Abstract: A product is used in creating an active capping layer across submerged (and optionally exposed) surfaces of contaminated sediment, with the product including multiple, dry particles composed of variable types and amounts of inert material, reactive material and binding material. To create optimal characteristics for controlled and relatively rapid settling through a water column, the dry particles can selectively comprise different sizes, size gradations and shapes (as a function of procedures for manufacturing and processing) as well as different density, or specific gravity (as a function of optionally including relatively very dense minerals). The dry particles are manufactured by implementing the sequential steps of material mixing into a flowable paste, paste drying, crushing and optionally sieving.