This research evaluated the removal of inorganic and organic contaminants by a variety of amendments and mixtures of amendments. A series of removal and retention batch experiments were conducted to identify the best treatment for metal removal in fresh and salt water. Metal removal by the amendments was evaluated by calculating the partition coefficient and percent removal. Retention of metals by the amendments was evaluated in retention (desorption) studies in which residue from the removal studies was extracted with 1 M MgCl2 solution. The results indicated that phosphate amendments, some organoclays, and the biopolymer, chitosan, were very effective in removing and retaining metals in both fresh and salt water. Removal and retention of organic contaminants was evaluated in sorption experiments involving 12 sequestering agents including organoclays, zeolites, rock phosphates, biological apatite, and calcium phytate. These experiments showed that organoclays and biological apatite were very effective sorbents for phenanthrene, pyrene, and benzo(a)pyrene. Mixtures of organoclay and rock phophate have high potential for remediating both organic and inorganic contaminants in sediments and soils. Remediation of sites contaminated with mixtures wastes is generally more difficult than sites contaminated with a single contaminant, since metals and organic contaminants have different chemistries, transport mechanisms, and fates in sediment and water. Our work suggests that organoclay by itself or mixed with small amounts of rock phosphate can effectively remediate sites with mixed-waste, and has high promise, not only as a component in active caps for sediment remediation, but for contaminant remediation in other environments as well.