Although the 30.48m long Vigilant looks very similar to its sister tug Valor, which Crowley acquired last year (Maritime Journal - September 2007), the vessel has been modified for use in the harsh Alaskan waters. The tug's hull has been strengthened for use in ice, boasting a 9.5mm (3/8-inch) thick belt of steel along the hull, adding 80 additional tons of steel to the boat.

The vessel's decks are also heated, along with some of the tanks, for added protection and improved operation. Other noteworthy features aboard Vigilant include 6,770 horsepower main engines, a bollard pull in excess of 90 tons and a speed of 14 knots. The horsepower ratings are among the highest for stern drive tugs in the US and 92 tons bollard pull ahead and 90.5 tons astern.

Crowley are also building two additional Avik class tugboats for their petroleum distribution fleet in Alaska. Crowley Maritime Corporation's technical services group has awarded a construction contract to Diversified Marine in Portland, Oregon USA to build two of the purpose designed 23.16m vessels. The first tug of a similar type, named Avik, was delivered to Crowley in June 2004 and has proved to be highly successful.

This latest pair will closely follow that design and enter service in the first quarter of 2009. The tugs will handle barges transporting fuel and general cargo to communities in Alaska, where shallow water and lack of docking facilities are common. In those circumstances, tugs and barges make a beach landing to load and unload cargo.

With the addition of these two new Avik class tugs, Crowley will be able to serve the Western Alaska communities more efficiently. One tug will work Bristol Bay and the lower Kuskokwim coast, and the other new tug will be deployed on the Yukon River.

Avik class tugs are designed for both shallow water and ocean towing operations and are the first step in the company's plan to modernise its Alaska river fleet, replacing two existing tugs. The new tugs feature a raised bridge for improved visibility, an electric Markey single drum towing winch for coastal towing and fendered push knees for river or beaching operations. They will be powered by three Caterpillar C18 diesel engines generating a total of 1,362bhp.

Environmentally friendly features include engines that meet IMO emissions requirements, holding tanks to retain treated sewage, electric deck machinery instead of hydraulic and fuel tanks surrounded by void spaces to minimise the chance of fuel spills.