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CHAPTER 7
Aligning Hazardous Materials
with Varying Levels of Capability
This chapter brings together your prior work on filling out the hazardous materials portfolio
to develop a risk metric that reflects how well your emergency response capability is aligned with
the hazmat present in your jurisdiction. A new term, vulnerability, is added to support calculation
of the risk metric.
Adding Risk to the Hazardous Materials Portfolio
Until this point, the various incident scenarios that could occur in the region have been iden-
tified and the consequences assessed without regard to likelihood or frequency. The vulnerability
term, which will be discussed next, provides a way of assigning a risk level to each scenario. The
measure of risk described in Chapter 1 was called the risk metric because it is not a quantitative
measure of risk, for example, the risk of an incident occurring involving a hazardous material
being released on a local rail line or highway. The risk metric provides a way of prioritizing the
emergency response shortfalls. Given that resources are always going to be limited, it is wise to
fix the shortfalls that result in the greatest reduction in risk. Addressing shortfalls that would result
in only slight reductions in risk might not be worth the cost, even if funds were available.
The vulnerability term is a measure of the likelihood that the population or environment
will be exposed to threats produced by an incident. There are two ways to address vulnerability:
(1) consider potential release probabilities based on historical or scientific data, and (2) consider
the quantity and frequency of materials present. In both cases, vulnerability is expressed on an
annual basis. Table 20 shows the range of values used in this Guide for the vulnerability term for
both of these approaches (based on likelihood of release and based on frequency of presence).
These approaches apply to both fixed facilities and transportation. The frequency approach
addresses how often the materials are present in sufficient quantities to be of concern at the
facility, whereas the transportation approach refers to the frequency of shipments along a
particular transportation corridor or through the community. These values could be assigned to
Freight Analysis Framework (FAF 2010) truck volume levels and the Commodity Flow Survey
(CFS 2007) hazmat percentage of truck tonnage. The vulnerability levels for a particular scenario
can often be estimated from experience. For example, the history of hazmat responses can be used
to assign an overall vulnerability level for the region. Typically, that level will be high or very high.
If a CFS is available, assuming the same incident rate for all transport on each mode, then the
vulnerability level by hazmat class and division can be obtained by multiplying the overall
likelihood of a hazmat incident in the area by the class/division distribution of shipments
from the CFS. If you desire to factor in the likelihood or probability of a package breach given
an incident for hazmat like gasoline, the likelihood can be reduced by an order of magnitude
(i.e., by a factor of 10), and for other bulk commodities the likelihood can be reduced by two orders
of magnitude (i.e., by a factor of 100). The likelihood of a fire or BLEVE is at least two orders of
37
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38 A Guide for Assessing Community Emergency Response Needs and Capabilities for Hazardous Materials Releases
Table 20. Vulnerability levels.
Vulnerability Level Approximate Range
Value Description Likelihood of Release Frequency of Presence
5 Very High > 1 per year many times per day
-2
4 High 1 to 10 per year several times per week to daily
-2 -4
3 Moderate 10 to 10 per year a few times per month
-4 -6
2 Low 10 to 10 per year a few times per year
1 Very Low < 10-6 per year < a few times per year
magnitude--one vulnerability level--below the vulnerability level assigned using the estimated
incident frequency from historical data.
For estimating the likelihood of a release at a fixed facility, you must rely on estimates obtained
through discussions with the companies that have inventories of hazmat. LEPCs will have access
to the company's safety officer and planning documents for any facility that falls under EPA
or Occupational Safety and Health Administration (OSHA) regulations, because hazmat are
present above the prescribed threshold values. In some cases, these planning documents will
include a discussion of the likelihood of a release requiring non-company emergency response
support. If the documents do not include that discussion, you can estimate the likelihood based
on discussions with the safety officer. The safety officer will be familiar with process upsets
and near-misses, serious incident scenarios that were stopped by the intervention of safety
systems or trained operators at the local facility and other similar facilities operating around the
United States. The vulnerability level for a serious incident will be one or, in a few cases, two.
Thus, if several facilities of similar design have been operating for a total of 1,000 plant years and
there was only one known near-miss, then the vulnerability level is probably "low" because there
are typically several near-misses before there is an actual release. For purposes of this example,
the vulnerability will be judged as "moderate," somewhere in the range of 10-2 to 10-4 per year
(or 1 in every 100 to 10,000 years). There might be more than one type of hazardous material
present at a facility, and the vulnerability term could be adjusted upwards accordingly. The size
and nature of the facility matters as well. If the facility was the only producer of a key product in
a region or had another similar characteristic, the vulnerability level probably should be set
higher from a security perspective.
The vulnerability term would also be used if the major threat was viewed to be security rather
than safety. The vulnerability would be associated with iconic targets or critical infrastructure,
and the fraction of the time a material could damage the targets or infrastructure would be used
to assign a value to the vulnerability term. Based on the last column in Table 20, the vulnerability
term would be assigned as "low" if the hazardous material that could damage the iconic structure
or the critical infrastructure were present in the area only a few times a year.
When you consider vulnerability from the safety perspective, the term for a transport corridor
has several components: number of vehicles carrying the hazardous material, incident rate for those
vehicles, hazmat involvement, and hazmat release. While an individual skilled in risk assessment
might not have any difficulty assigning values to those terms, a simpler alternative might be
to just focus on traffic volume. Consider each mode separately. If the region is traversed by a
Class 1 railroad, with 25 or more trains a day traversing the region, a "high" vulnerability should
be assigned for all the hazards believed to be present in the area. From an incident perspective,
if there were 25 trains traversing the area every day, then there are millions of rail car miles per
year passing through the region, and there could be several train incidents per year. It follows
