NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

Support for this study was provided by the U.S. Department of Energy, under Grants No. DE-FC01-94EW54069 and DE-FC01-99EW59049. All opinions, findings, conclusions, and recommendations expressed herein are those of the authors and do not necessarily reflect the views of the Department of Energy.

Cover Image: The U.S. Department of Energy is engaged in an effort of national importance to address the legacy of environmental contamination resulting from its Cold War defense mission. Many U.S. defense complex sites are highly contaminated with radionuclides and hazardous chemicals and cannot be cleaned up with current technologies (top image). These sites must be managed to isolate and contain the waste (fence image in center), in some cases in perpetuity (hourglass image). These contaminated sites will require long-term institutional management to protect the land and the people who live “outside the fence” (bottom image). The bottom image also embodies the hope that in at least some instances the principles of long-term institutional management, diligently applied, make the need for the fence eventually to go away, as sites that are contaminated today are cleaned up in the future with new technologies.