Risk-based methodologies are developed to establish criteria for regulating contaminant concentrations in sewage sludge for various disposal options. The paper describes the methodology developed for landfilling. The methodology is structured into three tiers. The first tier compares the results of an extraction test to health-based criteria. If the extract concentration for a contaminant is below the criteria, no further analysis is required. If the concentration exceeds the criteria, a Tier 2 or 3 analysis is required. Tiers 2 and 3 are based on application of analytical models to predict groundwater and vapor contaminant levels at the landfill property boundary. Tier 2 uses some site-specific data, such as hydraulic conductivity and soil type, along with literature values for adsorption and degradation. In Tier 3, site-specific field and laboratory studies are conducted to refine estimates of physical and chemical parameters affecting contaminant transport. The paper describes the algorithms and models employed to simulate each element and the input data required.