Dredgers of the Month: Dredgers in retrospect

D'Artagnan. Credit: DEME

This article was first published in the December 2005 edition of DPC. Correspondent Bert Visser declared which five vessels had impressed him the most over the
course of that year – a good choice with those vessels still being known in the dredging industry today

A lot can happen in a year’s dredging and 2005 was no exception, with the construction and delivery of several newbuildings, plus conversions of many important existing vessels.
In this final issue of the year, we take a look at five of the most significant dredgers in Europe and the US – two heavy dredgers, two dredgers designed for the sand and gravel industry, and lastly, a dredger significant to a specific region.

Heavy-duty dredgers

There can be little argument about the importance of the first dredger mentioned here, which is without doubt the most significant in 2005. We are of course talking about d’Artagnan, the most powerful heavy-duty cutter suction dredger in the world, whose impact can be summed
up in three ways:

D’Artagnan’s design combines high cutter and pump power with the ability to withstand strong ocean swell, making it suitable to carry out jobs previously considered too difficult or too costly and time consuming. For many ports worldwide, this means long-desired access channel or harbour-deepening projects can now be completed within acceptable budgets.
The vessel’s operational versatility makes it highly efficient when dredging both rock and sand.

Several innovative techniques have been applied to d’Artagnan’s design, which are likely to be copied in future generations of dredgers. Examples include a buffered spud carrier and a specially designed ladder end that enables the quick-and-easy change of cutters. D’Artagnan was built by IHC Holland Merwede, now Royal IHC, for DEME subsidiary Société de Dragage International and it sails under the French flag.

Jan De Nul’s backhoe dredger Il Principe. Credit: Jan de Nul

The backhoe dredger Il Principe, owned by Belgium’s Jan De Nul, is our second significant heavy-duty dredger of 2005. Built at Shipyard De Donge in Vlissingen, the Netherlands, it is one of the largest and most powerful backhoe dredgers in Europe, with an impressive penetration capacity of about 110 tonnes. Able to dredge to a depth of 31 m with a Liebherr P995 Litronic backhoe crane, Il Principe also features a unique propulsion system that allows it to operate independently of assisting vessels when dredging.

Since delivery in June 2005, it has been deployed at Spain’s port of Valencia, where Jan De Nul was involved in the construction of a new quay and pier – part of a 330,000 m2 port infrastructure development in preparation for the 2007 America’s Cup sailing tournament. The Autoridad Portuária de València, which is responsible for development of all infrastructure required for this event, has already expressed its satisfaction with Il Principe’s efficiency at coping with the port’s difficult soil conditions, where over 3 million m3 of material had to be dredged.

Sand gravel dredgers

As Western Europe’s demand for industrial and construction aggregates escalates, marine sources of sand and gravel are increasingly being mined – partly because existing land-based pits are emptying, but also because local governments discourage the exploitation of new ones to prevent landscape and environmental damage.

Trailing suction hopper dredgers (TSHDs) suitable for sand and gravel dredging at sea are therefore gaining in prevalence, no more so than in Holland’s Zeeland province, where several companies with a combined fleet of almost 20 vessels operate.

Although still functioning adequately, many of these ageing dredgers have restricted production capacities, which has prompted investment in newer, larger additions to the fleet. Orisant and Scelveringhe were built in 2002 and 2004, respectively, when Oosterlee of Breskens decided to improve the efficiency of its fleet through renovation.
When French dredging group Dragages Ports put the combined trailing suction/grab hopper dredger Opale up for sale, Oosterlee immediately saw the potential to transform it into an efficient and highly productive sand and gravel dredger.

Rio. Credit: Henk Kouwenhoven

After acquiring the ship, Oosterlee transported it to the Scheepswerf Boer Sliedrecht shipyard, where a radical renovation was carried out, converting it from the original 1,000 m3 capacity split hopper design into a ship with a traditional hull enlarged to 2,430 m3.

The original Liebherr grab crane, previously used for maintenance dredging, was replaced with a hydraulic Hitachi crane, increasing maximum dredging depth from 18 m to 35 m and a system of conveyor belts was installed for dry discharging the hopper.

After the conversion was completed in May 2005, the newly transformed aggregates dredger successfully underwent trials under its new name Rio. And since then, it has proven to be a highly efficient addition to the Zeeland-based fleet, delivering numerous loads of dredged material from the North Sea and Western Scheldt to clients in the Netherlands, Belgium, and Northern France.

Aggregates dredging is also in strong demand on France’s Atlantic coast, where several companies operate, one of which – La Rochelle’s Dragages Transports et Travaux Maritimes – recently ordered a new hopper dredger from Holland-based Barkmeijer Shipyards, now part of Thecla Bodewes Shipyards, for delivery in September 2005.

André L is the largest and most modern vessel involved in sand and gravel dredging off the Atlantic coast of France and its future looks promising: the land-based mining of alluvial aggregates for the concrete industry is strictly limited in France, which means increasing demand for marine aggregates. It is estimated that France’s major Île-de-France region alone will need about 7–10 million tonnes of marine aggregates over the coming years.

Andre L. in La Rochelle. Credit: HASENPUSCH. DIETMAR

André L combines a high production capacity with a fast sailing speed, which allows it to exploit high tides when entering ports. Tidal differences in the region are very large – up to 6 m – so it is advantageous to enter a port at high tides to avoid long periods of unproductivity. The vessel has a 2,500 m3 hopper capacity, a service speed of 13–15 kt, while its 25 m normal dredging depth can be increased to 40 m when a suction pipe extension is fitted.

Regional dredgers

Port maintenance dredging and beach replenishment works are of vital importance to the Dutch economy and take place on an almost continuous basis. Alongside large dredging contractors like Boskalis and Van Oord, a few smaller Dutch companies, including Van der Kamp, operate from Zwolle.

The contractor has a fleet of four medium- and small-sized TSHDs, one of which is the 1979-built Hein, which over the years has carried out several maintenance dredging campaigns for the port of Rotterdam as well as beach replenishment jobs for Rijkswaterstaat.

Notably, in 2004, Hein carried out most of the dredging required to deepen the cruise terminal near Wilhelminakade at the centre of Rotterdam so it could accommodate the world’s largest cruise ship Queen Mary II. However, at over 25 years of age, Hein was in bad need of a makeover, so in mid-2005, Van der Kamp decided to give it a thorough upgrade, simultaneously boosting its capacity.

It was sent to the Remontowa shipyard in Gdańsk, Poland, for renovation, where it was extended by 14 m and its hopper capacity increased from 2,860 m3 to 3,653 m3. The onboard propulsion system was also upgraded.