel line that transmits water from Castaic Lake to the Jensen Water Treatment Plant (WTP), was

damaged where the 170-inch diameter line splits into two 85-inch treatment plant inlet lines. A

circumferential crack on a bell of the eastern 85-inch line was repaired within three days after the

earthquake. The MWDSC East Valley Feeder and pumping station were activated so that water

could be provided to the affected areas in the San Fernando Valley from the Colorado River

Aqueduct/State Water Project - East Branch.

LADWP’s Los Angeles Aqueduct No. 1 and No. 2, which supply water for the

LADWP’s Los Angeles Water Filtration Plant (WFP) from the Owens Valley, were also

damaged. Aqueduct No. 1 was damaged at welded steel and reinforced concrete siphons.

Damage to Aqueduct No. 2, a welded steel pipeline, shut down the line for 12 days after the

earthquake. During the shutdown of Aqueduct No. 2, Aqueduct No. 1 was operated at a low flow

rate. After temporary repairs were made to Aqueduct No. 2, Aqueduct No. 1 was shutdown for

two months while temporary repairs were made. In addition to reliance on the redundancy

provided by the two aqueducts, reservoir storage, groundwater supplies and the Colorado River

Aqueduct/State Water Project - East Branch were used as alternate supplies during the outages.

The arrangement of, and failures on these aqueducts and other transmission lines are

shown in Figure 2.

Other Water System Components

There was a significant amount of nonstructural damage and some sloshing and

settlement damage at the MWDSC 550 million gallon per day (MGD) Jensen WTP, and the

LADWP 600 MGD Los Angeles WFP. Most damage could be easily repaired and did not

significantly affect plant performance. However, transmission line damage upstream and

downstream of the plants shut the plants down for several days.

Seven LADWP water storage reservoirs were damaged during the earthquake. Failure of

inlet/outlet piping caused by tank uplift and tank roof collapse were the primary types of damage.

One tank collapsed. Most damage occurred in steel tanks that did not meet current American

Water Works Association tank design standard seismic provisions. Because the earthquake

occurred early in the morning, tanks were much more likely to have been full than if the

earthquake had occurred in the late afternoon or evening. Tank failure effects on water system

operation were not documented.

There was only minor pump station damage reported. However, some stations did not

have emergency power and were not functional due to loss of commercial power.

Distribution pipe damage was the major contributor to loss of water service. Over 1,100

repairs were made in the San Fernando Valley by as many as 50 crews in the 20 days following

the event. Liquefaction/lateral spread, ground lurching and ground rupture were apparently

responsible for most of this damage (O’Rourke, 1997). In addition to pipe damage, air release

and vacuum valves were sheared from ground shaking and some fire hydrants ruptured (possibly

from water hammer).

Large areas lost water pressure because the distribution pipe damage was so extensive.

Failure of the chlorination system at the Los Angeles WTP, and the threat of contamination from

infiltration resulted in a boil water order issued the morning of the earthquake that was not

completely lifted for 12 days.

WHY IS WATER IMPORTANT FOLLOWING EARTHQUAKES?

Water is important following earthquakes to fill three needs: 1) fire suppression, 2) public

health, and 3) system restoration.

Water for fire suppression was limited following the 1995 Hanshin, 1923 Kanto, 1906

San Francisco earthquakes, with catastrophic results. Each event was accompanied by a major

fire. Water from alternative supplies helped suppress fires following the 1989 Loma Prieta

Earthquake (water from San Francisco’s Portable Water Supply System), and the Northridge

Earthquake (water from swimming pools).

Water for public health includes that used for drinking, bathing, food preparation, and

possibly laundry. Outage durations following the Northridge Earthquake were limited so there

was limited negative public feedback. Following the Hanshin Earthquake, public response

intensified to the point where a 30 day outage duration was set as the limit for future planning.

Water system restoration is required to restore pre-earthquake societal functions,

including residential occupancy, and business function. Commercial and industrial business

interruption can have a significant economic impact of the community. One example, while not

water supply disruption, is the large economic impact that resulted from the closure of the Port of

Kobe following the Hanshin Earthquake. Another example due to water supply disruption was

during the 1993 flood in the mid-west in the United States. The Des Moines, Iowa, water

treatment plant was out of service for 12 days, and the city had no water. Hotels and restaurants

were only allowed to operate on a limited basis. One major insurance company office had to

severely curtail operations because they had no water for cooling computers, running the air

conditioning system, and to charge the fire sprinkler system.

