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May 15, 1998
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FARALLONS CRUISE
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A survey of the Farallon Islands Radioactive Waste Dump site was
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recently completed using the NOAA ship McArthur. The survey
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was a collaboration among the U.S .Environmental Protection Agency,
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the U.S. Geological Survey, the British Geological Survey, and the
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Gulf of the Farallones National Marine Sanctuary. Approximately
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47,800 barrels of low-level radioactive waste were dumped at 3 sites
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between 1946 and 1970. The barrels litter a 1400-square-km area,
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most of which is now within the boundary of the Gulf of the
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Farallones National Marine Sanctuary. Previous studies in 1990,
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using SeaMARC 1A, identified objects on the seafloor at the site
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which were interpreted as barrels. This interpretation was confirmed
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by video footage during the sidescan cruise, and subsequently in 1994
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using the U.S. Navy submersible 'Sea Cliff' and the unmanned
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Advanced Tethered Vehicle. Systematic regional data on seafloor
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radioactivity were obtained on the McArthur using the BGS-towed
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sea-bed gamma-ray spectrometer (EEL) system. More localized data
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were also collected with the system at known sites of barrel clusters.
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Sediment samples were collected, both regionally and around the
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known barrel clusters, for subsequent laboratory analysis. Studies
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were focused on the shallower parts of the dump site where commercial
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fishing is carried out. About 90 line-km of EEL trackline were
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obtained in the shallowest part of the dump site (the '90 m site'),
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and 9 sediment samples were collected at locations determined
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by the variation in the EEL "signature". Approximately 80 line-km
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of EEL data were gathered in the intermediate-depth section of the
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site (the '900 m site') and extending towards the deepest part
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(the '1800m site'). Six sediment samples were collected on the
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tracklines at the 900-m site. In addition, 10 samples were collected
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clustered around known barrel clusters. The deepest EEL survey line
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was towed in 1500 m of water, extending the previous record for the
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system (600m) by a considerable margin. Preliminary interpretation
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of the data suggests that the observed variations in seafloor
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radioactivity can be attributed to geological features. There were no
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indications of man-made radioactivity, suggesting that, if present on
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a regional scale, it is only at very low levels. Further information
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will become available when data and sample analyses are completed.
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Participants on the cruise were Dave Jones and Phil Roberts (BGS),
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Dan Howard (GFNMS), and Bob Hall and Lynn Karr (USEPA) (who due to
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circumstances beyond our control, were replaced by Scott Faller (USEPA)),
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Pat Shanks (USGS-Denver), John Chin, Michael Hamer, Gita Dunhill,
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Fred Payne, and Herman Karl. MarFac, coordinated by Steve Wallace
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and Dave Hogg, as usual, provided excellent support in getting
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this cruise out to sea, and shipping equipment back to England.
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Owing to the efforts of all above, this cruise was highly successful,
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despite extremely adverse conditions. It is one cruise that Herman
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Karl is glad to have behind him, however! Of note, and of unknown
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significance, is that a rainbow appeared both at the start and end
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of the cruise, just as the McArthur sailed under the Golden Gate.
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For a snapshot of the cruise go to:
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http://www.pmc.noaa.gov/mcarthur/ar9803.htm to view the website
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prepared by Kaye Kinoshita.
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