M/V SELENDANG AYURESPONSE: MIXING AND SEDIMENT RELOCATION ON OILED COARSE SEDIMENT BEACHES

Abstract

ABSTRACT The grounding of the M/V Selendang AYU on Unalaska Island in the Aleutian Island chain, Alaska, in December 2004, resulted in a spill of an estimated 339,538 gallons of primarily intermediate fuel oil that affected approximately 300 km of coastline in a remote area. The majority of the oil that stranded was deposited as heavy concentrations on coarse sediment beaches within a few tens of kilometers of the spill site. The shoreline cleanup operation focused on manual methods to minimize sediment removal and waste generation. Mechanical removal, dry mixing, or sediment relocation techniques were approved for eight locations where deeply-penetrated oil could not be effectively or efficiently removed by manual means. On several of the high-energy exposed beaches, the oil had penetrated or been buried to depths greater than 2 m, necessitating the excavation of considerable volumes of sediment to ensure that no untreated oil residues remained. One element of the Unified Command shoreline treatment oversight process required preparation and implementation of a monitoring and sampling plan. The plan included documentation of SCAT observations, surveyed beach profiles, photography, and mussel tissue chemistry. Evaluation of the data collected during the monitoring and sampling program showed that the relocation resulted in little adverse impact. Between 2005 and 2006, SCAT observations and photographs documented steady decreases in shoreline oiling, beach profiles were quickly restored by even modest storm events, and aromatic hydrocarbons in mussel tissues declined significantly. Although in situ treatment does not “clean” beaches, accelerating the weathering of the subsurface oil and decreasing the amount of oil remaining on the beaches ostensibly reduced the residence time of the oil and therefore, also reduced the exposure or risk to coastal birds and animals.