Examination of bottom sediments in port canals
One of the numerous tasks performed by the Port of Gdansk Authority SA is the construction, expansion, maintenance and modernisation of port infrastructure, which includes, among other facilities, port water regions - approach fairways, canals, turning areas and basins. Measures aimed at the maintenance of ship lanes navigational bed and quay depths, the repairs and restoration of the existing quays and the construction of new quays and terminals entail dredging work.
Vessels with deep hull draught, while navigating port canals, cause the displacement of sediments, especially silt residues. This mainly affects the canal axis and makes its central part as well as the both sides of the fairway become slightly shallower. Smaller vessels approach the quays using their own drive system or run a test drive of the device capacity at the quay performing from several up to a dozen or so propeller rotations. If such action is repeated a number of times in the same location, the bottom depth may become shallower or deeper thus exceeding the permissible tolerances.
In order to eliminate the areas that have become shallower in relation to technical (operational) depths and to the inclination of underwater embankments in the water region resulted from utilizing port basins, canals and waterways, it is required that recurring cleaning and dredging work be conducted.
Prior to the commencement of dredging work, bottom sediments in the area of the projected work must be examined in order to determine whether the output is free from pollution. The scope of examination includes the contents determination of:
- polycyclic aromatic hydrocarbons (PAH)
- polychloride biphenyls (PCB)
The number of samples submitted for examination depends on the estimated volume of dredging work.
The examination of bottom sediments conducted in most of the water regions under the management of PGA SA shows that the dredged output is free from contamination and may be deposited in the sea.