Pre-nuclear era (until 1965)

The Aleutian people settled in the Aleutian islands 10,000 years ago (Bernstein and others Reference Bernstein, Lungren, Brooke, Drinan, Flemming, Goldberg, Gromoff, Marutani and Mitchell1982). On Amchitka Island, archeological sites date back 3600 to 4600 years. Of the Rat Islands, Amchitka Island hosts the largest number of settlement sites, 73 of the total 86 in the island group, and estimates indicate that the island may have been home to more than 1,100 people (McCarthy Reference McCarthy, Merritt and Fuller1977).

Russian exploration into the Aleutians began in 1743, and the first documented account of Russian landing on Amchitka Island was Vorob'ev's exploration of 1760 to 1763. The pre-contact population of the Aleutians is estimated to have been between 12,000 and 15,000; this was reduced, by exploitation and disease to fewer than 4000 by 1830 (Merritt Reference Merritt, Merritt and Fuller1977b). On Amchitka Island, the Russian hunters forced the relocation of the island's inhabitants, and sometime after 1821, 85 Amchitkans were moved to Adak and Atka. Some of the Amchitkans may have been returned sometime after, but records indicate that the last permanent native settlement on Amchitka was abandoned by 1849 (Merritt Reference Merritt, Merritt and Fuller1977b; Kohlhoff Reference Kohlhoff2002).

The United States purchased the Alaskan territory from Russia in 1867, by which time, the Aleut population had declined to around 2,000. In 1913, President Taft signed an executive order that created the Aleutian Islands Reservation, whereby the islands were designated ‘as a preserve and breeding ground for native birds, for the propagation of reindeer and fur bearing animals, and for the encouragement and development of fisheries.’ However, the order also stated that ‘[t]he establishment of this reservation shall not interfere with the use of the islands for lighthouse, military, or naval purposes. . . .’ In 1940, the reserve was renamed the Aleutian Islands National Wildlife Refuge (Merritt Reference Merritt, Merritt and Fuller1977b).

In June 1942, World War II came to Alaska when the Japanese bombed military installations in Dutch Harbor and occupied Attu and Kiska Islands. These attacks and invasions by an enemy on US soil prompted the Aleutian campaign, involving US and Canadian troops, of 1942 and 1943 (Merritt and Fuller Reference Merritt and Fuller1977; Bernstein and others Reference Bernstein, Lungren, Brooke, Drinan, Flemming, Goldberg, Gromoff, Marutani and Mitchell1982; Garfield Reference Garfield1995; Kohlhoff Reference Kohlhoff2002). During the Aleutian campaign, the Aleutian population and culture was further eroded and irrevocably damaged by the US government's relocation and internment of Aleuts and Pribilof Islanders from 1942 to 1943; following internment, many villages were never re-established (Bernstein and others Reference Bernstein, Lungren, Brooke, Drinan, Flemming, Goldberg, Gromoff, Marutani and Mitchell1982).

On 12 January 1943, 2100 American engineers and army troops landed on Amchitka Island following scouting activities in December 1942, which included the bombing of the abandoned village. A landing strip was constructed soon after, marking the beginning of the island's use as a military site. An estimated maximum 15,000 military personnel would eventually be stationed at Amchitka prior to military evacuation in 1950. (Merritt Reference Merritt, Merritt and Fuller1977b; Garfield Reference Garfield1995; USDOE 1998).

Nuclear Era

Amchitka Island was used as an underground test site from 1965 until 1971. The energy released in the three tests conducted there represents roughly 16% of the energy released during the entire US underground nuclear testing programme, and the Cannikin test was the largest ever detonated in the programme (US Congress 1989; Robbins and others Reference Robbins, Makhijani and Yih1991; Norris and Arkin Reference Norris and Arkin1998; USDOE 2006).

