2

Determining Appropriateness

RELEVANT DISTINCTIONS BETWEEN INLAND AND OFFSHORE OIL BEHAVIOR AND RESPONSE

Key differences exist between the offshore environment and the inland environment, such that the Bureau of Safety and Environmental Enforcement (BSEE) Estimated Recovery System Potential (ERSP) Calculator may not be suitable for use in inland waters (Casey and Caplis, 2014). In the inland environment:

• The presence of shorelines and shallow depths define the size and geometry of the waterway, affecting its flow characteristics as well as corresponding slick behavior and its recovery options.
• The type of the shoreline and its vegetation cover (if any) significantly affects the volume of oil that can adhere to it, its persistence, and its remobilization potential.
• Oil can pool in confined areas at higher film thickness, smaller surface area, and reduced evaporation compared to open waters.
• Currents and tides have a strong influence on oil spreading.
• Some oils that would typically float in seawater can be denser than freshwater and may submerge due to density difference or through adherence to suspended sediments, which are more prevalent in inland waters.
• Waters may be significantly affected by the seasonal presence of ice and seasonal variation in the water flow.
• An individual spill may pass through various types of water bodies and flow regimes before it is stranded or recovered, making it difficult to predict its final fate and properties.

This non-exhaustive list of considerations highlights the complexities of processes affecting fate and behavior of oil spills in inland waters as well as their availability for surface recovery (see Appendix A for more details).

In addition to the important environmental (i.e., physical, chemical, and biological) distinctions between inland and offshore oil spill scenarios, there are also important distinctions in spill response strategies in the inland and offshore environments (see Appendix A).

In the offshore environment, and in the absence of the use of alternative response measures such as the application of dispersants or in situ burning, the primary tactic for recovering oil is mechanical recovery utilizing advancing skimming systems. There are also relatively fewer environmental variables to consider in offshore spill scenarios, since the shallow depths, currents, and shoreline constraints mentioned earlier are not typically factors. As such, the development of an effective offshore calculator for determining the ERSP has proven to be an improvement over the former method of calculating EDRC.

In the inland environment, on-water mechanical recovery of oil is not the only response tactic and, in many cases, is just one in a series of tactical approaches to the cleanup. For example:

• Booms can be used for protection of sensitive and difficult-to-clean areas.
• On-water recovery can be delivered in two different configurations: on-water response using booms and skimmers (similar to the open-water environment) and diversion of oil toward the shore for subsequent recovery at a fixed location.

• Oil in small streams can be recovered by using either diversion booms or other methods such as underflow dams, sorbents, etc. (USCG, 2001).
• Oil can also be recovered from the shorelines using a variety of methods (e.g., building barriers, ditches, dams, berms, trenches, or sumps or collecting oil with heavy machinery, vacuums, manual removal, passive recovery, or sorbents).
• For additional examples, see Appendix A.

This diversity of response methods is in part due to the variability of conditions in the inland environment. In these situations, the specifics of local conditions define oil behavior and response tactics more so than oil properties as would be expected in open-water, offshore environments. Responders in the inland environment often must employ a variety of tactics to mitigate spills, many of which do not include the use of advancing skimming systems (NOAA, 2010). In addition, when supported by local infrastructure, mobilization, operation, and demobilization of these response tools in some inland locations could be easier, faster, and more sustainable than in offshore environments.

The current design of the USCG Inland ERSP Calculator is modeled after the BSEE ERSP Calculator, which estimates the recovery capacity of an entire skimming system in the offshore environment. Although all elements of a skimming system (e.g., skimmer, booms, and temporary storage) are represented as key components of offshore mechanical recovery, the USCG Inland ERSP Calculator evaluates only an open-water “skimming system” (i.e., skimmers and booms), which is only one of many possible inland response strategies. For example, the USCG Inland ERSP Calculator is not designed to consider situations where there is little to no current in a stagnant body of water, or situations where flow to a collection point has been impeded by changing characteristics of the nearshore environment that affect flow direction and flow regime. These location-specific details are important for response planning in the inland environment. Specifically, geographic response plans (GRPs; encompassing plans, strategies, and local response tactics) are critical and take on a holistic approach regarding overall tactics and their planned use. The focus of the USCG Inland ERSP Calculator solely on on-water recovery may drive responders to focus solely on skimming capabilities, while reducing the preparedness for, and risking removing attention from, other response strategies. This problem is similar to the EDRC approach, which resulted in focusing response compliance efforts on skimmers alone, rather than on the complete response system (NRC, 2013).

