Page 161 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

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hazard complicates the response of emergency personnel. A2. Chronic hazard
Long-term exposure effects must be assessed using an addi-
tional scale. Long-term health effects will be covered in the A very serious threat from a pipeline is the potential loss of life
assessment of chronic hazards associated with product spills. caused by a release of the pipeline contents. This is usually
Toxicity is covered in more detail in the following section. considered to be an acute, immediate threat. Another quite
As defined in NFPA 704, the toxicity ofthe pipeline product serious threat that may also ultimately lead to loss of life is the
is scored on the following scale [26]: contamination of the environment due to the release of the
Nh = 0 No hazard beyond that of ordinary combustibles. pipeline contents. Though not usually as immediate a threat as
Nh = 1 Only minor residual injury is likely. toxicity or flammability, environmental contamination ulti-
Nh = 2 Prompt medical attention required to avoid tempo- mately affects life, with possible far-reaching consequences.
rary incapacitation. This section offers a method to rate those consequences that
Nh = 3 Materials causing serious temporary or residual injury. are of a more chronic nature. We build on the material presented
Nh = 4 Short exposure causes death or major injury. in the previous section to do this. From the acute leak impact
Appendix A lists the N, value for many substances consequences model, we can rank the hazard from fire and
commonly transported by pipeline. explosion for the flammables and from direct contact for the
toxic materials. These hazards were analyzed as short-term
Acute hazard score threats only. We are now ready to examine the longer term
hazards associated with pipeline releases.
The acute hazard is now obtained by adding the scores as Figure 7.4 illustrates how the chronic product hazard associ-
follows: ated with pipeline spills can be assessed. The first criterion is
whether or not the pipeline product is considered to be haz-
Acute hazard (&I 2 pts) = (Nf+ N, + N,,) ardous. To make this determination, US. government regula-
tions are used. The regulations loosely define a hazardous
A score of 12 points represents a substance that poses the substance as a substance that can potentially cause harm to
most severe hazard in all three of the characteristics studied. humans or to the environment. Hazardous substances are more
Note that the possible point values are low, but this is part of a specifically defined in a variety of regulations including the
multiplying factor. As such, it will have a substantial effect on Clean Water Act (CWA), the Clean Air Act (CAA), the
the total risk score. Resource Conservation and Recovery Act (RCRA), and the
Few preventive actions are able to substantially reduce acute Comprehensive Environmental Response, Compensation and
hazards. To be effective, a preventive action would have to Liability Act (CERCLA, also known as Superfund). If the
change the characteristics of the hazard itself. Quenching a pipeline product is considered by any of these sources to be
vapor release instantly or otherwise preventing the formation of hazardous, a reportable spill quantity (RQ) category designa-
a hazardous cloud would be one example of how the hazard tion is assigned under CERCLA (Figure 7.4). These RQ desig-
could be changed. While the probability and the consequences nations will be used in our pipeline risk assessment to help rate
of the hazardous event can certainly be managed, the state of hazardous products from a chronic standpoint.
the art is not thought to be so advanced as to change the acute The more hazardous substances have smaller reportable spill
hazard of a substance as it is being released. quantities. Larger amounts of more benign substances may be
spilled before the environment is damaged. Less hazardous
Direct measurement of acute hazards substances, therefore, have larger reportable spill quantities.
The designations are categories X, A, B, C, and D, correspon-
Acute hazards are often measured directly in terms fire and ding to spill quantities of 1, 10, 100, 1000, and 5000 pounds,
explosion effects when contact toxicity is not an issue. In the respectively. Class X, a 1-pound spill, is the category for sub-
case of fire, the possible damages extend beyond the actual stances posing the most serious threat. Class D, a 5000-pound
flame impingement area, as is readily recognizable from spill, is the category for the least harmful substances.
approaching a large campfire. Heat levels are normally meas- The EPA clearly states that its RQ designations are not
ured as thermal radiation (or heatflux or radiant heat) and are created as agency judgments of the degree of hazard of
expressed in units of Btu/ft2-hr or kW/m2. Certain doses of specific chemical spills. That is, the system is not intended to
thermal radiation can cause fatality, injury, andor property say that a 9-pound spill of a class A substance is not a prob-
damage, depending on the vulnerability of the exposed subject lem, while a 10-pound spill is. The RQ is designed to be a
and the time of exposure. Thermal radiation effects are dis- trigger point at which the government can investigate a spill
cussed in this chapter and quantified in Chapter 14 (see also to assess the hazards and to gauge its response to the spill.
Figure 7.8 later in this chapter). The criteria used in determining the RQ are, however, appro-
Explosion potential is another possible acute hazard, in the priate for our purposes in ranking the relative environmental
case of vapor releases. Explosion intensity is normally charac- hazards of spills.
terized by the blast wave, measured as overpressure and Classifying a chemical into one ofthese reportable quantities
expressed in psig or Wa. Mechanisms leading to detonation are categories is a nontrivial exercise outlined in U.S. Regulations,
discussed in this chapter and a discussion of quantification of 40 CFR Parts 117 and 302. The primary criteria considered
overpressure levels can be found in Chapter 14. include aquatic toxicity, mammalian toxicity (oral, dermal,
The amount of harm potentially caused by either of these inhalation), ignitability and reactivity, chronic toxicity, and
threats depends on the distance and shielding of the exposed potential carcinogenicity. The lowest of these criteria (the worst
subjects. case) will determine the initial RQ ofthe chemical.