The series was designed by Hepworth, working closely with the owner's technical staff, and has evolved from the highly successful but smaller Afon Cefni built by Hepworth in 2002.

Key requirements listed in the owner's specification are shallow draft, versatility and the ability to support a wide range of marine civil engineering and dredging activities.

In keeping with its predecessors Afon Caradog is classed by Lloyds +100 Tug, has a full load-line certificate and complies with the UK MCA Code of Practice Category 1 for operation 150 miles from a safe haven.

The tug has an overall length of 26.8m, a beam of 9.0m and depth of 3.6m and a working draft of 2.4m. A single chine hull design gives the shallow draft hull the buoyancy necessary for lifting over the stern and using the powerful deck crane, and good sea keeping characteristics. The hull features a semi-raised foredeck and the bulwarks are 'stepped in' to prevent damage and provide safer access for personnel.

This tug will carry more fuel than the earlier vessels, with a capacity of 160m Domestic fresh water tanks have a capacity of 15m 3and additional tanks for ballast and transfer to other vessels have a total capacity of 33.5m 3.Electrically operated high capacity Desmi pumps and a purpose designed hose reel delivery system enable fuel and water to be transferred rapidly to other vessels.

Two Cummins KTA 38M2 main engines running at 1,800rpm generate a total of 2,600bhp.

Power is transmitted to a pair of fixed pitch propellers, rotating within Kort nozzles, via ZF reverse reduction gearboxes.

Twin rudders, of Hepworth's own semi-balanced, high lift, 'fishtail' design are fitted and controlled by Servi electro-hydraulic steering gear from a 'jog lever' in the wheelhouse. A Kort KT-250 bow thruster is driven by pumps on the auxiliary engines. On trials Afon Caradog achieved a bollard pull of approximately 34 tons and a free running speed of over 11 knots.

Electrical power is supplied by two Cummins powered 50kvA generator sets and hydraulic pressure for the deck machinery and bow thruster is provided by two further Cummins diesels.

A new feature on this class of vessel is provision to retrofit a fire fighting system in the near future, comprising one external monitor on the superstructure and its associated pump coupled to the free end of one main engine.

A very large clear work space is protected by hardwood cladding and has well sited deck machinery. The North Sea Winches GMP-1700 hydraulically powered towing winch is of the twin-drum 'waterfall' type with a 45 ton line pull and a capacity per drum of 700m of 44mm diameter steel wire rope. North Sea Winches also supplied a 10 ton tugger winch, the anchor windlass and a powered rope storage reel.

Another essential piece of equipment is the powerful 90 tons/metre Heila HLRM 90/55 'knuckle-boom' crane. The hydraulically powered long reach crane is capable of lifting 29,700kg at 2.89m reach and 5,100kg at 14.47m. A lifting winch, wire and hook are also incorporated.

Afon Caradog sports the same superstructure and wheelhouse layout as previous tugs and is configured to allow maximum flexibility of use. Four control stations are available, three on the full width forward console and one aft. The navigational and communications package includes magnetic and GPS compasses, an auto-pilot, two daylight viewing radars, a Navtex receiver, GPS navigator and chart display, much of which can be viewed on a series of large integrated visual display units. Communications equipment installed includes two VHF radios, one with DSC, a medium frequency DSC radio, and GSM telephone and fax.

Immediately after completing trials on the Humber, Afon Caradog sailed for Mostyn in North Wales to work on a new wind farm project in the Mersey estuary.