Innovative active capping techniques offering both containment and treatment are effective, low-cost means of managing the sediments that endanger the health of our nation's waterways. This project seeks to advance the implementation and acceptance of these under-utilized technologies by validating their efficacy at the Anacostia River where historic industrial, municipal, and military activities have resulted in toxic levels of PAHs, PCBs, metals, and other contaminants. Objectives are to demonstrate, on a field scale, the ability to design, construct and place caps that will provide long-term treatment of sediment contaminants while simultaneously providing containment. Cap materials under consideration included Aquablok, a commercial product designed to reduce the permeability at the sediment-water interface, zero-valent iron and Bion soil, which encourage reductive dechlorination conditions, apatite, designed to sorb or bind metals and coke breeze and an organo modified clay, both capable of absorbing hydrophobic organic contaminants. After treatability testing, Aquablok, apatite and coke breeze have been selected for placement in the demonstration which will occur in fall 2003. Evaluation of post-placement effectiveness is expected to take place through 2005. A summary of activities and results to-date will be presented.