VESSEL REVIEW | Seaway Trident – Maintenance tug designed for US inland waters

Great Lakes St Lawrence Seaway Development Corporation (GLS), a wholly government-owned corporation under the US Department of Transportation, has expanded its fleet of maintenance vessels with the acquisition of a newly built harbour tug from Maine shipbuilder Washburn and Doughty Associates.

Seaway Trident was designed by Seattle-based naval architecture firm Glosten Associates. It will be used for duties including maintenance of lock gates, maintenance of aids to navigation, emergency response, and removal of accumulated ice from lock walls on the US portion of the St Lawrence Seaway. The customised tug was adapted to be able to withstand the icy conditions of the seaway, portions of which also pass through Ontario and Quebec in Canada.

At 60 feet (18.3 metres) in length and with a draught of only 10.5 feet (3.2 metres), the tug is compact enough to manoeuvre inside lock chambers, with a wide beam of 28 feet (8.5 metres) to improve performance in ice and enhance stability for deck crane operations. Two Schottel Z-drive units are powered by a pair of Caterpillar C18 diesel engines turning carbon fibre shafts for a combined 1,300 hp (969 kW) at 1,800 rpm, making the tug highly responsive to operator input. The propulsion arrangement generates a bollard pull of approximately 21 tons (19 tonnes).

To enable the tug to effectively perform its duties in ice, the hull was strengthened to American Bureau of Shipping Ice Class C0 standards. The deck is outfitted with a Markey Machinery headline winch and a fully foldable Heila Marine deck crane. A specialised scraping arm is also fitted to help clear lock walls of any ice buildup.

Arrangements have been optimised to facilitate harbour operations and improve safety even for small two- or three-person crews. Glosten added that the vessel is designed to capitalise on the many operating advantages afforded by a broad bow form with a semi-raised foc'sle deck, and full visibility and control from a single operating station in the pilothouse. It features a steel hull and house, with single curvature hull plates for ease of construction.

The navigation electronics include a Furuno radar.

Seaway Trident has already begun operating in the St Lawrence Seaway, replacing an earlier tug in the GLS maintenance fleet. The owner said the new tug also boasts lower emissions compared to its predecessor.

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