Thanks to the combination of unique characteristics suchas an extremely long suction pipe, a large transport capacity with limited  depth and an additional heavy duty rock draghead, the multidisciplinary ship can be used effectively in shallow water and in hard soils.

Technological optimisation
With the ‘Bonny River’, DEME is responding to the macroeconomic trend of maritime sand extraction at greater depths and further offshore. A long suction pipe with a built-in submersible pump facilitates sand extraction from more than 100 metres deep. Thanks to the hull’s optimised design, the ‘Bonny River’ with its transport capacity of 24,000 tonnes has a limited depth when loaded, making the ship highly suitable for coastal protection assignments, even in regions with shallow beaches. An additional asset is the second, shorter suction pipe for dredging works on a harder seabed. By equipping the vessel with a 75 tonnes draghead, the ‘Bonny River’ is multidisciplinary: as a trailing suction hopper dredger the ship can also remove hard soil which wasn’t dredgeable in the past.

Environmental optimisation
The ‘Bonny River’ will be able to minimise the turbidity generated by process water and enables dredging in environmentally vulnerable areas. Moreover, the hydrodynamic hull and the dual-fuel engines (diesel and LNG) ensure further optimisation of the fuel consumption and a minimal CO2 footprint. The ‘Bonny River’ will carry a ‘Green Passport’ and a ‘Clean Design’ classification, a certification for owners and contractors which make the conscious decision to build and operate their ships in an environmentally friendly way.

Modern and efficient fleet
The ‘Bonny River’ – named after the Nigerian river of the same name – is the sixth ship that DEME has on order, besides the multipurpose ship the ‘Living Stone’, the self-propelled jack-up vessel ‘Apollo’, the heavy lift crane vessel ‘RAMBIZ 4000’ and two additional trailing suction hopper dredgers.

The order for the ‘Bonny River’ has been placed at Royal IHC. The ship will be built by Cosco at its shipyard in Guangdong, China. Cosco is one of the world’s largest ship owning and operating companies, as well as a leading shipyard group, building general cargo, offshore and special customised vessels.

The TSHDs are scheduled for delivery this year, the contract between Rosmorport and Krasnoye Sormovo Shipyard having been signed in April 2014. Keel laying of the Sommers was held in November 2014. The other two dredgers are to be named Kronshlot and Kadosh respectively.

The dredger is 62.6 metres in length, with a 14 metre draught, a hopper capacity of 1,000 m3, and a deadweight of 1,685 tonnes. The 500 mm diameter trailing pipe works at a maximum dredging depth of -20 metres. It is connected to a diesel-driven Damen dredge pump, type BP5045MD, designed for both hopper loading and discharging purposes. The TSHD 1000 series are able to operate at water temperatures between -2 °C to + 20 °C.

All three of the vessels will be tailored to meet client requirements and to operate in local climatic conditions. The TSHD 1000 vessels will feature a state-of-the-art package of dredging solutions, including dumping through bottom doors or a pre-dumping door and pumping ashore through a bow coupling unit as well as rainbowing.

The yard is on schedule to deliver all three TSHDs on time. The vessels will perform maintenance dredging in the basins and access channels of the ports of Ust-Luga, Big Port St. Petersburg and Tuapse.

Shane Perumal, Project Manager, said: “There has been a huge safety commitment from the Project Managers, the main contractor Stefanutti Stocks AXSYS Joint Venture, and subcontractors, to provide continual training, preventative programmes, communication of safe work practices, sharing of lessons learned from observations and incidents and good site safety vigilance. This ensures that everyone – from labourers to senior management- works safely every day.”

He said this was notwithstanding the special nature of work being executed on this project and the tight deadlines.

The R1.6 billion project forms an integral part of Transnet’s Market Demand Strategy which aims to enable the effective, efficient and economic functioning of an integrated port system to promote economic growth.

It involves the reconstruction and deepening of six of the 15 berths in this precinct. Once completed the berths will have a draught of 14.5 m enabling them to handle vessels with draughts up to 13 m, however the Maydon Wharf entrance channel will still need to be deepened thereafter to enable these vessels to sail in fully laden.

Scope
Maydon Wharf is the largest break bulk and dry bulk handling precinct in the Port of Durban covering 120 ha of port land. The reconstruction project aims to ensure safe operations, meet the needs of larger vessels calling at the port and enable increased throughputs.

The quay walls in the precinct were originally designed to handle vessels of approximately 20 000 DWT versus the 55 000 DWT vessels now calling. Bigger vessels call mainly half laden due to the current draught and width restrictions.

Berths 1-2 and 13-14 are currently under construction, following the reconstruction of berth 12, which was completed in November 2012. Berths 3-4 will be under construction early in 2016.

The work has involved demolition of paving, rail track work and services, construction of new steel sheet piled quay walls, demolition of existing piled crane beams, extraction of timber, concrete piles and a limited number of steel sheet piles and removal of the existing quay wall and capping beams.

Work includes driving of inclined grouted steel anchor piles (being used in South Africa for the first time), backfilling behind the quay walls, construction of new reinforced concrete capping beams, supply and installation of bollards, fenders, ladders and quay services, construction of railway tracks, layer works and paving, dredging of material adjacent to the berths and construction of rock scour protection.

The main challenges have been balancing operations and the project, including site access, executing work around the existing ship loader foundations and conveyor, as well as obstructions and incorrect as built information supplied. The project team has also had to contend with strong winds and wakes formed by tugs operating in the precinct affecting floating equipment used for construction.

As a result the team has implemented night and weekend shifts and mobilised additional plant to ensure that the project remains on track.

Among other achievements to date include a satisfactory audit report, the successful pull out test on the anchor pile system and the completion of all piling and the new cope on Berth 1,2 & 13. A record 4500 tonnes of steel was offloaded, transported and stacked during a continuous 84 hour operation.

“This safety milestone of 1 million hours without an LTI could not have been achieved without an enormous amount of hard work and effort by everyone working on the project,” said Perumal.