Management of environmental uncertainty in maintenance dredging of polluted harbours in Norway

High levels of toxic chemicals such as tributyltin (TBT) have been found in the bottom sediments of many Norwegian harbours. Norwegian environmental authorities consider maintenance dredging of such harbours to be potentially harmful to the environment due to the suspension and spread of polluted sediments during the dredging operation. Accordingly, permission to dredge may be denied, or special environmental measures may be required on a case-to-case basis. In this paper, we describe the prevailing uncertainty in the assessment of the environmental effects. Employing Jerome Ravetz' distinction between practical and technical problems in the analysis of a case study from Northern Norway, we show the disadvantages with an exclusive focus on technical solutions. Finally, we discuss, informal and simple means to strengthen the presence of the practical problem in the decision process and thereby improve the management of uncertainty. © IWA Publishing 2005.