The Impact on Lifelines on the Estimation of Natural Hazard Loss
July 2005
When projecting loss estimates as the result
of a potential earthquake or extreme wind hazard, the primary focus for many
entities is typically on the potential damage to the buildings and possibly
the damage or loss to important equipment, and stock and supplies. Also of significant
concern to many corporations and public entities is the time that their facility
will be out of service or that their capacity to produce their product or service
will be curtailed. This level of "downtime" is often referred to as "business
interruption" and can be expressed in term of time, dollars, or a combination
of both.
by Nathan
C. Gould, D.Sc., P.E., S.E. and Donald Ballantyne,
P.E.
ABS Consulting
In the development of business interruption estimates, the impact of damage
to "lifelines" that support a facility is often ignored. Lifelines are the utilities
and transportation networks that service a facility. If the critical lifelines
are damaged and unavailable for facility operations, significant business interruption
may result.
Lifelines
Lifelines that are typically considered as part of an earthquake or extreme
wind loss estimate are the utilities and primary transportation networks that
serve the facilities or are critical to the delivery of the product. The lifelines
most often considered are:
-
Electric Power
-
Water
-
Telecommunications
-
Highway Transportation
-
Wastewater
-
Natural Gas
Depending on the business, other transportation systems such as air (airports),
water (ports and harbors), and rail (railway bridges) may be critical. Figure
1 shows damaged pipes on fuel jetty at the Port of Kandla, Gujarat, India, after
the 2001 India Earthquake.
FIGURE
1
Services related to information technology (IT) often are included under
the telecommunications category. However, if a facility utilizes highly specialized
IT networks or equipment, additional lifeline categories may be added to the
list above.
Lifeline system performance is a function
of individual system component performance, and their interaction with one another
in the system. Component performance is a function of both the hazard and the
vulnerability of the particular component to that hazard.
Electric Power
Historically, electric power system outages in earthquakes and other natural
disasters have been caused predominantly by damage to electrical substations
and their equipment, primarily damage to elevated porcelain equipment at 230
and 500 kV substations. Heavy, unanchored circuit breakers and transformers
can also be susceptible to sliding and overturning damage as a result of strong
motion.
Major power-generating facilities in California and Japan have seen limited
exposure to major earthquakes. However, many of the existing fossil fuel generating
facilities serving major metropolitan areas are located adjacent to rivers on
what may be liquefiable soils. This may result in damage to the generation facility
itself as well as the loss of the ability to move coal to the facilities.
Transmission and distribution lines (both aboveground and underground) may
experience isolated pockets of damage in areas of fault rupture or ground failure.
Wire slapping may result in short circuits, resulting in tripping of circuit
breakers, but can usually be reset within hours
When determining the potential business interruption issues related to the
electrical power, attention should focus on the number of electrical substations
and distribution networks that currently feed the facility, or that could possibly
be rerouted to provide electrical power to the facility in the short term. Even
if a facility has dual feeds from different substations, both of those substations
may be fed from a single high voltage substation higher up in the system. Facilities
located in regions that have only a single source of power are more vulnerable
as compared to facilities with multiple sources of power. This can be due either
to the configuration of the distribution network and/or the generating facilities.
Water
Water systems are composed of a range of system components for: water supply,
transmission, pumps stations, storage, and distribution. Failure of any of these
components can result in failure of the overall system.
Treatment plants are particularly vulnerable to power outages, equipment
and piping damage, process tank baffle failure, building damage (particularly
if constructed of unreinforced masonry), and structure settlement due to liquefaction.
Pump stations are vulnerable to loss of power, equipment and piping damage,
and building damage. Storage facilities can fail due to shaking of reservoir
embankments causing liquefaction, seismically induced hydraulic loading on reservoir
walls, sloshing wave impact loads on reservoir roofs, roof displacement due
to seismic loading, and damage to connecting piping due to differential movement.
Historically, pipeline damage has had the greatest impact on system operation.
Transmission and distribution pipelines are particularly vulnerable if they
are constructed of brittle materials, such as cast iron. They are the most vulnerable
where the ground deforms as a result of liquefaction or significant settlement.
Water systems following the 1994 Northridge Earthquake in Los Angeles, and
the 1995 Kobe Earthquake in Japan, were not fully restored due to pipeline damage
for 9 days, and 60 days respectively. Figure 2 shows a tank at a water reservoir
that experienced "Elephant's Foot" buckling as a result of the Northridge Earthquake.
FIGURE
2
Telecommunications
Communications systems suffer from several types of impacts in earthquakes:
overload of the system resources, damage to equipment and facilities, loss of
service resulting from power outage, and loss of cooling as a result of loss
of water supply. The two-way nature of telephone service distinguishes it from
other utilities, where service is limited to one-way delivery of a physical
resource. For telephone service, no storage of resources is necessary, and no
supplies are imported.
Continuity of service depends on the operation of critical links in the system
(i.e., switching facilities and central offices), and operability of local circuits.