In general, when an underground nuclear device is detonated, the billions of atoms contained in the bomb release their energy nearly instantaneously, creating pressures of several billion Pascals and temperatures around 100 million °C. Surrounding rock and metal bomb material are vaporised, and the gas pressures created will begin to form a cavity. Seismic waves similar to those released by an earthquake will propagate outward from the detonation. Within a few seconds after detonation, molten rock surrounding the detonation cools and solidifies in the bottom of the cavity. Eventually, gas pressures decrease in the cavity to a level that will no longer support the overburden. At this point, the overlying rock will break and collapse into the cavity, creating rubble and a chimney, which may or may not reach ground surface. This collapse may take hours to months after detonation. Much of the radioactive material released by the detonation will become trapped in the vitric, or cooled molten, material, however, some will partition between gas, liquid, and solid phases underground. Some radionuclides are highly absorbed onto rubble and other rock material, but some of the more soluble nuclides may infiltrate into groundwater and be transported (US Congress 1989; IAEA 1998a). This process is illustrated in Fig. 2.

Fig. 2.

Illustration of the phases of an underground nuclear detonation (a) after tens of microseconds, (b) after hundreds of microseconds, (c) after tens of milliseconds, (d) after minutes to hours. Adapted from IAEA 1998b.

Initial post shot assessments: Long Shot

Geological investigations conducted by the USGS from 1963 until shortly after the Milrow test are summarised by Carr and others (Reference Carr, Gard, Bath and Healey1971). No geological impacts associated with the Long Shot and Milrow tests were observed. However, the authors note that ‘a few minor slumps or rock falls occurred along the sea cliffs.’ An earlier report by McKeown and others (Reference McKeown, Young, Williams and Brethauer1967) reported more specific observations regarding the immediate observable effects of the Long Shot test. They noted fractured ground, mostly in unconsolidated ground, as far as 2255m (7400ft) away from surface ground zero (SGZ), tilted ponds, ponds and streams with slumped banks, and several mud geysers.

Following the Long Shot detonation, sampling revealed leakage of radioactive hydrogen (tritium), iodine-131, and krypton-85 to the surface and near surface environment, assumed to be attributable to the upward migration of radioactive gases due to expansion and displacement from cavity collapse and/or displacement due to groundwater infiltration. Initially, ¹³¹I was detected in a slump pond 100m from the Long Shot SGZ in November 1965. Tritium was detected in several slump ponds and drainage ditches in the vicinity of SGZ, and was monitored until May 1969 by contractors for AEC. A maximum tritium concentration of approximately 16,600 pCi/L was detected in a ditch 60m east of SGZ in September 1966. This concentration was higher than the background at that time, however, was less than the drinking water limit for tritium of 20,000 pCi/L (Castagnola Reference Castagnola1969; Seymour and Nelson Reference Seymour, Nelson, Merritt and Fuller1977; Faller and Farmer 1998; Dasher and others Reference Dasher, Hanson, Read, Faller, Farmer, Efurd, Kelley and Patrick2002; USDOE 2006).

Amchitka Bioenvironmental Program

As a result of the status of Amchitka Island as part of a national wildlife refuge, the Amchitka Bioenvironmental Program was created by the AEC and administered through the Nevada Operations Office of the AEC, now known as the USDOE, in order to predict and mitigate the effects of the Milrow and Cannikin tests, to establish baseline information prior to the tests, and to document their impacts. The studies conducted under this programme began in 1967, following the Long Shot detonation, and ended in 1973 after the Cannikin detonation. The results are summarised in a series of papers published under the title The environment of Amchitka island, Alaska (Merritt and Fuller Reference Merritt and Fuller1977). The impacts to the environment of the Milrow and Cannikin tests are summarised in the following.

Long term hydrological monitoring

The USGS installed several shallow groundwater wells in 1971 following the documented tritium release to the surface associated with the Long Shot test. The United States Environmental Protection Agency (EPA) began a sampling these wells and analysing for tritium and gamma-ray emitters in 1977 and lasting until 1997 as part of the Long term hydrological monitoring programme. No gamma ray emitters were detected, and tritium was found in the vicinity of Long Shot SGZ, with the zone of maximum contamination between 60 to 100m (200 and 300ft). During the years of monitoring, tritium concentrations were decreasing, due to decay and dilution (Faller and Farmer Reference Faller and Farmer1997).

Investigations of potential surface leakage of radionuclides

In 1996, Greenpeace collected samples of aquatic biota from Amchitka Island with the aim of investigating the potential surface release of radionuclides. In 1996, Miller and Buske reported that the samples indicated the release of americium-241 and plutonium-239 + 240 in the vicinity of the Cannikin test shot. In 1998, Buske and Miller (Reference Buske and Miller1998) reported on additional analyses and indicated the potential release of americum-241 from the Long Shot, Milrow, and Cannikin test shots.

