FEDERAL EMERGENCY MANAGEAMENT AGENCY FEMA-221 October 1991 
Collocation Impacts 
on the 
Vulnerability of Lifelines During 
Earthquakes with Applications 
to the 
Cajon Pass, California 
Study Overview 
Published in Support of the 
Decade for Natural Disaster Reduction 
Earthquake Hazard Reduction Series 59 
COLLOCATION IMPACTS ON LIFELINE EARTHQUAKE VULNERABILITY
Figure 1: General Location of the Cajon Pass, California 3
Figure 2: Identification of Lifeline Collocations at
Figure 3
Figure 4
Figure 5
Figure 6: Power Line, Natural Gas and Petroleum Products
Figure 7: Power Lines at a Ravine Edge at the San Andreas
Figure 8
Figure 9
EXECUTIVE SUMMARY 1.
ADDITIONAL CONCLUSIONS. 2
STUDY RESULTS 5
The Screening Tool 5
Cajon Pass, California. 6
Communication Lifelines. 7
Electric Power Lifelines. 10
Fuel Pipeline Lifelines. 13
Transportation Lifelines. 17
Cajon Pass 
4: Fiber Optic Conduits Hung Under a Water 
Distribution Pipe On a Bridge Over a Railroad 8: Fiber Optic Conduits on a Bridge On An Abandoned
Portion of Highway 66. 9: Details of Fiber Optic Conduit Supports on a Highway 
Culvert Wall 9
Pipelines Over the San Andreas Fault. 11
Fault. 12: Electric Power Towers in a Landslide Scar (Directly
Above a Fuel Pipeline and a Railroad). 12: Two Natural Gas Pipelines, One Exposed One Buried,
Next to Highway 138. 14
Figure 1O: A Railroad Bridge Estimated to -Collapse Onto 
Highway 138. 18
Figure ll: Railroad and I-15 Bridges in Cajon Wash Subject
to Liquefaction Damage. 19
AT THE CAJON PASS, CALIFORNIA
STUDY OVERVIEW
TABLE OF CONTENTS ITEM 
PAGE
List of Figures
COLLOCATION IMPACTS ON LIFELINE EARTHQUAKE VULNERABILITY
AT THE CAJON PASS, CALIFORNIA
STUDY OVERVIEW
EXECUTIVE SUMMARY
Lifelines are those systems and facilities that deliver vital 
services and products to a community. These include transportation
facilities; electric power systems; fuel transmission pipelines and
facilities; communication facilities; and such health facilities as
drinking water and sewer systems. For a number of reasons,
lifelines frequently are collocated or routed in close proximity to 
each other. The current emphasis on the use of "utility corridors,"
has increased the likelihood of lifeline collocation.
Under at-risk conditions1 such as natural events like earthquakes
or large storms or man-made disasters like train derailments or
explosions, failures on one lifeline can increase the risks of
subsequent damage on a collocated or nearby second lifeline. A
1989 train derailment just south of the Cajon Pass! California,
damaged a collocated gasoline transmission pipeline. The
subsequent explosion and fire destroyed a number of homes and
resulted in several fatalities.
In response to these and similar accidents and disasters, the 
Federal Emergency Management Agency (FEMA) authorized this study of
lifeline systems at the Cajon Pass, California (see Figure 1 on
page 3), and how their collocation may influence each lifeline's
vulnerability to failure during an earthquake event. The study has
produced two important products: 
1) the development of a management screening tool that can be 
used by lifeline owners, designers and providers, operators,
users, and regulators to sort through numerous collocation 
conditions to identify critical locations and to provide an
estimate of the increased risk that results when collocated
facilities are subjected to an earthquake event; and
2) the analysis of the lifelines in Cajon Pass, California, to 
demonstrate how the screening tool can be used and to examine
specific conditions in the Pass.
Important conclusions developed during the study include: 
* Lifeline collocation can produce both benefits and increased
risk of failure during earthquake events. For example, a 
benefit of closely located transportation lifelines is that 
the second lifeline can provide the detour or access route to 
the damaged sections of the first lifeline. However, the
failure of one intersecting lifeline generally increases the 
risk of failure of the lifelines) it crosses. 
* Topographic conditions understandably have led to the routing 
of lifeline systems that repeatedly cross over each other.
Additionally, Federal and State policies and requirements as
well as economic considerations were a significant contributor
to the decisions to collocate widely different lifelines in
very close proximity to each other.
* lifeline siting practices have not fully considered 
the serious impacts that one lifeline may have on
another lifeline;
* special design or routing considerations generally
are not required where the lifelines cross known
active faults; and
* although it was found that each lifeline owner has
prepared some type of study as to how they would
respond to a earthquake event that damaged their
lifeline system, the resulting analyses varied
significantly in their scope and detail. As a
result, lifelines at the same location are designed
and operated to significantly different standards
and accepted risk levels.
