Preliminary Report, a Cursory Radiation Survey of Selected Islands of Eniwetok Atoll

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A CURSORY RADIATION SURVEY OF SELECTED ISLAM>S OF ENIWETOK ATOLL Selected islands of Eniwetok Atoll were surveyed for radiological conditions from July 14, 1971 to July 21, 1971, by Mr. Charles F. Ccsta, focused on the islands of Engibe (JANET) and Runit (YVOWE), the islands of immediate interest to the PACE Program. The survey of all islands * visited, however, was necessarily brief due to the allotted survey time (six days) and the number of personnel (two monitors). The following is a listing of islands surveyed during the above-mentioned Geographical Name Code Name Siij iri TILDA Aranit (or Aomon) SALLY considerable vegetation, enough . that movement through the'interior of the islands was, in general,&i&Q, cult. A sumsary of the island cover follows:

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MESSERSCBMEDIA ARGEHTA (BEACH HELIOTROPE) Found on all islands, generally dense, and up to 20 plus feet in height. Found on all islands, generally dense, and up to 20 plus feet in height. Found on all islands, forming a dense ground cover. Found on all islands, forming spotty ground cover. CASSYTBA FILIFORXIS (LAUREL DODDER, KAANIN) Found on most islands, forming ground and tree cover. Single specimen found on the northeast tip of Aranit (SALLY). Single specimen found-in the middle of Aranit (SALLY). Observed on the northwest tip of Bogon (IREhE). Few trees observed on Engibe (JAh'ET)and Runit (YVONKE). The following types,of instruments were used to perform this survey. Exposure rate measurements were taken three feet above the ground. Since contact readings were generally similar to exposure rate measurements, : only exposure rates are reported unless the difference was significant. Where the difference was significant it is noted on the attached survey

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Engibe, a triangular shaped island situated on the north end of the atoll, possessed considerable vegetative growth. Movement through the island was limited to existing test roads, the shoreline, and a large runway on the north end of the island. The island is the home of a large tern rookery situated on the northern end of the island. A survey of the is&d resulted in measured exposure rates rangin,0 from lo-100 a/hour inland and ’ 2-4 &hour along the beaches. Scrap metal with contact gamma readings up to 12 mR/hour was observed. Exposure Rate Readings Engibe can be divided into three distinct measurement areas: the area north of the airstrip,.the area south of the airstrip, and the areas around the EASY, X-RAY, and Im surface ground zeroes (SGZ). In the inland area north of the airstrip, the exposure rates ranged from 20-60 &/hour, while measurements ranging from 10 to 20 @/hour were observed in the inland areas south of the airstrip. Measurements were made along selected radials from the SGZ's as ground . cover would allow. At the site of the RASY Event, the maximum exposure rate observed was 70.a/hour on a radial,of 135O true, 200 feet from the SGZ, in an area of dense vegetation. In general, 20 m/hour was observed throughout most of this area with the exception of the area east of the SGZ which was indicating 40-50 a/hour. At the site of the X-RAY Event, the maximum exposure rate observed was 100 &/hour (120 m/hour ground contact) on a radial of 030°.true, approximately 400 feet from the,SGZ (also densely vegetated). General exposure rates around the SGZ ranged from 50-70 m/hour. At the site of the ITEM Event (the only readily apparent SGZ on Engibe), the crater of which appears as a large burned out area on the northern ti? of the island, the maximum :x?osure rate observed was about 5 &/hour. This rather low level is probably due to the lack of vegetation,

