Remediation of soils and sediments contaminated by halogenated aromatic hydrocarbons (HAH) such as PCBs, PCDDs, and PCDFs is a major environmental problem. HAH are the major contaminants found in sediments in the US. A novel abiotic reductive dehalogenation technology using ferrous iron has been developed in our laboratory that completely degrades tetrachloroethene (PCE) to non-chlorinated and non-toxic products. Preliminary experiments have shown that the process can also dechlorinate HAH such as hexachlorobiphenyl, pentachlorophenol and 1,2-dichlorobenzene. The process combines the degradation agent with agents such as Portland cement that solidify the soils/sediments so that both inorganic and organic contaminants are held in the sediments. In this manner, the treatment process reduces risk in two ways: by limiting transport of contaminants to humans or the environment and by degrading toxic compounds. These results indicate that development of an inexpensive treatment method is possible for soils and sediments contaminated with HAH. The overall goal for the proposed project is to develop data needed to demonstrate the effectiveness of the ferrous iron dehalogenation process and identify optimal conditions for its application to treatment of soils and sediments contaminated with HAH. A five-part experimental plan is proposed: 1) Validate analytical and experimental methods, 2) Define the effect of pH, temperature, iron dose, and target concentration on the kinetics and products of degradation of 2,2',3,3',4,4' hexachlorobiphenyl in slurry reactors, 3) Identify the form of active reductant, 4) Develop techniques for predicting porewater pH in treated soils and sediments in order to insure optimal chemical environment for degradation, 5) Demonstrate effectiveness of treatment of real soils and sediments contaminated with HAH such as PCBs, PCDDs and PCDFs.