* A very useful screening tool has been developed during this 
study. The tool can be used to identify the critical lifeline
collocation locations and the conditions that make them
critical. It can identify areas of technical uncertainty and
poor siting practices, and its use can identify important
research and development activities that can lead to lowered
risk of collocation-inducted lifeline failures. It will be of
value to lifeline owners, designers and providers, operators,
users, and regulators. An improvements in earthquake analysis
of lifeline systems are developed, they can be easily
introduced into the screening tool method.
* At the Cajon Pass over 100 separate collocations involving 
over 250 potential lifeline interactions were evaluated. The
collocations evaluated are identified in Figure 2. In most
cases there was a dominant lifeline failure that led to the
principal impacts on the other collocated lifelines.
ADDITIONAL CONCLUSIONS 
The development of the analysis methodology as well as its test
application to the Cajon Pass has highlighted several additional
important conclusions.
* Earthquake shaking is the dominant factor that leads to
building damage. Ground movement is more important for
lifeline components, especially buried lifelines and electric
transmission towers. There is considerable less available
data base on earthquake-induced ground movement compared to
shaking intensity data. This suggests that future studies
need to emphasize obtaining ground movement information.
Figure 1: General Location of the Cajon Pass, California
* The analysis tool has been successfully applied to the Cajon
Pass. It has. identified for this semi-desert region that: 
The Cajon Junction, Lone Pine Canyon (which contains the
San Andreas fault zone), Blue Cut, and the area just 
south of the interchange between I-15 and I-215 are the
critical locations in terms of collocation impacts.
Fuel pipeline failures have the greatest impact on other 
lifelines during the immediate recovery period.
Current siting practices for fiber optic cables and 
increased reliance on these lifelines indicate that more
severe telephone communication failures (than have been 
experienced in past earthquakes) can be anticipated in 
future earthquakes. 
Lifeline siting practices have not fully considered the 
impacts that a new lifeline will have on existing 
lifelines and visa versa. 
Transportation service restoration is highly dependent on 
sequential repair since the lifeline itself often 
provides the access to the next damage site. Parallel 
repair operations are more probable for the other
lifeline systems. When multiple lifelines are
collocated, repair times increase because of local
congestion and the concern that work on one lifeline 
component could lead to damage on another lifeline component. 
Figure 2: Identification of Lifeline Collocations at Cajon Pass 
SCALE 
MILE 
EXPLANATION 
STUDY RESULTS 
The Screening Tool
The screening tool is described in detail in the project report
"Collocation Impacts on Lifeline Earthquake Vulnerability With
Application to the Cajon Pass, California", August 1991. That
report represents the first published work on how to systematically
examine collocation impacts on lifeline vulnerability because of
earthquakes. The specific details of the method are focused on
earthquake response analysis, but the sequence of analysis steps
could equally be applied to other regional natural disasters such
as floods or hurricanes. In those applications, of course, new
details on the response of individual lifeline components and
systems to the forces generated during the disaster event would
have to be identified and used
In the case of earthquakes, the screening tool builds upon earlier
FEMA studies that used collective expert opinion and actual lessons
learned from specific earthquakes to identify the earthquake
loadings on individual lifelines and each lifeline's subsequent
damage state, the probability that the damage state occurred, and
the time required to repair the lifeline back to its needed
operational performance level. The analysis method emphasizes the
need to conduct detailed site reconnaissance surveys to guide the
selection of the specific earthquake/lifeline data from the FEMA-
sponsored previous. studies and from other local sources.
The screening tool introduces the concept of a "zone of influence!
within which one lifeline failure could impact the performance of a
second lifeline, and the "most probable restoration time". The 
latter relates the probability of actual damage occurrence with the
sum of: the estimated time to obtain the equipment and material
needed to repair a lifeline failure, the estimated time for the
equipment and repair personnel to reach the damaged section of the
lifeline, and the estimated time to repair the damaged section once
the equipment and personnel have been assembled at the damage
location. Once the critical collocations have been identified by
the screening process, their total impact (which has been defined
as the most probable restoration time) can be used to characterize
the impact of lifeline collocation during the analyzed earthquake
event. However, in many cases it would also be appropriate for
subsequent, more detailed analyses of those collocation conditions
to be performed to reduce the level of uncertainty and to identify 
specific, appropriate mitigation approaches that could be applied
to each lifeline. This could involve conducting field examinations
such as developing soil borings, and conducting detailed stress and
equipment response analyses to further define the lifeline damage
state. 