As a result of the 1996 report, sampling excursions occurred in 1997 and 1998 jointly by the US EPA, USDOE, Alaska Department of Environmental Conservation (ADEC), the Aleutian and Pribilof Islands Association (APIA), Greenpeace, and the University of Alaska Fairbanks. These sampling efforts included water, vegetation (freshwater moss and marine algae), lichen, soils, sediments, and freshwater fish both from the watersheds of the three test shots as well as control samples. The samples were analysed for tritium, gamma and alpha emitters, and the ratio of plutonium-240 to plutonium-239, which can be compared to global fallout and regional means for the latitude. The investigations did not indicate any release of tritium, radioactive americium, nor other radionuclides from the test cavities to the surface terrestrial or freshwater environments, other than those associated with the documented release of tritium from the Long Shot test (Dasher and others Reference Dasher, Hanson, Read, Faller, Farmer, Efurd, Kelley and Patrick2002; USDOE 2006).

Groundwater modelling

The conceptual model for the transport of radionuclides released in the subsurface by the detonations to the surface environment is illustrated in Fig. 3. In this model, mobile radionuclides, if present, would be transported with groundwater flow from the test cavities to the ocean floor. The results of early predictive groundwater modelling and radionuclide transport for the Cannikin test shot were reported by Fenske (Reference Fenske1972). The model predicted that groundwater from the Cannikin shot chimney should be transported to the Bering Sea ocean floor with an average groundwater travel time of more than 3000 years, where the model assumed dilution and mixing in the ocean following seepage to the sea floor. A later model by Wheatcraft (Reference Wheatcraft1995), determined a travel time for water from the Long Shot cavity to the ocean floor of between 800 and 1700 years, depending largely on the location of the freshwater/saltwater transition zone, a region characterised by an increasing salinity with depth. The model considered a spatially and temporally constant recharge and a single hydraulic conductivity for an isotropic, homogeneous subsurface. Wheatcraft suggested that the model could be improved by consideration of a layered geologic system.

Fig. 3.

Conceptual model of the Amchitka Island hydrology. It is noted that the depth of the transition zone varies widely amongst the three test sites. For a more detailed discussion of island groundwater hydrology, see Fetter Reference Fetter2001.

Hassan and others (Reference Hassan, Pohlmann and Chapman2002) modelled the radionuclide transport to determine travel times and potential seepage locations from all three test shots in an effort to improve risk assessments. Their models were two dimensional and included extensive uncertainty analyses using Monte Carlo techniques. The uncertainties considered included: hydraulic conductivity, recharge, fracture porosity, dispersivity, as well as less detailed analyses regarding uncertainties in heat driven flow and three dimensional considerations. The models considered a homogeneous hydraulic conductivity with a range of values. Analyses of the results indicated that the shortest peak arrival time to seepage locations from the test cavities for tritium of 20 to 30 years for Long Shot and 100 to 125 years for Milrow and Cannikin. The shorter travel time associated with Long Shot resulted from estimates that placed the Long Shot detonation above the freshwater/saltwater transition zone, while the Milrow and Cannikin detonations were assumed to have occurred in the transition zone. The mass breakthrough times for test related radionuclides was over 2,200 years for nearly all of the Monte Carlo realisations at the three test sites. The model was determined to be highly sensitive to fracture porosity, diffusion of radionuclides into the matrix rock, and uncertainties in the locations of the transition zones for the three test locations.

The Consortium for Risk Assessment with Stakeholder Participation (CRESP) began investigations aimed at addressing these and other uncertainties regarding the transport of, and health risks associated with, the radionuclides in the subsurface at Amchitka Island in 2002. As part of the CRESP investigations, magnetotelluric (MT) surveys were performed across transects intersecting each of the three test sites in 2004. The results of the MT surveys resulted in improved estimates of the depths to the transition zone and the variation of effective porosity with depth. The MT survey indicates that all three of the test shots were located in the transition zone. Unsworth and others (Reference Unsworth, Soyer, Tuncer, Wagner and Barnes2007), report an effective porosity of 10–20% at the ground surface, decreasing with depth to 1–3% at 3000m below ground. These authors indicated that the location of the test shots in the transition zone, as opposed to the saltwater zone, would result in shorter path lengths to the ocean floor, hence reducing travel times. However, the higher porosities determined by MT would result in longer ultimate travel times (Powers and others Reference Powers, Burger, Kosson, Gochfeld and Barnes2005; Unsworth and others Reference Unsworth, Soyer, Tuncer, Wagner and Barnes2007). It is noted, however, that the large scale of the MT measurements (3km depth) allows large scale interpretations of effective porosities in the subsurface, however, the results of MT investigations cannot be applied to interpret fluctuations in porosities which will occur with geologic layers in the subsurface rock.

