Risk of Vessel Accidents and Spills in the Aleutian Islands Designing a Comprehensive Risk Assessment - Special Report 293 (2009) / Chapter Skim
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6 Technical Approach to the Aleutian IslandsRisk Assessment
6 Technical Approach to the Aleutian IslandsRisk Assessment
Pages 110-141
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From page 110... ...
These semiquantitative portions of the Phase A assessment, such as traffic characterization and projections and estimation of spill rates and sizes, will rely heavily on historical data and, where appropriate, experience from prior risk studies and expert opinion. The traffic and spill risk studies will help the Management Team and Advisory Panel identify geographic locations and spill scenarios for a limited number of focused environmental impact investigations, to be carried out in the Phase A consequence analysis.
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From page 111... ...
Although the risk assessment is structured into discrete phases and steps, the identification and prioritization of risk reduction options should be an ongoing, iterative process throughout all of these efforts, reflecting analysis results as they become available, changing circumstances, and emerging technologies and opportunities. The second section of this chapter describes the Phase A effort to evaluate the identified risks, develop a list of potential risk reduction measures, and prioritize those measures.
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From page 112... ...
PHASE A PRELIMINARY RISK ASSESSMENT: SEMIQUANTITATIVE STUDIES The purpose of this portion of the Phase A Preliminary Risk Assessment is to identify the more significant risks related to spills from shipping and provide a basis for the identification and initial ranking of possible risk reduction measures. These semiquantitative studies are intended to provide a high-level understanding of relative risks, taking into consideration types of vessels and hazardous substances and locations where discharges are most likely to occur.
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From page 113... ...
are of sufficient concern to merit assessment of risk reduction measures. This information will be used during the brainstorming of potential risk reduction mea sures and as input into the accident scenario and causality analysis (Step 5 below)
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From page 114... ...
For instance, drift grounding simulation may be needed to gain an understanding of the likelihood of a disabled vessel drifting aground, particularly for vessels transiting to the south of the Aleutian Islands. However, the use of simulations or expert opinion to predict the likelihood of major spill events should be minimized to the extent possible.
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From page 115... ...
Communication with weather routing services and shipping companies may also be required to augment these data. Determinations of concentrations of fishing vessels, locations of seafood processors, movements of barges transporting refined products to the outer Aleutian Islands, and other local vessel movements will require review of local data sources, such as the Marine Exchange and the Alaska Commercial Fisheries Entry Commission, as well as communication with pilots and industry representatives.
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From page 116... ...
Ship data should be evaluated to determine design characteristics required for the risk analysis, such as the percentage of single-hull versus double-hull tank vessels, the extent of doublehull protection provided for fuel tanks, and the range of bunker tank capacities applicable to the various vessel types. The categories of vessel types and sizes should be sufficiently fine-grained to allow assessment of measures that may be particular to a given trade or vessel type.
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From page 117... ...
Over the 25-year study period, changes in the design of ships transiting the Aleutian Islands can be anticipated. For example, only a few containerships greater than 8,000 TEUs in size are currently in operation, but more than 100 ultralarge containerships are on order, ranging in capacity from 8,000 to 13,000 TEUs.
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From page 118... ...
Estimate the spill frequency and projected spill size distribution by vessel type. The accident types most likely to lead to large spills are collisions, powered and drift groundings, structural failures, and fires and explosions.
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From page 119... ...
2b. Develop the oil spill baseline over the 25-year study period as the product of the projected movements of oil and other hazardous materials and the estimated average spill rates.
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From page 120... ...
The type of oil or other hazardous substance, the location of the spill, and the time of year the spill occurs influence the extent of damage to natural resources, cleanup costs, and socioeconomic costs, and they should be considered along with spill size when consequences are evaluated. To illustrate the importance of substance type, spills of persistent oils, such as the heavy fuel oil used for bunkers of large commercial ships, have properties different from those of the diesel oil and marine gas oil used for propulsion of smaller craft, such as fishing boats.
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From page 121... ...
The Phase A consequence analysis, then, should cover a mix of spill sizes, substance types, and locations. As noted in the preceding section, the specific parameters to be addressed by the analysis should be determined on the basis of the results of the traffic, spill baseline, and spill likelihood and size studies.
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From page 122... ...
For example, it might be found that the important accidents are collisions and drift groundings involving cargo ships operating in and around Unimak Pass, drift groundings of tank barges, and founderings and groundings of fishing vessels operating in particularly environmentally sensitive regions. For each of the dominant accident types, the Risk Analysis Team should develop representative accident scenarios.
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From page 123... ...
PHASE A PRELIMINARY RISK ASSESSMENT: QUALITATIVE ASSESSMENT AND PRIORITIZATION OF RISK REDUCTION OPTIONS To complete the Phase A preliminary risk assessment, a qualitative assessment of risk reduction options should be performed by the Advisory Panel and Management Team. This effort should include populating the risk matrices, compiling a list of risk reduction options, qualitatively assessing the benefits and costs of those options, and prioritizing the options.
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From page 124... ...
