Study shows purpose-driven design can improve performance

When a ship is disabled at sea, an appropriate rescue vessel must respond quickly to prevent an accident. Towing can be dangerous, especially in rough weather, because the rescue tug must get close to connect a towline.

Challenging environment in Alaska

Map showing the tanker traffic lane. The tankers must pass through a relatively narrow area between Hinchinbrook and Montague Islands when entering or leaving Prince William Sound to or from the Gulf of Alaska. A rescue tug with the right features has the best chance of preventing a spill.
Alaska requires a tug stationed in the vicinity of Hinchinbrook Entrance, the narrow waterway which connects Prince William Sound to the Gulf of Alaska. The tug remains on standby to assist or escort tankers through the entrance and out into the Gulf of Alaska.

Hinchinbrook Entrance is a narrow waterway that connects Prince William Sound to the Gulf of Alaska. The weather and sailing conditions in the gulf can change rapidly and are often severe.

Tankers carrying millions of gallons of oil regularly pass through the Entrance. Alyeska’s Ship Escort/Response Vessel System must have a tug stationed at the Entrance when laden tankers travel through Prince William Sound.

What is the right tug for this role?

The Council recently asked the experts at Glosten, naval architecture and marine engineering firm, to help answer this question.

Glosten began by reviewing designs and technologies for existing tugs. They summarized the ideal tug design, describing the dimensions, power, propulsor (propeller) types, shape, ability to withstand rough seas, machinery, and towing gear, among other features and equipment.

Glosten then compiled a database of around 4,000 tugs in use around the world. Using the ideal summary as a guide, they narrowed the list to tugs:

  • Built in 2005 or later
  • Between 130 and 260 feet long
  • Able to exert between 130 and 200 tons of pulling or towing power
  • Capable of speeds of 18 miles per hour
  • Within a reasonable cost to design, build, and operate

Fewer than 400 were left.

Tasks the tug must perform

Glosten then outlined the demands placed on the Hinchinbrook tug at each stage of response. Based on these demands, Glosten concluded a state-of-the-art design for the Hinchinbrook tug must provide exceptional performance in three categories. The ideal tug must be able to maintain these in a broad range of sea states:

  • A high free-running speed
  • A high degree of maneuverability and agility
  • High bollard pull (towing ability) and towing efficiency

After ranking the 400 tugs according to all these features and abilities, they were down to the 17 top scoring tugs.

Finding the right balance

After balancing performance with costs, Glosten determined that the existing vessel most closely matching the needs for an ideal Hinchinbrook tug was the Luz de Mar: a tug operated by Spain’s Maritime Safety and Rescue Society.

The creators of the Luz de Mar designed it for offshore ship rescue and response. This means the Luz de Mar is maneuverable and agile due to a powerful propulsion system, has adequate bollard pull, can aid a disabled tanker in a variety of ways, and is still fast enough for a quick response.

How does the current tug compare?

Glosten studied the differences between the Luz de Mar and the current tug serving Hinchinbrook Entrance, the Ross Chouest.

Their study showed that a tug designed specifically for that role would improve safety and efficiency, improve response times, and reduce the chance of an oil spill.

Conclusion: Purpose-built tugs work better

The researchers noted that many believe the largest and most powerful tugs are ideal for rescue operations. In fact, the design of these larger vessels does not prioritize the features most important to a successful emergency response.

They concluded that a tug designed with this purpose in mind offers significant advantages, especially when a rescue tug works close to shore.

More details

A recent issue of International Tug and Salvage has a more detailed article by Peter Soles of Glosten and Alan Sorum of the Council, available on the magazine’s website: Defining the best technology for emergency rescue tugs

Glosten’s full report:

Hinchinbrook Emergency Towing Vessel (ETV) Best Available Technology (BAT) Assessment (20.4 MB)

Report on towline trials conducted in summer 2021: 

PWSRCAC Emergency Towline Deployment Practical Trial Summary Report (1.7 MB)

Repairs to Prince William Sound’s radar in the works

Screenshot of AIS system
The Coast Guard is using other technologies, such as the Automatic Identification System (AIS) pictured here, to monitor traffic while radar repairs are underway.

Coast Guard planning long-term project to replace entire system

Radar that helps the U.S. Coast Guard monitor vessels in Port Valdez is undergoing repairs.

This radar is part of the Coast Guard’s Vessel Traffic Service, or VTS, which monitors and manages vessel traffic movements in busy waterways such as Prince William Sound. Three radar sites across Prince William Sound relay information to Valdez, where the data is integrated with other technologies onto an electronic display.

All three sites have struggled to stay online recently because of the harsh Alaska environment coupled with normal wear and tear. The Coast Guard plans to have at least one radar at each of the three sites operational by September 2021.

Planning for further upgrades

U.S. Coast Guard Commander Patrick Drayer joined a Council meeting in January to report that the Coast Guard’s long-term plan is to develop plans to upgrade all of the VTS radar systems nationwide. The Coast Guard will begin an in-depth review starting this summer to help plan these upgrades. The timeline and cost for replacement is not yet known as it is still early in the planning process.