As part of the CRESP science studies, groundwater modelling with improved data on the transition zone depths and bathymetry were performed for the Long Shot test site (Powers and others Reference Powers, Burger, Kosson, Gochfeld and Barnes2005) and the Cannikin site (Wagner Reference Wagner2007). Various simulations performed in these analyses included consideration of isotropic subsurface, anisotropic subsurface at ratios of 1:2 and 1:10, longitudinal dispersivity, and varying rates of recharge to the island from precipitation. No retardation effects on radionuclide transport due to diffusion and sorption of radionuclides into matrix rock or decay were considered. Groundwater travel times at the Long Shot site from the test cavity to the ocean floor ranged from 1,400 to 4,700 years for the various scenarios considered. However, previous investigations indicate that the Long Shot detonation occurred in an andesite sill, a geological unit characterised by a high hydraulic conductivity due to an extensive fracture network. When the influence of the andesite sill was considered in the model, the groundwater travel time ranged from 400 to 1,400 years. Groundwater travel times at the Cannikin location from test cavity to ocean floor ranged from 2,100 to 4 million years. While these estimates of groundwater flow are similar to the 2002 model, Wagner (2002) notes that this commonality is the effect of different considerations of effective porosity and anisotropy. The 2002 model considers a low porosity as compared to the 2007 model, which leads to shorter transport times, while the 2002 model also considers a higher anisotropy, which leads to longer transport times as compared to the 2007 model. Therefore, further investigations to reduce these uncertainties were recommended (Wagner Reference Wagner2007).

Diffusion coefficients and porosities of samples of rock from pre-shot exploratory cores, most in the vicinity of the Cannikin test shot, have been measured in laboratory experiments by the authors (Benning Reference Benning2008). The results of the experiments indicate that on a finer scale than indicated by MT investigations, porosities vary significantly with geologic layers from approximately 9% for andesites, to 12–14% for basalts, to 13–29% for breccias, with low porosities layers interspersed with high porosity layers throughout the depth of a core. The diffusion coefficients correspondingly range by more than two orders of magnitude for the low and high porosity samples. These results indicate that, as suggested by Wheatcraft (Reference Wheatcraft1995), a layered subsurface system is a more likely scenario for modelling the transport of radionuclides through Amchitka Island's subsurface. The andesite sill layer at the Long Shot test site modelled by Wagner (Reference Wagner2007) indicates that this layer represents a potential preferential flow path due to its extensive fracture network, and when this layer is considered, short groundwater travel times from test cavity to ocean floor result. The low porosity and low diffusion coefficient for andesite indicates that there would be relatively little retardation and storage of radionuclides in this layer, and thus radionuclide travel times in this layer would be much closer to groundwater travel times.

Hassan and Chapman (Reference Hassan and Chapman2006) revised their 2002 statistical groundwater model using data derived in the CRESP studies to reduce uncertainties in the model. The 2006 model incorporated the results of the MT surveys regarding the depths of the transition zones and effective porosities at the three sites, as well as bathymetric data summarised in Powers and others (Reference Powers, Burger, Kosson, Gochfeld and Barnes2005). The additional data was determined to have dramatically reduced uncertainties in the 2002 model. The groundwater velocities were decreased by approximately an order of magnitude, as a result of the increased effective porosity provided by the MT surveys; and for all realisations, the travel times were greater than the 2,200 year modelled time scale.