The Advisory Panel, in consultation with the Management Team and Risk Analysis Team, should determine the frequency and consequence categories that are appropriate and the criteria to be applied for each category. These criteria are for purposes of ranking scenarios and accidents by level of risk and eventually effectiveness of risk reduction options and will not necessarily be the basis for the final decision on which options will be implemented.
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From page 125... ...
TABLE 6-3 Example Criteria for Consequences by Consequence Category Consequence 1 -- Incidental 2 -- Minor 3 -- Serious 4 -- Major 5 -- Catastrophic Natural resources No significant wildlife kill Destruction of unique or rare or habitat impact habitat Health and safety of public No significant exposure Significant exposure for many people Health and safety of crew Minor injury at most Multiple fatalities or permanent disabilities Release of oil or cargo Recordable event with no Significant release or irreparable outside notification (e.g., damage with long-term effects onboard containment, placarding, mistowage) Socioeconomic impact No significant disruption Total loss of asset/multiple of industry or society industries affected; multi generational community impact Damage to reputation No adverse news coverage International adverse news coverage
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From page 126... ...
. The Advisory Panel, in consultation with the Management Team and Risk Analysis Team, should develop a risk priority matrix format suitable for this assessment.
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From page 127... ...
Using the priority risk matrix, scenarios should be consolidated into four or five risk categories. The Advisory Panel, in consultation with the Management Team and Risk Analysis Team, should attempt to further rank the accident scenarios within each group, producing an overall ranking of accident scenarios.
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From page 128... ...
Many of the likely members of that group are responsible for measures on the committee's list of potential risk reduction options, and many have local knowledge of the waterways, the environment, the infrastructure, and shipping in the Aleutian region. They have the expertise and the interest to augment the work of the Risk Analysis Team in this important way.
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From page 129... ...
This can be represented as an overall relative risk reduction score (e.g., 1 + 2 = 3) , which can be used to rank the effectiveness of the risk reduction options identified in Step 7.
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From page 130... ...
On the basis of this prioritization effort and the recommendations of the Advisory Panel, the Management Team may decide that there is sufficient justification to recommend immediate implementation of some of the potential risk reduction measures.
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From page 131... ...
The results of this effort should provide the Management Team and Advisory Panel with sufficient information to make recommendations with regard to the implementation of risk reduction measures and produce a report documenting the justification for these recommendations. The potential risk reduction measures identified during Phase A as warranting further study will largely dictate the scope of the Phase B assessment.
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From page 132... ...
Human factors analysis can also be resource-intensive and should focus on those areas where high risk has been identified and where potential risk reduction measures are practical and enforceable. Phase B Analysis and Techniques The Phase B risk analysis should follow the basic steps outlined for Phase A
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From page 133... ...
. Need for More Detailed Causal Modeling, Particularly in Areas Where Risk Reduction Measures Are Being Considered Normally, the level of detail of risk analysis is influenced by data availability.
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From page 134... ...
Use of Formal Methods for Employing Expert Opinion Study of the risks associated with complex man-made and natural systems always involves subjects for which data or models either do not exist or are not cost-effective. In such cases, expert opinion becomes an important resource for the analyst.
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From page 135... ...
See Appendix E for further discussion of uncertainty and sensitivity analyses. Consequence Analysis The extent of additional consequence analysis required for the Phase B assessment will be influenced by the types of risk reduction measures to be evaluated and the possible need for monetizing of benefits, such as avoidance of natural resource damage and socioeconomic costs.
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From page 136... ...
In cost–benefit analysis, both costs and benefits are monetized. The results make it possible to compare all risk reduction measures according to a common metric and reduce reliance on the use of professional judgment to compare benefits qualitatively.
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From page 137... ...
Results of cost-effectiveness analysis can be misleading, however, when the effectiveness measure does not properly map consequences or when disparate types of benefits are combined. For example, the consequence of an oil spill is influenced by the type of oil spilled and the size and location of the spill; this makes it difficult to compare different accidents and risk reduction measures on the basis of barrel of oil spill avoided.
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From page 138... ...
Evaluating the costs of natural resource damage can be expensive, depending in part on the availability of the necessary biological data. After reviewing the Phase A results, the Management Team, in consultation with the Advisory Panel and Risk Analysis Team, should decide on the extent to which the costs of natural resource damage and socioeconomic costs will be evaluated.
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From page 139... ...
For the more costly and far-reaching measures, successful implementation may well require a collaborative agreement among decision makers and the support of stakeholders, and some such measures, such as those that require the involvement of IMO, may take longer to implement than changes that can be made at the local level. The Management Team and the Advisory Panel should prepare a final report providing recommendations to decision makers in a way that documents the basis for those recommendations in the risk assessment.
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From page 140... ...
The goal of the risk assessment that is the subject of this report is to improve the level of safety related to spills from ships operating within the Aleutian Islands region. The implementation of risk reduction measures identified by this assessment should result in risk falling at or below the tolerable level (although it may not be possible to define such a level with precision)
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From page 141... ...
Experience with other systems having the complexity of shipping through the Aleutian Islands suggests that risk cannot be reduced to zero by risk reduction measures that can feasibly be undertaken. REFERENCES Abbreviations NRC National Research Council TRB Transportation Research Board USCG U.S.
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