WHAT IS ACCEPTABLE RELIABILITY IN TERMS OF ADVERSE CONSEQUENCE

LEVELS?

It is useful to establish performance objectives to provide guidance in water system

planning and design. One approach is to define performance objectives in terms of probability of

occurrence, and associated acceptable outage time. We often define two levels of earthquake

ground motions, an operating basis earthquake (OBE) (50% probability of producing a ground

motion exceeding the calculated threshold in 50 years), and a design basis earthquake (DBE)

(10% probability of producing a ground motion exceeding the calculated threshold in 50 years).

Table 1 shows proposed acceptable adverse consequences for life safety, property

damage, and the three needs described in the previous section for the OBE and DBE. The intent

is to have policy makers adopt such performance objectives, which would allow water system

professionals to use them to guide planning and engineering decisions.

Using the performance objectives proposed in Table 1, we can evaluate water system

performance in the Northridge Earthquake. For life safety, there was no loss of life related to

water system failure. For fire suppression, less than 70 percent of the water system was

functional in the San Fernando Valley. However, there was an alternative supply available for

fire suppression, water from swimming pools. On that basis, it appears that the water “system”

met the performance objective for fire suppression. For public health, less than 50% of the

system was functional in the San Fernando Valley. It appears that the water system did not meet

the proposed performance objectives.

Table 1 - Water Performance Objectives -

Acceptable Adverse Consequence Levels For Two Earthquake Levels (Ballantyne, 1994)

ACCEPTABLE ADVERSE CONSEQUENCES

PERFORMANCE CATEGORY

Operating Basis Earthquake (50% chance in 50 years)

Design Basis Earthquake (10% chance in 50 years)

Life Safety Minimal – Injury or loss of life are not acceptable consequences

Minimal - Injury or loss of life are not acceptable consequences

Fire Suppression Minimal - With the exception of small isolated areas that are not densely populated, water for fire suppression should be available for entire service area.

Moderate - Water for fire suppression should be available for a minimum of 70% of the service area including all industrial areas and densely populated business and residential areas.

Public Health Low – Water should be available for all but a few isolated areas. Boil water order acceptable for up to 48 hours.

Moderate - Provide service for at least 50% of system. Boil water order, or delivery by tanker truck acceptable. Restore100% service in 1 week.

System Restoration Low – Water should be available for all but a few isolated areas.

Moderate - Service should be available for at least 50% of system. Restoration to 100% service within one week.

Property Damage Low – Any damage should not affect facility functionality and should be repairable.

Moderate - 100% loss of nonessential facilities acceptable if not cost-effective to upgrade, and other performance objectives are met.

HOW CAN WE DETERMINE THE RELIABILITY OF OUR EXISTING SYSTEMS?

Most water systems are in place, so we must use methods to assess reliability of these

existing systems. There are a variety of approaches that can be used to assess post-earthquake

water system reliability (Ballantyne, 1997):

Conduct deterministic assessments of each water system component and use the

component assessment results to develop a system performance scenario. This approach

must consider seismic hazards, component vulnerability, and expected system

performance.

Establish fragility curves to define component vulnerability and use probabilistic

techniques to evaluate system reliability (Monte Carlo simulation).

Use of system reliability assessment techniques such as fault tree analysis. Fault trees can

be used to calculate failure probabilities, identify paths that may lead to failure, and to

identify those events that are most likely to lead to failure.

Geographic Information Systems allow calculation and graphic presentation of system

risk assessment results that can be easily used and interpreted by planners, emergency

response personnel and engineers.

These methods have been applied to numerous systems in the United States, but the author is

unaware of such a reliability analysis of the LADWP system

WHAT SYSTEM COMPONENT FAILURES HAVE HAD THE GREATEST IMPACT

ON “SYSTEM” PERFORMANCE IN HISTORIC EARTHQUAKES?

Eight U.S. and Japanese earthquakes, one fire and one major flood disaster were

evaluated to determine which water system component failures had the greatest impact on overall

“system” performance. The results were as follows (Ballantyne, 1997):

Very High Impact - Pipe damage due to permanent ground deformation (PGD).

High Impact - Pipe damage due to wave propagation.

Moderate Impact - water treatment plant damage, loss of power, and tank piping damage.

Low Impact - tank structural, well, and equipment damage, and surface supply failure.

Pipeline damage was the primary contributing factor to loss of service in some areas of

the LADWP system following the Northridge Earthquake (O’Rourke, 1997).

