Dredging of Vila do Conde harbor, Portugal - Contamination of sediments

In Portugal, the dredging of small harbors represents the main exploitation cost for these infrastructures. These costs can significantly increase depending upon the degree of sediment contamination, as their disposal can concern an important amount of the overall costs. Therefore, a methodology for zoning the contamination areas was developed and it is summarized. This methodology was applied to the dredged material of an ancient wharf, used since the Middle Age, at Vila do Conde harbor, North of Portugal. Considering the resultant contamination zoning, for different years, an evolution analysis of the contaminated areas before and after dredging operations was carried out. This approach intended to evaluate if the contaminated areas are similar after dredging operations in order to identify the possible contamination sources and, subsequently, to eliminate them. Thus, an important part of the dredging cost may well be reduced, since the elimination, or reduction, of contamination sources in a harbor can increase the environmental beneficial use of the dredged sediments.