The screening tool is an important development for several reasons: 
1) it is the first documented method for examining multiple 
collocation conditions and it is applicable to all lifeline
facilities. As improvements are made in the fundamental 
analysis methods for individual lifelines or earthquake
conditions, they can be readily introduced into the screening
tool to improve its predictive ability;
2) its use can identify the most critical collocation
conditions at a specific study area, thereby allowing limited
resources to be focused on the most important conditions for
improving the overall ability of the lifelines to survive an
earthquake event;
3) its use can identify technical areas of uncertainty and/or
poor siting practices. This can identify the need for and
lead to further research and studies to reduce the identified
technical uncertainty, or it can identify ways to mitigate
siting practices that are more vulnerable to inducing
collocation failure conditions; and
4) by being documented and made widely available by FEMA, it
is anticipated that it will stimulate the earthquake and
lifeline communities to developed improvements in the analysis
method or even to develop new, improved screening methods.
Cajon Pass, California
The Cajon Pass is a natural opening between the San Bernardino and
the San Gabriel mountain ranges. As such, it has been used for
years as a major lifeline route between the Los Angeles coastal
plain and the high desert regions. Included in the Pass are
interstate and state highways, railways, and their bridges; natural
gas and-petroleum products pipeline systems; hydroelectric power
generation, substations, and high voltage electric power
transmission lines; and radio towers, fiber optic, and telephone
tower systems. There are also a number of smaller, local, water
and sewer systems, low pressure natural gas distribution pipelines,
low voltage electric power distribution systems, and local wood
pole-mounted telephone systems.
Figure 2 is a composite plot of all of the lifelines studied at the
Cajon Pass. It shows that the lifelines are concentrated in a band
that roughly follows the valley floor of the Pass. However, the
close and crossing routings of the lifelines was not imposed by the
topology of the Pass, as it varies from about 0.5 miles wide at its
narrowest at Blue Cut to over several miles wide at the southern
and northern ends of the Pass. The dark circles indicate the 101
collocation locations studied. The figure shows that although
there are collocation sites all along the lifeline routes, they are
mostly bunched into six or seven groupings. When the estimated
earthquake impacts of landslide, ground liquefaction, and fault
surface displacement were considered, it was-found that the most
significant lifeline damage was concentrated at about six
locations.
From the study the following general results were identified.
Although there are many collocations for each lifeline, the
controlling or major impact locations varied from one to eight,
depending on the lifeline. In most cases, there was a dominant
lifeline failure that led to the principal impacts on the other
collocated lifelines. Thus, all the lifelines do not have to have
postulated damage before a collocation effect can lead to problems.
Conversely, communication lifeline failures have no immediate
effect on the other collocated lifelines, although the collocation
itself was judged to be the cause of the communication lifeline
failure (for example, a fiber optic cable hung from a bridge as is
done in Cajon Pass will fail from shaking intensities that are not
strong enough to significantly damage the bridge).
Finally, some collocation may be a benefit since it provides for
system redundancy within the lifeline system. However, collocating
pipelines in the same trench or power transmission lines from the
same towers does not add redundancy, it lowers the separate system
reliabilities to the lowest value of the two lifeline (e.g., the
weakest link sets the overall reliability of both systems). In
general, intersecting different lifeline systems increase the most
probable restoration time to return service on each individual
lifeline system.
The additional minimum delay, due to collocation, before temporary
service can be restored through the Cajon Pass was determined and
is given below. The additional time is the increase in time due to
collocation impacts compared to the estimated time to restore
service if the lifeline were assumed to be isolated from any
collocation impacts.
Minimum Additional Delay Before
Lifeline Temporary Service is Restored days
Fiber Optic Telephone Communication 61 
High Voltage Electric Power Transmission 19
Natural Gas Bulk Transmission 25
Petroleum Products Transmission 41
Interstate Highway Traffic 35 
Railroad Service 17 
Communication Lifelines 
Within Cajon Pass there are several communication transmission
towers: including radio, microwave, and cellular telephone towers.
Since they are isolated from the other lifelines, they have no
collocation impacts on the other lifelines. Also, there are wood
poll-mounted and hard-wired telephone systems that essentially
serve local customers within the Pass. They were not analyzed as 
this study examined the lifelines that serve regional customers. 
From the southern section of the study area north to just below 
Cajon Junction the old Highway 66 (now a county road called the 
Cajon Blvd. extension) runs west and parallel to the new I-15
alignment. The eastern side of this divided road has been
abandoned, 
and the 
western side 
has been 
converted to 
a two lane 
county road. 
