The risks to marine life in the water column arising from dredging for phosphates at depths of between 190-300 m on Namibia's continental shelf are assessed in this study. The study is to be integrated into a multidisciplinary assessment of effects of the proposed mining. Information about ecosystem functioning in the mining licence area was obtained from consulting local experts and extrapolated from reports on other surveys done in Namibian and southern African waters. Additionally the scientific literature topical to dredging was drawn on. No fieldwork was done for the project. A standard impact assessment methodology is used to predict the severity of impacts arising from the following typical dredging activities: disposal of wastes from regular vessel operations; exchange of ballast water; discharge of overspill from dredge hoppers; and excavation of the seabed. Where possible measures to prevent or otherwise minimise negative effects are given.