2 or 3 to occur (less than 5% damage expected). At those
conditions, collocation induced additional damage would be slight
or none at all. However, the facilities are very sensitive to
ground movement and there are a number of potential landslide or
lateral spread (or liquefaction) locations along the lifeline
routes that coincide with MMI = VIII. North of the San Andreas 
fault the earthquake risk comes predominantly from shaking, but
most of the peak shaking intensities are VII with a few isolated
locations of VIII.
Another important activity of the data acquisition phase of the
study is to divide each lifeline into segments for subsequent
analysis. Figures 6 and 7 were used to guide the segmentation 
process. The communication lifelines were divided into 12 to 14
segments, depending on the route of the individual fiber optic
conduits; the electrical power transmission lifelines were divided
into four segments (the Arrowhead Calelectric-Shannin line at the
southeast corner of the study area was analyzed as a single
segment); the natural gas pipeline lifelines were divided into five
or eight segments; the petroleum products pipeline lifelines were
divided into 10 segments; the railroad lifelines required 30
segments; and the interstate highway required 36 segments. The 
subsequent vulnerability calculations for the communication,
electrical, and fuel pipeline lifelines were performed by hand;
those for the transportation lifelines were performed with a
standard computer spreadsheet. These approaches recognized the
number of calculations that would be required.
5.2 Lifeline Collocation Vulnerability Analysis Results
Figure 7 identifies the locations of the 101 collocations that were 
subsequently analyzed in this study. These collocations involved
over 250 separate potential lifeline interactions. Table 15 was
prepared to identify the collocation and the lifelines that were
involved at that location. As the collocation evaluation was
prepared, the results were tabulated against the index, thus
assuring that all potential interactions were located and
evaluated.
Table 15 and Figure 7 identify several critical clusters of
interactions. With this in mind, a collocation damage scenario was
developed for each critical cluster of interaction. Using a 
standard collocation damage scenario at the critical clusters
helped assure the overall consistency of the interaction analyses4
The clusters where the standard collocation damage scenario was
used were:
1. The liquefaction zone south of the interchange of I-15 and
I-215. There were 10 separate potential interactions
involving I-15, railroad bridges, several fiber optic lines,
the 16-inch natural gas pipeline, and the 8-inch and 14-inch
55
INTERSECTION 
NO. 
1 
2 
3 
4 
5 
71 
10 
23 
11 
12
10X 
13 
14 
16 
17 
is 
19 
24 
25 
26 
2 7 
28 
29 
Table 15 
MATRIX OF LIFELINE COLLOCATIONS AND INTERACTIONS 
HIGH-RAIL-POWER FIBER NATURAL PETRO 
WAYS ROADS LINES OPTIC GAS LINES 
A B C D E A B C A B C D E F A B C D A B C A B 
X x x 
X X 
X X X 
X X X 
X X XX X 
X X XX
X X X 
X
x X 
X 

X 
X X 
x 
X X X X X X X 
X X 
X X X 
X 
x xX 
=X-X l X = XX 
X X 
= : x I XXXXx 
X X XX XXX 
X X X X 
I XI X X X 
Table 15 (Continued) 
MATRIX OF LIFELINE COLLOCATIONS AND INTERACTIONS 
FIBER NATURAL PETRO
INTER-HIGH-RAIL-POWER 
OPTIC GAS LINES
SECTION WAYS ROADS LINES 
A B
NO. A B CD E A B C A B C D E F A B C D A B C 
30 X X
31 X X 
32 
xx xx x
33 X X 
34 X ,X 
35 
x x H 
XX*36 XX XX x 
37 X X XX 
38 .XX xx 
3S XXXX XX 
40 X XX X XXXX 
41 X xX XX X X X X 
42 XX x
43 X XX 
44 X X XX i XX XXXX 
X45 X X 
46 X 
XXXX X
47 
I X X
48 X X X X
49i 
X X X .s5 
51 xx 
52 . X X XX 
53 X XX 
54 X X X
55 X X XXXX 
56 x xxxx xx 
57 X X X
58 X X XXXX XX 
Table 15 (Continued) 
MATRIX OF LIFELINE COLLOCATIONS AND INTERACTIONS 
INTER-HIGH-RAIL-. POWER FIBER NATURAL PETRO 
SECTION WAYS ROADS LINES OPTIC GAS LINES 
NO. A B C D E A B C A B C D E F A B C D A B C A 3 
59 X X X X X 
601 X X xXX X X 
62 x x x xxx X 
63 X
64 X X 
65 X X 
66 X XX 
67 XXX XX 
68 X X 
69 X X 
70 x x 
71 = X 
72s x x 
73 xxx x x 
74 x x x xx xx 
75 1 I 
76 x x x x 
77 81_X' X X X 
7 8 I 
E l2 x x x xx 
84 .x x x x 
86 X XXX 
87 X X X X 
58
Table 15 (Continued)
MATRIX OF LIFELINE COLLOCATIONS AND INTERACTIONS
INTER-HIGH-RAIL-POWER FIBER NATURAL PETRO 
SECTICON WAYS ROADS LINES OPTIC GAS LINES 
NO. A S C D E A B C A 8 C D E F A 3 C D A BC A B 
8X X X XX 
89 HX XX X XX 
90 X X X 
NOT USEDX 
93 H 
NOT USED = X XXX 
96 
9397 _X 
X 
HX I 
XX 
X X XX 
98 X 
99 X 
100 X X 
101 XX 
X X 
103 X X: 
petroleum products pipelines. All of the buried lifelines
were found to have incurred damage state 7 (catastrophic) with
The assumed
probabilities that the damage occurred of 40%. 
collocation interaction was that the petroleum pipelines could
drain 1-2 miles of pipe but that no secondary fires or
explosions would occur. This contributed to an additional 30
day delay to the site before repair could commence, due to the
requirements to assure that fire conditions and environmental
concerns could be alleviated before work could start on the
individual lifelines. An additional 10 days of delay were
hypothesized due to the need to coordinate the work on so many
individual lifelines.
