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Division of Operational a n d In your teletype of November 29 t o Mahlon Gates (R291515Z Nov. 78) and confirmed by your direct request a tour ineeting i n Germantown on December 13, 1978, we have been asked t o supply the final radiological dose assessment a t Enebietak Atoll after the conclusion o f the clean-up activities. The Nevada Operations Office was a t the same time asked t o supply a sample collection and analytical program t o supply the data base for the assessnient. assessment isto be part of the verification and certification of HQ, must now include an assessnient of the potential doses due t o 137Csand 'OSr a s well a s the transuranic s. \<!ea re willing to assume this responsibility but several points need clarification : The final dose assessment, as indicated by A. Subsistence crops are essentially unavailable i n the northern part of Enewetak Atoll. dose assessment will be primarily predicated on concentration soil for137 Cs, 3oSr,Pu and Am) developed from our research Atoll ) . Current and future radionuclide concentrations i n the soil throughout the depth of the root zone are required t o produce this evaluation. soils are required to evaluate the resuspension pathway. than the transuranic s, data for other radionuclides are not available.It is therefore necessary t o develop a post clean-up data base which delineates the radionuclide soil concentration asa function of depth in order to complete As a result the final Radionuclide data in surface 8. We have as yet not received official taskinq t o provide the final dose assessnient. This I feel is essential in vie\.r of the critical nature of this final assessment. C . This assessment will have t o be done i n conjunction with the pending assessment of Eneu Island a t Bikini Atoll and t h e various assessments associated with the recently completed mu1ti - atoll survey t o which we are a1 ready conimi tted.
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D. The present available data base i s inadequate t o permit a final dose assessment for 137Cs and 90Sr for Enewetak Atoll E . \le are still uncertain asto what i s completely necessary for final verification and certification of clean-up a t Enewetak Atoll. Nil1 the assessment have t o include Run it Island, islands Alice through Daisy and will it have t o include the transuranic s as well asl3 Cs and 90Sr? If additional radiological data are required for these islands and for the transuranic s then a sampl ing,analytical and assessment program greater than described herein will have t o be In view of the fact that the entire radiological portion of the clean-up project has been directed toward the transuranic radionl;cl ides little effort has been directed toward developing a data base which would be adequate for making the final evaluation of the 137Cs, 90Sr situation in the northern atoll. As a result,a considerable effort is now required between January and the wind-down o f the DOE support of the clean-up activities (which i s now scheduled for June of 1979) in order t o develop a data base upon which we can,with sone confidence, make a final assessment of the northern part of Enewetak Atoll. A more critical situation is to develop an adequate data base for Engebi Island i n time t o meet the May commitment, which you discussed a t the December Enewetak Meeting, for providing a s assessment of that key residence island. As a result of the urgency o f the situation, Vic lloshkin and I met with the NVOO people on December 19 and 20 to evaluate the current situation and outline a sampling and analytical program that would, i n the short time available, provide a data base for final assessment. In order to meet t h e commitments made a t Enewetak on December 1 thru 6 the following will be necessary and adequate support must be directed from tiQto meet the goals : 1 . A. Priority 1is Engebi Island. This is the largest island, the major residence island and the island that the people would prefer to use. and analytical program will be directed toward this Sampling will be on a 50 mgrid which will generate 325 sampling sites. This density of sampling i s required because of the history of events on Engebi Island resulting in a very inhomogeneous distribution of radionuclides and the recent soil removal activities.In addition, we have received no direction from HQ as to what is really required from their point of view for final assessment for verification of clean-up. I t was mentioned i n our December 13 meeting that perhaps the final assess-lent should be done on a scale as small a s an individual Wato. I feel that this is unrealistic and unlikely,but to in sure
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a data base which would be adeqiuate t o permit such a possible analysis we have decided thata 50 m grid for soil sampling should be completed on Engebi Island. Samples on a 100 mgrid will initially be analyzed and additional samples will be analyzed asis deemed necessary. All soil sampliog will consist of soil profiles through 60 cm. I am attaching a brief memo I sent to Roger Ray discussing what would be needed i n the way of soil sampling and data in order to evaluate Enewetak Atoll after clean-up. Itis estimated that the sample collection would take 16-20 days and the analytical program about 11 weeks. Therefore, i f the go ahead were given immediately for supplying support for the sampling program and additional funding were made available to allow analytical work a t Albuquerque a s well asat Enewetak Atoll, we could probably generate an assessment of En geb i Island inthe May time frame previously discussed. Itis emphasized that support such a s backhoes, boats, personnel, analytical capacity,etc. must be available as soon as possible to have any hope of meeting the May time line for En geb i Island and for developing an adequate data base for the rest of the Northern part of the atoll by the scheduled wrap-yp of the clean-up project. However, all samples and all analytical work should be handled through for the analytical work. They doof course need tasking and support t o accomplish the program. Ne will work directly with NV OO and have access tothe data for developing our final assessmefits. Our plans for assessment of Engebi Island include using an island average for soil radionuclide concentrations, or perhaps, divide the island into three of four areas if the data generated from the sampling program justify such an approach. They have a sampling program in place and a quality control program 1.B.A very important feature of all of our dose assessments isthe assumed diet which isthe basis for estimating the daily radionuclide in take. This has been an area of uncertainty and apart of the dose model which has concerned me f o r a long time. Previous diet models were based upon published data developed by observation a t many atolls for short periods o f time during the 1950 ' ~ ~by some of our staff for a two week period and with discussions with an anthropologist living in the Marshalls but where main objectives were not detailed evaluation of diet. The initial diet generated froin these sources and used i n post dose assessments was thought to be conservative (i.e.possibly over estimated the daily in take) and was appropriate in the previous assessments to evaluate the general situation at the atoll and ensure an initial, safe pub1 ic health approach. Itis now critical to better define an average diet and make the dose assessments as realistic as possible to provide a basis for
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the difficult decisions which have t o be made concerning future use of the atoll. themselves supply us with information on average, normal daily in take and on in take during famine situations. and thorough information available and we plan t o use the information in our final asseszment model. this opportunity t o develop a more reliable diet model and concur i n its use for the final dose assessnient. We have made arrangements t o have the Enewetak people This will be the most reliable Itis important that DOE and DO1 recognize 2 . Second priority will be the Aoinon-Bijire complex and the other islands in the northeast quadrant of the atoll including Bcken (Irene)to the x est of Engebi. A 50 m sampling grid will also be used on these islands. The logistics are such thata 50 m sampling grid is as feasible as any other and will supply a more detailed data base. A lesser sampling grid \vi11 save very little time. A detailed assessment of the Aomon-Bijire Complex as a possible residence island complex and evaluation of the other northeast islands or agricultural islands will be made at a later date consistent with sample collection and the analytical program. I n summary, when we and NVOO have received tasking and support from HQ t o develop the sampling, analytical and assessment program for Enewetak Atoll we are prepared t o proceed as rapidly as possible to meet committed time lines consistent with doing a scientifically and professionally sound job. Terrestrial and Atmospheric Sciences Envi ronmental Sciences Division