The Department of Energy's Office of Environmental Management's (EM) mission is the safe cleanup of sites associated with the government-led development of nuclear weapons and nuclear energy. While many of these legacy sites have completed cleanup, the largest and most complex sites have not been fully remediated. The cleanup of these sites is proceeding under legally enforceable agreements with timelines for hundreds of milestones. EM is reviewing alternative approaches to increase effectiveness and improve cost efficiencies of its cleanup activities, especially for sites that will have residual contamination when active cleanup is complete. This report is the summary of two workshops convened in October 2013 and January 2014 on best practices for risk-informed remedy selection, closure, and post-closure control of radioactive and chemically contaminated sites that present significant difficulty for remediation to unrestricted release. The workshop series aimed to explore best practices that promote effective, risk-informed decision making and future opportunities to improve remediation approaches and practices.In the Workshop #1 section of Best Practices for Risk-Informed Decision Making Regarding Contaminated Sites, the report examines holistic approaches for remediating sites with multiple contaminant sources and post-closure uses, and approaches for incorporating a sustainability framework into decision making regarding site remediation, closure, and post-closure control. In Workshop #2, the report focuses on post-closure controls, assessment of long-term performance of site remedies, and best practices for risk-based remediation decisions.

Following the President's decision in January 2010 to withdraw the license application for a geologic repository at Yucca Mountain, Nevada, the Secretary of Energy established the Blue Ribbon Commission on America's Nuclear Future (BRC) to consider alternatives to the nation's current institutional arrangements for management and disposition of used fuel and defense high-level nuclear waste. In February 2012, the BRC issued its final report. Among its recommendations was a call for a new, single purpose organization to be established to replace the Office of Civilian Radioactive Waste Management (OCRWM) in the U.S. Department of Energy (DOE) that had been established under the authority of the 1982 Nuclear Waste Policy Act. The BRC suggested that a congressionally chartered federal corporation offers the most promising model, but the commission left open the possibility of alternative concepts to achieve the desired ends. In response to this recommendation, DOE asked the RAND Corporation to examine alternative organizational models for such a new management and disposition organization (MDO). Our study supports the work of DOE's Office of Nuclear Energy and the Management and Disposition Working Group(MDWG) formed to consider implementation options and activities.