Letter Report on a Technical Peer Review of the Buzzards Bay Risk Assessment (2013) / Chapter Skim
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1 Letter Report Transportation Research Board of The National Academies Technical Peer Review of the Buzzards Bay Risk Assessment SUMMARY Over the past 72 years, eight maritime incidents in Buzzards Bay, the Cape Cod Canal, and the vicinity have resulted in significant oil spills and environmental impacts. The most recent, the Bouchard B-120 spill in April 2003, resulted in the loss of 2,333 barrels of fuel oil.
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2 At the request of MassDEP, the Transportation Research Board (TRB) of the National Academies (TNA)
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3 1. INTRODUCTION Study Objectives and Charge MassDEP requested that TRB conduct a technical peer review to evaluate the methodologies and conclusions of the BBRA.
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4 technical review of the BBRA focuses on the following key questions posed by MassDEP: 1. Is the scope of the analysis (type and extent of data gathered)
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5 meeting and discussions, the committee deliberated in closed session and prepared this letter report outlining its findings and conclusions and the rationale that led to these conclusions. This letter report adheres closely to the committee's statement of task (Enclosure D)
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6 The Buzzards Bay–Cape Cod Canal navigation route is a major throughway for tank barges transporting oil to parts of the Northeastern United States. Since 1969, several tank barge groundings have resulted in the discharge of oil into Buzzards Bay, Massachusetts.
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7 On August 30, 2007, USCG published a final rule to implement the revisions that were proposed in the 2006 NPRM to amend the existing RNA for navigable waterways within the First Coast Guard District. Navigation safety measures required by these regulations can be found at 33 CFR § 165.100.
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8 Description of the BBRA To clarify and focus the discussion between USCG and MassDEP on particular risk mitigation options of interest in Buzzards Bay, the two agencies commissioned HS SEDI to undertake a study of the technical risks and risk mitigation options associated with oil spills in Buzzards Bay and the Cape Cod Canal. In particular, the parties were interested in evaluating the risk reduction benefits and any environmental, economic, or other quantitative or qualitative costs associated with the use of marine pilots and tugboat escorts for all vessels towing laden tank barges.
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9 environmentally sensitive habitat and resources at risk, threatened and endangered species, seasonality associated with vulnerabilities, and limits to available oil spill containment and recovery techniques due to weather or environmental factors. An evaluation of risk mitigation costs and benefits associated with a requirement that federally licensed pilots who are not also members of the crew be on board all doublehull tank barges transiting the RNA.
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10 relatively short, and step-by-step details of some of the analyses are not present. Thus, the committee believes that its comments are appropriate for the scope of the work.
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11 General Approach: Starting Without a Hazards Analysis First, the committee believes that a different framing of the initial approach would have been beneficial in establishing the structure of the study and justifying the conclusions. Generally, for assessments like this, a hazards (or root cause)
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12 Although only a qualitative assessment was used to determine the relative effectiveness of each mitigation measure in reducing the likelihood of a spill, a quantitative analysis was used to rank the measures on the basis of a calculated return on investment (ROI)
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13 electronic charting) , and waterways management (e.g., Vessel Movement Reporting System)
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14 FIGURE 3 Oil spill volume from tank vessels worldwide, 1974–2012. (SOURCE: Data are from ITOPF 2012.)
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15 FIGURE 4 Oil spill volume (gallons) from tank barges in U.S.
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16 FIGURE 5 Relative casualty and spill frequency trends, with 2001 values indexed at 1.00. (Data are from Figure 18, page 34, of HS SEDI 2013.)
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17 This, in turn, will affect the cost–benefit calculations that are used to justify the options. As written, the probability and spill-size estimates are not applicable to the risk assessment.
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18 A similar problem occurs with the analysis of escort tug operations. Since January 2011, the Commonwealth of Massachusetts has imposed the requirement that an escort tug be used for all oil barges, both single and double hull, transiting Buzzards Bay and the Cape Cod Canal.
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19 realized from the behavior and the resulting operation that was not considered in the scope of the analysis. These issues are discussed in detail in the next section.
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20 this as an option is lacking, particularly since there are no other adverse-weather-only escort tug operations in this country and none that the committee is aware of internationally. Sentinel tugs, in some applications, are deployed only in adverse weather; however, escort tugs typically escort at all times.
