Environmental disturbance characterised through spillage from underwater dredging/mining cutting

During underwater dredging and mining operations most cutting equipment experiences spillage from the cutter and suction configurations. The environmental impacts of this spillage can be severe, causing change and often degradation in habitat for both benthic and mid water species. While spillage causes an increase in turbidity levels it can also release metals and other contaminants into the water column. These may be components of a mining ore or large deposits lying at the bottom of harbours that are released during dredging. This paper reports on spillage tests, using turbidity as an indicator, in a specially designed tank with a transverse axis dredging/mining cutter, suction cowl and pump systems. The paper concludes on the levels of increased turbidity relative to the cutter systems and highlights the influence of the cowling design in reducing spillage levels. A description is given of future tests with a range of dredging/mining cutters.