Following the 1994 Northridge
earthquake, the author surveyed the performance of 479 seismic
gas shutoff valves (SGSVs) at 255 sites, and the responses
of 15 fire departments to gas-related incidents. The locations
and performances of these SGSVs during the mainshock have
been mapped along with the locations of gas-related fires
and areas with the most damaged buildings. Most surveyed SGSVs
within 29 km of the mainshock’s epicenter closed; with one
exception, the closest nonactuated SGSV was over 14 km away.
SGSVs prevented numerous gas-related fires or explosions,
which reduced the need for water, firefighters, and other
emergency services. Los Angeles-area fire departments received
numerous calls reporting gas leaks, fires, and other incidents.
Fire departments responded to over 1,000 reported gas leaks
and at least 50 gas-related structure fires. The gas utility
reported over 14,000 leaks on consumers’ lines, including
162 buildings where a SGSV closed. If the earthquake had been
stronger, occurred during regular business hours, or been
accompanied by strong winds, many neighborhoods might have
burned and lives could have been jeopardized from fire or
smoke--a potential catastrophe for any seismically prone urban
area. In 1995, Los Angeles adopted a law requiring an approved
SGSV to be installed on all gas-serviced new construction
and commercial remodels over $10,000. Los Angeles’ City Council
is reviewing a draft ordinance that would expand its program
to include installation of an approved SGSV on all remodels
over $10,000, and all transfers of ownership within one year.
Los Angeles’ Public Works Committee has recommended that the
Building & Safety Department should start planning the
best way to expand the program to include every building within
the City, and explore the establishment of operational design
standards that would upgrade those established by the national
and California standards. A proposed new national standard
for SGSVs, expected to be published in late 1997, would allow
devices that are capable of reopening during an aftershock.
The U.S. Consumer Products Safety Commission launched an investigation
in March 1997 into the safety of all SGSVs manufactured or
sold in the U.S.
The author began collecting performance
data immediately following the Northridge earthquake as a
volunteer effort on behalf of two Committees of the American
Society of Civil Engineers (ASCE): the Lifeline Investigations
Committee of the Technical Council on Lifeline Earthquake
Engineering (TCLEE), and the Standards Committee on Earthquake
Actuated Automatic Gas Shutoff Valves. Persons responsible
for one or more SGSVs were asked the following questions:
1) What was the size, make, and model of the SGSV? 2) When
was the SGSV installed? 3) Was the SGSV tripped by the mainshock?
4) Were there any gas leaks? 5) If the SGSV tripped before,
when? 6) Was the SGSV tripped by any aftershocks?
Respondents were not asked if
their SGSV(s) had automatically reopened. It could be difficult
to determine whether an installed SGSV with this capability
had closed and then reopened on its own during an aftershock,
or simply not closed at all. By design, over 84% of the surveyed
SGSVs are unable to reopen on their own; over 10,000 SGSVs
that can, however, have been installed since the Northridge
Performance OF SGSVS
As many SGSVs as possible, regardless
of make, were surveyed. Sources included: SGSV manufacturers,
plumbers and plant engineers who returned questionnaires distributed
at trade shows, and the author’s sales files. Nine brands
were included in the survey: Dove (2), Engdahl
(5), Koso (404), McCray (3), Quake Defense
(5), Quake Master (23), Safe-T-Quake (1), Sentinel
(16), and Sismo (12); unknown (8). The large number
of Koso (also known as California) SGSVs in
the survey is primarily because the author has represented
their manufacturer, Pacific Seismic Products, Inc., since
1987; but also because a majority of the installed SGSVs in
southern California during the earthquake were Kosos.
Most of the surveyed Quake Masters were installed in
1985--1987, when the author represented their manufacturer.
Three SGSV manufacturers provided information on the performance
of 22 SGSVs; two declined to participate. All the surveyed
SGSVs, except for the McCrays and Sentinels,
were certified by California’s Office (since renamed Division)
of the State Architect, which became a requirement in California
in 1987. 83% of the surveyed sites were commercial, institutional,
or governmental buildings; 17% were single-family dwellings,
duplexes, or small apartment buildings. 42% of the Kosos
were industrial-type valves or seismic actuators; 74% of the
Quake Masters and 94% of the Sentinels were
also industrial-type valves.
