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SeaRiver Maritime, the marine shipping arm of ExxonMobil, announced in late July plans for construction of two new crude oil tankers. Construction is to begin in 2012 and the new vessels are expected to begin service in Prince William Sound during 2014.

"All cargo and fuel compartments will be equipped with double hull protection. Both vessels will feature the latest in navigation and communications equipment. Main engine and auxiliary systems will be energy efficient and generate lower air emissions than what is required by current regulatory standards," according to a July 25 press release from the company.

These ships will be among the first U.S. oil tankers built to meet specifications in the Common Structural Rules for Oil Tankers. These rules were developed in 2006 by the three biggest ship classification societies, the American Bureau of Shipping, Norway's Det Norske Veritas, and the U.K.'s Lloyd's Register. Ship classification societies are non-governmental organizations that establish and maintain technical standards for the construction and operation of ships and offshore structures. The 2006 rules combined best practices of these three societies into one commonly accepted set of rules.

The new ExxonMobil ships will be designed to withstand operations in the North Pacific for a minimum of twenty-five years without suffering hull metal fatigue. Previous standards used by the company were based on a twenty year design life. The new tankers are designed to carry 730,000 barrels of oil, which is about 12 percent less than the vessels they will be replacing, the Kodiak and Sierra, which were built in the late 1970's.

The new ships will be driven by a single slow-speed diesel engine and will have an oil mist and gas detection system for the space between the double hulls. This system will detect the presence of these flammable materials and help prevent fires from occurring aboard the vessels. While the ships will not be constructed with double propellers, engines, or rudders, a SeaRiver representative indicated the design does include other navigational and propulsion redundancies. Specifically, SeaRiver has tried to eliminate the possibility of single points of failure leading to loss of power or navigational failure. This will include items like the inclusion of redundant engine cooling water, installation of additional low fuel level alarms and increasing the reliability of things like fuel flow meters.

The new tankers will be capable of ballast water exchange using either the "pump-out and refill" method or the "flow-through" method, which entails pumping sea water into segregated ballast water tanks and allowing it to overflow back into the sea until three times the vessel's total ballast water capacity has been pumped. However, it is expected that later this year the Coast Guard will require any new oil tanker to meet a rule set by the International Maritime Organization's Marine Environment Protection Committee Convention of 2004. Should this happen, SeaRiver's design allows for an on-board ballast water filtration and chlorination unit to be added. With this unit, as new ballast water enters the tank, the water is filtered and then treated with low levels of hypochlorite sufficient to eliminate non-indigenous species. SeaRiver plans to use an initial dosage of 5 to 8 parts per million of hypochlorite and they expect that level to drop to 3 to 5 parts per million during transit. The hypochlorite will be neutralized using sodium bisulfite, a common food preservative, when the ballast water is discharged.

The ships will have an anti-fouling coating applied to the hull. An anti-fouling coating slows the growth of organisms that attach to the hull. SeaRiver is considering the use of newer low-friction Teflon-type coatings that can slow the attachment of marine organisms, once the ships reach their first dry-dock period five years after entering service.