Conceptual Site Models as a Tool in Evaluating Ecological Health: The Case of the Department of Energy'S Amchitka Island Nuclear Test Site

Abstract

Managers of contaminated sites are faced with options ranging from monitoring natural attenuation to complete removal of contaminants to meet residential health standards. Conceptual site models (CSMs) are one tool used by the U.S. Department of Energy (DOE) and other environmental managers to understand, track, help with decisions, and communicate with the public about the risk from contamination. CSMs are simplified graphical representations of the sources, releases, transport and exposure pathways, and receptors, along with possible barriers to interdict pathways and reduce exposure. In this article, three CSMs are created using Amchitka Island, where the remaining contamination is from underground nuclear test shot cavities containing large quantities of numerous radionuclides in various physical and chemical forms: (1) a typical underground nuclear test shot CSM (modeled after other sites), (2) an expanded CSM with more complex receptors, and (3) a regional CSM that takes into account contaminant pathways from sources other than Amchitka. The objective was to expand the CSM used by DOE to be more responsive to different types of receptors. Amchitka Island differs from other DOE test shot sites because it is surrounded by a marine environment that is highly productive and has a high biodiversity, and the source of contamination is underground, not on the surface. The surrounding waters of the Bering Sea and North Pacific Ocean are heavily exploited by commercial fisheries and provide the United States and other countries with a significant proportion of its seafood. It is proposed that the CSMs on Amchitka Island should focus more on the pathways of exposure and critical receptors, rather than sources and blocks. Further, CSMs should be incorporated within a larger regional model because of the potentially rapid transport within ocean ecosystems. The large number of migratory or highly mobile species that pass by Amchitka provide the potential for a direct pathway to the local human population, known as Aleut, and commercial fisheries, which are remote from the island itself. The exposure matrix for receptors requires expansion for the Amchitka Island ecosystem because of the valuable marine and seafood resources in the region. CSMs with an expanded exposure/receptor matrix can be used effectively to clarify the conceptualization of the problem for scientists, regulators, and the general public.

We thank the people who contributed to the development of the Science Plan that provided the initial framework for this project, including David Kosson, Barry Friedlander, John Eichelberger, David Barnes, Lawrence Duffy, and Stephen Jewett, as well as Monica Sanchez, Runore Wycoff, and Peter Sanders (Department of Energy, National Nuclear Security Administration, Nevada), Jenny Chapman (Desert Research Institute), Anne Morkill (U.S. Fish & Wildlife Service), Robert Patrick (Aleutian/Pribilof Island Association), Ron King, David Rogers, and Doug Dasher (Alaska Department of Environmental Conservation), and the people of the villages of Unalaska, Nikolski, Atka, and Adak in the Aleutians. Over the years, our thinking about the characterization of contaminated sites has been influenced by B. D. Goldstein, J. Clark, and A. Upton. This research was funded by the Consortium for Risk Evaluation with Stakeholder Participation (CRESP) through the Department of Energy (AI numbers DE-FC01–95EW55084, DE-FG 26–00NT 40938). J. Burger and M. Gochfeld were also partially supported by NIEHS ESO 5022. The results, conclusions, and interpretations reported herein are the sole responsibility of the authors, and should not in any way be interpreted as representing the views of the funding agencies.

Notes

Department of Energy. 2002a. Amchitka Island surface closure report. Department of Energy, Las Vegas, Nevada.