The Joint OES-FEMA Disaster Field Office (1995)
printed a two-map set showing the locations and performances
of the surveyed SGSVs, locations of gas-related fires, and
areas with the most damaged buildings. One of the maps in
the first edition is reproduced in Honegger (1995) and includes
the first 412 SGSVs surveyed. The second edition includes
the locations and performances of all 479 surveyed SGSVs,
plus the locations of 260 of the 841 SGSVs that were reset
by Southern California Gas Company. A third edition is expected
to be finished before this Conference (EQE International,
in preparation). The maps show that the closest surveyed SGSVs
to the epicenter that did not close during the mainshock,
with the exception of one valve in Northridge, were 14--18
km away, in the Santa Monica Mountains; most SGSVs within
29 km of the epicenter closed. The furthest surveyed SGSV
from the epicenter that did not close was in Costa Mesa (79
km). At Long Beach Naval Station (51 km), which is built on
fill, all 38 SGSVs installed in 1989 closed for the first
time, while in downtown Long Beach (53 km), both surveyed
SGSVs did not close. Most surveyed SGSVs closed within areas
where a large number of buildings were damaged.
The local utility found a gas leak in 162 of
the 841 buildings for which it was requested to reset a SGSV
(Southern California Gas Company, 1994). Four of the surveyed
SGSVs shut off the gas to a building with a broken gas-piping
system. A 3" (76-mm) SGSV shut off the gas to Santa Monica
College’s Arts Building, which suffered a broken gas line
on the roof, and Science Building, which has been demolished
(See Figures 1 and 2). A 4" (102-mm) SGSV shut off the gas
at an industrial plant in Chatsworth whose gas piping broke
in several places. A 3/4" (19-mm) SGSV shut off the gas to
a mobilehome in Santa Clarita whose flex piping beneath it
was broken in 4 places when it fell off its foundation. At
CSUN, the SGSV on the campus’ main line closed, as did both
SGSVs at the Student Union’s satellite facility, which is
a block north of the Student Union building. The SGSV at the
Student Union building did not close; it is the same brand
as the 2 at the satellite facility that did, although its
setpoints and orientation were different. The Student Union
building’s SGSV was installed in 1991 in an east-west direction
about 1’ (254 mm) above grade, on a 3" (76-mm) manifold that
was braced to the western wall of a concrete-block enclosure.
The Student Union’s maintenance supervisor observed early
on the morning of January 18, 1994, that the SGSV was open;
and he is certain that no one else would have turned it back
on if it had closed (Strand, 1995). The SGSV and the manifold
it was installed in were removed after the survey (S. Larson,
personal comm., 1997). Pacific Seismic Products, Inc., the
manufacturer, examined the SGSV in June 1997, found no defects,
and performed 3 shake-table tests along each horizontal axis.
The average setpoints in the longitudinal direction (E-W)
were 23.2% g at 1 Hz, 11.4% g at 2.5 Hz, and > 40% g at 10 Hz; in the latitudinal direction (N-S),
the average setpoints were > 30% g, 13.2% g, and > 40% g, respectively.
3" (76-MM) MODEL 315-HPF KOSO SGSV THAT
SHUT OFF THE GAS LINE TO THE ARTS BUILDING & SCIENCE BUILDING
AT SANTA MONICA COLLEGE DURING THE NORTHRIDGE EARTHQUAKE
1-1/2" (38-MM), SCHEDULE 40, BLACK-IRON
GAS PIPE THAT BROKE IN A THREADED AREA NEAR A COUPLING ON
THE ROOF OF THE ARTS BUILDING AT SANTA MONICA COLLEGE WHEN
THE HVAC UNIT ON THE RIGHT SHIFTED ABOUT 14" (356 MM)
Response of Fire Departments to Gas-Related Incidents
The author surveyed 15 fire departments,
most of which experienced a tremendous surge in calls after
the mainshock. It was impossible to record all the calls and
responses due to the large volume or the failure of their
computer systems with the area-wide loss of power. Responses
to reports of gas odors, gas leaks, or gas-related structure
fires or explosions comprised a large portion of the recorded
responses (See Table 1).
FIRE-DEPARTMENT RESPONSES ON JANUARY 17, 1994
||Gas odors & leaks:
||Total fires/ explosions
||Total responses (normal
|Los Angeles Co.
In Fillmore, a gas line was severed near the
meter when a mobilehome fell off its foundation, resulting
in a total loss. Another fire, which lasted over 2 hours,
started when a 15- to 30-m-high column of natural gas escaping
from a break in a 6" (152-mm) main beneath Highway 126 was
ignited by static electricity; ironically, the fire scorched
the front of a sprinkler-system plant (Chief Askrin, personal
In Los Angeles, gas-related fires occurred in
24 single-family dwellings, 5 apartment buildings, 3 businesses,
and 6 mobilehome parks. Causes included broken lines to 21
water heaters, 5 trailers, 2 floor heaters, and 2 dryers;
plus leaks in an attic, a kitchen, at 2 meters, and between
a meter and a building. Two fires occurred prior to the meter:
one where a block wall fell on a meter and another where a
large main ruptured (Los Angeles Fire Department, 1994); the
latter burned five homes. Two of the mobilehome-park fires
burned 54 and 59 trailers; in all, 144 trailers were lost
to fire in Los Angeles. Los Angeles’ Fire Marshall, Chief
Parsons, is concerned that if the mainshock had occurred during
the middle of the day, more leaks may have been reported that
needed the gas company or the fire department to respond,
and that some fires would have spread into the surrounding
neighborhoods (Cluff, 1994).