SPECTRUM OF PLANNING AND MODELING CRITERIA FOR DETERMINING APPROPRIATENESS

Through a review of the supporting documents, and sponsor answers to committee-generated questions, the committee understands that the intent of the USCG Inland ERSP Calculator is as a planning tool (e.g., USCG, 2021a,b,c). This definition aligns with that of the USCG Research and Development Center, who describes the Inland ERSP Calculator as a planning tool, specifically not designed to measure or predict actual oil spill recovery performance in the field (Meier et al., 2020). The term “planning” has broad meaning in the oil spill response industry, from both a regulatory and a tactical preparedness standpoint. The distinction is important in evaluating the overall appropriateness of the calculator, and the committee struggled at times with answering the question “how good is good enough” given the uncertainty of the calculator’s purpose.

In conducting their review, the committee therefore thought about a continuum of complexity, or a spectrum, that exists between a regulatory planning standard and a predictive model (Figure 2.1). A planning-standard approach requires consistency, simplicity, and verifiability of the input parameters; clarity and transparency of the calculations and output values; easy comparison between users, scenarios, and systems; and clear understanding of their ultimate use.

A predictive model, which has a goal of providing an accurate prediction of a given event, is on the other end of the spectrum and requires a high level of complexity and sophistication to attempt to estimate how much oil could be collected in a specific spill scenario. It requires incorporation of the specific details related to the spill scenario, environmental factors, details of response tactics, and more. Although it does not incorporate all the nuances and inefficiencies of the real response under actual conditions (e.g., equipment damage, adverse weather, and human error) and it is not used to predict performance in the actual responses, it may allow users to calculate system performance under optimal conditions in a specific scenario and geographic location. This could allow users to evaluate different response tactics and optimize the combinations of response equipment for the maximum recovery efficiency. This approach is much more complex, requires an experienced user, and does not lend itself to a simple verification or comparison between scenarios because of the large number of variables.

A calculator designed to accomplish tasks of both regulatory planning and predictive modeling is difficult to use and inherently must sacrifice certain aspects of each. As currently designed, the USCG Inland ERSP Calculator falls in the middle of the planning and predicting continuum, having incorporated a larger number of parameters reflective of specific response scenarios than the BSEE ERSP Calculator, but not in sufficient detail to accurately predict the specific operating conditions that are required for development of oil spill response plans. The complexity and variability introduced by these parameters would make it difficult to use a calculator as a regulatory planning tool because the users will likely find it challenging to use and the USCG will find it equally challenging to verify inputs and outputs for different scenarios.

POTENTIAL USERS AND PURPOSE

The BSEE ERSP Calculator allows users to evaluate an idealized recovery potential of a complete multicomponent skimming system using a limited number of environmental variables. It focuses on variables specific to the skimming system, rather than the operating environment, and is suitable for offshore response regardless of a specific location. This allows the user to evaluate a system’s theoretical performance in different configurations, identify parameters reducing or increasing potential volumes of recovered oil, and ultimately optimize a system’s configuration for the maximum theoretical recovery effectiveness.

The USCG Inland ERSP Calculator is also meant to evaluate an idealized recovery potential of a multicomponent skimming system with a broader range of scenarios than the BSEE ERSP Calculator. The broader range of scenarios is provided by the Oil Behavior Module, “a component of the Inland ERSP Calculator that calculates the weathering and emulsification of spilled oil by Oil Group to determine the amount of recoverable oil” (USCG, 2021b). Although the Oil Behavior Module provides greater flexibility in scenarios, it is important to remember that the calculator is not designed to assess a system’s performance in any specific situation (e.g., it should not be expected to estimate a system’s performance for a 50,000-barrel spill in the Potomac River).

According to the USCG Research and Development Center responses to committee-generated questions (accessible in the National Academies public access file through the Public Access Records Office), the intended users of the USCG Inland ERSP Calculator are “not oil spill experts, but plan holders responsible for developing oil spill response plans for their facility/vessel located in the inland environment.” Furthermore, oil spill removal organizations (OSROs) may “also use the calculator to determine the approximate estimate of spill recovery equipment that may be needed for spills in the inland environments.” The committee believes that the value of the calculator’s output is highly dependent upon the skill level of the user. Inexperienced planners without knowledge of spill mitigation tactics would likely not use this tool effectively. Furthermore, current regulatory standards and reporting requirements would limit an OSRO’s use of this tool for planning purposes.

The committee initially identified several potential purposes of the USCG Inland ERSP Calculator, including to allow comparisons between response options and to act as an educational tool. The committee determined that it would be important to educate any potential users on the limits of the calculator in the inland environment.

The use by “planners” means that it is meant to allow for comparisons of recovery using different tactics and equipment. For any tool that a planner must use, a plan reviewer must be comfortable with it as well. This requires that all tactics and equipment be compared against the same inputs and is why the BSEE ERSP Calculator only provides one scenario. The planning mode allows a user to identify limiting components in a system and to identify the system characteristics to maximize performance. For instance, given a specific skimmer, one can determine the swath width and storage needs to maximize performance.

