Subsurface Completion Report for Amchitka Underground Nuclear Test Sites. Long Shot, Milrow and Cannikin

摘要

Three underground nuclear tests were conducted on Amchitka Island, Alaska, in 1965, 1969, and 1971. The effects of the Long Shot, Milrow, and Cannikin tests on the environment were extensively investigated during and following the detonations, and the area continues to be monitored today. This report is intended to document the basis for the Amchitka Underground Nuclear Test Sites: Long Shot, Milrow, and Cannikin (hereafter referred to as 'Amchitka Site') subsurface completion recommendation of No Further Remedial Action Planned with Long-Term Surveillance and Maintenance, and define the long-term surveillance and maintenance strategy for the subsurface. A number of factors were considered in evaluating and selecting this recommendation for the Amchitka Site. Historical studies and monitoring data, ongoing monitoring data, the results of groundwater modeling, and the results of an independent stakeholder-guided scientific investigation were also considered in deciding the completion action. Water sampling during and following the testing showed no indication that radionuclides were released to the near surface, or marine environment with the exception of tritium, krypton-85, and iodine-131 found in the immediate vicinity of Long Shot surface ground zero. One year after Long Shot, only tritium was detectable (Merritt and Fuller, 1977). These tritium levels, which were routinely monitored and have continued to decline since the test, are above background levels but well below the current safe drinking water standard. There are currently no feasible means to contain or remove radionuclides in or around the test cavities beneath the sites. Surface remediation was conducted in 2001. Eleven drilling mud pits associated with the Long Shot, Milrow and Cannikin sites were remediated. Ten pits were remediated by stabilizing the contaminants and constructing an impermeable cap over each pit. One pit was remediated by removing all of the contaminated mud for consolidation in another pit. In addition to the mud pits, the hot mix plant was also remediated. Ongoing monitoring data does not indicate that radionuclides are currently seeping into the marine environment. Additionally, the groundwater modeling results indicate no seepage is expected for tens to thousands of years. If seepage does occur in the future, however, the rich, diverse ecosystems around the island could be at risk, as well as people eating foods from the area. An independent science study was conducted by the Consortium for Risk Evaluation with Stakeholder Participation (CRESP) in accordance with the Amchitka Independent Science Plan (2003). The study report was published on August 1, 2005.