Container dock developments at Naples

The design of the new terminal involves the clean-up and the management of polluted materials, the quantifying and characterisation of the landfill material, the construction of a groundwater cut-off wall and design of drainage pipe system to control piezometric levels have all had to be considered.

The challenging contract to carry out this development has been given to Trevi Construction and the work to build the new container terminal has to be carried out whilst the port remains an active passenger and goods destination. Naples is one of Italy’s largest seaports with capacity to handle 25M tonnes of cargo and 500,000TEU each year as well as almost 9 million passengers. Demand for facilities is expected to increase further and this project will more than double the capacity of the container handling facilities.

The extension of the Eastern Dock will add a further 200m of quay to the existing 11.5km of docks Naples but the overall length of the new quay will be 670 metres allowing two container ships to be handled at the same time. The length of the new quay will allow two 6000 TEU ships to berth at the same time or one 11,000 TEU ship. Before the new dock cranes can offload the first cargoes, Trevi needs to complete work on constructing the cofferdam for the new docks. This task is complicated by the geology of the site and the need to keep the rest of the port operational throughout the work.

The existing Levante terminal that is being modified has around 7ha of open water that is partially enclosed by two 250 metre long piers, each of which is 70 metres wide, and which are separated by a 70m length of quay wall. Water depth in the terminal varies from 7m to 15m. The new quay will have the possibility of being dredged at a later date to an average water depth of 18m, which will allow the port to accept some of the world’s largest container ships. Within the current plans however the water dept will be limited to 14 metres.

The new quay is being created by constructing a cofferdam structure that will then be backfilled using sediments dredged from within the port, so the quay structure must be completely waterproof.

The Port of Naples lies between two volcanic areas the main one being nearby Mount Vesuvius and this gives an indication of the challenging ground conditions at the site. The geological sequence is covered by backfill from the construction of the dock which overlies sandy-silty soils and tufa over more sandy soils.

Construction of the cofferdam structure called for Trevi to install sheet piles, bored piles and a diaphragm cut off wall into the tufa layer which extends 20-25m below average sea level. The main structure is being formed using a double wall of sheets piles with sealed joints that are driven into the tufa layer and which will be the seaward extent of the construction. Bored piles will be constructed once the cofferdam has been completed and backfilled and these will be the main support structure used to support the weight of the container cranes at the dockside.

Trevi’s work on the dock itself has been combined with construction of a settlement tank which will form part of the cooling circuit for the Tirreno Power Plant, which is also being built in the container terminal. For this element of the work, the company is using a combination of diaphragm walls to reduce permeability to 10 m/s around the tank construction area, and jet-grouting to consolidate the seabed around the tank’s intake and discharge area.

Trevi is also undertaking mini-piling and grouting work to one of the existing piers and dredging to remove contaminated sediments from within the construction area.

The basic construction work is expected to be completed early next year which will then allow work to start on the installation of the container handling equipment and facilities. The total surface area that will be created by the filling in of the Levante Dock area is approximately 263.000 square metres and this will be equipped with container handling equipment supplied by the container terminal operator Conateco. For discharging the ships there will be 8 ship to shore container cranes that will have a 60 tonne capacity and which will be sized to handle containers from post-Panamax ships.

These container cranes will be supplemented by 22 straddle carriers to move containers around the site. It is anticipated that the terminal will be able to handle around 1 million teu per year. It is planned to include a rail connection into the terminal and also to improve the road connections to the existing motorway network. Considerable sums will also be allocated to provide the back up infrastructure such as the facilities for the 500 staff expected to be employed at the site and the necessary customs and administration facilities.

A spokesperson for the port authority commented, “The construction of this new terminal will not only expand the container facilities at Naples but will also remove the environmental risk of this polluted area of the port. In addition the in-fill required to fill the new dock area has been reclaimed from the dredging of the main channel in the port and provided a safe depositary for this polluted material”.

By Dag Pike