Low-activity tank wastes will be generated during cleanup of high-level radioactive tank wastes on the Hanford site. The low-activity tank waste will be among the largest volumes of radioactive waste within the U.S. Department of Energy (DOE) complex and is one of the largest inventories of long-lived radionuclides planned for disposal in a low-level waste facility. The Department of Energy's Office of River Protection is evaluating several options for immobilization of low-activity tank wastes for eventual disposal in a shallow subsurface facility at the Hanford Site. A significant portion of the waste will be converted into low-activity waste (LAW) glass with a conventional Joule-heated ceramic melter. In addition, three supplemental treatment processes are presently under consideration by the DOE to treat wastes in selected tanks with the goal of accelerating the overall cleanup mission at the Hanford site. These are: 1) bulk vitrification (BV), 2) cementation or the cast stone (CS) process, and 3) steam reformation (SR). The DOE is expected to select by October 2003 one or more of these supplemental treatment technologies for more detailed evaluation. As part of the selection process, a preliminary risk assessment is being performed to evaluate the impacts of the disposal facility on public health and environmental resources.The same computational framework used to conduct the 2001 ILAW performance assessment will be used for all three waste forms. Cast stone will be modeled with a diffusion-advection transport model and bulk vitrified glass and steam reformed LAW will be modeled with a reactive chemical transport simulator. Modeling waste form performance requires the determination of a number of wasteform specific input parameters. The required input parameters for BV and SR waste forms are derived from a mechanistic model that describes the effect of solution chemistry on contaminant release rates. The single-pass flow-through test is the principal method used to obtain these input parameters, supplemented by product consistency test measurements and physical property measurements. The diffusiveadvective transport model for cast stone requires measurements of effective diffusion coefficients and hydraulic properties.