Screening risk assessment

The USDOE prepared a draft screening risk assessment report in 2005 as part of the site investigations of the long term management of the site. However, the ADEC and APIA did not accept the results of this assessment, and instead requested that USDOE efforts should focus on the development of the long term management plan. As stated in the later USDOE report (USDOE 2008: 3–17): ‘ADEC and the Stakeholder group have serious concerns regarding the human health risk assessment and lack of ecological risk assessment. If discussion of the risk assessment is included, a clear statement should precede these sections stating that ADEC and the Alaska Stakeholder group do not concur or approve of the risk assessment.’

Amchitka independent science assessment

The CRESP science plan for Amchitka Island was developed through active participation and collaboration of the major stakeholder parties for the island through all stages of planning and research (Burger and others Reference Burger, Gochfeld, Kosson, Powers, Friedlander, Eichelberger, Barnes, Duffy, Jewett and Volz2005). The development of a conceptual site model was a necessary step to defining the problem and identifying the potential receptors and stakeholders (Burger and others Reference Burger, Mayer, Greenberg, Powers, Volz and Gochfeld2006a). The major stakeholders concerned with the potential release of radionuclides to the environment from the Amchitka underground nuclear tests include: the Aleutian Pribilof Islands Association (APIA), the Alaska Department of Environmental Conservation (ADEC), US Fish and Wildlife Service (USFWS), and the US Department of Energy (DOE). The major objectives of the science plan were to assess the current safety of consumption of subsistence and commercial food sources derived from the environment surrounding Amchitka, to provide baseline data and to promote scientific studies to reduce the level of uncertainties in the transport modelling and risk assessment of radionuclides released underground at Amchitka (Burger and others Reference Burger, Gochfeld, Kosson, Powers, Friedlander, Eichelberger, Barnes, Duffy, Jewett and Volz2005; Burger and others Reference Burger, Gochfeld, Powers, Kosson, Halverson, Siekaniec, Morkill, Patrick, Duffy and Barnes2007a). The results of the execution of the science plan are summarised in the 2005 report entitled ‘Amchitka independent science assessment’ (Powers and others Reference Powers, Burger, Kosson, Gochfeld and Barnes2005). The results of some of the physical assessments are summarised in the preceding section, and the biological components are summarised in the following and described in several papers (Burger and others Reference Burger, Gochfeld, Burke, Jeitner, Jewett, Snigaroff, Snigaroff, Stamm, Harper, Hoberg, Chenelot, Patrick, Volz and Weston2006b, Reference Burger, Jewett, Gochfeld, Hoberg, Harper, Chenelot, Jeitner and Burke2006c, Reference Burger, Gochfeld, Powers, Kosson, Halverson, Siekaniec, Morkill, Patrick, Duffy and Barnes2007a, Reference Burger, Gochfeld and Jewett2007b, Reference Burger, Gochfeld and Jewett2007c, Reference Burger, Gochfeld, Kosson, Powers, Jewett, Friedlander, Chenelot, Volz and Jeitner2007d).

Since the major concern of several stakeholders was the potential for radionuclide contamination of biota in the marine environment surrounding Amchitka, CRESP researchers held several meetings in the Aleut villages and with other natural resource trustees. These meetings served to identify the species that stakeholders were most concerned about, to seek additional input concerning other biota to sample, and to solicit any other views about the sampling plan. These meetings resulted in changes to the initial sampling plan, as well as the inclusion of Aleuts on the expedition to collect samples in their traditional manner (Burger and others Reference Burger, Gochfeld, Powers, Kosson, Halverson, Siekaniec, Morkill, Patrick, Duffy and Barnes2007a, Reference Burger, Gochfeld and Jewett2007b).

The sampling plan included collecting specimens from the marine environment around the three Amchitka test shots and at a reference site (Kiska Island). Specimens collected in the summer of 2004 included in the marine biota, representatives of different trophic levels (kelp, invertebrates, fish, birds) and subsistence and commercial foods. One important aspect of the sampling plan was that several different species were collected at each trophic level to ensure that radionuclide bioaccumulators were included. The inclusion of Aleuts as participants in the sample collection ensured that some biota were collected in the traditional manner from typical fishing and hunting locations. Their inclusion also allowed the expedition to add traditional foods not previously included in the initial sampling plan. Further, the Aleut researchers could report the results back to their villages from first-hand experience.