On the day of the mainshock--and also on the
day after--the Los Angeles County Fire Department (LACFD)
had a five-fold increase in the number of recorded responses,
based on 20-year daily averages (See Table 2). On the fourth
day after the mainshock, the total responses were down to
200% of normal.
LOS ANGELES COUNTY FIRE DEPARTMENT’S RECORDED
RESPONSES ON JANUARY 17-18, 1994
||Gas leaks & other
|Total calls/ responses
|January 17, 1994
|January 18, 1994
The widespread loss of power forced the LACFD’s
Command and Control (CC) to switch to the Area Command (AC)
mode, in which engines went from site to site. The AC never
told the CC the number of responses it made, because the Initial
Incident Commander was too busy to write down any of the responses.
Calls made to the Santa Clarita Sheriff’s Office or the Santa
Clarita EOC were also not recorded, because structural damage
to their buildings forced those agencies to move to Santa
Clarita’s City Hall; from where they were moved again into
communications trailers and tents in the parking lot when
it was discovered that City Hall was damaged, too. Three mobilehome
parks within LACFD’s jurisdiction had fires, including one
that burned 11 trailers. When the mobilehomes came down, they
dropped flat and sheared the lines near the meters (Chief
David Horn, personal comm., 1995).
Pasadena’s single earthquake-related fire was
caused by a gas leak near a stove in a restaurant; activation
of the fire-sprinkler system kept the fire from spreading
(D. Rosetti, personal comm., 1995). In Santa Monica, leaking
gas caused 4 fires, one of which began as an explosion due
to a ruptured line on the second-floor of a 10-unit apartment
building, which was a total loss; 3 adjacent structures were
ignited, but were saved by the local fire department. The
other 3 fires were caused by leaks in a crawl space, a kitchen,
and a second-floor bedroom (Chief Collier, personal comm.,
1995). In Simi Valley, 3 gas-related fires were caused by
a leak in the connecting pipe to a water heater, a flame from
a central-heater pilot, and a water-heater pilot that ignited
paper boxes that fell from shelves (Alex Sanchez, personal
California’s Division of Codes and Standards,
Department of Housing and Community Development (1995), reported
that 176 mobilehomes were burned following the mainshock.
Because most of those fires were gas-related, a report by
the Seismic Safety Commission, State of California (1995),
recommended that a SGSV be installed on the main service line
at all mobilehome parks, and that the Public Utilities Commission
(PUC) conduct hearings and workshops to determine the best
method for providing SGSVs for mobilehome parks and appropriate
performance standards. Provisions that would have required
a SGSV on the main service line at all mobilehome parks in
California by the year 2000 A.D. were deleted from SB 577
before it was passed. The author believes that for mobilehome
parks, the best solution is to install a SGSV not only on
each park’s service main, but also on the service line for
each trailer, because the large volume of gas in most parks’
distribution lines would still pose a hazard to trailers with
damaged gas lines.
14,062 natural gas leaks were
reported in customer facilities after the Northridge earthquake
(Southern California Gas Company, 1994). Southern California
Gas Company’s restoration efforts included 61,172 leak orders
and 122,300 restores. 88% of the 150,800 outages in 3 regions
were due to customers shutting off the gas themselves; 9,100
were left off due to structural damage (Cluff, 1994). FEMA
processed over 400,000 claims for water-heater damage and
over 700,000 claims for all gas appliances, including stoves,
furnaces, ranges, and dryers); amounts claimed ranged from
minor repair to replacement (Honegger, 1995).
Update on Legislation and Standards Development
Los Angeles Ordinance 170641, which took effect
on September 1, 1995, requires the installation of a Los Angeles-approved
seismic gas shutoff valve on all gas-serviced new construction
and commercial remodels valued over $10,000. It also raised
the nonactuation level of 0.08 g horizontal acceleration for
frequencies of 1 and 2.5 Hz, which was established by ANSI
Standard Z21.70 and California State Building Standard 12-23-1,
to 0.20 g, and requires each SGSV to be braced to the outside
wall or foundation of the building it protects and to be warranted
by its manufacturer for 30 years. To meet Los Angeles’ higher
nonactuation level for 1 and 2.5 Hz, manufacturers of 7 brands
of Los Angeles-approved SGSVs modified their products’ trigger
mechanisms from what they were in April and May of 1995, when
shake-table tests were performed for ASCE’s Standards Committee.
