ForewordThe Characterization of Systems (CoS) Task under the Groundwater/Vadose Zone Integration Project is responsible for establishing a consistent set of data, parameters, and conceptual models to support efforts at the Hanford Site to estimate contaminant migration and impacts. As part of these efforts CoS is assembling a series of catalogs to identify the depth and breadth of existing data and to facilitate access to those data. The preparation of these catalogs is aimed at facilitating the development of comprehensive, useable, and scientifically defensible database(s). However, it is also envisioned that these catalogs will be "living documents" that will continue to evolve as other existing data is found and new data collected.This catalog summarizes information on models that have been used to simulate release of chemical and radioactive contaminants from waste sources on the Hanford Site over the past 14 years. v Summary Models have been used to simulate the transport and fate of contaminants at the Hanford Site to assess the effectiveness of various environmental restoration and waste management activities and to estimate impacts to environmental and human receptors. Part of the process includes the ability to simulate the release to the vadose zone and groundwater of a wide range of contaminants from a wide range of waste sources that have been generated at the Hanford Site as a result of over 40 years of defense production activities.Mathematical formulas that express the release of contaminants from various waste sources and their application in past assessments are documented in many reports published over the past 14 years. The sheer number of reports in which such information is reported makes it difficult for individuals to access this information in a timely manner. To provide users carrying out Hanford assessments with improved access to the information and data on release model capability, researchers at the Pacific Northwest National Laboratory (PNNL) consolidated these sources of information and data into a single location. This work was conducted under the Vadose Zone Groundwater Integration Project managed by Bechtel Hanford Incorporated for the U.S. Department of Energy -Richland Operations (DOE-RL).This report provides summaries of release models used in Hanford Site assessments published over the past 14 years (1987 to 2001). Mathematical formulations that commonly have been used in recent years (i.e., salt-cake, cement, soil-debris, reactor block, glass, and corrosion) are described, along with associated parameter definitions and their units. Tables in this report provide links to data sources needed to implement the models. These links enable users to quickly locate the specific release model information and data sources they need for applying the models to future to site assessments.During the compilation of the catalog, the authors became aware of significant differences in the level of complexity of release models applied over the years to meet Hanford Site assessment objectives...