Technology study demonstrates importance of the Council’s independent research

Photo shows Coast Guard officer firing a messenger shot line from one Coast Guard vessel to another. This is one method of connecting tow lines between a tug and a tanker.
In this 2016 photo, a U.S. Coast Guard officer fires a messenger line from one military vessel to another. This is one method of connecting tow lines between a tug and a tanker. Photo by Pasquale Sena, U.S. Coast Guard.

A new study evaluating methods of establishing tow lines between an escort tug and a tanker in distress is a prime example of why the Council’s studies are vital.

The Council often hires experts to review equipment technology used in the Prince William Sound oil transportation industry. Sometimes these studies fill a hole or gap where independent research is lacking.

“Very little has been previously written on this topic,” said Alan Sorum, who managed this project and other similar technology reviews for the Council. “In a literature review it conducted, the Council’s contractor, Glosten, found that there is a general lack of published material on this subject and in particular, little guidance on best use practices or what is the most appropriate device to use for a given situation.”

The study looked at a specific piece of equipment called a “messenger line.” Passing a messenger line is the first step in setting up a tow line between a tug and a tanker in distress. The lighter weight messenger line helps responders connect the heavy tow lines.

Retrieving a messenger line can be difficult and dangerous in the rough weather often encountered in Prince William Sound. Depending on the vessel and the technology on board, they may be passed by hand, heaved or thrown aboard, projected by mechanical means, or picked out of the water.

Tough equipment required for Alaska’s harsh climate

Alaska has a state law that requires tankers to carry specially designed towing equipment when traveling through Prince William Sound. This equipment includes a towing wire, floating line and buoy, and a heavy-duty shackle.

These components are all specifically sized to match the weight of the vessel and be able to handle the high winds and seas often encountered in Prince William Sound.

Having this specialized equipment on hand allows rescue tugs to quickly and safely help move a stricken tanker to a safer location.

Conducting the study

Researchers reviewed what devices are commercially available for deploying messenger lines. Next, they developed criteria to evaluate the equipment according to: effectiveness, feasibility, transferability, compatibility, age and condition, availability, environmental impacts, and cost.

These eight criteria were based on another Alaska law, which requires industry to use “best available technology.” This requirement is intended to ensure that equipment meets and is maintained to a high standard.

The equipment options were each assessed and scored.

How will the Council use this information on tow lines?

The Council’s influence depends on quality, accurate research. The Council uses reports like this to help make sure advice given to industry and government officials is well-informed and supported by the best science available. The findings of this latest research effort are being shared with equipment manufacturers, the oil transportation and shipping industries, and regulators.

Read more about the researcher’s recommendations:

Tanker Towline Deployment BAT Review (10.3 MB)

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

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