The suitability of material dredged from the lagoon bottom for use as a soil growth medium is uncertain. Little data are available on the fertility of the lagoon bottom sediments, but what is known suggests this material will be high in salt content (at least until the salts are leached out) and extremely nutrient and organic poor (see Figure S and Table 1). It is probable that the nutrient and organic content of lagoon sediments are quantitatively similar to that which would occur in the island sediments after removal of the top 50 cm or so of contaminated soils. Thus, from a soil fertility standpoint there appears to be no advantage to be gained from topping with sediments dredged from the lagoon bottom. Oceanography Tidal exchange, wind driven currents, and wave action all contribute Significantly to circulation and turnover of lagoon waters (Von Arx 1954). The general circulation pattern in Bikini lagoon is produced primarily by the northeast tradewinds blowing across the lagoon water surface, and influenced secondarily by ocean waves, tides and the North Equatorial Current. Throughout most of the year the ocean currents, waves and swell approach Bikini Atoll from an east-northeasterly direction, driven by the northeast tradewinds and break on the reefs primarily between Aomen Island (to the north and Eneu Island (to the east). Minor wave action also occurs along the southern atoll? reef west of Lokoj Istand and along the northern reefs between Aomen and Nam Isiands. This persistent attack from the ocean generally subjects the northeastern windward shorelines of the atoll to strong erosive forces and constantly drives water across the windward reef flats into the lagoon during all stages of the tide during prevailing tradewind conditions. This flushing action is particularly significant and effective because the flow is unidirectional into the lagoon which maximizes turnover. As described previously, the stretch of reef flat between Eneu and Sikini- Islands is especi- ally susceptible to this flow pattern. Ouring the summer and autumn months the tradewinds weaken and the ocean currents and swell become more variable. Substantial tidal exchange also occurs at ali other passages through the reef and over the shallow reef flats along the reef platform where islands are not situated. The deep passage at Enidrik probably has a major influence on deep lagoon circulation and water quality. Figures 7a and 7b show the generalized circujation of Bikini lagoon during the winter months when the tradewinds dominate. During the summer months when- the trades weaken the lagoon circulation becomes more variable. De, Hydrology Since the water supply is limited and periods of drought are relatively frequent in the Marshall Islands, any large-scale rehabilitation program must plan for its water supply. Resettlement plans should specifically consider the catchment and storage of rainfall, as well as possible groundwater development and use during drought periods. Rainfall catchment techniques are straight- forward and would most likely invotve direct capture of water from rooftops with storage in cisterns as well as collection (and possible treatment) of water from the runway on Eneu. In order to properly design rain catchment and storage systems, additional rainfall) data, especially their time distribution, must be collected. To do this, the program of meteorological data collection presently underway on Eneu by the Lawrence Livernore Laboratory, should be continued. nf ff