Those tests were done only on SGSVs that were rigidly mounted
in their normal upright position; none of the SGSVs were shaken
in a tilted position (Diehl, 1995).
Los Angeles’ Public Safety Committee is reviewing
a revised version of Ordinance 170641, which, if adopted,
would increase the City’s program by requiring an approved
SGSV to be installed on all remodels valued over $10,000,
and all transfers of ownership within one year of sale. Los
Angeles’ Public Works Committee recommended to the City Council
that it direct the Building & Safety Department to make
recommendations within ten months on the best way to expand
the program to include every gas-serviced building within
the City, explore the establishment of operational design
standards that would upgrade those established by the national
and California standards, and put manufacturers and installers
on notice that the City reserves the right to upgrade the
standards in the future (AlarcÛ n, 1997). Public Works Committee
Chair Richard AlarcÛ n wants to be assured that only high-quality
devices are being installed, and believes that the Building
& Safety Department should be responsible for reviewing
the quality of SGSVs and possible design flaws, such as the
potential for reopening during an aftershock.
In connection with the development of the first
ANSI standard for SGSVs, Southern California Gas Company prepared
a list of 9 criteria for an ideal SGSV (Davis, 1978). Number
two on its list was that:
Once closed [a SGSV] should not be subject
to being accidentally opened by the service line in which
it is installed being sharply displaced from its original
vertical or horizontal orientation, or by sudden changes
in the upstream gas pressure whether increasing or decreasing.
I.e., once the valve has closed, it should remain "locked
out" until it is reset by an outside agency.
It seems odd, therefore, to find Southern California Gas Company‘s
logo on SGSVs that do not meet that criteria. Southern California
Gas Company’s parent, Pacific Enterprises, created a subsidiary
called Energy Services (PEES), that has heavily marketed its
SGSVs since September 1996, when the PUC granted the utility
permission to install Los Angeles-approved SGSVs on its side
of the meter, with the understanding that it would no longer
sell SGSVs. Much controversy has ensued since the PUC’s ruling,
primarily because of widespread complaints from within the
plumbing and heating profession about the inherent unfairness
of trying to compete against a monopoly, but also because
of questions that have been raised about the safety of PEES’
SGSVs (California Energy Markets, 1997; Hays, 1997a; and Wartzman,
1997). In late April 1997, the PUC made a tentative decision
in favor of a complaint filed on behalf of the California
Association of Plumbing, Heating and Cooling Contractors that:
By the very nature of SoCal’s monopoly position
in the energy and energy services market, its access to
comprehensive customer records, its access to an established
billing system, and its ‘name brand’ recognition, it must
be presumed that SoCal enjoys significant market power
with respect to any new product or service in the energy
field (Hays, 1997b).
The PUC also started a Rulemaking and Investigations
Docket to consider whether any utility or any affiliate of
a utility should be allowed to enter any of the unregulated
services fields, where they would be competing with private
contractors (Hays, 1997b).
ASCE’s Standards Committee on Earthquake Actuated Automatic Gas
Shutoff Systems submitted its proposed national standard to
public balloting in March and April, 1997. Three respondents
each proposed a new provision that would require a SGSV to
remain closed, regardless of tilt, until manually reset. Standards
Committee Chair Doug Honegger believes that none of the arguments
made in support of adding any of the three proposed provisions
are persuasive. It remains to be seen if the rest of the Committee
will express enough support for one of the proposals to require
a Committee vote. If the proposed standard remains as it is,
it will likely be published by the end of 1997; if it is modified,
it might not be published until spring 1998, because it would
have to be submitted to public balloting again (Doug Honegger,
personal comm., 1997).
California’s Seismic Safety Commission has recommended
that the Division of the State Architect review its SGSV-certification
requirements and revise them to improve the reliability of
SGSVs (Seismic Safety Commission, State of California, 1995).
The Division of the State Architect will likely wait until
the proposed new national standard is published before it
takes any action.
The National Institute of Standards and Technology
(NIST) recognizes the potential of SGSVs to reduce the number
of gas-related fires, and has suggested that to better understand
their short- and long-term advantages and disadvantages, NIST
should encourage a partnership of interested organizations
to quantify the performance of SGSVs during past earthquakes,
identify potential improvements in design or application,
quantify the benefits, risks, and costs associated with SGSVs,
and establish SGSV performance criteria for service and distribution
lines (Chung et al, 1995).