The USCG Inland ERSP Calculator is intended to be generic and not location- or scenario-specific, but simultaneously introduces multiple variables related to the spill scenario, surrounding environment, released volume, oil properties, and more. In increasing the number of potential input values, the calculator becomes more of an educational tool, although limited output information restricts its utility as such. This approach, however, complicates the use of the USCG Inland ERSP Calculator and creates a false impression that the calculator estimates a potential recovery specific to a location or spill scenario. Because of great variability of inland scenarios and response configurations at individual locations (many of which are not covered in this calculator; see USCG, 2021a, app. E, E.1.3), it is not possible to predict even a theoretical system’s capability at a specific location without considering the details of oil behavior and response configurations at that location. It is possible to evaluate theoretical performance of inland standalone response systems in a fashion similar to the BSEE ERSP Calculator’s by focusing on the recovery system itself, reducing the number of inputs, and making it truly nonlocation- and non-scenario-specific. However, the reduction of the “system” to the boom and skimmer alone, without the corresponding storage, would limit

the utility of this analysis. An actual capability estimator would need very detailed input to be able to recreate a specific scenario.

The committee recognizes that ERSP is an improved concept over EDRC with respect to a skimming system’s estimated potential for mechanical recovery of oil, and that the prototype calculator attempts to capture and refine this within the inland environment. That said, the committee has some concerns that the USCG Inland ERSP Calculator, in its current form, would have limitations as an effective tool for the stated user groups. Oil spill planners have a primary concern in ensuring that the contracted response resources listed in their plan meet the applicable regulatory requirement. Because the USCG Inland ERSP Calculator’s output does not consider its impact on the existing regulatory planning standard, it may have limited importance and use to the planner. Furthermore, oil spill response plans are driven in large part by the inclusion of GRPs. These GRPs are an integral part of planning considerations for developing appropriate strategies and tactics for oil spill response. Because these GRPs are site-specific and include tactical plans based on specific geographies and conditions, the use of a “generic” tool may have limited value in this process. Furthermore, and as previously mentioned, there is some risk in distracting an inland planner’s focus away from more prevalent response strategies in trying to apply or adapt the USCG Inland ERSP Calculator to their unique situation.

CRITERIA FOR ASSESSMENT

The committee carefully evaluated suitability of the USCG Inland ERSP Calculator using the following criteria:

• Overall methodology for describing response conditions in inland waters,
• Usability and accuracy of the calculator,
• Appropriateness of inputs,
• Ease of use for user,
• Ability to verify input parameters,
• Transparency of the calculations,
• Clarity of the outputs, and
• Consistency with documentation (i.e., consistency with BSEE’s ERSP methodology).

In this section, the committee outlines their understanding of each of these criteria and the factors that were considered in their evaluation. Committee responses to the Statement of Task items are summarized in Box 2.1.

When reviewing the overall methodology for describing response conditions in inland waters, the committee considered the suitability of the methodology for describing different conditions in inland waters, the adequacy of the methodology for response planning in inland waters, and the adequacy of the calculator for response planning in inland waters. The terms “usability” and “accuracy” were specifically identified in the committee’s statement of task (see Box 1.1, task #2). The committee understood this criterion to mean ability of a user to decide on the values of the inputs, and agreement of inputs and outputs, for particular scenarios with conditions for practical field operations and accepted standards. In terms of the appropriateness of inputs, the committee considered the adequacy of inputs for describing different conditions and response planning in inland waters, the appropriateness of the inputs for use of skimming systems, and the relevance of inputs for response planning in inland waters. The ease of use was evaluated based on the simplicity of the inputs and ease of use, the level of detail to be provided as inputs versus desired output for planning purposes, the user qualifications to provide the inputs for appropriate planning decisions, and the ability of the user to distinguish between the input parameters with significant effects on the outputs versus those that are less significant. In evaluating the ability to verify parameters, the committee considered the ability of the user to verify relative significance of inputs on the estimated outputs

and to identify and manipulate the inputs to develop appropriate planning strategies. The committee considered the criteria of tracking the calculator methodology to estimate appropriate oil skimmer response planning capacities and understanding the relative significance of the inputs on the estimated output when evaluating the calculator’s transparency. Regarding the clarity of the outputs, the committee reviewed how the calculator presents the result as well as the clarity and appropriateness of the detail provided in the output for planning decisions. Finally, when evaluating the consistency of the calculator with documentation (i.e., consistency with BSEE’s ERSP methodology), the committee considered the comparison of the present calculator with the capabilities of the BSEE ERSP Calculator from the perspective of inputs and outputs and ability to estimate the recovery potential. The committee also evaluated the suitability of accompanying documents to guide the user through the calculation process.