Napoli, Cofferdam


Construction of a double-wall cofferdam for the "Napoli Orientale" power plant.

To create a pumping station and a channel for the pipeline of the cooling system for the power plant, in a site of national interest that required a preliminary remediation treatment due to the presence of contaminated groundwater and sediments.

Our solution

Double-wall cofferdam

For the construction of the wall cofferdam ARCELOR AU20 and AU23 profiles were used and a polyurethane product, Roxan®-System ensured that the sheet pile wall was watertight. The sheet piles were driven partly by sea and by land. A self propelled pontoon and a hydraulic crane were used to fix the AU profiles until an under layer of tuff was reached. The AU20 and AU23 sections in S 355 J0 steel grade have an average length of 20 m and an elastic section modulus of 2270 cm³/m.

Perimetral sheetpiling diaphragm cofferdam

The pumping station perimeter was built using ARCELOR AZ37-700 profiles of 22m long until the same under layer of tuff was reached.

Pumping station

  • Earthmoving to level and clean the working area
  • Excavation inside the perimetral sheet pile diaphragm to reach level of –6.70m MSL with hydraulic excavators
  • Construction of the reinforced concrete structures such as slab, internal walls etc.
  • Installation of steel elements (beam, plates, grill)


Bentonite wall and drainage system

They were built to intercept the contaminated groundwater flow and collect it to a treatment plant.

The 650 m bentonite wall was built using new equipment developed from diaphragm wall cutter technology. It consists of cutting and mixing drums mounted on compact hydraulic motors. The drums are essentially designed to combine high penetration rates with excellent soil/ cement mixing.

Real-time processing of the construction parameters ensures optimum control and a high quality product.

Before the wall’s execution several mixes were tested in order to identify the optimum mixture to be used to guarantee that the structure was waterproof to the level of K=10-9 m/sec.


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