On a regional and national scale, the flexible nature of the network provides
plenty of redundancy and numerous opportunities to reroute service around failed
nodes. Locally, loss of a central office will likely result in loss of service.
Little evidence of circuit damage due to strong ground shaking has been seen
in previous earthquakes, and there have been several instances of good telecommunications
system performance in areas of significant ground failure. Accordingly, damage
to underground cables is expected only in the most severe instances of ground
failure.
Damage to the central office and its contents may occur in severe ground
motion, and be amplified by ground failure. Loss of power is only a concern
if the central office lacks adequate backup power capability.
Highway Transportation
Bridges are vulnerable to earthquakes due to four general damage mechanisms:
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Bridge spans fall off supports because of inadequate seat width and/or
lack of anchorage of the span to the seat. This can result in catastrophic
collapse and an extended period of restoration.
-
Support columns fail in shear due to inadequate design to carry lateral
loading. This can result in minor damage to catastrophic collapse.
-
Foundations fail due to liquefaction/lateral spreading. This can result
in minor damage to catastrophic collapse.
-
Approaches settle due to consolidation of the soil behind the abutment.
This can result in minor damage that can be quickly repaired.
With the exception of foundation failure, all of the above failure mechanisms
were observed after the 1994 Northridge Earthquake in Los Angeles. As a result
of the bridge failures, traffic was slowed until detour routes were established
and alternate transportation modes were established. The California Department
of Transportation had experience of extensive bridge damage in the 1989 Loma
Prieta earthquake, and had diverted millions of dollars in subsequent years
to seismically upgrade bridges. As a result, less than 10 bridges collapsed
in the 1994 Northridge Earthquake, a small percentage considering several thousand
that were exposed. Without this accelerated program, it would have likely taken
years to restore the Los Angeles highway system to its pre-earthquake performance
level. In contrast, in the 1995 Kobe Earthquake, all types of failure mechanisms
occurred, paralyzing traffic for months.
Wastewater
Components vulnerable to damage in earthquakes include sewers that collect
and transmit the sewage, pump stations, and treatment plants. Damage to sewers
is normally difficult to detect, other than on the basis of visual spills or
odors, because the pipelines flow by gravity, and will continue to flow even
when damaged as long as they are not obstructed.
Sewer collapse is unusual except when significant ground movement occurs.
In the 1994 Northridge Earthquake in Los Angeles, approximately 10 "pump arounds"
were required where sewers collapsed, compared to well over 1,000 water pipeline
failures that occurred in the same area. Sewers constructed of brick are dependent
on the arching structure of the brick across the crown. If the ground surrounding
the sewers liquefies, the sewers may collapse.
Treatment plants and pump stations can fail due to loss of power, damage
to inlet or outlet piping, internal equipment and piping damage, building damage
due to shaking, and movement due to liquefaction. Many pump stations have emergency
generators to keep them functional if the power fails. In most cases, if a treatment
plant or pump station fails, raw sewage will overflow into receiving water before
it backs up into a building.
Natural Gas
Natural gas systems are damaged in earthquakes primarily due to the damage
of buried pipelines. Pipelines subjected to permanent ground movement from soil
liquefaction/lateral spread are the most vulnerable.
Welded steel and polyethylene pipelines can accommodate most ground movements.
Cast iron lines, sometimes used in low-pressure distribution systems and in
older systems in many metropolitan areas, are vulnerable to ground deformation
and shaking due the brittle nature of cast iron.
Summary
When projecting loss estimates as the result of a potential earthquake or
extreme wind hazard, attention should be given to the major lifelines that support
the facility’s operations. Loss of service of key lifelines can lead to increased
downtime following a major natural disaster and may result in significantly
elevated business interruption costs.
Donald Ballantyne is an internationally
known expert on the performance of lifeline systems in earthquakes, other natural
hazards, and man-induced events. He has conducted vulnerability assessments
of over 60 lifeline systems across the United States and abroad including major
assessments of systems serving Vancouver, BC, Seattle, Portland, San Francisco,
and San Jose/the Silicone Valley. He participated in the development of HAZUS,
and has applied it in several major U.S. cities. He has been an invited speaker
for earthquake conferences in the United States, Japan, China, and New Zealand.
He is a past Director of the Earthquake Engineering Research Institute, and
Chair of the ASCE Technical Council on Lifeline Earthquake Engineering. Since
September 11, 2001, Mr. Ballantyne has become certified to train instructors
to conduct security vulnerability assessments of water systems using the Sandia
Laboratory Risk Assessment Methodology, and has evaluated the security risk
and recommended improvements of numerous water and wastewater systems. He has
had the opportunity to participate in reconnaissance missions following major
hazard events in the United States (California and Washington), Costa Rica,
the Philippines, and Asia (Turkey, Japan, India, and Sri Lanka). He authored
publications for the AWWA—Minimizing Earthquake
Damage, A Guide for Water Utilities, and NIST—Reliability
and Restoration of Water Supply Systems for Fire Suppression and Drinking Following
Earthquakes.
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