Page 69 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

3/48 Third-party Damage Index
Example 3.1: Scoring the depth of cover tion and pipe coatings, if not the pipe itself. Birds and other
smaller animals and even insects can also cause damage by
In this example, apipeline section has burial depths of 10 and their normal activities. Again, coatings and instrumentation of
30 in. In the shallowest portions, a concrete slab has been aboveground facilities are usually most threatened. Where such
placed over and along the length of the line. The 4-in. slab is 3 activity presents a threat of external force damage to the
ft wide and reinforced with steel mesh. Using the above pipeline, it can be assessed as a contributor to activity level
schedule, the evaluator calculates points for the shallow sec- here.
tions with additional protection and for the sections buried The activity level item is normally a risk variable that may
with 30 in. of cover. For the shallow case: IO in. of cover + 24 change over time, but is relatively unchangeable by the pipeline
in. of additional (equivalent) cover due to slab = (10 + 24)/3 operator. Relocation is usually the only means for the pipeline
pts = 11.3 pts. Second case: 30 in. of cover = 30/3 = IO pts. operator to change this variable, and relocation is not normally
Because the minimum cover (including extra protection) a routine risk mitigation option.
yields the higher point value, the evaluator uses the IO-pt The evaluator can create several classifications of activity
score for the pipe buried with 30 in. of cover as the worst case levels for risk scoring purposes. She does this by describing
and, hence, the governing point value for this section. sufficient conditions such that an area falls into one of her clas-
A better solution to this example would be to separate the sifications. The following example provides a sample of some
10-inch and 30-inch portions into separate pipeline sections of the conditions that may be appropriate. Further explanation
for independent assessment. follows the example classifications.
In this section, a submerged line lies unburied on a river bot-
tom, 30 ft below the surface at the river midpoint, rising to High activity level (0 points) This area is characterized by
the water surface at shore. At the shoreline, the line is buried one or more of the following:
with 36 in. of cover. The line has 4 in. of concrete coating
around it throughout the entire section. Class 3 population density (as defined by DOT CFR49Part
192)
Points are assessed as follows: The shore aonroaches are 0 High population density as measured by some other scale
II
very shallow; although boat anchoring is rare, it is possible. No Frequent construction activities
protection is offered by water depth, so 0 pts are given here. The 0 High volume of one-call or reconnaissance reports (>2 per
4 in. of concrete coating yields 5 pts. Because the pipe is not week)
buried beneath the river bottom, 0 pts are awarded for cover. Rail or roadway traffic that poses a threat
Many other buried utilities nearby
Total score =O + 5 + 0 = 5 pts Frequent damage from wildlife
Normal anchoring area when offshore
Frequent dredging near the offshore line.
B. Activity level (weighting: 20%)
Medium activiy level (8 points) This area is characterized
Fundamental to any risk assessment is the area ofopportunity. by one or more of the following:
For an analysis of third-party damage potential, the area of
opportunity is strongly affected by the level of activity near the Class 2 population density (as defined by DOT)
pipeline. It is intuitively apparent that more digging activity near Medium population density nearby, as measured by some
the line increases the opportunity for a line strike. Excavation other scale
OCCUTS frequently in the United States. The excavation notifica- No routine construction activities that could pose a threat
tion system in the state of Illinois recorded more than 100,000 Few one-call or reconnaissance reports (<5 per month)
calls during the month ofApril 1997. New Jersey’s one-call sys- Few buried utilities nearby
tem records 2.2 million excavation markings per year, an aver- Occasional wildlife damage.
age of more than 6000 per day [64]. As noted previously, it is
estimated that gas pipelines are accidentally struck at the rate of LOW activity level (I5 points) This area is characterized by
5 hits per every 1000 one-call notifications. all of the following:
DOT accident statistics for gas pipelines indicate that, in the
1984-1987 period, 35% of excavation damage accidents Class 1 population density (as defined hy DOT)
occurred in Class 1 and 2 locations, as defined hy DOT gas Rural, low population density as measured by some other
pipeline regulations [87]. These are the less populated areas. scale
This tends to support the hypothesis that a higher population Virtually no activity reports (<lo per year)
density means more accident potential. No routine harmful activities in the area (agricultural activi-
Other considerations include nearby rail systems and high ties where the equipment cannot penetrate to within 1 ft of
volumes of nearby traffic, especially where heavy vehicles the pipeline depth are sometimes considered harmless).
such as trucks or trains are prevalent or speeds are high.
Aboveground facilities and even buried pipe are at risk because None (2Opoints) The maximum point level is awarded when
an automobile or train wreck has tremendous destructive- there is virtually no chance of any digging or other harmful
energy potential. third-party activities near the line.
In some areas, wildlife damage is common. Heavy animals The evaluator may assign point values between these cate-
such as elephants, bison, and cattle can damage instrumenta- gories, but should make an effort to ensure consistency.