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Specially designed shallow-draft ATBs head north to serve remote Alaskan villages

Jun 27, 2012 01:04 PM

Vitus Marine has taken delivery of two shallow-draft ATBs specially designed to bring crucial supplies of fuel and heating oil to remote villages along the coast of Western Alaska.

Sneed Shipbuilding of Channelview and Orange, Texas, delivered twin 76-foot ATBs and two nearly identical barges to the Alaska Village Electric Cooperative (AVEC). Vitus Marine LLC of Anchorage, Alaska, will operate the vessels.

Alaska’s severe winter weather means there is a restricted season for delivering fuel in Western Alaska. The rivers freeze around mid-October and don’t thaw until June. It is only within this limited period that operators are able to deliver the fuel that is relied upon for heating and power generation in the rural communities of Western Alaska, along the Bering Sea and Arctic Ocean.

Vitus was formed in 2009 to serve the needs of AVEC. Using custom-designed tugs and barges, Vitus Marine works with AVEC to bring fuel at reasonable cost to AVEC’s rural generation facilities.

The first tug and barge, Cavek and AVEC-208, were delivered on July 8, 2011, followed by Naniq and AVEC-183, on Sept. 6, 2011. The tugs and their barges serve two predominantly indigenous populations, in about 53 communities.

Naniq means source of light in the Inupiat language and cavek means harpoon or metal in Yupik.

Designed by Jensen Maritime Consultants of Seattle, Cavek and Naniq are the only shallow-draft ATBs operating in western Alaska. The 76-foot tugs have a light draft of just 4 feet and a loaded draft of 4.5 feet. They displace 225 tons. With their blunt bows, the tugs have been primarily designed for pushing in rivers and inshore waters and will spend almost all of their time in the notch.

 “Because of the towns and villages these vessels service, shallow draft and maneuverability is a must,” explained Jensen’s Vice President of New Design Development, Jonathan G. Parrott.

The tugs’ matching barges are unusual not only in their shallow draft but in their dry cargo ability. Both have fuel and deck-cargo capacity and the ability to load and unload via a 28-foot-by-17-foot bow ramp. This is especially important when calling on remote villages without conventional wharfage.

 “The ability to carry both oil and deck cargo broadens the capabilities of these vessels immensely,” Parrott said. “The ATB feature provides the extra maneuverability for the large cargo area, and the spud allows the barge to pin itself against the shore in fast moving rivers and provides an additional measure of security. (The barge) has a heavy-duty ramp that allows unloading of heavy machinery directly ashore. These barges are also some of the largest in the near shore service in this area.”

Parrott said that some compromises were necessitated by the shallow draft requirements, including a reduction in deck cargo capacity in order to decrease the weight of the supporting structure.

“We also increased the length a bit to achieve the desired draft,” he explained. “While the 4-foot draft target cannot be achieved with full deadweight, the target draft can be achieved with the necessary load for delivery to the more remote villages. The barges took advantage of a law that allows oil barges operating in Western Alaska to be single skinned. While much safer in an ecological sense, a double-skinned barge for the same size and draft loses a large amount of capacity, which is critical for operations in these remote areas. With limited operating seasons, it is critical to deliver as much as you can with each mission.”

Costs, of course, also influenced design and construction decisions.

“ATBs present unique operating features, but they can cost a bit more than a powered barge,” Parrott said. “They are a bit more complicated than constructing a similar powered barge, but some of opportunities may offset some of these drawbacks.”

Vitus CEO Mark Smith said that the decision to build the new ATBs in a Gulf of Mexico shipyard was simply an economic one. “We looked at the cost of building on the West Coast, but even with the cost of delivering the tugs to Alaska, the Gulf still made more sense.”

The coupler system is a Taisei Engineering Articouple FRC-35 from Japan — a forecastle side-mounted, two-pin supporting articulated coupler of the combined friction/tooth-engagement type.

The tugs are propelled by three Caterpillar C18 diesels delivering a total of 1,800 hp and a maximum speed of 10 knots. The engines drive 40-inch propellers in nozzles provided by Rice Propulsion of Sinaloa, Mexico. Reductions gears are by Twin Disc.

The auxiliary power is provided by Caterpillar C4.4 and Caterpillar C2.2 gensets. Total fuel capacity is 9,410 gallons.

The engine room is equipped with a Kidde Total Flooding Fire Suppression System. Fendering is by Schuyler Companies of Broussard, La.

 Deck equipment aboard the tugs includes a bow-mounted capstan by Hawboldt Industries of Chester, Nova Scotia, Canada, and an 80-ton deck crane from ESI in South Windsor, Conn. There are no winches aboard the tugs.

The tugs have accommodation space for five to six crew. While the tugs can carry 3,980 gallons of potable water capacity, they are also equipped with a 900-gallon-per-day AquaMatic 900-1 watermaker.

For navigation gear the tugs have Furuno MFD12 NavNet 3D and Furuno DRS12A radars, a Furuno SC30 satellite compass, Furuno FA-50 AIS, Furuno FCV-620 echo sounder. The autopilot is a ComNav Admiral P3 model. Engine controls are Kobelt Triple Engine model 6515. Communications equipment includes an Icom M802 SSB radio and an Icom M504-21 VHF marine transceiver with a loud hailer. Satellite communications are a KVH TracPhone V3 satellite phone with a Furuno IF-NMEA serial cable data interface.

The barge AVEC-183 is 183-feet overall with eight 1,000-barrel tanks for a total capacity of 8,000 barrels. AVEC-208 is slightly longer at 208 feet and has a total capacity of 10,000 barrels carried in 10 tanks of 1,000 barrels each.

Both barges have a light draft of 4 feet and a loaded draft of 7.75 feet. Their deck loading capacity is 3,000 pounds per square foot. Clear deck space on each vessel is 3,121 square feet and 4,168 square feet respectively.

For deck equipment, each barge is equipped with two Hawboldt AW38 anchor windlasses. Tank pump is a dual 6-inch Blackmer driven by a Caterpillar C4.4 engine.

Vitus CEO Mark Smith is enthusiastic about the project and in partnering with AVEC.

“Vitus and AVEC are excited to bring the ATB technology to the Western Alaska market that combines the economics of tugboat and barge operations with the speed and sea-keeping ability of a ship,” Smith said.

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