Issues of Environmental Management in the Gulf of the Farallones 



Measuring Radioactivity from Waste Drums on the Sea Floor 



David G. Jones, Philip D. Roberts, and Johannes Limburg 



South and west of the Farallon Islands, off- 

 shore from the Golden Gate and the San 

 Francisco Bay region, is an area of sea 

 floor commonly referred to as the "Farallon 

 Islands Radioactive Waste Dump." This area 

 was where approximately 47,800 large con- 

 tainers, mostly 55-gallon drums, of low-level 

 radioactive waste were dumped between 

 1946 and 1970. The containers were to be 

 dumped at three designated sites, but they 

 actually litter an area of sea floor of at least 

 540 square miles in water depths ranging 

 from about 300 feet to more than 6,000 feet. 



The Gulf of the Farallones and adjacent 

 areas support a major commercial fishery and 

 are also used extensively for sport fishing and 

 other forms of recreation. Fears of radioactive 

 contamination from leaking containers have in 

 the past had an adverse impact on the fishery. 

 However, the actual locations of the drums 

 on the sea floor was unknown, and therefore 

 evaluating potential hazards from radiation or 

 contamination was nearly impossible. 



In the early 1990's, the U.S. Geological 

 Survey (USGS) and the Gulf of the Farallones 

 National Marine Sanctuary surveyed part of 

 the waste dump using sidescan sonar a tech- 

 nique that uses sound waves to create images 

 of large areas of the ocean floor (see chapter 

 on Search for Containers of Radioactive Waste 

 on the Sea Floor). By using new techniques 



to enhance the sonar images, USGS scientists 

 were able to identify many objects that they 

 believed to be radioactive-waste containers. 

 These identifications were confirmed in 1994 

 using U.S. Navy submersibles. 



In late 1994, discussions between the 

 USGS and the British Geological Survey 

 (BGS) led to a proposal to carry out a radio- 

 activity survey of parts of the area where the 

 drums had been mapped, using the BGS's 

 proven towed seabed gamma-ray spectrom- 

 eter system. This system, called "EEL" 

 because of its eel-like appearance, is towed 

 along the sea floor and had to be modified 

 to operate in the deeper waters found in the 

 survey area. Previous attempts to measure 

 radioactivity on the sea floor in the Farallon 

 Islands Radioactive Waste Dump had been 

 restricted to the analyses of samples of 

 water, sediments, and marine animals and 

 plants. Sediments from only a relatively 

 small number of sites had been sampled, 

 although in the mid-1970's some samples 

 were collected from areas near drums found 

 by chance using submersibles. 



Using drum locations indicated on the 

 USGS sidescan-sonar images, a survey was 

 designed to investigate regional-scale levels 

 of radioactivity in the sea floor sediments of 

 the gulf. In 1998, the BGS EEL was used to 

 make continuous measurements of sea-floor 



radioactivity in the gulf along several track- 

 lines. These were mostly at depths between 

 300 and 3,000 feet, but some extended down 

 to a maximum depth of about 4,900 feet. 

 Samples of sea-floor sediment were col- 

 lected on the basis of the EEL results and 

 also were collected in areas where clusters 

 of drums had been previously identified 

 but where the seabed topography was too 

 rugged for safe bottom towing of the EEL. 



Both measurements made by the EEL on 

 the sea floor and laboratory analyses of sedi- 

 ment samples indicate only very low levels 

 of artificial radionuclides (radioactive atoms, 

 such as Cesium- 137, that do not occur natu- 

 rally but are produced by nuclear reactions) 

 in the surveyed areas of the Farallon Islands 

 Radioactive Waste Dump. These results are 

 similar to those that had been reported in the 

 limited previous studies. 



The results of the EEL survey suggest 

 some leakage from drums in the Farallon 

 Islands Radioactive Waste Dump, but it 

 appears that this has caused only a localized 

 increase in radionuclides on the sea floor 

 in the gulf. The data do not suggest any 

 significant elevation of radionuclide levels on 

 a regional scale. Most of the observed vari- 

 ations in sea-floor radioactivity are due to 

 changes in natural radioactivity and show a 

 good correlation to geological features, and 



some of the very low levels of artificial radio- 

 nuclides detected in the area surveyed may 

 simply be from fallout from atmospheric 

 nuclear testing done during the Cold War. 



It should be borne in mind that no data 

 have yet been obtained for large areas of the 

 Farallon Islands Radioactive Waste Dump. 

 In particular, the deeper water areas where 

 the majority of containers are believed to 

 have been dumped remain virtually unstud- 

 ied, both in terms of the radionuclide content 

 of the sediments and the actual locations of 

 the containers. 



To date, container locations have only 

 been mapped in 15 percent of the Farallon 

 Islands Radioactive Waste Dump and radio- 

 nuclide concentrations examined in only 

 about 10 percent of the dump area. Although 

 the areas studied are the shallower parts of 

 the site most accessible to people and where 

 contamination would be of most concern, 

 further studies must be done to fully evalu- 

 ate the possible hazards from radioactivity 

 in the Farallon Islands Radioactive Waste 

 Dump. This could be important because, as 

 many fish stocks have declined in the shal- 

 low coastal areas of the Gulf of the Faral- 

 lones, some fishermen have been forced to 

 fish in the deeper waters of the Continental 

 Slope to fill their nets (see chapter on Conti- 

 nental Slope Communities). 



68 Issues of Environmental Management in the Gulf of the Farallones 