2. A second cluster exists along the Cajon Blvd. extension
into the Cajon Pass from north of the I-151I-215 interchange
to Blue Cut. There are two separate locations where
landslides (with a probability of occurrence of 45%) 
and two liquefaction areas (probability of occurrence of 20% and 40%)
are possible, including eight separate collocation impact
areas where there are collocated power lines, railroads, and a
natural gas pipeline. At the two landslide areas along the
Cajon Blvd. extension (which was the prior highway 66 before
I-15 was built), a natural gas pipeline and the railroads are
located at the toe of the slide area, and landslide debris is
expected there. Debris removal for clearing the railroad
would be required before work on the pipeline (which is
located in the railroad right-of-way and sometimes under the
rail bed) could begin. The debris removal was assumed to
cause a 30 day delay before work on repair of the pipeline
could occur.
3. At Blue Cut itself there is another landslide and
liquefaction zone. Due to its proximity to the San Andreas
fault rift zone, a 70% probability of occurrence was
estimated. At that location, a power line, a natural gas
pipeline, and a railroad are in the flow area of the slide,
which could cause the pipeline to surface and rupture as well
as to be covered with debris. The collocation damage scenario
assumed that an explosion and fire could result, increasing
the damage to the power line and its repair time by an
additional 20 days, compared to the delays described for the
other slide area, to repair the more extensive damage the fire
caused. The potential for landslides blocking the Cajon Creek
with a slide dam, and the subsequent impact on downstream
lifelines if the dam should catastrophically fail were
considered to be outside the scope of this study. 
At Blue Cut itself, the liquefaction zone has a 50% probability of
occurrence.
4. In the San Andreas fault rift zone there are six
collocation points that involve the power lines, 
the railroads, the fiber optics, a natural gas pipeline, the two
petroleum products pipelines, and the Cajon Blvd. extension.
Fuel spills are assumed to require a 30 day delay for
alleviating environmental and fire concerns. An additional 60
day delay was assumed for the petroleum products pipelines
because the estimated extensive damage to their right-of-way
along the fault trace will require regulatory review and
acceptance before the pipeline can be worked on. 
An additional 30 day delay for the other lifelines was 
Assumed because of the general congestion in the area. Since the
fault displacement causes catastrophic failure of the
lifelines, the collocation damage scenario does not assume any
further damage.
With these scenarios in mind, the collocation vulnerability
analysis was performed for each separate lifeline system.
Communication Lifelines
Figure 9 shows the communication lifeline routes in the study area. 
The location of the photographs presented in this section of the
report are also shown on the figure. The microwave, radio, and
cellular phone communication towers are sited such that they are
not collocated with other lifelines. Thus, they do not enter into
the analysis of the impact of collocation. The impact of degraded
communications (if these towers should fail) on the ability to 
restore the other lifeline systems to acceptable delivery
conditions is beyond the scope of the present study..
There are five fiber optic systems located in the study area. They
include American Telephone and Telegraph (AT&T), Continental
Telephone (Contel), MCI Communications (MCI), WTG West (WTG,
formerly WilTel), and US Sprint.
The individual fiber optic cables are multi-layered with an inner
structure that allows the cable to be pulled and maintained in a
state of tension without placing tension on the individual glass
fibers. This assembly is then wrapped with various insulating
materials, including a metal sheath. In the fall of 1986, the U.S. 
Forest Service provided MCI and WTG right-of-ways on the basis that
they would each provide two conduits and that each conduit would be
four inches in diameter so that cables from two different systems
could be placed in each individual conduit (thus, provisions were
made to lay eight cable systems along the two routes through the
Forest Service land). Furthermore the Forest Service required that
the routes be combined as quickly as, practical. Thus, the MCI and
Contel systems enter the study area from the north along Baldy Mesa
Road, while the AT&T, WTG, and US Sprint systems enter from the
north along the access road to I-15. The routes join together just
south of the separation of I-15N and 1-15S (about 1.8 miles north
of the Cajon Junction of I-15 and Highway 138). From there they
travel together as a bundle of four conduits. Much of their route
is along the Cajon Blvd. extension where they are laid in the
median strip. Also routed along much of the median strip are the 
two petroleum products pipelines (the Cajon Blvd. extension was the
former divided highway 66, but only the western two lanes are still
maintained for traffic). For the purposes of this study, the fiber
optic cables are analyzed as buried conduits. Because of their
collocation, if one conduit fails, all fail.
When the conduits, (which are normally buried) are routed to a
bridge location, they are generally brought to the surface and hung
with light anchors from the bridge. Figure 10 shows them on a 
typical bridge crossing on the abandoned portion of Highway 66;
Figure 11 shows some of the details of the bridge hangers and the
conditions of the conduits; Figure 12 shows them hung from a
highway culvert wall just south of Cajon Junction; Figure 13 shows
some of the details of the wall anchors, near the culvert location
of Figure 12. Just south of the culvert shown in Figure 12 the
II COMMUNICATIONLIFELINEROUTS.
Figure 9 COMMUNICATION LIFELINE ROUTES 
SCALE 
Larger Scale Figure
Located at 
EXPLANATION 
End of Document