ENVIRONMENTAL IMPACTS OF THE 1985 ARCO ANCHORAGE OIL SPILL: 1988 CONCLUSIONS1

ABSTRACT The beach of Ediz Hook, Port Angeles, Washington, was heavily oiled by Alaska North Slope (ANS) crude oil spilled subsequent to the grounding of the Arco Anchorage on December 21, 1985. Intertidal crude oil concentrations measured in beach sediments ranged from less than 50 to 20,000 ppm, with an average of 2,240 ppm. Beach reclamation efforts, concluded in April 1986, reduced average crude oil concentrations to 670 ppm. An intertidal and subtidal sediment chemistry and benthic invertebrate monitoring program was initiated at Ediz Hook in 1986 and was concluded in early 1988. Sediment chemistry data indicated a decline in mean intertidal concentrations from 670 to 110 ppm between April 1986 and July 1987. Shallow subtidal concentrations decreased from a mean of 460 to 110 ppm in the same time period. Benthic invertebrate population indices, developed with core and box sampler data, generally demonstrated a negative correlation with sediment crude oil concentrations. Organism density, taxonomic di...