Summary
In 1989, following the Exxon Valdez oil spill, it became apparent that the United States was inadequately prepared for a major oil spill response. The introduction of the Oil Pollution Act of 1990 and Executive Order 12777, however, helped address this deficiency through the implementation of guidelines related to the prevention of, response to, and financial responsibility for oil spills within the navigable waters of the United States. Some of the safeguards provided by these regulations included mandating contingency planning and setting new requirements for vessels and crew.
The planning standard for mechanical oil skimming systems in the United States has long been the Effective Daily Recovery Capacity (EDRC). However, after the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, EDRC was deemed inadequate for calculating mechanical oil recovery spill response equipment needs. As a result, the Bureau of Safety and Environmental Enforcement (BSEE) commissioned Genwest Systems, Inc. (Genwest) to assess the EDRC planning standard and to consider improvements or alternatives. The Genwest (2012) report proposed an alternative performance-based method or “tool,” known as the Estimated Recovery System Potential Calculator (BSEE ERSP Calculator), to estimate the recovery potential of skimming systems under variable environmental and operational conditions.
Unlike the EDRC, which uses only the nameplate rating of the skimmer to determine recovery, the BSEE ERSP Calculator treats the “recovery system” (e.g., boom, skimmer, and storage) as a unit being operated in a defined manner (e.g., swath width, advance speed, encounter rate, and operating hours) to determine the system’s recovery potential in a defined scenario. The BSEE ERSP Calculator allowed users to determine the ERSP for recovery systems in an open-water environment.
In the years since, there has been a recognition that the BSEE ERSP Calculator may not be applicable to inland and nearshore spills. Recognizing this potential limitation, the United States Coast Guard (USCG) contracted with RPS Group (RPS) to modify the BSEE ERSP Calculator for application to inland and nearshore systems. First, the USCG hosted a workshop in 2017 with subject-matter experts where it was agreed that significant challenges existed in attempting to apply the BSEE ERSP Calculator to spills in the inland and nearshore environment. Second, the USCG Research and Development Center entered into a contract with RPS in 2018 to develop a conceptual model based on a review of the literature, research, and interviews with subject-matter experts. That group finalized a list of the features and factors that needed to be included in a new, Inland ERSP Prototype Calculator (USCG Inland ERSP Calculator); produced a conceptual model report that provided an overview of the calculator and described the relationship of all factors in worst-case, maximum most probable, and average most probable discharge scenarios; produced a design document containing all algorithms needed for calculator function; produced a quick-start guide serving as a user manual for the calculator; and produced a validation and verification document detailing the process for the development of the prototype calculator. The resulting USCG Inland ERSP Calculator is the subject of the present review.
This committee was asked by the USCG to review the Inland ERSP Prototype Calculator and associated quick-start guide for the software. The committee was to scientifically assess, and provide recommendations for improving ERSP methodologies; to inform oil spill planning and preparedness for the inland and nearshore environments; and to provide recommendations for new ERSP methodologies and guidelines, if any, for mechanical response systems deployed in inland and nearshore operating environments.
The committee interpreted its task as consisting of two parts. The first part of the statement of task was an assessment of the prototype calculator to determine the ERSP of a mechanical skimming system when deployed in inland and nearshore environments. Part of this assessment was the inclusion of an explanation of the criteria used in the evaluation and justification for the committee’s disposition on the appropriateness determination. The committee considered appropriateness in two ways: (1) the calculation (e.g., inputs, algorithms, and outputs) and (2) the calculator’s use in spill response planning (e.g., inputs
and outputs). The second part of the statement of task sought the committee’s recommendations for improving current USCG Inland ERSP Calculator methodologies and recommendations for new USCG Inland ERSP Calculator methodologies and guidelines. The committee considers the request for improving methodologies to be their suggestions for modifications to the calculator inputs and algorithms as presented. The committee considers the request for new methodologies to be their suggestions beyond ERSP calculators for mechanical recovery system planning in the inland and near nearshore environments.
The committee’s deliberations and review were focused on the calculator’s capabilities, review of appropriate standards and literature, and information provided during a series of public meetings and presentations, drawing on expertise from academic, governmental, and nongovernmental communities.
In addition to a recorded presentation about the Inland ERSP Calculator that USCG presented at the International Oil Spill Conference in 2021, the committee was provided six files specific to the USCG Inland ERSP (i.e., Conceptual Model Report, Design Document, Quick-Start Guide, Verification and Validation Document, calculator software, and calculator source code). To support information-gathering efforts, the committee held four virtual, public meetings where experts from federal and local governments, industry, and academia were invited to talk to the committee. During these meetings the committee discussed the statement of task, considered the calculator design, prototype, and user guide, and resolved outstanding questions. Other topics of discussion included oil spill response, oil behavior, and practical considerations in inland oil spill response.
Regarding the first part of the statement of task, the assessment of the prototype calculator to determine the ERSP of a mechanical skimming system when deployed in inland and nearshore environments, the committee found ways in which the calculator was both appropriate and inappropriate. For example, although the committee agrees that the ERSP concept is sound and an improvement over the EDRC regardless of operating environment, and recognizes the effort USCG and various collaborators have put into the identification of the numerous challenges in applying the calculator to the inland environment versus the offshore environment, they also found that the calculator only evaluates certain aspects of an overall “skimming system,” while ignoring or discounting other elements, and has limited outputs that are insufficient for the user to confirm accuracy, identify the source of potential errors, or identify system improvements. In terms of justifying their determination of appropriateness and explaining any criteria used, the committee again found both appropriate and inappropriate aspects of the prototype. For example, while the use of BSEE open-water algorithms for estimation of the skimming system ERSP for open-water recovery in a wide river or lake systems is valid, the prototype calculator lacks constraints on several parameters (e.g., forward speed, river width, distance to shoreline), allowing the user to input unrealistic values which produce misleading results.
Regarding the second part of the statement of task, which sought the committee’s recommendations for improving USCG Inland ERSP Calculator methodologies for new methodologies and guidelines, the committee considered potential calculator modifications. For existing USCG Inland ERSP Calculator methodologies, the committee found that the software has conceptual design flaws (e.g., lack of consideration of oil mass balance and lack of guardrails for some input values), is incomplete (e.g., lacks storage), and has software errors (e.g., interface does not always update calculation with changing entries). The software and the documentation are inconsistent, and the software is incompatible with certain computer operating systems. The committee made a series of recommendations for methodological improvements, designed to improve the calculator approach and achieve its intended purpose. For example, at a basic level, the calculator should undergo a thorough verification/quality assurance testing regimen by independent third-party reviewers prior to consideration for release. Further, the calculator software should be universally compatible, especially with Windows and Apple operating systems.
For new USCG Inland ERSP Calculator methodologies, although the committee was told that the intent was for the calculator to be used for planning purposes, particular inputs suggested that the creators intended for the calculator to do more. Also, the committee was not clear about whether “planning purposes” include potential incorporation of this calculator into the relevant regulations.
The committee made recommendations for new methodologies, largely dependent upon the intended uses of the calculator. For example, if the intended use of the calculator is to serve as a planning tool
and to be focused on evaluating a maximum recovery potential of the recovery system regardless of geography or scenario, the inputs related to the scenario and oil behavior should be limited to the minimum, similar to the BSEE ERSP Calculator, so calculation is truly focused on the recovery system, not the environment.
