NaNaeee cinle ee nllAaialtaeR ft RE me Foam te menegh, Talhge Beppe Te ree opeSede DLpielnicaete tee tee eeee 1975 BIKINI SURVEY PROGRAM Bikini Soil and Gamma’ Exposure Rate Survey Program Purpose: Soil Survey The soil sampling program is designed to identify the primary radionuclides contributing to the external gamma exposure and to determine the geographical distribution of these radionuclides in the soil on Bikini and Eneu Islands of the Bikini Atoll. Every possible effort will be made to integrate this sampling program with previous programs to avoid undue duplication of effort. The actual number of samples and their specific collection sites will be a function of (1) the expected activity levels, (2) future home-construction plans, (3) future agricultural plans, and (4) the number and locations of recent soil samples collected by other programs. Methods and Measurements Two types of soil samples will be collected for analysis: (1) a 15-cm-deep surface core sample of 60 cm* area, and (2) a profile collection based upon sidewall sampling in a trench in which samples of 100 cm 2 area are collected at 15~cm depth increments to a total depth of 90 cm. For purposes of planning the survey, Bikini Island may be divided into the north, central, and south sections along the respective second baseline roads. Eneu may be divided into the north and south sections divided by the airstrip. The approximate numbers of surface and profile samples to be collected within these sections are shown in Table 1. Note that a major fraction of the surface samples will be collected within the central section of Bikini Island. This is due to the relatively higher and more variable gamma exposure rates in this area and to the fact that a major fraction of the returning Bikinians will most likely reside within this section. Only a few profile samples are planned in this area be- cause several samples have already been collected during previous surveys. The north and south sections of Bikini Island and all of Eneu exhibit relatively lower contamination levels; hence, the sampling density is lower. Special emphasis, however, will be given to the lagoon side of both islands since future homes may be erected in these areas. Table 1. Number of soil sample locations on each island. No. of Sample Locations Surface (0-15 cm) Bikini North of second Baseline N Central Section South of second Baseline § ° Profiles (0-90 cm) 25 2 200 4 25 2