Salinity measurements of the ocean floor conducted under this programme indicated that there was no major freshwater discharge, which would occur if there were preferential flow from the island's subsurface to the ocean floor through faults, and hence no major preferential pathway for radionuclide transport was detected. The studies, however, also revealed regions of ocean floor adjacent to the Cannikin and Long Shot test locations with large sediment accumulations. These deposits, which in previous risk assessments had been assumed not to exist, have potential to accumulate radionuclides, if there were seepage from the subsurface, whereupon there would be potential to enter the food chain via accumulation of exposed sedentary biota such as kelp (Powers and others Reference Powers, Burger, Kosson, Gochfeld and Barnes2005).

The results of the 2004 sample analyses and risk evaluations indicated that there was no current risk from radionuclides to humans or environmental receptors from the underground testing at Amchitka Island (Burger and others Reference Burger, Gochfeld and Jewett2007c, Reference Burger, Gochfeld, Kosson, Powers, Jewett, Friedlander, Chenelot, Volz and Jeitner2007d, Reference Burger, Gochfeld, Kosson, Powers, Friedlander, Stabin, Favret, Jewett, Snigaroff, Snigaroff, Stamm, Weston, Vol and Jeitner2007e). None of the biota sampled in 2004 displayed any detectable amounts of iodine-129, cobalt-60, europium-152, strontium-90, or technetium-99. Some samples contained trace amounts of americium-241, uranium-236, plutonium-239 and -240, and caesium-137; and nearly all samples contained uranium-234, -235, and -238. Comparison of Amchitka Island samples to samples collected from the reference island, Kiska, and other global reference locations did not indicate that the presence of these radionuclides could be associated with the Amchitka Island nuclear tests. However, the analyses indicated that plutonium and uranium tended to concentrate in algae, kelp, and filter feeders, such as jingles Pododesmus macroschisma, while the marine fish, especially those on higher trophic levels tended to concentrate caesium. Thus, CRESP recommended that the long term stewardship plan should include monitoring of both sedentary and mobile biota that represent different levels on the food chain, commercial fish, and subsistence species (Burger Reference Burger2007).

The results of the radionuclide analyses of the full suite of biota also provided data to assess the current risk to commercial and subsistence foods. However, further radionuclide analyses were required to provide enough data to identify the biota at each trophic level that were the greatest accumulators of radionuclides, since these would provide the earliest warning of any potential problems (Burger and others Reference Burger, Gochfeld, Kosson and Powers2007f). CRESP recommended two species of kelp, Fucus and Alaria fistulosa, a filter feeder invertebrate (blue mussel Mytilus edulis), dolly varden as a commercial and subsistence fish that is anadramous, black rockfish Sebastes meanops because of its subsistence value, pacific cod and halibut as top level fish predators of subsistence and commercial value, and glaucous-winged gull (Larus glaucescens) because it is local, long-lived, and the eggs are a subsistence food (Powers and others Reference Powers, Burger, Kosson and Gochfeld2006, Burger and others Reference Burger, Gochfeld, Kosson and Powers2007f). This combination of species represents key trophic levels, as well as commercial and subsistence foods.

Long term surveillance and maintenance plan for Amchitka Island

The USDOE published their plans for the long term stewardship at Amchitka Island in February 2008, in a report titled ‘Long-term surveillance and maintenance plan for the U.S. Department of Energy Amchitka, Alaska, Site’ (LTSMP). The stated objectives of the LTSMP are: to collect and report data to verify that human and ecological health is protected, to maintain site records for future generations, to plan for contingencies, and to provide a venue for stakeholder and regulator involvement (USDOE 2008).

The LTSMP employs institutional controls and monitoring to ensure the protection of human and environmental health in association with the risks posed by the radionuclides released to the subsurface in the underground testing on Amchitka. The institutional controls include: warnings to all potential visitors to the island of the radionuclides and appropriate access restrictions to be administered through USDOE, USFWS, and the National Oceanic and Atmospheric Administration (NOAA); specific restrictions against activities that would cause surface disturbances in restricted areas and/or ground penetration; future deed restrictions, if necessary, on pending native claims on the island, if awarded; the maintenance of monuments at the surface ground zeros of each of the three test sites, Long Shot, Milrow, and Cannikin; and the maintenance of surface covers on the previously closed drilling mud pits. USDOE intends to conduct site inspections at 5 year intervals to ensure the continued protection of these control measures (USDOE 2008).