WHAT APPROACHES CAN BE USED TO ENHANCE RELIABILITY?

This section describes elements of a mitigation program to improve water system

reliability, and the significance of each of these elements in the post-earthquake operation of the

LADWP and MWDSC systems.

Water system reliability can be improved through implementation of an effectively

designed mitigation program. The mitigation program will likely include a combination of

system hardware improvements, and development of emergency response capability. Availability

of emergency water supplies is another mitigation option that will enhance system reliability.

System Hardware Improvements to Improve Reliability

Addition of redundancy, upgrade, or replacement of system components are all

considered to be hardware improvements. Their benefits were demonstrated in Northridge, where

LADWP had redundant aqueducts delivering water from the source into the San Fernando Valley.

One was kept in service while the other was repaired. MWDSC also had the capability to deliver

water to the San Fernando Valley from either the north or the east. When the north feed was

damaged, they supplied water from the east. MWDSC’s Jensen WTP, and LADWP’s Los

Angeles WFP are also redundant in emergency situations.

LADWP and MWDSC had implemented upgrade and replacement programs in their

systems after the 1971 San Fernando Earthquake which had also impacted the San Fernando

Valley. MWDSC had undertaken a soil improvement program at the Jensen WTP, installing over

1,000 gravel columns to mitigate liquefaction. As a result, there was only limited liquefaction

damage in the Northridge event at the Jensen site. A new dam (Los Angeles Reservoir) was

constructed to replace the Van Norman Dam, that nearly failed due to liquefaction in 1971.

LADWP had designed the Los Angeles WFP in the late 1970’s with seismic resistance in mind

after their experience in the 1971 San Fernando Earthquake.

In the Northridge Earthquake, LADWP suffered approximately 1,100 pipeline failures.

They had only a limited amount of ductile iron pipe in the system; about 75 percent was cast iron

and 10 percent small diameter steel which was subject to corrosion. Both cast iron and corroded

steel are vulnerable where as newer ductile iron pipe is more resistant to earthquake damage.

(The Kobe water system had 90 percent ductile iron or welded steel pipe in the system subjected

to the 1995 Hanshin Earthquake.) LADWP has not pursued a significant pipeline replacement

program because of the high cost. Poor performance of piping was the major contributor to loss

of service.

Emergency Response Capability to Improve Reliability

Response capability can include both plans to organize an effective response and the

acquisition or installation of equipment to allow that effective response.

LADWP’s emergency plan worked well. Staff reported to prearranged locations to

inspect for damage. Tasks undertaken the first day following the earthquake included: assessing

and prioritizing resources, assessing damage and areas without water, stopping loss of water,

issuing a boil water order, and mobilizing water deliver trucks to areas without water. As time

progressed, repairs were reprioritized, and crews reassigned from areas that were back in service.

Administration and engineering staff responsibilities included coordinating mutual aid,

dispatching leak repair crews, coordinating water truck deliveries, preparation of Federal

Emergency Management Agency report documentation, and purchasing. MWDSC found that

stockpiled goods were of limited value because most materials could be delivered from anywhere

in the U.S. overnight (Young, 1995).

Problems that arose during response and recovery included communications and

inadequate capability to provide food, water and shelter for emergency crews. Communication

systems were overloaded. The problem was compounded by failure of one of the radio repeater

stations.

Following the poor response to 1989 Loma Prieta Earthquake, and the 1991 Oakland

Hills Fire, both in Northern California, California water utilities decided to further develop their

mutual aid capabilities. When the Northridge event occurred, the II Water Agency Response

Network (II WARN) was in place, and worked to make mutual aid capability available to the

impacted area (Riordan, 1995). Fourteen mutual responders came with fully equipped crews to

assist in system repair.

Availability of resources in Los Angeles may be unusual. Los Angeles regional events

over the last 30 years have resulted in significant damage locally, but have had limited impact to

areas say, 15 km or greater from the epicenter. In addition, Southern California has a huge

resource base readily available to the affected area because of its large population. Earthquakes

in other parts of the country may have an impact on a larger area because of different tectonic

structures, limiting resource availability. In addition, other areas may have a smaller resource

base to begin with, as a result of a smaller population.

Earthquake monitoring and control systems provide an emergency response capability to

isolate damaged sections of the system, or to save stored water. LADWP had no such systems in

place. Their perspective prior to the earthquake was that they were expensive to install and

maintain, and didn’t provide much control flexibility. In one case in the MWDSC system, a

leaking transmission line was kept on-line because it was delivering water to the City of San

Fernando, where it was being used for fire suppression. With an automated monitoring and

control system, this supply may have been shut down.

