EXCAVATION AND DISPOSAL OF SOIL This alternative involves the removal of vegetation and soil layers from contaminated islands to a depth that eliminates most of unstable cesium from the soil, thereby preventing its uptake by subsequently cultivated food crops. Although this approach would be considered the only certain way to eliminate cesium uptake, it is also the most expensive from both the environmental and economic standpoints. This alternative would also require disposal of contaminated soil. Feasible disposal options include using the excavated soil to expand Bikini Istand along specific shoreline sectors (where food crops would not be grown), disposal of soil on another islet (such as Nam which is large enough to handle the entire stockpile), and disposal in BRAVO crater or another large crater in the lagoon. Excavation will probably require replacement soil, fertilizers or additives to stimulate the growth of new plantings and crops and reduce the time needed to develop all the subsistence crops for the returning islanders. Groundwater itself would not be cleaned up directly by excavation, but contamination levels would be expected to decline significantly once overlying contaminated soils are removed and leaching of residual contaminants occur. Use of contaminated soil to expand the size of Bikini Island may also result in back contamination of the groundwater of the island, unless the fill area is isolated using some sort of barrier (impermeable liners, etc.), if warranted. B. LESS DESIRABLE PLANS. The Committee is still investigating the feasibility of all available alternatives and thus, none have been completely eliminated at this time. However, some (below) appear to be less desirable or feasible based upon existing information. Biological Extraction. This is a technique to reduce radioactive cesium levels in the soil involving the cultivation and growth of plants, the uptake. of the radionuclides by the plants, and the periodic harvesting and disposal of the plant crop. This alternative does not seem feasible because the plant growth needed to tender this approach effective does not seem possible without heavy irrigation and fertilization. Even under a most favorable scenario, biological extraction might not reduce significantiy tne time required to reduce radioactive cesium levels in the soil to safe and acceptable levels for crop production. Washing Soil with Seawater. This alternative involves the washing down of unstable cesium layers from the upper soil horizon (within the root zone of crops) using large volumes of seawater pumped inland from the shoreline. Removal of most vegetation would not be needed. If this technique is feasible, plant uptake of radioactive cesium within the root zone of the plants would be reduced to safe levels without the need to excavate and dispose of the contaminated soil. However, studies to date have not provided evidence that this approach would be effective. Additional studies on washing are planned to acquire an ultimate determination of its effectiveness. E-10