A design-to-delivery time of 18 months made a challenging project of Chetzemoka, the first in a new class of Washington State Ferries vessels
A design-to-delivery time of 18 months made a challenging project of Chetzemoka, the first in a new class of Washington State Ferries vessels
A swift build time of 18 months dictated the nature a number of the approaches to the design and construction of new ferry Chetzemoka. Washington State Ferries’ (WSF’s) first vessel in its new Kwa-di Tabil Class will serve the Port Townsend to Keystone route in Puget Sound and is due for delivery around the beginning of August.
The design is based on the Massachusetts Steamship Authority’s Island Home, built in 2007 by VT Halter Marine, but with modifications. Ron Wohlfrom, WSF’s project engineer, explained the driving force behind the build: “We discovered that our four Steel Electric class vessels needed extensive repairs due to the hull steel condition. These ferries were built in 1927, so there have obviously been multiple rule changes since then and to replace as much steel as we needed to was not deemed economically feasible. Therefore we pulled them from service in November 2007.”
Since then WSF has been temporarily leasing Steilacoom II from Pierce County but still urgently required new tonnage. So the owner looked for an existing design it could modify, which would reduce build time. “We needed a vessel that had been built in the US so that it would make the regulatory review go quicker and smoother,” says Mr Wohlfrom. The principle requirements were a capacity of 100 cars or less and the vessel had to be able to safely transit Keystone Harbour’s cross-current of 4-4.5 knot.
WSF worked on the project with the Elliott Bay Design Group in Seattle and chose Island Home because it was the most suitable recent American build that adhered to US Coast Guard rules. “When we started this process, Island Home was only 3 months old and had been designed 2 years prior to that point, so we only had a couple of years of Coast Guard requirement changes to update,” explains Mr Wohlfrom.
The process was made easier by the fact that the vessel was a previous design of Elliott Bay. That company’s chief concept engineer said, “We were able to incorporate the changes to that design that WSF wanted and get that package out to the yards fairly quickly.”
The design modifications included eliminating bow thrusters and bow doors, which meant that smaller generators could be used.
Mr Wohlfrom commented, “Our service will run in calmer conditions than The Steamship Authority’s vessels, so it doesn’t need as much protection for the passenger or vehicle deck.” WSF also wanted the front end cut in a ‘pickle fork’ type arrangement to improve bow visibility from the pilot house. “This meant adding a 1.2m long piece,” he said. “Due to the way we load on and off the ramp we needed more of a spoon-like look.”
A 5.8m long mid-body section was also added. “This was driven by stability requirements and the need to maintain a capacity for traffic growth through the vessel’s life,” Mr Wohlfrom explained. WSF also substantially increased the fuel capacity by adding larger fuel tanks to facilitate operation of the vessel, which has a different fuelling cycle to The Steamship Authority’s ferries.
Removal of the hoistable car deck decreased the car capacity from 76 to 64. “It was eliminated because of the time it would take to lower the lift deck,” said Mr Wohlfram. HVAC systems were also reduced due to the cooler climate of the west coast, and two staterooms were removed. Furthermore WSF changed the shaft material from carbon fibre to steel, following concerns about the robustness of the former.
The Chetzemoka design had also to take into account a number of regulatory considerations. WSF does not use classification societies for its vessels; instead it complies with US Coast Guard requirements.
The Americans with Disabilities Act is being updated this year and meant that the pitch of the stairs on board had to be modified from the 36 degrees of Island Home’s specification to 32 degrees. In the USA a large passenger vessel’s design is governed by the Code of Federal Regulations, chapter 46, sub-chapter H. “We also modified the stairwells according to the H class rules on fire protection zones,” said Mr Wohlfrom. “We followed the H class rules without requesting any exemptions so that it would be easier to get through the permitting process. This also meant our vehicle deck was enclosed, unlike our more traditional vessels, because of concerns that a vehicle fire might spread to the mezzanine and the passenger deck via the windows. As they are now blocked out, fire could not spread that way.”
Green considerations were also part of the design process. Environmental rules in Puget Sound prohibit the discharge of sewage and the company’s policy is not to discharge cooling water from the main engines, although that is allowed. “We use fresh water flushing, pumping the sewage ashore with fresh water mixed in. If we were to pump salt water ashore we could kill the microbes in the various sewage treatment plants,” reports Mr Wohlfrom. Keel coolers will also be installed aboard, which take jacket water from the main engine, cool it outside the vessel and then return it to the engine. He adds, “We have eliminated one piping system within the ship, saving space and reducing maintenance.”
The Washington State legislature specified that the funding it provided for this project must be used to maintain the local shipbuilding industry. The US$65 million contract went out to tender in September 2008 and a bid was accepted from Todd Pacific Shipyards of Seattle in December that year. With a Summer 2010 delivery slot, Todd had to employ a variety of techniques to meet the rapid deadline.
Some long lead times for parts manufacture were eliminated as the pair of 12-cylinder Electro-Motive Diesel 710 main engines and the generators were appropriated from another vessel design that has been held up by litigation.
Tom Perrine, Todd’s senior director of new construction, said, “We used ShipConstructor’s three-dimensional product-modelling software to build the vessel and that allowed us to be able to visualise the spaces and to come to a quick agreement with WSF on the arrangements.”
The software was also useful when Todd had to sub-contract a number of different roles to other yards to meet the stringent timeline requirements. Brian Evert, director of new construction, told PST, “Jesse Engineering in Tacoma built the ends of the hull, which were then shipped by barge to our building hall and erected with the rest of the Todd hull. The aluminium superstructure was built by Nichols Brothers of Whidbey Island and fabrication of the mezzanine level and final outfitting is being carried out at Everett Shipyard.”
Todd also worked with Guido Perla & Associates to finalise the design and prepare all the working drawings. Mr Perrine adds, “To have four sites simultaneously building components really taxed them because they have to supply information to everybody.”
Following delivery, there will be four to six weeks of crew training on board as the entrance to Keystone Harbour is very narrow. “Four sets of 10-person crews need time to familiarise themselves with the operating characteristics of Chetzemoka as they will need to stop the vessel within 900ft [274m],” observes Mr Wohlfrom.
Chetzemoka is the first of three vessels. The second, Salish, is already underway at Todd Pacific and due for delivery on the same route in March 2011. The contract for the second and third vessels was awarded in November 2009 and is worth US$114 million. The third ferry, Kennewick, should be delivered in winter 2012 and deployed on the Port Defiance to Tahlequah route. For these builds, the compressed build timeframe should be easier to adhere to. “The engineering is essentially already complete for the second and third vessels, with WSF only requesting minor changes from Chetzemoka’s design,” adds Mr Evert. The yard is applying lessons learned with Chetzemoka to the second ship, and Salish is reported already to be at least a month ahead of the initial build’s progress.
Depending on the outcome of discussions at the next Washington State legislature sessions at the beginning of 2011, there is also an option for a fourth Kwa-di Tabil class vessel, but WSF would prefer to use any funding for a new 144 car vessel. Todd has also won the design/build contract for this vessel, should it go ahead. PST
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