Monitoring Sludge Spill of the AMORAS Under Water Cell

Bart De Maerschalck, Maarten van Esbroeck, Stefaan Ides, Yves Plancke, Styn Claeys

Friday 3 july 2015

12:36 - 12:39h at South America (level 0)

Themes: (T) Sediment management and morphodynamics, (ST) Basin-wide sediment management, Poster pitches

Parallel session: Poster pitches: 15J. Sediment - Basin & Environment - Wetland

In 2006 the Flemish authorities in association with the Antwerp port authority launched the AMORAS project as a sustainable solution for maintenance dredging material from the port of Antwerp. AMORAS stands for Antwerp Mechanical Dewatering (Ontwatering), Recycling and Application of Sludge. The building of the site started in October 2008. End of 2011 the installation became operational. After separating the sand from the dredged material, the remaining sediment is mechanically dewatered and stored. The ambition is to finally recycle the dewatered sediment for other beneficial uses, e.g. in construction materials. Dredged material is temporarily stored in the AMORAS under water cell (under water cell). An electrically powered cutter suction dredger picks up the sediments from the underwater cell and pumps it to the sand separation. The underwater cell is a local deepening, up to 16m depth in the shelter dock along the main port navigation channel. The underwater cell is separated from the navigation channel by an underwater steel dam reaching up to 9m below the surface. In 2013 it was noticed that from all the dredged material dumped into the underwater cell only 70% was recovered again by the cutter suction dredger and send to the sand separator. Since summer 2013 both de dredging activities inside the port and the production rate of the cutter dredger and the AMORAS dewatering site have been increased. Since that time no more that 50% of the delivered material could be removed from under water cell by the cutter dredger. At the same time the Antwerp port authorities noticed an increasing mud layer in the neighbouring navigation channel. However, in order to pump sludge with a preferable density of around 1.12ton/m³, the operator of the cutter suction dredger needs to operate the cutter at a depth of 12m below the surface. For both the operator of the AMORAS site and the authorities it was necessary to get a clear view on the spill mechanism of sludge at the underwater cell. Different techniques and surveys have been executed in order to monitor mud layer responses, mud densities and shear resistance, consolidation processes inside the underwater cell and sediment plumes during dumping. Results of these analyses and recommendations to the operators and authorities will be discussed in the proposed paper.