SR-416-004 (2)
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January 12, 1988
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Santa Monica, California
rNFORMATION ITEM
TO:
Mayor and City council
FROM:
City Staff
SUBJECT:
Automatic Gas Turn-off Valves
INTRODUCTION
The following outlines the pros and cons of installing automatic
gas turn-off valves to insure against gas leaks in the event of
an earthquake.
DISCUSSION
Features of the Automatic Gas Shut-off Valve Product
In recent years, several manufacturers have introduced automatic
gas turn-off valves which can be installed at the meters of
private residences, businesses and institutions. Such valves are
designed to turn off gas flow to meters in the event of an
earthquake of moderate magnitude, thereby mitigating against the
gas leakages which can trigger explosions and fires after an
earthquake.
Installation of automatic gas shut-off valves has been criticized
due to their tendency to be triggered by any sizable vibration,
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be that vibration a mild earthquake or the result of movement of
nearby heavy equipment. Whenever such a mal function occurs, a
Gas Company representative or a licensed plumber must restore gas
service to the affected user. When this issue was discussed with
a seismic engineer currently being used by the City to design an
earthquake bracing program for City structures, he commented that
although the product has malfunctioned in the past, many of the
shut-off valve products currently on the market have been
perfected to insure that the automatic shut-off feature is only
triggered by substantial ground shaking resulting from a moderate
to severe earthquake.
Position of the Southern California Gas Company
The Southern California Gas Company has developed a position
paper on the installation of automatic gas shut-off valves, a
copy of which is attached for Council review. In essence, the
Gas Company questions both the reliability of the product and the
necessity of installing such devices to mitigate against gas
leakages and fires in the event of an earthquake.
In particular, the Gas Company argues that, based on the
behaviour of the gas line system in past earthquakes of moderate
to severe magnitude, very few fires resulted from gas leakages
and, as such, automatic shut-Off of gas flow to residences and
businesses was not warranted. In addition, considerable delays
in the restoration of gas service could result were Gas Company
employees forced to perform system tests on hundreds or thousands
of residences after an earthquake.
As such,
individual
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residences and businesses could be forced to go for days without
the comfort of gas service.
Position of City staff
It is the opinion of City staff that, although individual
homeowners and businesses may elect to install automatic gas
shut-off valve devices, it is not advisable for the City to
require their installation due to the potential for product
malfunction, the past performance of gas systems under moderate
to severe earthquakes, and the procedures for central gas
shut-off by the Gas Company in the event of a severe magnitude
earthquake. It may be advisable, however, to investigate the
installation of such devices on all City facilities since the
City employs several staffmembers qualified to restore gas
service in the event it is shut-off. Such installation would
help to insure that City structures were protected in the event a
moderate to severe earthquake occurred during evening hours when
City structures are sparsely staffed.
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SOUTHERN CALIFORNIA 19_osl COMPAND
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100 EAST NUT'NOOD SfI'IEET . 'NGLEWOOC. CALIFORNIA
NORMA L GONZA!..ES
Dtstpct Manage"
MA'L1f';G ADDRESS 1228 FIFTH SfREET SANT... MONICA CALI~Ol=iNIA 90401
(213) 330 2277
(213) 393 0395
January 7, 1988
Ms. Lynn Barrett, Assistant City Manager
Santa Mon1ca
1685 Maln Street
Santa Monlca, Ca. 90401
Dear Lynn:
Thank you very much for your telephone call advising me of the
upcoming study session next Tuesday, January 12, 1988.
Enclosed for your 1nformation 1S the Southern California Gas
Company's background paper on "Earthquake Shutoff Devices For
a Building's Gas Piplng System.ll
Will you please feel free to call me 1f I may be of help.
Cordially,
'4 -L~ d
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NLG: cb
Attachment
cc: B. R. I>lare
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BACKGROUND PAPER:
Earthquake Shutoff Devices For a Building's Gas Piping System
Introduction
Commonly~ aftex each major earthquake, numerous proposals
are made at the state and local levels of government to
mandate natural ga8 automatic shutoff devices.
Southern California Gas Co. (SoCalGas) believes there is no
compelling evidence to warrant mandating the public to spend
millions of dollars installing this equipment. For example,
'preliminary information from tbe recent Whittier earthquake
shows that only five minor fires, resulting in an estimated
$2,000 in ~otal damage, were caused by broken natural gas.
lines. At the same time, as many as 3 million customers
would have been without service if shutoff devices had been
mandated.
This paper explains the gas company's position on proposals
~o mandate the installation of automatic shutoff equipment.
