TARBALL DATA FROM THE OREGON COAST

Abstract

ABSTRACT Approximately 300 kilometers of the coast of Oregon were surveyed following the spill from the New Carissa and a long-term observation program focused on the documentation of stranded tarballs in the vicinity of the spill site. Field documentation methods applied to shoreline oiling after the spill in February 1999 initially followed standard SCAT reporting procedures. After a brief period of relatively heavy oiling, most of the stranded oil took the form of oil pellets of various sizes (“tarballs”). As the amounts of oil on the shoreline diminished, the standard SCAT method resulted in evaluations of oil quantities that were invariably too high. Field observations were conducted for a year after the incident and the data presented in this discussion cover tarball observations in two segments adjacent to the accident site and at two distant locations over the period March 1999 to June 2000. Data output from the study included maps, tables, and histograms of stranded tarball volumes and concentrations (gm/m2). The semi-logarithmic scale time-series plots of the tarball concentration proved the most useful format for identifying trends, as the data spanned as many as nine orders of magnitude. When plotted on conventional histogram, only the larger values can be identified and smaller trends are masked in the time series. Long-term (> 1 year) data on the monthly median tarball size and the monthly tarball volume are provided for four sites.