This project comprises the first phase needed to develop a comprehensive risk-based decision-making approach for onsite/decentralized wastewater treatment and management. Risk is implicitly included in current permitting regulations for onsite wastewater treatment systems. However, estimation of explicitly defined risks associated with such rules has not been accomplished, due primarily to the lack of a standardized method for integrating disparate risks into a comprehensive approach that can be applied at various sites and geographical scales. This project will develop a general risk-based framework for integrating the results from four different types of assessments into a single cohesive risk assessment framework for individual onsite wastewater treatment systems. The types of component risk assessments that will be addressed include engineering, ecological, public health and socioeconomic. The general framework will consist of problem formulations for individual systems, a component framework for each type of assessment, an approach to integrating the results of each component assessment, and a brief discussion of risk management issues.