The U.S. Consumer Products Safety Commission
launched an investigation in March 1997 into the safety of
all SGSVs being manufactured or sold in the United States,
after it was demonstrated to them that at least two brands
currently on the market can reopen themselves when tilted
or shaken. The Commission is also looking into other safety
aspects of SGSVs.
Alarcón, R. (1997). "Communication
from Chair, Public Works Committee Relative to Requiring Installation
of Earthquake Shut-Off (EQSO) Valves in all Existing Buildings
and Structures," Unpublished ms., Los Angeles City Council
File No. 95-0217-S1, 5 pp.
California Energy Markets (1997). "Gas Shut-Off Valve Ordinance
Approved in LA; Controversy Rises," California Energy Markets, February 28,
1997, no. 402, pp. 11-12.
Chung, Riley M. et. al. (1995). "Post-Earthquake Fire and
Lifelines Workshop; Long Beach, California, January 30-31, 1995, Proceedings,"
U.S. Department of Commerce, Technology Administration, National Institute of
Standards and Technology, NIST Special Publication 889, p. 15.
Cluff, L. S. (1994). "Minutes of Workshop on Seismic Safety of
Natural Gas Systems," Unpublished ms., Sponsored by the California Seismic
Safety Commission and the Utilities Safety Branch of the California Public
Utilities Commission, Los Angeles, 32 pp., with attachments.
Davis, Oliver C. (1978). "Letter to Mr. S. L. Bachman, Chief
Methods Engineer, A.G.A. Laboratories," February 23, 1978, Unpublished ms., 2
pp., with attachment.
Diehl, J. G. (1995). "Vibration Testing of Fifteen Earthquake
Actuated Automatic Gas Shutoff Systems: An Engineering Evaluation," Report
prepared for the ASCE Prestandards Committee for Earthquake Actuated Automatic
Gas Shutoff Systems, Agbabian Associates Report 9515-6580.
Division of Codes and Standards, Department of Housing and
Community Development (1995). "Mobilehome Park Statistics, Northridge Earthquake
Response," Unpublished ms., 3 pp.
EQE International (in preparation). "The Northridge Earthquake
Natural Gas Report."
Hays, Scott (1997a). "Earthquake Safety Valves," Reeves Journal,
v. 77, no. 5, April 1997, pp. 20-22, 24, and 26.
Hays, Scott (1997b). "Let’s Get Ready to Rumble!" Reeves
Journal, v. 77, no. 6, June 1997, p. 6.
Honegger, D. G. (1995). "Automatic Gas Shutoff Device Actuation
Requirements Based on Damage in the January 17, 1994 Northridge Earthquake,"
Report prepared for ASCE, EQE Report 52316.01.
Joint OES-FEMA Disaster Field Office (1995). "Location of
Automatic Gas Shutoff Valves and Fires Related to Gas Leakage," Northridge
Earthquake Disaster DR-1008, Unpublished ms., 2 maps.
Los Angeles Fire Department (1994). "Natural Gas Related Fires
as a Result of the January 17, 1994, Earthquake," Unpublished ms., 4
Seismic Safety Commission, State of California (1995).
"Northridge Earthquake, Turning Loss to Gain," Report to Governor Pete Wilson in
response to Governor’s Executive Order W-78-94, SSC Report No. 95-01, 145
Southern California Gas Company (1994). "1994 Northridge
Earthquake Effects on SoCalGas Piping System," Unpublished ms., 3 pp.
Strand, C. L. (1995). "Gas Leaks, Gas-Related Fires, and
Performance of Seismic Gas Shutoff Valves During the Northridge Earthquake,"
in O’Rourke, M. J. (1995). "Proceedings of the Fourth U.S. Conference on
Lifeline Earthquake Engineering," ASCE’s Technical Council on Lifeline
Earthquake Engineering, New York, New York, pp. 692-699.
Wartzman, R. (1997). "Gas Company Accused of Unfair Power Play,"
The Wall Street Journal, March 12, 1997, p. CA2.
The author thanks all the survey participants, the 15 fire
departments, and Southern California Gas Company for sharing their information;
Earthquake Safety Products, Engdahl Enterprises, and Quake Defense for providing
performance data for their SGSVs; EQE International for including the survey’s
data on SGSVs and gas-related fires on their maps; Doug Honegger for sharing his
insights during our five years together on ASCE’s Standards Committee; and
Anshel Schiff and LeVal Lud for their training and guidance during our nine
years together on ASCE/TCLEE’s Earthquake Investigations
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