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the lack of any top soil or other loose ground cover, and the sweeping effect of the tide - the crater was open to the ocean side of the reef. Scrap metal (contact readings) Large quantities of activated scrap metal were found near the SGZ's, probably constituting the major radiological hazard on Engibe. The maximum reading observed on scrap metal was 12 mR/hour. This reading was obtained from a large twisted I-beam wrapped around a metal collimator located on the northwest end of the island, just north of the large No surface alpha activity was detected on Engibe. Runit is a long slender island situated on the eastern s_ideof the atoll.. "nuuiL possesseci somewhat less vegetative cover tnan r;ngibe,tnus making location and identification of SGZ's easier. Travel on the island was done mostly on the main road running the length of the island. A survey of Runit resulted in measured exposure rates ranging from a few @/hour to 1 mR/hour. Scrap metal with contact gamma readings up to 35 mR/hour was observed. Alpha contamination in soil and in vegetation was detected near the FIG Event site. Count rates up to 3000 cpn (measured with a PAC-1s) in wet soil were observed. Exposure Rate Readings One day was allotted to the radiation survey of Runit, thus allowing only enough time to survey the northern half of the island. Heasured exposure in the middle portion of the island averaged 15 a/hour. persisted to within about 300 feet of the CACTUS crater lip. a transect across the island through the ZEBU Event site indicated exposure rates ranging from 4 to 8 a/hour. Readings along a transect across the island through the FIG Event site ranged from 1 to 6 a/hour. The highest measured exposure rates on the entire atoll (1 mR/hr) *. occurred on top of the crater lip located at the southern end of the CACTUS

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crater. At the crater's immediate edge (crater filled with water) readings ranged from 40 to 100 &hour. Scrap Metal (contact readings) Large quantities of activated scrap metal were observed near the CACTUS and LACROSSE Event sites. Trenches excavated for the purpose of collecting soil and ground water samples exposed considerable metal debris. The maximum reading observed on scrap metal was 32 mR/hour closed shield, 35 mR/hour open shield. This piece of scrap metal, a partially buried I-beam, was observed on the island road near bunker Hartack Station 182-01 (Greenhouse Station 57). General scrap metal contact readings ranged from Alpha contamination was detected along a 65 foot length of the berm on the ocean side of the beach near the FIG Event. The contamination was confined to a vein of relatively dark sand, from 3 to 8 inches thick, found exposed on the berm near Redwing Station 1311.05 (bunker). The wet soil yielded, up to 3000 cpm (measured with a PAC-1s) on the vertical face of the vein. Some black plastic sheeting and cables were observed in this layer. To determine the extent of the alpha contamination, a trench was dug between the FIG SGZ and the beach. Alpha contamination was detected at a depth . of 8 inches. Two additional trenches, one 300 feet north and another 200 feet south of the FIG SGZ, just off the ocean side of the road, yielded no detectable alpha activity to a depth of two feet. However, alpha activity was detected on bunch grass located adjacent to the north trench. Rojoa, Biijiri, and Aranit islands are three.larger islands on the northeast portion of the atoll. They are connected by a bridge (Rojoa and Biijiri) and a causeway (Biijiri and Aranit). All of the islands are generally densely vegetated with the exception of the northeast end of

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Aranit which was found to be free of dense ground cover. Exposure Rate Reading Measured exposure rates on Rojoa and Biijiri were relatively low, S-10 @/hour and 1-4 a/hour respectively. On Aranit, the maximum exposure rate observed was 150 &/hour near the western end of the island. Exposure rates throughout the island averaged between 60 and 100 &hour. Very little scrap metal was evident on any of the above islands. On Biijiri, a piece of scrap metal on the northeast end of the island had a contact reading of 1 mR/hour while scrap metal evident on Aranit ranged from 250 to 800 &/hour on contact. No surface alpha activity was detected on Rojoa, Biijiri, or Aranit. Bogairik'kisland now consists of nothing more than a small, sparsely vegetated "islet", which is almost an extension of the sandbar originating from the southwest corner of Bogon. Bogon is much larger, with considerable vegetation and several large bushes. Movement in the interior b of Bogon was very difficult due.to the extensive growth of CUSYTI;A FILIFOILS!IS,which not only covered the ground, but also formed a formidable barrier on trees and on bunkers. Exposure Rate Readings Measured exposure rates on Bogairikk averaged 10 @/hour. On Bogon, exposure rates were considerably higher. On the southeast side of the SWZXOLE crater on what appears to be darkened coral, exposure and ground contact rates up to 300 @X/hour were measured. The average exposure rate was about 100 &/hour. Along the northern half of Bogon, exposure rates

