Measurements of the exposure rate at 1 m above the ground will be made with the NaI scintillator at each of the soil sampling locations on both islands. The ionization chamber will be primarily used for measurements within the central section of Bikini Island with additional measurements to be made at selected areas. Thus, from this program a comprehensive bw 3 ¥ picture of the gamma-ray exposure rates will be available for both islands. Bikini-Ground Water Program Purpose: To establish a network of well locations on Bikini and Eneu Islands in order to assess the ground water quality and to systematically study the hydrology and geochemisty of radionuclides, major and trace elements in the ground water system. Water movement and residence times will be assessed to deduce the transport rates and mechanisms for radionuclides deposited in the soil zone or taken up by vegetation. Methods and Measurments "4a er BS -GO-Li wknd Approximately 7 holes will be drilled with a ground power auger at selected locations along the centerlines of Bikini and Eneu Islands. Pits will be dug with a backhoe to a maximum depth since the ground water reservoir surface will be approximately 2 mters below the ground surface. We must emphasize that the progress of this program will be seriously hampered if a backhoe is not available to support our effort. The auger will penetrate the ground water lens to a depth of approximately 3 to 5 feet. Each hole will be cased with slotted 2" diameter PVC pipe and the pipe will be extended to the soil surface. The pit will be backfilled to essentially provide no environmental impact on the area. The first hole will be located near the island center. The salinity of the water will be measured with an in-situ conductivity probe. Two holes will then be drilled to bracket the center hole and the salinity will be measured in each. We will continue drilling up to 7 holes on each island proceeding in the direction toward the freshest indicated ground water; this will provide the maximum number of well sites having the freshest water for potential utilization. Water will be pumped from the wells, filtered, and sampled. Radionuclides, major elements, nutri- ents, and bacteria measurements will be made at the Laboratory to provide data for water quality. Specific wells (to be defined in the field) will be pumped continuously over a day and serially sampled to follow the changes in water quality as a function of usage. Recommendations will be made on the potential usefulness of the ground water reservoir for agriculture, household, or drinking purposes. Two closely spaced wells, located in high Csl137 disturbed soil columns on the local ground water quality. Soil leaching and lysimeter experiments are also planned. The well loca- tions, ‘drilling, and sampling, however, are our first priorities during the two weeks allotted for this program.