Sub-aqueous placement of water-based suspensions and method of manufacture and use

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.