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up to 400 m/hour were observed with an average reading of 100 &/hour. Readings along the southern portion of Bogon ranged from lo-50 a/hour. No surface alpha activity was detected on Bogairikk or Bogon. metal was observed on both islands, most of it concentrated SENINOLE crater. Contact readings ranged from 0.3 to 0.5 The collection of environmental samples was limited to the islands of Engibe and Runit. On Engibe, surface (l-2.5 cm) and profile (20 cm) soil samples were collected from the EASY, X-RAY, and ITE>fEvent sites. Also, several surface soil samples were collected at the site of the beryllium contaminated area on the northwest tip of the island. Two ground wi;ter mately 6 to 8 feet in depth. A surface water sample was obtained from the water in the ITEM Event crater. On Runit, surface and depth soil samples were collected from the CACTUS, LACROSSE, and FIG Event sites. One ground water sample (from the island's . fresh water lens) was collected and one vegetation (bunch grass) sample was collected near the FIG site. All samples are presently being analyzed by EPA/KEFU and the results will be available at a later date. As a preliminary evaluation, it seems apparent from the cursory radiological survey performed that Runit (YVOm) presents the greatest radiologictil hazard of any of the islands surveyed. Large quantities of scrap metal are evident along the reef near the LACROSSE site and to a lesser extent inland. The maximum contact reading on scrap metal (35 mR/hour) was observed on

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this island. If this is indicative of what low level activated surface scrap metal reads, then it is realistic to expect to find buried scrap metal of significantly higher activity. Alpha contamination was found on the ocean side of Runit (a review of several earlier reports on decontamination attempts on Runit suggests alpha contamination to be buried on the lagotinside) near the site of the FIG Event. Contamination appears to be confined to a vein of darkened sand.which in some places along the beach is exposed to the wear and tear of the elements. The maximum reading observed on this contaminated wet sand was 3000 cpm measured with a PAC-1s. Alpha activity was also observed on bunch grass located approximately 300 m north of the FIG site. The boundaries of the contaminated area were not delineated because of the lack of time. Also, predictions of the levels of contamtinationone can expect buried near the FIG site cannot be made based on results of this The highest measured exposure rate levels on the atoll were also found on Runit, at the lip of the CACTUS crater. A maximum exposure rate of 1 &hour . was measured at that location. Runit has been used by both Kantron and Coast Guard personnel stationed on Eniwetok as a recreation island. The radiological conditions of the other islands are significantly better c than that on Runit. The only problem area appears to be surface - and thus the possibility of subsurface-activated scrap metal, especially on Engibe and kanit. On Engibe, near the large concrete bunker past rocket tests. a portion of the northwest tip of the island has been contaminated with beryllium from The following are our recommendations based on the radiation survey. These recommendations may be modified somewhat when the sample results are com-

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A Comprehensive radiation survey of the entire atoll should be made to document the radiological situation as it exists to date, preferably prior to any possible alteration of the atoll eco-system as a result of PACE program activities. me boundaries of the alpha contaminated area on Runit should be defined and posted as an off-limit no digging area as soon as possible. In conjunction with this, modifications to the berm possessing the layer of alpha contaminated sand should be made in order to stop further erosion of contaminated soil onto the beach. Radiation warning signs should be placed on the lip of the CACTLS Agencies working on the atoll should be advised that removal of scrap metal is prohibited without rad-safe approval. In light of the objectives of the ?-4CEprogram, continuous rad-safe w~??T+ of the nrogrzm in rPrn=sended to evaluate the radioloeical_ conditions and hazards of any metal debris and contaminated soil uncovered or resuspended by excavation and other test activities.