EN@rosut — L Draft #2 12/3/79 Mrs. Ruth G. Van Cleve, Director Offiee of Territorial Affairs U. S. Department of the Interior Office of the Secretary Washington, D.C, 20240 Dear Mrs. Van Cleve: Reference is made to your letter of October 22, 1979, in which you state that the Department of the Interior is considering the agricultural redevelopment of Enjebi Island and the reestablishment of a community on that island for the Enjebi people. As part of this consideration you requested estimates of the time which must elapse before exposure levels on Enjebi Island would meet exposure limits. Current estimates of the number of years which must pass if exposure limits are to be adhered to are based upon the potential dose estimates provided in the Preliminary Dose Assessment Report prepared by the staff of the Lawrence Livermore Laboratory (LLL). These dose estimates have been compared to the exposure guidance, and, based upon known radioactive decay rates of the radionuclides involved, time intervals have been calculated. U. S. Federal Radiation Council recommended exposure levels (adopted also by the Environmental Protection Agency) are 500 mrem to the maximum exposed invididual in any one year (and assumes that the maximum exposed individual does not vary from the average population exposure by more than a factor of 3, resulting in a recommended average population exposure level of 170 mrem per year) and 5000 mrem over a 30 year period. Atomic Energy Commission recommendations, recognizing the uncertainties inherent in such nce for the maximum dose estimates, were one-half of the FRC guida