September 9, 2022
Diesel oil from sunken Aleutian Isle ‘nonrecoverable’
Zach Kortge

An oil boom protects a sensitive area of shoreline along San Juan Island, part of the multi-agency response to the sinking of a fishing vessel last month. (U.S. Coast Guard photo)

September 9, 2022
Diesel oil from sunken Aleutian Isle ‘nonrecoverable’
Zach Kortge

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More than 200 feet below the surface of Haro Strait — a major shipway for British Columbia — a fishing vessel has settled on the sea floor near Sunset Point off the west coast of San Juan Island.

The 49-foot purse seiner Aleutian Isle began sinking on Aug. 13, sending waves of a glossy diesel sheen two miles north of the sink. What was initially a search-and-rescue response quickly turned into minimizing the environmental impact. 

Following the spill, there was immediate concern about the health of marine mammals, specifically the endangered Southern Resident killer whales. Tracking of the mammals determined they were out of the danger zone surrounding the sink. However, difficult containment conditions and the presence of the sunken ship still pose a risk for other nearby organisms and environments.

A map provided by NOAA notes the location of the sunken Aleutian Isle.

The spill response was coordinated by a unified command which included the U.S. Coast Guard, Washington Department of Ecology, San Juan County Office of Emergency Management and the Swinomish Tribe, according to Ecology’s website. Additionally, several other agencies assisted the response, including the National Oceanic and Atmospheric Administration (NOAA). 

“In a case like the Aleutian Isle, where there are complicated currents and weather and critical things like that, [the Coast Guard] calls us because we can tap into the rest of the agency and provide [scientific support],” said Doug Helton, Regional Operations Supervisor for NOAA.

Major risk

Even a small diesel oil spill poses a major toxic risk to plants and animals, according to NOAA. While there has never been a reported fish kill from diesel in open water, other concerns include harm to marine birds and shellfish, as well as diesel soaking into coastal soil. 

One of the first things the Coast Guard often asks for is an assessment of the resources at risk,” said Faith Knighton, a scientific support coordinator with NOAA.

She said the investigated impacts could be anything from environmental to cultural and social. Once collected, that information is given to other agencies as they begin the response. 

“And when you look at an area, that can get very complex [considering] all the different layers that could be impacted,” she said.

Knighton said marine mammals were some of the first concerns brought up after the sinking. 

“Southern Residents frequent that area; where are they?” she said, recounting the initial response. The agency worked to identify their location and proximity related to the sheening observed that night.

While the Southern Residents were determined to be at a safe distance, they were not the only animals of concern in the area.

Dive crews have finished cutting away free-floating netting from the vessel and securing all remaining entanglement hazards. They were also able to begin operations necessary to attach the rigging that will be used to lift the vessel. (Ecology courtesy photo)

As a part of its collection of information, NOAA uses computer programs and habitat maps to determine which species is most at risk for a given spill area. These environmental sensitivity impact maps show exactly where these vulnerable populations are. 

Around San Juan Island’s Sunset Point, there are a variety of animals shown on the map. To the north, bivalves and cephalopods such as clams, oysters and squids are found. Around the point itself are waterfowl, gulls and terns. Low Island, a wildlife refuge, is just to the south. 

Research into oil spills on the water surface have also discovered the risk for small and microscopic organisms. A study from 2006 details the risks for these smaller creatures such as plankton as well as fish eggs and larvae for commercial fish species. 

In the case of the Aleutian Isle, there have been no reported fish or animal carcasses around the spill site according to Ecology. As a precaution, coastal areas have been protected using about 5,000 feet of oil booms, barriers placed in the water to keep oil contained, according to department updates.

The diesel sheen

Initial reports of the sinking said there were about 2.500 gallons of diesel on board the Aleutian Isle. This diesel, and the sheen it creates, poses a unique issue for agencies tasked with its maintenance and cleanup. 

Helton said 75 gallons of oil could cover a square nautical mile of ocean, with the sheen on top of the water being extremely thin. 

“The thing about diesel is that it’s relatively light; it spreads very thin sheens,” he said. “So when they’re talking about seeing a sheen, that may be a few ounces of oil.”

The quickly spreading diesel along the water surface leaves agencies with little time to respond. Additionally, the way diesel dissipates on the water creates its own challenges.

Response vessels with vacuum trucks on board were part of the initial response when the Aleutian Isle began to sink. (U.S. Coast Guard photo)

In the Ecology response updates, most of the sheening has been deemed “nonrecoverable.” While the thin sheen accounts for some of the difficulty, additional issues come via weathering. Weathering has several factors but can include the evaporation of the oil or the oil being degraded by organisms in the water. 

Current status

As of Sept. 8, the Aleutian Isle remains on the sea floor. Since its initial sinking, the fuel wells on the vessel have been capped, and netting has been cut away.

Sheening has continued intermittently, according to Ecology updates, although the diesel oil has dissipated quickly.

Safety zones for vessels and the above airspace have been in place as divers continue operations. The current plan is to lift the vessel from the water, an operation that is still several days away as divers prepare the ship in water currents that complicate the dive. 

[For additional insight into the challenges facing oil spill prevention and oil spill recovery, see “Anticipated Salish Sea vessel traffic increases spark calls for more environmental protections,” Salish Current, Jan. 28, 2022.]

— Reported by Zach Kortge

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