It includes a brief explanation of how the devices operate
and problema presented by their operation_ Also included is
a summary of experience from previous earthquakes, a brief
description of the gas company's emergency procedures and
steps customers can take to improve the safety of their
natural gas appliances in the event of an earthquake.
~ow Dev~ees Operate
Only three earthquake shutoff devices have been approved for
sale in California by the state architect. Each of them
closes off a buildinq's natural gas supply when vibration or
ground acceleration reaches a predetermined level. They
will do this whether or not damage has occurred to the gas
lines they are designed to protect.
For example, earthquake shutoff equipment has been known to
be triggered by vibrations from an earthquake that is
centered miles away. During the recent Whittier earthquake,
these devices abut off natural gas to homes as far away as
Riverside (45 ailes). None of the gas lines to these homes
were damaged during the earthquake.
~e~~oring ,~erv1ce
Because theEe is 80 much more involved than merely turning
~he meter back on, only a licensed plumber or trained gas
company service Eepreaentative is fully qualified to restore
natural gas service after it has been interrupted.
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When ou~ service people resto~e service, they close the
pilots on all appliances and check to make sure there a~e no
leaks in the system. They also make su~e that ai~, which
may have been allowed into the piping by the gas being shut
off. 1s purged from the system before ~eli9hting the
appliances. Additionally, ou~ se~vice ~epresentatives
inspect ell the gas appliances to make certain they a~e
operating and venting properly.
. Restoring natural gas service properly to one home normally
takes from 20 to 30 minutes. More time would be needed if a
potential problem is detected.
AfteE an earthquake. it likely will take awhile until a
service person can get to the home to reset the shutoff
device and restore service. For example, during the
Whittier earthquake. 21,074 customers turned off their gas
needlessly. It took approximately 150 people, workinq
lO-hour shifts, one week to resto~e service to everyone.
The restoration problem would have been astronomical if
shutoff devices had been mandated. SoCalGas estimates
3 million of the company's 4.37 million customers would have
been without se%vice. From two to three months and mo~e
than $25 million in needless expense would have been
~equl~ed to put all customers back on line.
Emergency Procedures
In any emergency situation, our primary concern is to
protect the public safety. Thus, during an earthquake, we
first would check our system and repair any leaks or
pipeline breaks that might have occu~red. We also would
restore service to facilities needed during the emergency,
such as hospitals or evacuation centers. Resetting closed
earthquake shutoff devices would be a low priority and would
be done only after all emergency conditions are resolved.
There are 9as company employees, ranging from executives to
service people, on-call 24-hours-a-day. In the event of an
earthquake, they.know where to go and what to do. Some
employees. for example, will check our major pipelines to
dete~1ne if any have been damaged and must be shutdown. At
the same time, other employees will report to the company's
Emergency Response Center. These employees will monitor
activities in the field, make needed policy decisions and
coordinate efforts to obtain equipment or people from other
parte of the company ox other utilities.
The company's emergency p~ocedu~es are tested during
extensive, annual training exercises. Company
representatives also pa~tlcipate in appropxiate community
committees dealing with emergency prepa~edness issues.
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Experience From Previous Earthquakes
Experience from earthquakes since 1933 indicates that
natural gas leaks and resulting fires have been minimal.
No fires involving natural gas occurred during the
earthquake in Palm Springs in July 1986. Also, only three
minor leaks were discovered in customers' house piping. All
of the leaks were at appliance connections, and two of the
three may have existed before the earthquake.
Mexico City, which experienced an earthquake measuring 8.1
on the Richter Scale in September 1985, does not have a gas
distribution system similar to that of SoCalGas. In Mexico
City, residents use a mixture of liquid propane and butane
tbat is stored in tanks on the roofs of buildings. However,
a town, just 20 miles north of Mexico City, does have a
system similar to OurS. In this town, as well as Mexico
City, there were no deaths, fires or explosions attributed
to natural gas leakage caused by the earthquake.
On Oct. 15, 1979, an earthquake measuring 6.5 on the Richter
Scale shook Imperial Valley. There were no deaths, but
property damage fram the temblor was valued at millions of
dolla~s. Still. the earthquake caused no major damage to
company gas lines and there were no natu~a1 gas related
f1res. About 75 gas leaks in homes may have been caused by
the earthquake. About 45 of these apparently occurred when
water heaters toppled. Although 98 mobile homes were jolted
1ram their supports, no natural gas fires resulted.