Since the main pathways of concern for radionuclides from the subsurface to the surface environment, as identified by the previously discussed assessments for Amchitka Island, are through groundwater discharge to the marine environment, the continued monitoring of the marine environment and biota is deemed sufficient to identify potential releases and their associated health risks (Powers and others Reference Powers, Burger, Kosson, Gochfeld and Barnes2005; USDOE 2008). Essentially following the recommendations provided by CRESP (Powers and others Reference Powers, Burger, Kosson, Gochfeld and Barnes2005; Powers and others Reference Powers, Burger, Kosson and Gochfeld2006), the USDOE plans to sample and monitor the following species on 5-year intervals: cod, dolly varden, greenling (kelp or rock), halibut, rockfish (black or dusky), sea urchin, mussels, gumboot chitons Cryptochiton stelleri, gull eggs, and kelp (Fucus and Alaria fistulosa). The kelp species are included because these are high bioaccumulators of plutonium, uranium, and americium isotopes and are good bioindicators for early warnings. Specifically, halibut is noted for its importance as a commercial and subsistence food source, and glaucous- winged gull eggs are of importance in the traditional Aleut diet. These samples will be analysed for: caesium-137, americium-241, plutonium-239 and -240, total uranium, gross alpha emitters, gross beta emitters, and gross gamma emitters, though it is noted that only the gross alpha, beta, and gamma will be included for analyses following the initial two sampling events, after which, the individual radioisotopes will be dropped from the analyses. Additionally, USDOE plans to sample seawater and analyse for tritium, as the most mobile radionuclide, at 5 year intervals (USDOE 2008).

The LTMSP includes review and re-evaluation of the plan at 5 year intervals. The availability of data and reports to the public and stakeholders is limited to ‘selected site documents’, to be accessed either by the Office of Legacy Management's (LM) website (www.lm.doe.gov) in libraries, such as the regional APIA library or the University of Alaska Anchorage Consortium Library, and at the USDOE Office of Legacy Management in Grand Junction, Colorado. The plan also details planning for participation and oversight of the site by ADEC, USFWS, and APIA through participation in routine site inspections and monitoring events, review of documents, and consultation regarding 5 year reviews and contingency planning. The plan furthermore includes a list of contacts of governmental officials and key stakeholder and community group leaders, all who are to be ‘kept informed of site activities and status changes’. USDOE's commitment to public awareness and involvement is discussed in the LTMSP, and includes: providing information and documents through the LM website; holding public meetings, as needed; and holding briefings with APIA and state and local officials, as needed (USDOE 2008).

Contingency planning is detailed in the LTMSP. As there is specific concern over the potential for catastrophic events at Amchitka Island, since the region is known for its high level of tectonic activity and frequency of large magnitude earthquakes, the USDOE intends to review plans and potentially increase monitoring following any earthquakes of more than 6.7 magnitude at Amchitka Island or within its vicinity. ADEC, USFWS, and APIA will be included in the review and planning following such an event. Volcanic activity, significant shifts along faults and subduction influenced movement on the island will be considered. USDOE indicates that it has plans to develop an ‘emergency response plan for the island’ (USDOE 2008).

In the event of the detection of radioisotopes above the acceptable levels for ingestion during the routine monitoring, the USDOE plans to consult ADEC, APIA, and USFWS on actions necessary for the protection of human health. It is noted that possible actions listed include the issuance of public warnings or temporary catch restrictions (USDOE 2008).

Uncertainties at Amchitka and their implications

There remain significant technological and scientific uncertainties that could have important implications for the long term fate and transport of radionuclides from the subsurface at Amchitka Island. One of these key uncertainties is the potential for catastrophic events, such as large magnitude earthquakes, to open new pathways for radionuclides from the subsurface to the surface, or marine, environment. Current scientific knowledge limits any understanding of the potential for such an occurrence, and therefore, the re-evaluation and possible monitoring following an earthquake over 6.7 magnitude, as recommended by USDOE, is considered the only appropriate and feasible means of ensuring public health in association with such an event. In addition to concerns of catastrophic events, however, there is also concern over the potential impacts to the transport of radionuclides resulting from the island's movement (Attu Island, for example has been shown to be moving relative to mainland North America at a rate of 3 cm/yr as noted by Eichelberger and others Reference Eichelberger, Freymueller, Hill and Patrick2002). Continued research into this issue has been recommended by APIA, as this uncertainty remains a significant concern to stakeholders (Pletnikoff Reference Pletnikoff2008).

