Great Lakes Areas of Concern (AOC) are designated geographical locations within the Great Lakes Basin with particularly degraded environmental conditions. There is a consensus among diverse sectors in the Great Lakes Basin that contaminated sediment is a major environmental problem and a key factor in many of the impairments of the human and nonhuman uses (beneficial uses) of the Great Lakes. This case study examines Randle Reef in the Hamilton Harbour (AOC) which is the largest Canadian contaminated sediment site in the Great Lakes containing 695,000 m3 of sediment contaminated with polycyclic aromatic hydrocarbons (PAH) and metals. The cleanup of the Randle Reef site is a major step in the process to restore Hamilton Harbour and remove it from the list of AOCs. The Randle Reef sediment remediation project is finally coming to fruition after more than thirty years of study, discussion, collaborations, and debate. As in the case of Randle Reef, environmental decisions are often complex and multi-faceted and involve many stakeholders with competing (sometimes conflicting) priorities or objectives representing exactly the type of problem that humans are poorly equipped to solve unaided. When professionals encounter complex issues, they often attempt to use approaches that simplify the complexity so that they can manage the problem at hand. During this process, valuable information may be lost, opposite points of view may be ignored and elements of uncertainty may be overlooked. A systematic methodology that combines both quantitative and qualitative data from scientific or engineering studies of risk, cost, and benefit, as well as stakeholder objectives and values to rank project alternatives, has yet to be fully developed for contaminated sediment decision-making. The main goal of this Ph.D. research was to develop a Decision Support System (DSS) framework to aid the complex decision-making in sediment remediation. The proposed DSS framework incorporates the five key themes that, through research, were found to be the most relevant for sediment remediation projects. These themes are 1)participation of appropriate actors with common objectives; 2)funding and resources; 3)decision-making process; 4)research and technology development; and 5)public and political support. There was a need to gather relevant information and data from various sources to develop the required DSS framework. For this purpose, expert interviews were conducted, responses were collected through a public survey, Qualitative Document Analysis (QDA) was performed on available policy and research documents, and a review was undertaken of how other jurisdictions have employed DSS to aid their decision-making process. The final DSS framework has six key components as follows: 1)data module; 2)communication module; 3)document module; 4)knowledge module; 5)tools module; and 6)DSS optimization module. This generic framework can assist practitioners in developing more systematic and structured decisions for sediment remediation by incorporating an Integrated Information Management System (IIMS) along with a DSS optimization module. This IIMS+DSS method can aid the decision-making process by making it documented, reproducible, robust, transparent and provide a coherent framework to explore and analyze available alternatives in an attempt to reach the preferred solution promptly. / Thesis / Doctor of Philosophy (PhD)