Recent approaches to the Solidification and Stabilisation (S/S) of Contaminated Dredge Material in Ireland

The increasing cost of disposing of contaminated dredge material through traditional methods combined with a tightening of environmental regulation has resulted in engineers’ exploring alternative solutions when designing projects that include dredging works. Previously, dredge material was disposed of in a range of ways including shore based land fill, dumping at sea or international transhipment. Larger projects usually involve several of these disposal methods. The critical determinants being the quantity of dredge material and level of contamination within that material. This paper examines the approach taken on recent marine projects in Ireland that treat and reuse the contaminated dredge spoil within the project site. The reuse of material is achieved through a process called Solidification and stabilisation (S/S), where a cementitious binder is mixed into the dredge spoil.

A range of proposed binders including Ordinary Portland Cement (OPC), Ground Granulated Blast Furnace Slag (GGBS) and Fly Ash are examined in terms of applicability and suitability with reference to the recent projects. An analysis of the trial mixing and testing methodologies employed on these projects is undertaken. The suitability of different binder mixes to match contamination levels and site type is assessed. This assessment will enable planners and engineers make more informed decisions on future marine projects involving contaminated dredge material.