Important questions that are asked by spill responders as well as those assessing potential impacts are: (I) What is the probability of oiling, above a threshold of concern, for each location near a potential spill site? (2) How soon will oil reach each site of concern? (3) How much oil contamination is expected (on average and worst case)? (4) Is there a potential for impacting biological resources with this oil? Using Applied Science Associates, Inc.'s (ASA) oil spill model (Spill Impact Assessment Package, SIMAP) in stochastic mode, these questions were evaluated for Florida Power & Light (FPL) for a variety of oil types and spill volumes, and for each of FPL's plants and terminals. The model was run many times, randomizing the start time over decade-long wind records. The model evaluates surface oil, shoreline oil, subsurface oil, and low molecular weight aromatics (the most toxic fraction of the oil). Both the mean and worst case exposure thickness/concentration are evaluated. The output includes contour maps, which may be interrogated (with the user interface) to determine the conditions under which worst case oiling occurs. The contours are overlaid on resource maps, showing where resources are most at risk and where protection would be most beneficial.

FPL uses SIMAP for contingency planning, drills, spill response, and evaluation of fates and impacts of spills. ASA has developed databases for use in the model for the locations around each of FPL's plants and terminals. These data include shore and habitat type mapping, locations of sensitive resources, and current data sets generated by ASA's hydrodynamic model.

The stochastic model may be used as a contingency planning tool or as a component of the ecological risk assessment process. It determines the range of distances and directions oil spills are likely to travel from a particular site, given wind and current data for the area. Practical uses for this information include the determination of which kinds of response equipment should be used in a particular area and where the equipment should be placed to be most effective, what areas are most at risk from possible spills at a specific location, and the expected magnitude of impacts.

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