Four fiber 
optic
conduits 
(each with a 
capacity to 
hold two or 
three fiber 
optic cables) 
and two 
petroleum
products
pipelines 
have been 
routed in the 
median strip 
between the Figure 3 Fiber Optic Conduits Fund Under
road beds. Distribution Pipe on a Bridge Over a Railroad 
The fiber optic conduit installation was completed in 1989. In the study area, they were 
buried next to the two petroleum products pipelines for much of 
their route. The mechanical trenching equipment used during their 
installation damaged the pipelines at several location, requiring 
local pipeline repairs. 
At the bridge locations along the Cajon Blvd. extension, the fiber 
optic conduits are brought to the surface and hung from the 
bridges, using light anchoring systems. The practice of hanging
the fiber optic cables from bridges and other lifeline structures 
is common throughout the Cajon Pass area, they are on bridges over 
railroads (see Figures 3 and 4 and on the bridges over the 
California Aqueduct. They are routed at the foot of a crib wall 
used to retain the 1-15 road bed, after which they are brought to 
the surface and hung from the wall of a concrete culvert that 
passes under 1-15. Figure 5 shows the details of the typical light 
wall anchors and supports that are used. 
The communication lifelines (the fiber optic cable systems) had no 
impact on increasing the probable time to restore service for any 
of the other lifelines. The fact that all four cable conduits are 
routed together for much of their routes through the Cajon Pass 
increases the potential that these valuable lifelines will be lost 
during an earthquake event. The practice of hanging the conduits 
from bridges and other lifeline structures using very light anchor 
supports increases the risk of failure of these communication 
lifelines at earthquake shaking intensities which would not impact 
them if they had been buried or supported by more robust anchors. 
Prior
earthquakes
have shown
that the most
vulnerable
telephone
lifeline
component is
the switching
equipment.
The current
industry
emphasis to
shift from
hard-wired to
fiber optics,
coupled with
the co-routing of
the fiber
optic cables,
is expected
to increase
probability Abandoned Portion of Highway 66
of telephone
line failures during earthquakes. The co-routing removes system
redundancy since an event that would cause the failure of one cable
will probably fail all of the cables. The fact that the fiber
transmit more
calls per cable
than do hard-
wired systems
means that the
impact of a
lost cable will
be more
significant
than the
impacts
previously
experienced 
when a hard-wired line has
been lost.
Finally, the
construction
practices do
not appear to
have considered
earthquake
impacts, Highway Culvert Wall 
increasing the risk to the fiber optic systems. However, since
these are not problems associated with collocation, they do not
necessarily impact the results of the present study. The fact that
a fiber optic cable fails on a bridge due to shaking failure of its
anchor system is not a collocation impact if the bridge itself does
not contribute to the failure.
Of the 55 fiber optic collocation conditions analyzed, nine were
estimated to lead to increased probable times to restore the fiber
optic systems to their intended service level. Most of the
significant time impacts occurred because of ground movements
(liquefaction and fault surface displacement) causing significant
damage to a collocated fuel pipeline. The earth movement was
hypothesized to fail the fiber optic cables, independently of the
other collocation lifelines. Thus, the collocation impact was not
a change in damage state, but an increase in both the probability 
of damage and the delay required to mitigate the hazardous
environmental conditions so that workers could repair the fiber
optic cables without undue risk to themselves. A special case was
where the fiber optic cables were buried at the foot of a crib wall
used to support the I-15 highway. Although the liquefaction
condition was not severe enough to cause the failure of the
highway, because the fiber optic cables are routed at the toe of
the crib wall, any soil movement could damage them. Thus, the
damage at the road was slight, but the delays in being allowed to
retrench the cables was found to be significant.
As previously stated, the overall estimate of the impact of
collocation was defined as the most probable restoration time,
which was the time to restore service compared to the time to
restore service if no collocations impacts were considered. For
the fiber optic cables this calculated to be: 
Increase in Probable Time Increase in Probable Time 
Lifeline to Restore Service, days to Restore Service. % 
Fiber optic Cables 61 86 
Electric Power Lifelines 
The electric power lifelines in the Cajon Pass include eight
separate high voltage transmission lines (two public sector nd
six private sector-owned lines), a major power substation (the Lugo
substation located in the north east corner of the study area), and
a hydroelectric power generation station. However, only the
transmission lines are directly involved in collocation situations.
The two public sector-owned 287.5 kV transmission lines (City of
Los Angeles owned) were constructed in 1936. Combined, they
transmit about 600 MW of power. They are the western most
transmission lines in the study area and are isolated from other
lifelines through much of their route. They are routed basically
from north to south, and they deliver power generated at Hoover Dam
to Los Angles. Six private sector-owned high voltage transmission
lines (Southern
California
Edison Company
routed through
the study area.
