Scat Surveys of Prince William Sound Beaches – 1989 to 2002

Abstract

A SCAT survey in 2002 documented conditions at 39 selected survey sites where EVOS oil persisted in 1992, at the time the Federal and State On-Scene Coordinators determined that further cleanup activities would provide no net environmental benefit. The 2002 field survey found isolated occurrences of residual EVOS surface oil (SO) in the form of weathered asphalt pavement at 15 of the 39 sites. SO, expressed as a continuous oil cover, was less 0.2% of the surface area surveyed. Seven of the 39 sites and 815 (68%) of the total 1182 pits contained no residual SSO. SSO was found primarily in middle to upper intertidal locations, where it occurred in discontinuous ∼3cm thick bands 5–10 cm below the boulder/cobble or pebble/gravel veneer. Despite evidence of continued oil weathering, both at the surface and in the subsurface, it is clear that the natural cleaning processes at these particular locations are slow. The continued but slow weathering rates are a consequence of the oil being sequestered from the environment because it occurs in mixed (coarse and fine) sediments on beaches where boulders and outcrops, shallow bedrock asperities, or boulder-armoring limit effective physical weathering action.

Potential for Sea Otter Exposure to Remnants of Buried Oil From the Exxon Valdez Oil Spill

“…These sites include, KN109A, KN117A, KN136C, EL056C, and EL058B in the NKI area, SM006B and SM006C on Smith Island, and LA018A-1 on Latouche Island (Table ). Two of these sites containing the most SSO reported ( , ) are located on Smith Island (sites SM006B and SM006C). The Smith Island sites contain about 40% of all of the SSO documented in 2001 () and are characterized by large boulders and cobble covering the shorelines.…”

“…Subsequent SCAT surveys documented that the extent and severity of shoreline oiling decreased rapidly after the spill to 10 linear kilometers in 1992 (). The extent of oiled shoreline and the amount of oil on a given shoreline continued to decrease ( − ). Short et al () measured the distribution and amounts of oil remaining on shorelines in PWS in 2001 and estimated an average oil loss rate of 20−25% per year, a rate confirmed by Page et al ().…”

“…That study found that 92 sampling quadrats (2.2%), of a total of 4249 surveyed, had heavy (HOR) or moderate (MOR) subsurface oil (SSO) residues ( , ). The SSO residues persist at specific locations on these shorelines because they are protected from erosion and tidal washing by surface armoring from large boulders and cobbles and by underlying layers of low porosity fine sediment, bedrock, or peat ( , ). By 2001, intertidal SSO residues were restricted primarily to these boulder/cobble shorelines.…”

Bioavailability of polycyclic aromatic hydrocarbons from buried shoreline oil residues thirteen years after the Exxon Valdez oil spill: A multispecies assessment

“…For most pits at oiled sites with visible weathered oil, the oil is concentrated in a 2‐ to 10‐cm thick band mixed with fine‐grained sediments at a depth of 10‐ to 30‐cm below the boulder/cobble or pebble/cobble surface veneer [29]. At some oiled sites, the band of oiled sediment is at or near the bottom of the pit, sometimes perched on a layer of peat.…”

Biomarkers of PAH Exposure in an Intertidal Fish Species from Prince William Sound, Alaska: 2004−2005

“…Fourteen shore sites were sampled in a 7-day period in June 2004 and seven sites were sampled during a 9-day period in June 2005. The sites initially oiled by EVOS are in Herring Bay, Lower Passage, and Bay of Isles in the northern part of the Knight Island group (Figure ) and represent a range of current oiling conditions based upon studies conducted in 2001 (), 2002 ( , ), 2004 (), and as noted at the time of fish collection. Sites where intertidal subsurface oil (SSO) residues were documented in 2001, in subsequent years, or at the time of collection are noted in Table .…”