On February 9, 1971, an earthquake measuring 6.4 on the
Richter Scale shook the San Fernando Valley and surrounding
areas. The earthquake resulted in the loss of 64 lives and
millions of dollars in property damage. None of these
deaths and very little of the property damage can be
attributed -to natural gas leaks. A summary of calls to the
Los Angeles Fire Department on February 9 and 10 showed the
Lollowing:
o ~ere we~e no calls due to explosion from natural
gas. ·
o There were 28 reports of natural gas leakage that
did not involve fire in the San Fernando Valley area
and 13 in other areas served by the department.
o 7bere were three calls in the San Fernando Valley
and three from other BEea. in the department's
jurisdiction involving fires associated with natural
gAS. The total estimated loss due to fire damage
was about $4,300.
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o There wexe six requests in the San Fernando Valley
and 10 from other areas served by the department to
respond to fires associated with heating equipment
(gas or electric). The cause of one of these fires
was determined to be the earthquake. The others did
not have a cause noted. The total estimated loss
due to these fires was less than $12,000.
A report published by the u. S. Department of Commerce after
this earthquake states;. "In general, the gas system
sustained the stresses of the earthquake remarkably well.
This was borne out by the fact that in many areas where
appreciable damage occurred to buildings, tbe gas system
remained intact." The report further states that although
there were isolated instances where water heaters overturned
and broke 1008e* .... damage to buildings by fires
associated with gas was nil or relatively minor."
California's worst experience with earthquakes occurred in
San Francisco in 1906. Historical records indicate that the
fire that followed the earthquake was not caused by escaping
gas, but primarily by wood, coke and coal fires that spilled
onto combustible floors. The fires raged out of control
because there was a shortage of water, caused by broken
water mains, to fight them. Since then, technology and fire
departments' capabilities have improved significantly,
making a repeat of this experience unlikely.
Info~ation on the 1933 Long Beach earthquake also is
sketchy. However, our review of accounts and examination of
photographs do not indicate that fire was a cause of great
damage. It also should be noted that the Long Beach
experience resulted in building code changes so all
structures built since then are more quake resistant.
Implication~ of Automatic Shutoff
After the Sylmar quake 1n 1971, gas was the only utility
service available in many areaS for comfort heating, cooking
and sterilization.of water. The health of infants, the
eldeEly. the Inf~r.m and others could be impaired if they
have to go a long- while without natural gas for beat,
sterilizing water and cooking unrefrigerated food.
Because existing earthquake shutoff equipment is triggered
by movement, rather than indication of a leak or pipeline
break, many people would be without se~vlce needlessly.
Still. they would have to wait until a gas company service
pe~son or a plumbeE-could get to their homes to check the
system and restore service. ~b18 could evolve into a
dangezDD& situation if someone were to become impatient and
~ry to restoE. service himself. Furthermore, aftershocks
can repeatedly close the reset earthquake valve.
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Alternatives to Shutoff Valves
If an individual wants the extra feeling of security that
migbt come from knowing that his or her natural gas service
will be closed automatically during an earthquake, then he
or she may want to install a shutoff device. The Gas
Company does not object ~o this voluntary action.
However, a person who smells gas can easily shut off the
service himself or herself with an open-end, adjustable
wrencb that Is heavy enough to provide the leverage needed
to shut off the service. Instructions on how to shut off a
meter with a wrench are ~istributed regularly to our
cus~omers. Instruc~ions, with illustrations, also are in
the .Survival Guide" of the telephone directory.
Customers can also take advance precautionary measures by
stabilizing their natural gas appliances to prevent gas
lines from twisting and cracking_ Hot water heaters, for
example, should be strapped to a nearby wall to help prevent
them from moving or falling over. In addition, this would
protect what might be the only sanitary water souxce
available after an eartbquake_
Conclusion
There is no compelling evidence that mandatory installation
of earthquake shutoff devices is needed to prevent fires
resulting from natural gas leaks during an earthquake. In
addition, experience indicates that many homes and
businesses would be without a fuel needed for survival for
an extended period of time. Therefore, SoCalGas does not
believe homeowners should be forced by law to spend millions
of dollars to install earthquake shutoff equipment.
Southern Californ!a Gas Company
OCtober 1987 ~
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AGENDA
CITY COUNCIL STUDY SESSION ON EARTHQUAKE PREPAREDNESS
JANUARY 12, 1988
6:00 PM
I) Introductory Comments (5 minutes)
II) Location and potential for Seismic Activity Involving
the city of Santa Monica (20 minutes)
Tom Heaton, Chief Seismologist
u.S. Geological Survey, Pasadena
III) Earthquake Preparedness Training and Coordinated
Earthquake Response Plans (20 minutes)
Laura Hernandez
Emergency Services Coordinator
IV) Pros and Cons of Automatic Gas Shut-off Devices (10
minutes)
Julia Griffin
V)
Seismic Safety Requirements for structures (20 minutes)
Bill Rome
Building Official
Peggy Curran
Director, Community and Economic Development
Department
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