Study evaluates places of refuge

Tanker in Prince William Sound

By Alan Sorum
Council Project Manager

Some locations won’t work for Prince William Sound tankers

A recent Council-sponsored study reviewed eight “potential places of refuge,” or PPOR, which are locations where an oil tanker in distress can anchor and take action to stabilize its condition. Of the eight reviewed in the study, none were found to be safe for use by tankers. However, several safe alternates were identified, analyzed, and proposed for future consideration.

Identifying these sites in advance allows decision-makers to save time during their critical initial response to a potential oil spill. Establishment of these places of refuge is recognized by the International Maritime Organization and other governmental agencies as an important marine safety and pollution mitigation measure.

The Council partnered with the Alaska Department of Environmental Conservation in 2004 to develop a matrix listing potential places a vessel in distress could shelter from weather and rough seas. A review of the department’s website showed that information developed in the 2004 effort has not been updated since it was published.

Technology helped safely evaluate locations

Working with the Alaska Maritime Training Center at AVTEC – Alaska’s Institute of Technology in Seward, Alaska, the Council sponsored development of a high-resolution navigational dataset for Prince William Sound in 2014. This upgraded navigation information, along with AVTEC’s simulators were used to verify the safety of eight sites in Prince William Sound that had previously been identified as PPOR for crude oil tankers.

Beginning in September of 2015, the Council started working with Safeguard Marine, LLC to evaluate the safety of eight of the places of refuge in Prince William Sound. Seven others have already been used by tankers and are known to be safe.

Safeguard Marine evaluated the sites using interviews with local subject matter experts and stakeholders and simulated ship maneuvers. The maneuvers were conducted by members of the Southwest Alaska Pilots Association using models representing Trans Alaska Pipeline System crude oil tankers in varying degrees of distress. Determining whether the PPOR is safe for the oil tanker in distress is a function of whether the vessel could potentially run aground if there is insufficient swing room when anchoring or mooring.

The Council has asked the U.S. Coast Guard and DEC members of the Alaska Regional Response Team to consider the recommendations developed in the study in future updates.

Establishment of preplanned places of refuge provide communities, regulators and industry a chance to consider local knowledge and conditions prior to a crisis. An accurate PPOR matrix provides the Coast Guard Captain of the Port with an additional tool in the decision-making process associated with placing a vessel in sheltered location. Gathering information on potential sites from stakeholders in advance of an incident is always a preferred planning approach and furthers the Council’s stated mission of promoting the safe transportation of crude oil thorough Prince William Sound.


Full report by Safeguard Marine, LLC:

Ship Simulation and Mariner Study of the Maritime Implications for Tank Vessels Utilizing Potential Places of Refuge, Mid-Prince William Sound Alaska (1.4 MB)

New study analyzes weather at Hinchinbrook Entrance

A recent Council-sponsored report found that wind and waves at Hinchinbrook Entrance may be under reported as observed by the Seal Rocks weather buoy.

Researchers from Tetra Tech analyzed wind and wave data to better define weather conditions at the Entrance, as well as how these conditions might affect rescue operations by the escort tugs. To do this, researchers looked at the frequency and duration of weather events when the Entrance was closed to laden tankers.

Average closure conditions

A "wind rose" graphic that shows the speed and direction of wind as recorded at Seal Rocks.
This “wind rose” graphic shows the speed and direction of wind as recorded at Seal Rocks.

Wave height alone was found to be the cause of most of the closures, occurring 10 to 26 times a year on average. Average wave height during closures was over 17 feet and the highest recorded wave was over 26 feet. Wind speed closes the Entrance one to three times annually, as do closures for both wind and waves. Winds average just over 54 miles per hour during closure and the highest recorded wind speed was over 61 miles per hour.

Closures for winds typically last less than two hours, while waves close the Entrance for an average of just over six hours.

Seal Rocks buoy’s data may not be precise

Read moreNew study analyzes weather at Hinchinbrook Entrance

Out-of-service buoy and winter storms raise concerns

An out-of-service buoy and a series of recent storms have combined to raise concern at the Council about tanker transit procedures during period with the high wind speeds and wave heights in which tankers are allowed to travel through Prince William Sound.

Seal Rocks buoy out of service


From May until December of 2018, a critical buoy located near Hinchinbrook Entrance was out-of-service. This buoy, referred to as “Seal Rocks buoy,” collects wind speed and wave height data. That information is used by the U.S. Coast Guard to make decisions as to whether Hinchinbrook Entrance is open or closed to outbound laden oil tanker traffic. When this buoy is inoperable, the U.S. Coast Guard uses data from two nearby buoys, Cape Cleare and Cape Suckling, along with reports from Edison Chouest Offshore, or ECO, tug crews that are sent out to observe wind and waves to make Hinchinbrook Entrance open and closure decisions.

In November and December, several winter storms came through Prince William Sound that raised concern about these alternate methods for reporting weather conditions at the Entrance.

Read moreOut-of-service buoy and winter storms raise concerns

Oil spill prevention and response services transition to new contractor

Link to more photos of new equipment
More photos of new equipment.

Prince William Sound was a hive of activity this summer. On July 1, Alyeska’s marine services contractor transitioned from Crowley Maritime Corporation to Edison Chouest Offshore.

This transition means all of the escort tugs and much of the spill prevention and response equipment in Prince William Sound are brand new, or new to the Sound.

Demonstrations of the new equipment

The Alaska Department of Environmental Conservation required that each vessel and crew member demonstrate their capabilities before beginning service. Each tug, as well as each tug’s captain, had to perform a set of maneuvers which differed according to the vessel and its purpose.

Read moreOil spill prevention and response services transition to new contractor

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