Sediment and Sludge Treatment

Environmental dredging in the harbour of Castletownbere (Ireland)

The project was completed in two phases performed during the temporary association of DEC – Land & Water. In the first phase, the plans were adopted and all the required environmental and other permits were applied for. In the second phase, the design of the operational method was determined and the dredging work was done.

The dredged sediment was under the responsibility of the joint venture and was either disposed of or reused as construction material after treatment and/or stabilisation. There were three levels dredged.

• The top layer was a layer of contaminated sediment. To dredge this layer as environmentally friendly as possible, we used a crane with a sight bucket. The dredged sediment could be treated, stabilised and buried but because of the contamination could not be reused.
• The second layer was a layer of non-contaminated sediment. This sediment was returned to the sea after dredging without further treatment.
• The third layer was rock, that was in the way of further depending of the harbour and entryway. That is why a portion of the rock layer was blasted and then the fragments were cleared away.

Dredging was necessary both at the base of the new quay and in an area of 25 m before this base, the manoeuvring zone, so that a new quay structure could be developed. Also the entry way to the harbour was deepened sufficiently. The work meant that the access to the port was no longer restricted by time.