ABSTRACT
The use of aerial dispersants is an effective method for addressing oil spills in coastal waters and deep offshore locations like the Outer Continental Shelf or Gulf of Mexico. Safety measures are put in place to protect the responders and nearby wildlife, such as establishing a buffer area around the affected site. To improve the accuracy of estimating the extent of spray drift during aerial dispersant application, the U.S. Department of the Interior's Bureau of Safety and Environmental Enforcement (BSEE) commissioned a research project that developed a Decision Support Tool (DST) in 2015. An effort was made in 2019 to enhance the DST by filling in data gaps in the prototype's modeling, adding more aircraft to the tool, and incorporating a contour plot output to show dispersant deposition. This paper presents the enhancements made to the DST tool and the subsequent research to advance its capabilities.
The first enhancement involved expanding and refining the database by incorporating direct input from Oil Spill Removal Organizations (OSROs) for 10 different airframes, increasing the original database of four airframes. Advanced Computational Fluid Dynamics (CFD) modeling was employed to generate a database of spray drift and mass deposition concentrations for dispersant particles based on factors such as altitude, speed, and wind conditions.
The second enhancement was the inclusion of a contour plot of the dispersant deposition in the DST. The previous DST only considered the 99th percentile touchdown distance of the dispersant, the updated tool now provides the dispersant deposition contours as well as the extremities. The DST generates a Response Surface Curve (RSC) for each airframe, based on a database that includes factors such as altitude, aircraft speed, and wind speed, to estimate the drift extent and mass deposition concentration of dispersant particles. Additionally, the research identified relationships between particle dispersant behavior and airframe types, as well as the impact of payload weight and particle size distribution on drift extent.
By providing information on areas potentially impacted by dispersant drift, the DST assists operational control personnel in establishing appropriate setback distances. Additionally, the DST provides a ground-level contour of mass deposition based on environmental and operational parameters, allowing users to predict where the majority of aerial dispersant is expected to land. The tool has been peer reviewed and the outcome of that process has not been incorporated into this version due to the time of the review and publication of this paper.