Three 500 kV
lines (which
transmit
approximately
1,700 MW)
travel
southwest and
then south from
the Lugo
substation to
Mira-Loma
substation
(which is
located outside
of the study
area). Two of
Products Pipelines Over the San Andreas Fault
and 2) were
installed in
the early 1960s and upgraded to 500 kV in the early 1970s. The
third line was added in 1983, and just south of the Lugo substation
it is collocated on the same transmission tower system as is line
#2. These three power lines and the two public sector-owned lines
account for all of the significant electric power collocation
impacts.
However, there are three additional privately owned high voltage
power lines in the study area. Although these three lines have a
number of intersections or collocations with other lifelines, the
predicted earthquake intensities and lifeline damage are small
enough that they have a minor collocation impact compared to the
five transmission lines discussed above.
Failure of other lifelines generally will have a small impact on
the electric power transmission lines since they are carried on
towers well above the other lifelines. However, if fuel pipeline
lifelines leak, the power transmission lines can provide an
ignition source, and the resulting fire could result in significant
damage to both the power lines and the other lifelines located in
the flame path. The other earthquake condition of importance
occurs when there is ground movement due to landslide,
liquefaction, or fault displacement. This could cause the tower
foundations to fail, dropping the transmission lines to a height
where they could have a direct interaction with the other
lifelines. With this in mind, the following describes where there
might be such potential interactions.
Figure 6 shows the location where the two separate electric power
transmission lines are in 
close proximity to both a In 
natural gas and the
petroleum products pipelines II 
in the vicinity of the San
Andreas fault zone.
Although the surface
features look pastoral, the
fact that the lifelines are I 
in the zone of the fault
trace increases both their
risk and the potential
magnitude of the damage that
could be induced. Figure 7
is a photograph in the
opposite direction to the
one shown in Figure 6. It
shows an electric power
transmission tower located
at the edge of a steep
embankment, suggesting that
a foundation failure may
also be a contributing
factor to causing the power
lines to drop to a height
where they could readily
interact with spilled fuel at the San Andreas Fault
South of the San 
there are two 
additional areas 
where the electric 
transmission lines 
pass through a region 
susceptible to 
landslides and where 
there are nearby 
railroad and buried 
natural gas pipeline 
lifelines. Figure 8 
shows two 
transmission towers 
that were rebuilt 
when the prior ones 
were damaged by a 
local landslide. Not 
shown at the bottom 
of the figure are a 
buried natural gas 
pipeline and a 
railroad. 
The electric power 
(Directly Above a Fuel Pipeline & a 
transmission towers are quite resistant to shaking intensity.
Although actual earthquakes have demonstrated that line vibration
can cause separate circuits on the same pole or support tower to
gallop and electrically short by either touching each other or by
arcing between adjacent lines, this failure mode has not been
characterized in the available data bases. Thus, only tower
failure by ground motions was considered in the present analysis.
Liquefaction and landslide conditions were identified as causing a
light, moderate, and heavy damage state, depending on the local
conditions; whereas, the surface displacement at the fault rift
zone causes a catastrophic damage.
The collocation impacts at the landslide locations included
increasing the damage state when there was a fuel pipeline present
as well as increasing the time delay to initiate repairs due to the
general congestion and the need to allow for debris removal from
collocated railroad beds or environmental cleanup to remove the
hazard from spilled fuels.
The overall estimate of the impact of collocation on the electric
power lifelines was: 
Increase in Probable Time Increase in Probable Time 
Lifeline to Restore Service, days to Restore Service, % 
Los Angeles City Lines 49 28 
So. California Edison 19 10 
Line 1 (Lugo-Mira Loma) 
So. California Edison 28 13 
Lines 2 & 3 (Lugo-Mira Loma) 
Fuel Pipeline Lifelines 
Within Cajon Pass there are two fuel pipeline transmissions
systems: natural gas and petroleum products lifelines.
Natural Gas Pipelines
From the north part of the study area traveling south, there are
two 36-inch natural gas pipelines. Sections of the pipeline were 
installed in 1960, 1966 and 1976. They are operated at 845-936 
pounds per square inch gage (psig). They presently supply about
600 million cubic feet of natural gas per day to the Los Angeles
Basin, although their combined capacity is up to about 1 billion 
cubic feet per day.
One pipeline is routed south along Baldy Mesa Rd. (two petroleum
products pipelines and two fiber optic conduits are also routed
along this road), and the other is routed southwest and south from
the eastern boundary of the study area. The two pipelines join at
a valve station located between the railroads and Highway 138,
north and east of Cajon Junction. From there one pipeline is
The other is routed south
routed south on the west side of I-15. 
but on the east side of I-15. The eastern most pipeline is buried
throughout its route, the western most pipeline has 18 exposed
locations with open spans ranging from 10 to 138 feet.
