Page 265 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

I11242 Distribution Systems
Property damage--consequences involving property dam- flow rates are potentially interrupted are modeled to also cause
ages and losses: higher outage consequences. In addition, we can assume that
Structure value the number ofusers potentially interrupted by a spill at a certain
High-value areas location is proportional to the nearby population. This is an
Contents assumption that will be incorrect in situations such as when a
Landscape transmission line runs through a populated area, but does not
Collateral. serve that area directly. Nevertheless, it is correct often enough
0 Environmental sensitivities-damages to areas that are and tends to overstate rather than understate the risk and hence,
especially vulnerable to damage, from an environmental is an appropriate modeling convenience.
viewpoint. The interruption time is thought to be a function of ease-of-
0 Business impacts-consequences resulting from business repair and response capabilities. Relative repair costs can capture
interruptions in the immediate vicinity of the spill and as a the ease-of-repair aspect and could be measured as a function of
direct consequence of spill effects. Damages related to serv- the variables such as these (underlying assumptions shown also):
ice interruptions are captured in the “outage” aspect of this
assessment since such damages are not necessarily limited Diameter-Larger diameters lead to more expensive repairs
to the immediate spill vicinity. due to higher material costs, greater excavation require-
Proper@ damage-this can be assessed through an exami- ments, increased repair challenges, and need for larger
nation of the following variables: population, property type equipment.
(commercial, residential, industrial, etc.), property value, Slope-Steeper slopes lead to more expensive repairs due to
landscape value, roadway vulnerability, and highway vul- difficulties in accessing and stabilizing repair site, the possi-
nerability, and other considerations. ble need for more specialized equipment, and general
increases in time needed to complete repairs.
The model weightings of various receptors should be based Repair readiness-This is a rating capturing the training and
on the perceived vulnerability and consequence potential of expertise of repair crews, the availability of equipment and
each receptor. This includes direct damages and secondary replacement parts, and other factors influencing the effi-
effects such as public outrage. Valuing of receptors is discussed ciency with which repairs can be made.
beginning on page 165. Surface type-Postexcavation repair of concrete and asphalt
surfaces are thought to be more expensive.
Outage Population-In general, increased population density leads
to more expensive repairs due to the need for increased pro-
Consequences of distribution system failures can also be tection of job site, traffic rerouting, avoidance of secondary
categorized as “outage related.” These include damages damages during construction, etc.
arising from interruption of product delivery, including the
relative time of the interruption. (See also Chapter 10 for a Response capabilities can include leak detection capabili-
detailed discussion of risk of service interruption assessment ties, emergency response capabilities, and availability of make-
techniques.) up supply during an outage. The latter, availability of make-up
Some customers are more damaged by loss of service than supply, can often require a complex network analysis with
others. It might not be realistic to link specific customers or many assumptions and possible scenarios. As a modeling con-
even customer counts to all potential spill locations. As a surro- venience, availability of make-up could be assumed to be pro-
gate, the volume or pressure transported in any portion of the portional to the normal flow rate under the premise that the
system could be assumed to be directly proportional to the crit- greater the flow rate that is interrupted, the more difficult will
icality of that supply. Therefore, failure locations where higher be the replacement of that supply.