those which concerned the extent of participation of military personnel would influence the ultimate location of camp sites, the nature of base facilities, and many other items of design and engineering significance, Meetings to resolve these policy matters were held at Los Alamos between November 15 and November 19, 1948, and, by the end of November, decisions had been made by the AEC in Washington, D. C., that planning for the Project would be on the basis of tests in 1951 and one additional set of tests. It was intended that the planning basis should be for base facilities which would last for approximately 5 years. Request was made, however, that analysis of the master planning problem be so arranged that the difference in cost between one-experiment use and two-experiment use would be determinable. With basic requirements and philosophies firm, the design and engineering phases of the Reconnaissance Report began to take shape. A letter from J-Division! clearly set forth the AEC position on criteria questions raised at the November meetings and resulted in immediate steps by the Engineering Division to collate the design data, previously worked up, along the lines indicated. Such sections as those which concerned camp layouts and base facilities, personnel buildings, power generation and distribution, water distillation, sewage and waste disposal, and surveys were rapidly moved toward final form in the light of agreed-upon principles. One of the most significant engineering contributions to the Reconnaissance Report was the development, in close coordination with the Operations Division, of a master plan with the flexibility which H & N experience with other scientific and research projects had shown to be essential. Because the type, number, and size of scientific stations could only be surmised, because work on the proposed experimental programs had barely begun, and because the population requirements and facilities requirements provided H & N were based on experience during Operation Sandstone (essentially ship-based) rather than upon the defined scope of this operation, it was necessary to make careful analyses with a view to future expansion of a major nature. For example it was necessary to plan locations of offices, laboratories, and personnel facilities to provide convenience and accessibility as well as room for possible expansion. That flexibility was designed into the master plan is evident from the fact that, of 28 recommendations of an engineering nature contained in the Reconnaissance Report, essentially 26 were followed throughout the Project in spite of radical changes in the experimental programs, in the numbers of personnel accommodated, in the greatly increased magnitude and complexity of the support required for scientific operations, and in the numbers of Users engaged in the scientific program. The master plans proposed in the report and in the various site layouts for base facilities and camps were followed, ani the necessary expansion was provided within these basic concepts as the changing requirements were encountered. AEC letter LAB-J-509, November 29, 1948 5-39