a suspension having a specific gravity greater than 1 . 0 that contains one or more reactive materials , said suspension containing a biopolymer that decomposes over time , thereby releasing the contaminant reactant for contact with the contaminants in the waterway bottom sediment or waterway floor material . in one embodiment , the suspension includes a water - buoyant material , that can be placed underwater over a sub - aqueous waterway bottom or floor that contains a contaminant to be treated or confined and remains in place for treatment and / or confinement . after the suspension is placed , it may be stabilized against movement by applying a confining or weighting layer , such as sand or a water - permeable or water - impermeable geotextile , thereover .