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21 of the novelty of this option, estimates of the costs and benefits must include associated uncertainties. In addition, some of the options evaluated are assessed relative to other options.
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22 Although many of the most critical model inputs were highly uncertain, none was subjected to sensitivity or uncertainty analyses. These decisions will be discussed in detail in this section.
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23 of positive or negative values in "impact scores" in the BBRA (Table 14 in the BBRA report) as compared with USCG's guidelines, where all scoring is based on more straightforward and easily understood positive-value scaling]
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24 Subjecting prospective risk reduction measures to cost–benefit analysis (monetized value of risk reduction benefits compared with implementation and other costs associated with the risk reduction measures) is common to many risk assessment approaches, for example, the International Maritime Organization's Formal Safety Assessment (TRB 2008)
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25 likelihoods of occurrence)
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26 with and without the risk reduction measures being examined. Such defenses appear to have been difficult to achieve in the BBRA study given the complexity of the underlying situation and the limits in time and financial resources.
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27 allows for more user-defined inputs on spill and location specifics and includes improvements in estimating costs when the number of events on which they are based is limited. NRC's Marine Board study on evaluating double-hull design alternatives (TRB 2001)
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28 concept of total economic value (TEV)
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29 relate to changes in welfare associated with the spill is not explained. Similarly, the true costs to society of future mitigation policies require analyses that were not done in this report.
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30 The impact score has seven possible values (–5, –4, –3, 1, 3, 4, and 5) , with negative scores indicating a decrease in the frequency of a risk event; 1 indicating no change in frequency; and 3, 4, and 5 indicating an increase in frequency.
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31 with each casualty, all collisions are scored as "major" or 5, all powered groundings and allisions are scored as "moderate" or 3, and drift groundings are scored as "minor" or 1. The three factors are then multiplied to compute a "total risk score" for each risk mitigation option for each type of casualty; negative scores indicate a risk reduction and positive scores indicate either no change in risk or an increase.
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32 the "switch from single to double hull" option received. Adding four multiplicative scores to achieve a single overall score is questionable (e.g., positive numbers of undetermined value are canceling negative numbers of equally undetermined value)
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33 Flawed Expert Judgment Elicitation Protocol Since the impact score is the only source of an "effectiveness" or risk reduction measure for each option, its value is critical to the analysis and requires solid justification. Unfortunately, this value was the only one that relied completely on expert judgment, and the expert elicitation that was done was not documented and appears not to follow any of the accepted protocols -- for example, those of the Nuclear Regulatory Commission 11 or EPA 12 or those concerning oil spill risk (TRB 2008)
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34 necessary." The impact scores (as well as the frequency and severity scores) that are used to develop the risk reduction rankings are identical for the two escort tug options.
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35 less effective (have a smaller negative total risk score) than an option that only decreased the frequency.
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36 the amount of oil shipped per year, more useful metrics would be oil spill volume per transit (or per volume of oil transported)
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37 Virtually everything in this approach is wrong. First, the basis for quantification of human error probability is incorrect.
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38 visibility conditions are recorded hourly and wave height and period data are available for the entrance to Buzzards Bay, the adjustments made in the BBRA can be eliminated and a detailed probabilistic model could have been constructed. See Enclosure H for a detailed weather analysis.
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39 concerning what was assumed about escort tug operations when the impact scores (risk reductions) were assessed.
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40 Statement of Task 1. Is the scope of the analysis (type and extent of data gathered)
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41 makes the assessment results appear unjustifiably conclusive. Decision makers relying on the assessment could place too much confidence in the risk mitigation rankings.
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42 The committee believes that the available data could have been used more appropriately. As has been mentioned, some data were pushed beyond their useful limit (e.g., spill histories)
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43 REFERENCES Abbreviations AWO American Waterways Operators HS SEDI Homeland Security Systems Engineering and Development Institute ITOPF International Tanker Owners Pollution Federation Limited MassDEP Massachusetts Department of Environmental Protection NRC National Research Council OECD Organisation for Economic Co-operation and Development TRB Transportation Research Board USCG U.S. Coast Guard Costa, J
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44 Hubbard, D
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