Figure 9 shows a section (north of Cajon Junction and next to
Highway 138) where the two pipelines are routed parallel to each
other. A 1990 realignment of Highway 138 (to remove curves) placed
the exposed section of the one pipeline about 40 feet from the road
bed. The gas line markers shown in the figure identify the route
of the buried pipeline.
From that location, the western most pipeline heads south and
crosses I-15. It continues south passing across Lone Pine Canyon
just north of Blue Cut. The San Andreas earthquake fault zone is
in that canyon, and the two petroleum products pipelines also are
routed parallel and in the fault zone. Thus, when the natural gas
pipeline crosses the petroleum products pipelines, it too is in the
fault zone. In addition, two high voltage power lines cross within
a few hundred feet from the pipeline intersections (see the
discussion for Figures 6 and 7 for additional details about this
collocation condition).
South from the San Andreas fault-pipeline-power line intersections,
the natural gas pipeline follows the route of the railroad (it is
located next to and frequently crosses beneath the track bed). At
Blue Cut the railroad and natural gas pipeline are at the foot of a
landslide prone region, and directly above them on the mountain
(and also in the landslide zone) are high voltage electric power
lines. A
similar
situation
exists about
2.5 miles
further south.
From the valve 
station north 
and east of 
Cajon Junction, 
the other 
natural gas 
pipeline is 
routed east of 
I-15 until 
about a mile 
north of the I-
15/I-215 
intersection, 
where it 
crosses under 
I-15 and it 
eventually -a On 
joins with the other natural gas pipeline. The mountains are steep
along the eastern side of I-15, and there has been a prior case
where a rain-induced landslide damaged the natural gas pipeline. 
After crossing under I-15, and about a mile north of the T-15/I-215
junction, the eastern pipeline crosses under the two petroleum 
products pipelines (which along with the fiber optic cable conduits.
are located in the median strip of Old Cajon Canyon Rd.). This is
a region of high water table subject to possible liquefaction
during an earthquake event.
After the two natural gas pipelines join together they are routed
under I-15 to a valve station and then south out of the study area. 
At the valve station a third 16-inch distribution pipeline leaves 
the valve station to provide gas to cities of Devore and San
Bernardino.
The buried natural gas pipelines are relatively insensitive to
earthquake shaking. The present study did not estimate the natural 
period of the 18 exposed sections of the western most 36-inch
pipeline, but it is possible that they could be impacted by shaking 
intensity if their resonant frequency is close to the earthquake
vibration frequencies. The principal cause of damage for the
pipeline was earth movement due to landslide, liquefaction, and
fault displacement. Since the movements result in catastrophic
failure of the pipe, the collocation impact does not increase the
damage state but it increases the time delays for beginning
restoration work. The dry climate of the study area means that the
unpaved roads provide sufficient access to the damage sites,
freeing these lifelines from dependence on the transportation
lifeline availabilities. Of the 61 collocation locations examined,
eight contributed to the estimated increase in probable restoration
time. 
There were two key collocation impacts at locations were ground
movement occurred. One was the spilling of petroleum products at
liquefaction areas. This was assumed to cause a delay in being
allowed access to the damage site while the environmental hazard
was removed. At the landslide locations it was assumed that the
debris on the railroad bed above the pipeline had to be removed and
then the pipeline exposed and inspected for damage. This was
required to lower the risk to workers that the construction
activities could *damage the pipe, causing leaks would be too great
a risk to allow them to work with a pressurized pipeline directly 
below them. Conversely, if a leak had occurred during the
landslides then the collocated high voltage power lines directly
above could cause an explosion and fire, increasing the potential
damage level. Either case would lead to a delay in the restoration 
of service. 
The triple collocation of high voltage power lines, petroleum
pipelines, and natural gas pipeline at the San Andreas fault rift
zone caused the largest single delay due to the resulting fire, the
need to remove spilled fuel that failed to burn, and the general
level of confusion and construction expected at that location.
Petroleum Products Pipelines
There are two petroleum products pipelines in the Cajon Pass. An
8-inch line was installed in 1960, a 14-inch was installed in 1969 1970, 
and a portion of the 8-inch line was rerouted in 1980 to
place it next to the 14-inch line. The two lines operate at
psig and transfer about 80,000 barrels per day of product.
They are the primary fuel source for several military air stations
and provide the bulk of the gasoline used in the Las Vegas area.
