Origins of the Present System
Within one year after the worst oil spill in U.S. history, Congress enacted the Oil Pollution Act of 1990, “OPA 90” (PL 101-380), to improve our nation’s capabilities for oil spill prevention and response. The Oil Pollution Act amended the Clean Water Act and created a national framework for oil spill preparedness, mitigation, and clean-up.
OPA 90 included several provisions that were specific to Prince William Sound, Alaska, where the Exxon Valdez oil spill had served as a national wake-up call about the risks of oil tanker operations. One of the most significant oil spill prevention measures in the Act was the requirement that all single-hull, laden oil tankers traveling through Prince William Sound be accompanied by two escort vessels (See statutory provision).
When the first laden oil tanker sailed from the Valdez Marine Terminal in 1977, it was escorted by a single tug until it had traveled through Valdez Narrows. This system remained in place until the Exxon Valdez oil spill spurred the Coast Guard to require that the escort system be enhanced to help prevent future accidents. As the nation witnessed in 1989, there are no good remedies once oil has spilled in the marine environment. So prevention must be the priority.
Photo: Valdez Marine Terminal, present day
Key Escort System Improvements Since 1989
The currently utilized Prince William Sound dual escort system has evolved over the past two decades to become the cornerstone of oil spill prevention and preparedness in Prince William Sound. It was developed through efforts of industry, the U.S. Coast Guard, the State of Alaska, and the Prince William Sound Regional Citizens’ Advisory Council. The currently utilized tanker escort system improves on the pre-Exxon Valdez single tug escort system in many ways, including these four:
1. At least two vessels now escort each single and double-hull oil-laden tanker.
2. New and better escort vessels – tugs and oil spill response vessels – have been custom built for the Prince William Sound trade.
3. Procedures have been improved to increase the odds of saving a tanker in trouble.
4. The escort path now extends through Prince William Sound out to Hinchinbrook Entrance (and a tug is on stand-by until the tanker has traveled 17 miles out to sea).
The Vessel Escort and Response Plan (VERP), prepared by industry, sets out operating procedures for the Prince William Sound Escort Vessel System. The VERP divides the Sound into three areas of operation: (1) Northern Sound Operating Area, (2) Central Sound Operating Area, and (3) Hinchinbrook entrance. These zones are shown on the map on the following page.
Escort Vessel Functions and Capabilities
At the heart of the Prince William Sound Tanker Escort System is the fleet of high technology prevention and response tugs and enhanced tractor tugs that function as escort vessels. Thanks to years of study and work by industry, government, and stakeholder groups, and considerable investment by the shipping industry, this safety and oil spill prevention system is considered to be among the best in the world. The two high-powered tugs that escort each laden tanker perform several important functions:
1. The escort vessels monitor conditions in the Sound and alert the tanker of any potential problems or dangers.
2. The escort vessels are available to provide immediate assistance to a tanker should it experience any problems with navigational or safety systems.
3. The escort vessels are capable of assisting a large tanker in distress under a range of adverse conditions and possible scenarios.
4. Should an incident occur, the escort vessels provide initial oil spill ready response capabilities that may help to contain a spill and reduce environmental damages. The tugs can also be used to tow oil spill response barges, which have been strategically placed at locations throughout Prince William Sound.
5. All of the escort vessels have significant firefighting capabilities that can be used to suppress a shipboard fire.
Map of Northern Sound, Central Sound, and Hinchinbrook Entrance Operating Areas
Operating Procedures
The VERP calls for two escort vessels to accompany all oil--laden tankers from the Valdez Marine Terminal out to Hinchinbrook Entrance. The configuration and type of escort vessels differs in each of the three Operating Areas, based on the operating environment and the navigational safety risks.
NORTHERN SOUND
Northern Sound Operating Area of Prince William Sound (map below) includes the Valdez Marine Terminal, Valdez Narrows, and Valdez Arm, and extends out to Bligh Reef. Two tugs escort the tanker through the Northern Sound Operating Area. From the Valdez Marine Terminal through Valdez Arm to a point just past Buoy 9, a primary tug is tethered to the tanker. A secondary tug remains within ¼ nautical mile, except when ice scouting. The Valdez Narrows is a special navigation zone where only one-way tanker traffic is allowed.
CENTRAL SOUND
Central Sound Operating Area of Prince William Sound (map below) starts at Bligh Reef and continues to Hinchinbrook Entrance Area. No tugs are tethered to the tanker in this area. The primary tug remains within ¼ nautical mile of the tanker. A second tug acts as a sentinel, typically dispatched from Naked Island, Port Etches, or the Valdez Marine Terminal, and must be underway and ready to assist the tanker.
HINCHINBROOK ENTRANCE
Hinchinbrook Entrance Operating Area of Prince William Sound (map below) starts at a point defined by a line drawn through Montague Point and Johnstone Point. No tugs are tethered to the tanker in this area. Both the primary and secondary tugs remain within ¼ nautical mile of the tanker through the entire Hinchinbrook Entrance Operating Area. As the tanker exits the Hinchinbrook Area and heads into the Gulf of Alaska, one sentinel tug remains at Cape Hinchinbrook until the tanker is 17 nautical miles seaward from Cape Hinchinbrook.
All inbound (un-laden or empty) tankers are escorted by one sentinel vessel. All tankers, laden and empty, must follow a vessel traffic scheme and must adhere to speed limits within Prince William Sound. Laden tankers may not exceed the maximum speed at which the escort vessels can be reasonably expected to safely bring the tanker under control.
The dual escort practice has proven its prevention and safety value over the last twenty years. Yet, from time to time a few industry representatives have question whether the presence of two escort vessels in the narrows of Valdez Arm may create “congestion.” It has been suggested that a scenario might occur where both tugs could become simultaneously incapacitated and therefore they might make it more difficult for the tanker to safely navigate through these narrow channels. This is extremely far-fetched.
It is much more likely that the presence of a second tug would provide an additional safety measure in the instance that one of the tugs or the tanker suffered a casualty – the second tug would be there to render assistance until additional response vessels could arrive on-scene. The two-tug system does not create crowding or congestion; it enhances safety by providing an additional layer of safety by ensuring that two tugs are available to provide immediate assistance in those areas where the margin for error is slim and the need for ready response is critical.
Download a pdf version of the information on this page:
Existing Dual Escort Vessel System in Prince William Sound
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Full Briefing Booklet, printer friendly version (prints double-sided)