Meanwhile, the Coast Guard is monitoring the Sound using other technologies. While other technologies serve valuable roles, the Council does not believe that other technologies can adequately replace the surveillance and collision avoidance capabilities that modern radar provides.

The Council is planning a review to better understand how these technologies work together to prevent accidents and potential oil spills.

Escort tug Courageous damages the tanker Polar Endeavour in January incident

One of the Polar Endeavour’s ballast water tanks was damaged during the incident. The Endeavour, seen here participating in a 2009 towing exercise, is undergoing repairs.

Just before midnight on January 11, the escort tug Courageous allided with the tanker Polar Endeavour, which had just finished loading crude oil at Berth 4 at the Valdez Marine Terminal.

An “allision” occurs when a moving vessel comes in contact with a stationary object or vessel.
A “collision” occurs when both objects or vessels are moving when contact occurred.

The Courageous is owned and operated by Edison Chouest Offshore, the contractor who provides spill prevention and response services for Alyeska.

The tug was approaching the fully loaded tanker to assist the tanker as it prepared for departure. The tug struck the hull of the Endeavour, damaging a ballast water tank. Some of that ballast water was released into Port Valdez. The Endeavour carries crude oil in cargo tanks that are separate from the ballast water tanks, so there was no oil in the damaged tank and none was spilled.

ConocoPhillips, the company that owns the Endeavour, made temporary repairs onsite. The U.S. Coast Guard inspected the tanker and approved it to sail to Long Beach, California, for permanent repairs.
One mariner aboard the Courageous received minor injuries and is expected to fully recover.

The U.S. Coast Guard is still conducting its investigation, however initial reports indicate it appears that the incident was caused by human error.

At the January meeting of the Council’s Board of Directors, Alyeska noted several remedial actions, including restricting the use of autopilot in certain areas and clarifying standing orders.

The Council is tracking this incident and the subsequent changes and will provide advice on how to prevent a similar incident in the future.

Inoperable radar in Prince William Sound concerns Council

No plans for repair in near future

The U.S. Coast Guard’s Vessel Traffic Service, or VTS, which monitors the location of vessels in Prince William Sound, has been operating without radar in recent months.

Screenshot of AIS system
This screenshot is an example of how AIS maps show the location, speed, and direction of vessels, among other details. However, smaller objects or vessels do not appear in the system.

The Coast Guard monitors traffic in busy ports around the country through these VTS offices. The VTS in Prince William Sound usually operates with a combination of Automatic Identification System, or AIS; VHF radio; cameras; and radar.

AIS is a map-based online monitoring system required to be on board larger vessels. Equipment streams the vessel’s position, along with its name, course, speed, heading, and destination to the system. VHF radio is used for two-way communications with vessels.

These various systems are integrated together and the information is relayed to the Coast Guard’s Marine Safety Unit VTS in Valdez.

Radar is an integral part of the Coast Guard’s monitoring of vessels in Prince William Sound as many small vessels and hazards only appear on radar.

Based on a National Transportation Safety Board report on the Exxon Valdez oil spill disaster, lack of radar is considered a contributing factor to the spill.

U.S. Coast Guard Commander Patrick Drayer joined a Council meeting earlier this fall. In answer to questions from Council members, Commander Drayer noted that all three radar systems in Prince William Sound are obsolete.

Drayer explained that the original manufacturers are no longer in business and that original design drawings are not available. Attempts to fabricate new parts to repair the existing equipment have failed, as the parts did not fit or were not compatible. He also noted that this problem is affecting systems around the country.

Not all vessels use AIS

Many of the vessels in Prince William Sound do not have, and are not required to have, expensive AIS transmitters on board. Only vessels larger than 20 meters (approximately 65 feet) and some passenger vessels* must broadcast their location. Smaller vessels such as commercial fishing vessels, recreational boats, or kayaks may not carry AIS equipment. AIS can also miss smaller objects floating in the water, such as icebergs.

In an October 2020 letter to Senators Lisa Murkowski and Dan Sullivan, and Congressman Don Young, the Council asked for help to secure funds to replace the equipment.

“Based on discussions with the Coast Guard, all of these radar systems have been inoperable for at least ten months,” the letter stated. “Based on limited funding and resources it will take considerable time to repair and eventually replace this aging and inoperable equipment. In addition to the Council’s maritime safety concerns over the lack of Coast Guard radar capability in Prince William Sound, there are also homeland/national security implications of such radar inoperability.”

“The Council is concerned that adequate resources are not yet committed to these priorities,” the letter continued.

All three members of Alaska’s Congressional Delegation responded to the Council’s letter by writing to the Commandant of the Coast Guard requesting information regarding how this problem can be addressed. The Council plans to continue to monitor and advise on this important issue.

* Correction from print edition of The Observer: The original version of this article mistakenly left out that some passenger vessels smaller than 65 feet are also required to broadcast their location, depending on the capacity of the vessel.

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