The locations where they are routed in close, parallel trenches
reduces their overall reliability as a failure to one pipeline is
expected to lead to the subsequent failure of the other. A train
derailment in 1989 in San Bernardino led to a rupture of the 14inch 
pipeline and to subsequent fires and fatalities (this event
was specifically identified in the congressional authorization for
the present study).
The 14-inch pipeline enters the study area from the south along a
railroad right-of-way. It periodically crosses back and forth
under the track bed. As previously indicated, just south of the I-
15/I-215 intersection it passes through a potentially liquefiable
area along with the railroads, a natural gas pipeline, and most of
the fiber optic conduits. North of that junction it is joined by
the 8-inch petroleum products pipeline and the fiber optic conduits
and they all are routed along and within the median zone of the
About a mile north of the I-15/ I-215
abandoned Highway 66. 
intersection, the two petroleum products pipelines enter a
potentially liquefiable area. There they are crossed at right
angles by a 36-inch natural gas pipeline.
At Blue Cut the two petroleum products pipelines separate from the
fiber optic conduits, cross the Cajon Creek, continue northwest,
and then turn and run parallel to and within the San Andreas
earthquake fault zone (this is Lone Pine Canyon). As previously
discussed, they cross a 36-inch natural gas pipeline and are near
to two high voltage electric power transmission lines collocated in
this region.
The petroleum products pipelines are similar to the natural gas
pipelines in their response to the earthquake loadings. Thus, they
are insensitive to the shaking intensities experienced at the Cajon
Pass, but are sensitive to ground movement. Since the movements
anticipated generally lead to catastrophic failures, the
an collocation impact is similar to natural gas pipeline case: 
increase in the time delays to initiate restoration work. Of the
32 collocation locations analyzed, eight contributed to the
collocation impacts.
In general, the petroleum products pipelines contributed more to
the delays in initiating repair for the other collocation lifelines
than did the other lifelines' impact the petroleum products
pipelines. This is because the spill of the petroleum products was
one of the more significant impacts. Liquefaction was the primary
cause of the ground displacements that impacted these lifelines,
but the probable increase in restoration time only ranged from two
to nine days. However, the impact at the San Andreas fault was
probably underestimated by the screening tool. There the increase
in probable restoration time was estimated at 30 days, but the fact
that the pipelines parallels several miles of the fault indicates
that there should be multiple pipe failures. There is a strong
possibility that the regulatory authorities would not allow the
pipeline to be rebuilt along the fault trace, thus the earthquake
could lead to the requirement to negotiate new rights-of-ways,
further increasing the estimated probable restoration of service
delay (but the increase would not be attributable to collocation).
The overall estimate of the impact of collocation on the fuel
pipeline lifelines was: 
Increase in Probable Time Increase in Probable Time 
Lifeline to Restore Service, days to Restore Service. % 
So. California Gas 57 64 
Western 36-inch line 
So. California Gas 25 83 
Eastern 36-inch line 
So. California 'Gas 8 80 
16-inch distribution line 
CALNEV Petroleum Products 41 63 
8-& 14-inch lines 
Transportation Lifelines
Highways
The Cajon Pass contains Interstate Highway I-15 and part of the I215 
connector to San Bernardino. This highway system was
originally completed in the late 1960s. It presently carries about
60,000 vehicles per day, on weekends this traffic includes about
28% large trucks. The other major paved highway is the State
Highway 138, and the intersection of I-15 and Highway 138 forms
Cajon Junction. In addition to these paved roads, there are
numerous unpaved roads used for fire equipment access, for
maintenance routes for the other lifelines, and for general off-
road recreation. The dry climate of the region means that most of
the unpaved roads are fully accessible throughout the year.
The highway bridges and road beds, in general, are not subjected to
damage from other nearby lifelines. The exception is when a
railroad bridge crosses over a highway. At such locations, the 
failure of the bridge has a direct impact on the highway. Figure 
10 shows one such bridge. Because of its skew and simple supports,
the bridge was estimated to collapse onto Highway 138, effectively
removing that segment of the road as a bypass or detour route for
traffic past I-15's 
damaged 
sections. 
It is noted 
that the 
bridge span 
that crosses 
Highway 138 
is the right 
span in the 
Figure. 
Very close 
to this 
bridge was a 
highway 
bridge over 
the 
railroad. 
Even 
it had the 
same amount 
of skew with Figure 10 A Railroad Bridge Estimated to Collapse 
respect to 
the road 
alignment, 
Onto Highway 138 (Highway 138 is located 
under the right span) 
its 
continuous column design is more robust and it was not estimated to
collapse onto the railroad. None of the highway bridges were
predicted to completely collapse, although partial collapse is
possible. Fortunately, the "diamond" interchange design used in
the Pass provides a direct detour route (although one with reduced
capacity compared to the I-15 road beds) past any partially damaged
bridge.