LADWP had planned for the use of fire company equipment if pump stations were not

functional. Twenty-five fire companies were used in the earthquake aftermath to pump across

failed pump stations for up to two weeks.

Emergency Water Supplies to Improve Reliability

Water system performance following an earthquake is at best, unpredictable. Planning

for emergency water supplies is an important element in an earthquake mitigation program to

increase water system reliability. The Los Angeles Fire Department reported a lack of water

pressure at hydrants in much of the western and northern areas of the San Fernando Valley

(Figure 1). The Balboa Boulevard fire, which received significant coverage by the media, was

controlled by drafting water from nearby swimming pools. It took 70 minutes and 14,000 gallons

of water to control this fire.

Other fires were also controlled by using water from swimming pools. Fire department

tank trucks and tank trucks provided by the military and the movie industry were used as

supplemental sources. United State Forest Service helicopter water drops were also used on

building fires.

In areas where distribution pipes were damaged, water was supplied by tanker trucks.

These trucks were provided by local water, beer and soft-drink bottlers, the U.S. Army, the

California National Guard, and local contractors. At the peak of the 13 day effort, tankers were

supplying over 100,000 gallons of water per day.

Pipeline Repairs

One of most time consuming problems encountered in the recovery effort is location of

pipeline leaks and breaks. The process requires filling the main, locating a leak (either by water

coming to the surface or by sound), excavating the pipe, draining the main, and repairing the

main. The process then starts again. It would be very beneficial to identify a method to locate

multiple leaks/breaks at one time, and/or to definitively identify breaks without excavation.

SUMMARY AND CONCLUSIONS

This paper has addressed five questions that lead to a rational approach to develop an

earthquake mitigation program. While we are not aware that LADWP has done a formal system

reliability assessment, they had incorporated many of the concepts described herein, prior to the

Northridge Earthquake. Many of the hardware improvements and emergency response capability

enhancements were implemented since, and as a result of, the 1971 San Fernando Earthquake.

With these improvements, LADWP appears to have nearly attained the proposed system

performance objectives following the Northridge Earthquake.

REFERENCES

Ballantyne, D.B., 1994, Minimizing Earthquake Damage, A Guide for Water Utilities, American

Water Works Association, Denver, Colorado.

Ballantyne, D.B., and Crouse, C.B., 1997, Reliability and Restoration of Water Supply Systems

for Fire suppression and Drinking Following Earthquakes, NIST GCR 97-730, National

Institute of Standards and Technology.

Cooper, William (MWDSC), 1994, presentation-Joint New Zealand/Los Angeles Lifeline

Workshop.

Earthquake Engineering Research Institute, “Northridge Earthquake Reconnaissance Report,”

Earthquake Spectra, Supplement C to Volume 11, April 1995.

EQE International, Report on Selected Fires Following the Loma Prieta and Northridge

Earthquakes, and Summary of the San Francisco Emergency Water Systems, Report

Prepared for The Fire Protection Equipment and Safety Center of Japan on Behalf of the

Tokyo Fire Department, March 1996.

Giles, Robert (LADWP), 1994, presentation -Joint New Zealand/Los Angeles Lifeline Workshop.

Lund, LeVal, and Cooper, Tom, 1995 “Water Systems,” Northridge Earthquake Lifeline

Performance and Post-Earthquake Response, TCLEE Monograph No. 6, ASCE.

O’Rourke, T.D; Toprak, S. and Sano, Y., 1998, “Factors Affecting Water Supply Damage Caused

by the Northridge Earthquake”, Proceedings of the Seventh U.S.-Japan Workshop on

Earthquake Disaster Prevention for Lifeline Systems, Sponsored by NIST and the NSF,

Donald Ballantyne, Editor. In press.

Riordan, Raymond A., 1995, “Mutual Aid and Emergency Response for Water Utilities”, Journal

of the American Water Works Association, May, 1995, Vol. 87, pp. 52-58, Denver, CO.

Young, Michael B., and Means, Edward G., 1995, “Earthquake Lessons Pay Off in Southern

California”, Journal of the American Water Works Association, May, 1995, Vol. 87, pp.

59-64, Denver, CO.

FIGURE 1- Water Outage Areas Following Northridge Earthquake

FIGURE 2- Water System Backbone Serving San Fernando Valley Damaged in Northridge Earthquake