The Coast Guard has taken an important step to assure continuation of the two-tug escort system for double hull tankers that traverse Prince William Sound, Alaska.
It published an interim rule on Aug. 19 that implements a section of the Coast Guard Authorization Act of 2010 which mandates dual escorts for double hull tankers over 5,000 gross tons that carry oil in bulk on the waters of PWS.
Effective Sept. 18, the interim rule will codify the current escort system, which has been industry practice since 2008.
Soon after the 1989 Exxon Valdez spill, Congress passed a law that required two escort tugs in PWS, but this applied only to single hull tankers, which were the industry standard at the time. Single skins were gradually phased out by the law, replaced by double-hull tankers that were believed to be safer against spills. The Coast Guard says that no single hull vessels have called on PWS since 2009.
With the single hull phase-out, there would have been no requirement for any tank vessel to maintain an escort system, according to the Coast Guard notice. The new rule ensures the continuing benefits of the dual vessel escort system by also applying it to all double hull tank vessels transporting oil in bulk.
The Coast Guard said the new rule will prevent any confusion about tug escorts and will offer an extra protection against oil spills. The notice said that potential environmental disasters have been averted when escort tugs have guided disabled tankers safely through the sound.
“We believe a two vessel escort system is beneficial in the event of equipment failure such as the loss of steering or propulsion,” the Coast Guard said. “If a tanker becomes disabled, the two escort vessels can influence the speed and course of the tanker, thereby reducing the likelihood of an allision, collision or grounding.”
Currently one company operates the 12 tugs that participate in the two-tug escort system.
The Coast Guard said that the rule would not impose new costs on the public or the industry, or change industry behavior.
Retaining the dual tug escorts has been a top priority for PWS residents and environmentalists.
And it appears that the two-tug escort system is working. The Coast Guard said it reviewed casualty data for tank vessels in PWS over a 15-year period from 1998 through 2012 and found no casualty cases involving a double hull tank vessel. All of these vessels were escorted by a two-vessel escort.