In the UK this is achieved by registering the dredged material and its intended beneficial use with the appropriate licensing authority, which may require evidence or justification on grounds of environmental acceptability. From the start of the study, however, it became obvious that most of the guidance could also apply to material arising from remedial dredging. It is worth noting that the study coincided with the interpretation of the EC Directive on Waste by the UK legal system. The study therefore experienced firsthand some of the pains that both regulators and dredging practitioners went through in understanding and adopting the EC Directive within the UK reality. The study found out that, in order to assess the potential for impacts on environmental resources of the disposal of dredged material on land for beneficial uses, the contaminant load of the dredged material is compared with the code of practice on sewage sludge being spread onto agricultural land or with regulatory standards derived solely for the remediation or end use of contaminated land.
Dredged material is, therefore, regarded either as sewage or as contaminated soil.
Table I. Criteria for sludges applied to agricultural lands for selected countries. The aim of this comparison is to limit, as much as possible, the contaminant load entering the soil and subsequently any surface and underground water resource, and the human food chain at large. However, it still stigmatises all dredged material as already containing as large quantities of available heavy metals as sewage sludge does. This comparison, however, overlooks the fact that dredged material is high in metal sulphides. These have a high potential of depleting oxygen sources and of resulting in a flux of heavy metals entering the interstitial water and later on other surface or underground water bodies - unless properly handled, disposed of and managed.