The groundwater models, and associated estimates of the transport of radionuclides through the subsurface environment, though significantly improved with regards to their uncertainties with the input of the results of the CRESP studies, still also remain as significantly uncertain. While the 5 year monitoring interval should be sufficiently protective to ensure public health against earlier breakthrough than is predicted by the groundwater models, it is still important to highlight and emphasise this as an uncertainty, particularly in light of the significant failures of groundwater models at other USDOE legacy sites. The NRC report (2000) cites the examples of the Idaho National Engineering Lab (INEL) and the Nevada Test Site (NTS) where the transport of radionuclides in the subsurface has been shown to be dramatically faster than had been predicted in models, demonstrating the consequences of relying on simplified fate and transport models for complex, multi-scalar, heterogeneous subsurface conditions and the need for further research.

At Amchitka Island, in particular, it is noted that the CRESP model that included consideration of preferential flow through the highly fractured andesite sill located at the depth of the Long Shot detonation resulted in significantly shorter travel times, 400 to 1,400 years (Powers and others Reference Powers, Burger, Kosson, Gochfeld and Barnes2005), as opposed to travel times greater than a 2,200 year model time in other conceptualisations (Hassan and Chapman Reference Hassan and Chapman2006). In addition to the potential impacts of increased flow through this sill layer, estimates on the diffusion into matrix rock in andesite indicate the probability of little retardation in this layer (Benning Reference Benning2008). Furthermore, uncertainties in the actual fracture porosities still exist, which is of concern since modelling has shown that the simulated travel time is very sensitive to this parameter. Thus, the estimated travel times are significantly increased or decreased when the porosity changes by a few percent, making the prediction of the exact radionuclide arrival times difficult. Data on the porosity and diffusion characteristics of the subsurface materials at the Cannikin location indicate a highly variable and structurally layered subsurface (Benning Reference Benning2008), which has not been included in groundwater modelling approaches to date. In the LTMSP, while it acknowledged the existence of the much shorter travel time indicated in the CRESP groundwater model, preference is given to the later modelling by Hassan and Chapman (Reference Hassan and Chapman2006) that indicated a much greater travel time. APIA also expresses concerns over the uncertainty of the groundwater model, stating that the models must be ‘accurate, properly interpreted, and must be verifiable.’ They furthermore recommend that additional porosity and transport studies are warranted for Amchitka Island, given the sensitivity of the modelled travel time to porosity (Pletnifkoff Reference Pletnikoff2008). The open acknowledgement of this uncertainty and continued efforts and investments to reduce the uncertainty are key issues that need to be addressed, as recommended by the NRC (2000).

The uncertainties surrounding the groundwater models result in uncertainties in the determination of the appropriate biomonitoring interval. That is, the time for transport of radionuclides to the marine environment, either though natural processes or catastrophic geologic events or disruptions, is difficult to predict. Further, once radionuclides reach the marine environment, there are several biological uncertainties, including biotic species composition at the site of any seepage, complexity of the food chain at the location of any seepage, the time to move up the food chain at the site of the seepage, and the mobility of each species. The timing of any seepage (seasonality) will influence the composition and abundance of biota at any marine location. That is, any seepage during the summer could result in more rapid transport up the food chain than would occur in the winter. Further, the location of any seepage (and thus the depth of water at that location) will affect all of the aforementioned uncertainties. There are also some analytical uncertainties involved with the lower precision of values when radionuclide levels are close to detection levels.

An additional and important uncertainty is how often and how much of the marine foods are collected by commercial fisheries and subsistence users. This value varies with conditions; in 2005, the halibut fishing was depressed near many of the Aleut villages and their fishermen went as far as Amchitka to meet their quotas (Burger and others Reference Burger, Gochfeld, Snigaroff, Snigaroff, Stamm, Jeitner and Burke2007g). The relative use of the marine environment around Amchitka becomes even more important if there is any seepage because an exclusion zone would have to be created to protect human consumers. While there is currently no discernible risk to humans from radionuclides released from the underground tests at Amchitka, the purpose of future biomonitoring is to provide early warning.