Expert Report

A Review of Genwest's Final Report on Effective Daily Recovery Capacity (EDRC): A Letter Report (2013)

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Produced at the request of the U.S. Department of Interior Bureau of Safety and Environmental Enforcement (BSEE), this letter report reviews a report by Genwest Systems, Inc., that presents a new approach for estimating the efficiency of oil skimmers when preparing oil spill response plans. The National Research Council committee found the new approach -- called the Estimated Recovery System Potential (ERSP) -- to be sound and a good basis for updating the way BSEE sets planning standards for response to offshore oil spill events. ERSP is a substantial improvement over the current method, Effective Daily Recovery Capacity, because the new approach reflects the full recovery cycle associated with on-water oil spill skimming systems. However, a number of simple improvements that would be extremely useful can and should be made to the ERSP approach.

Key Messages

  • BSEE should provide a "User Manual" that documents the limitations of use of the ERSP approach and provides guidance to the user for choosing input values in accordance with different planning scenarios. The User Manual should provide the ERSP calculator’s equations along with a clear definition of variables and their units of measurement. It should also explain the rationale for the assumptions used in the calculator and discuss the uncertainties associated with all fixed and input parameters.
  • The ERSP calculator should carry parameter uncertainties forward to provide estimates of uncertainties in the outputs. This would provide more informative results for evaluating response plans.
  • The utility of the new ERSP estimation could be significantly increased if the user is allowed to select values from a set of planning scenarios provided by BSEE in the User Manual. For example, the user could choose among options for entering estimates of oil thickness. The nameplate recovery capacity in the scenarios could be based on ASTM F2709-08, Standard Test Method for Determining Nameplate Recovery Rate of Stationary Oil Skimmer Systems, instead of the derated nameplate recovery capacity.
  • Given that environmental conditions may limit the effectiveness of oil skimmers, the best overall approach would be a "system of systems" plan in which mechanical oil skimmers are evaluated as one of a set of "tools" that could be used in spill response.