Either of the two prospective channels described above will be adequate for LCU access at high slack water when the lagoon outflow current is decreased. Either channel will be directly into the wind and the best direction for shallow draft craft. Once the reef is broached with the first large shot the current in Pokaekku passage will essentially be sero at all tide stages and emell craft can enter at any time necessary during the daylight. d. triangulation Survey It is probably advisable to execute a fairly precise survey at least to an extent which would allow establiehment of bench marks and merkers for berge positioning. It should be pointed out that the precision of the placemant of zero points does not require eny greet accuracy since all diegnostics will be zeroed in visually from the ship to marker lights on the barges. ce Estuarial Oceanographic Survey “No actusl measurement date of currents exists for Tacngi atoll. It is deensd mecessery, for the reasons set forth in connection vith the fellowt diseuscion under Item 4 above, to accumulate data on the surfece currents vithin the lagoon, their direction, the depths of eny subsurface current return paths, e@ check on the eccuracy of the soundings as chowm presently on the U. S. Navy Hydrographic Survey charts, and the currents across thé reef. At the present time tvo Scripps Institution of Oceanography personnel are attexpting to accumulate what meager data cen be obtained in a very short three day visit. d. Channels Within Lagoon Course lines for navigation within the lagoon mist be surveyed end tied into the triangulstion survey. A chennel muct be cleared to permit barge movezent up the lagoon to the first zero point and buoys and range merks installed if neceseary. eo Beachhees and Living Facilities The requirement for a beachhead and living facilities is mandetory to accazplish mecessexy work ashore prior to the Pirst shot, but it should be remexbered that the operetions plemning showld take into eccount the fact that living facilities must be evacuated before firing and will not de required again ashore. Recent conversations with T. G. 7.5 repregentatives have indicated the possibility o? an APL type barge being used for housing after e channel has been opened, end since the installations are so minimel this method of providing accamnodations may prove the most econanicel. f. Communications Since no need exists for personnel to men stations or live ashore after the first shot it is indicated thet a militery communications link such es vas uced during the post Crossroads Bikini re-entry at Tare ahould be considered. Such @ link would provide commmicatious to Fniwetok and it is believed thet no seed would exist for the transmittal of clasrified information during the ccnstrucetics phase. LANL ROA”