Railroads
Three railroads (the Southern Pacific, the Union Pacific, and the
Atcheson Topeka and Santa Fe (Santa Fe) generally run north-south
through the Pass. Most of the bridges are over 50 years old, and
the railroads were unable to provide descriptive material on their
design or their foundation conditions. The track bed receive
regular maintenance, and some realignment has been done to
eliminate the need for tunnels. About 75 trains per day travel
through the Pass.
The Union Pacific and the Santa Fe actually share track over part
of the Pass (sharing track is one of the positive aspects of their
collocation, it provides a redundancy for each of the railroads),
using one track for south bound traffic for both lines and the
other track for north bound traffic.
Buried next to and along side much of the rail track in the
southern half of the study area are either a 36-inch natural gas
is pipeline or a 14-inch petroleum products pipeline (its principal
product is gasoline). At several locations the rail bed (along
with the buried pipeline) are located at the foot of potential
landslide regions, and on the hillside above the railroad and
within the landslide zone are high voltage electric power
transmission lines. In the northern part of the study area there
are a number of small railroad bridges, often with a fiber optic
conduit or a natural gas or petroleum products pipeline routed
under the rail bed next to the bridge.
The bridges (see Figure 11) over the Cajon Wash (in the southern
part of the study area) are in a localized region of high ground
water tables, thus the ground could be subjected to liquefaction
during an earthquake event. Also in this general area are buried
36-inch and a 16-inch natural gas pipelines, a 14-inch petroleum
products pipeline, and fiber optic cable conduits.
The application of the screening tool to the highways and railroads
identified that failures of collocated lifelines, other than
transportation lifeline components, do not increase the damage
level in nearby transportation lifelines. That is, the failure of
a fuel pipeline or an electric power transmission line is not
expected to increase the damage level sustained by the highways,
railroads, or their bridges. Fuel spills can, however, increase
the time delay before work on the transportation system can be
initiated. That is because there is a delay time required to clean
up the fuel so that repair workers on the transportation lifeline
are not put at risk due to the potential fire hazard from the
spilled fuel. Similarly, in cases where high voltage electric 
lines sag or 
otherwise 
become close 
to the 
transportation 
n lifeline 
component, 
the power 
line must be 
de-energized 
or 
permanently 
restored for
large 
equipment 
needed for 
the 
transportation 
n lifeline 
repair can be 
too can delay 
Figure 11 Railroad and I-15 Bridges in Cajon Wash 
Subject to Liquefaction Damaqe the start of repair work on the transportation lifelines. The collocation of the transportation lifelines is both a benefit
and a problem. Nearby roads or railroads can provide the access or
detour route for the large equipment needed to repair a damaged
bridge or road or rail bed. This redundancy is a benefit.
However, the collapse of a bridge over a highway or railroad is a
case of one transportation lifeline component interrupting the
ability of the collocated transportation lifeline from functioning.
This, in fact, was the major cause for the increase in the
calculated time to restore the I-15 highway to its needed service
level.
In the case of the railroads, two locations were the major
contributors to the increase in the time to restore service. One
location was at Blue Cut where the railroad is collocated with a
buried natural gas pipeline (buried in the railroad right-of-way)
and two high voltage power transmission lines. The railroad and
pipeline are in the toe of a landslide zone and the power lines are
above and also in the slide zone. The major impact on the railroad
would occur if the pipeline had no noticeable ruptures. In that
case, the railroad repair would be delayed until the pipe could be
exposed and inspected to assure that it was not leaking gas.
Alternatively, the work on the railroad could continue and the gas
line should be shut down until the railroad work had been
completed. Then the gas line would be exposed, inspected, and
returned to service after it was confirmed that it was safe.
Just south of the intersection of I-15 and I-215 (see Figure 12),
the railroads are collocated with a natural gas pipeline, a
petroleum products pipeline, and fiber optic conduits. The area is
susceptible to liquefaction and the subsequent fuel pipeline
failures were estimated to add a thirty day delay while the hazards
from spilled fuel were mitigated (which was assumed to be necessary
before heavy equipment and work on the railroad bridges could
commence).
The overall estimate of the impact of collocation on the
transportation lifelines was: 
Increase in Probable Time Increase in Probable Time 
Lifeline to Restore Service, days to Restore Service, % 
Highway I-15 35 22 
Southern Pacific 17 8 
Railroad 
Atcheson Topeka & 85 33 
Santa Fe Railroads 
*U.S. GOVERNMENT PRINTING OFFICE: 1998 -617-775/90560