The New Carissa grounded February 4, 1999 near Coos Bay, Oregon and released an estimated 595 to 1,786 barrels (25,000 to 75,000 gallons) of IFO 280 and MDO. Stranded oil and tarballs were monitored on 56 segments over 280 km (150 nmiles) of central Oregon coast sand beaches for a period of over 18 months. Tarball samples were collected and analyzed by GC-MS Modified EPA 8270. Samples were qualitatively compared to oils known to be aboard the ship. To date, a total of 824 tarballs have been collected, of which 183 have been analyzed. Criteria used for selection of tarballs to be analyzed were: (1) representative of tarballs on the beach, (2) appeared to be anomalous to the New Carissa incident in terms of timing or distribution, and (3) anomalous in appearance. Samples were randomly selected within each category for analysis. Of the 141 random samples collected and analyzed, 69 (49%) were inconsistent with New Carissa source oils (NCSOs). Of 34 samples analyzed as anomalous in time and/or space, 16 (47%) were inconsistent with NCSOs, and of 8 samples analyzed as anomalous in appearance, 5 (63%) were inconsistent with NCSOs. In all cases, the relative frequency of inconsistent samples increased with distance from the vessel. In the winter and spring of 1999?2000 (10 months following the initial incident), data and samples were collected from two 1,000-m control beaches believed to be unaffected by New Carissa oil and 1,000 m of beach adjacent to the stern portion of the wrecked ship. Density of tarballs on control beaches was 0.01 g/m2 with 100% of the samples inconsistent with NCSOs. The beach adjacent to the wreck had a tarball density of 0.1 g/m2 with 70% consistent with NCSOs. Because of the small size of the tarballs, difficulty in observation in sand and frequent adverse weather conditions, the authors believe that the data collected likely underestimate the quantity of oil on the beach and is therefore conservative.
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