~GONSLREN Yet when all the objections have been aired and duly recorded, the hard facts remain. A 10-Mt weapon will inflict A-ring damage outto a radius of 4 miles from az with peak overpressures of 19 psi at 4 miles and 6.6 psi at 8 miles. Shelters built to withstand 30 psi might survive at 3% miles, and shelters built to withstand 100 psi might survive at 2% miles. These figures are rough estimates given in the absence of authoritative data. The crater of a 10-Mt ground burst would have a radius of 1; miles. Any unusual concentration of shelters in a potential crater or in a potential shelter destruction zone will surely draw enemy fire as a target of above average reward. If an attack is successful and accuracy of delivery is high, large numbers of people and a very costly investment.in shelters will be lost in spite of the expense of a national shelter program. This fact may be a prime argumentfor regional planning for reduction of urban vulnerability through dispersal. The heart of a plan for reduction of vulnerability should be a metropolitan regional plan for future development on a dispersed basis. Before a comprehensive plan can be drawn up, a numberof staff studies should be made. Many such studies already exist — routine products of city, county, and regional planning commissions; those of recent date need only be reexamined in-terms of the general goal of a broader distribution of densities. Preliminary Staff Studies For that part of a regional dispersal plan related to spacing of underground shelters certain preliminary staff studies should be made. These studies should include an appraisal and analysis of existing economic activity, with projections and estimates of the future total economic activity and its major components. The size, distribution, and composition of ihe future population of the metropolitan region at selected time intervals should be estimated. The relative strength of various interrelations among activities in the region should be analyzed to serve as a measure of the feasibility of geographically separating various groups of activities. Staff studies should also include an analysis of certain physical aspects of the metro- politan area. Existing.and potential service zones of the metropolitan center, as bounded or limited by comparable service zones of other metropolitan centers, should be studied. Major physiographic features that would exert influences on future development within the selected dispersed development district should also be studied. The major elementis topography, which affects routes and ease of movement, suitability of ground for building sites, possibility of underground construction with access through horizontal as opposed to vertical shafts, possibilities of gravity distribution of raw and treated water, possibilities and economics of developing sewer systems, possibilities of developing water-reservoir sites, etc. Other major elements are size and flow characteristics of waterways; location, capacity, and quality of underground water supplies; soil characteristics, including fer- tility for crops, porosity for septic-tank sewage disposal, and load-bearing capacity for heavy-building construction; and existing ground cover, particularly forests, rainfall, etc. A preliminary identification should be madeof areas that should be reserved for open space or very-low-density development. ‘Typical low-density land uses would be public or private forests; national, state, or local parks; watersheds; agricultural or residential estates; and summercottages. Preliminary identification, later modified by concurrent reappraisal of all area studies, should be made of general areas for location of nuclei of future dispersed development. The basic consideration here must be geographical separation sufficient to remove underground shelters of one nucleus from the potential crater area and high overpressure area of another nucleus. Potential high-speed transportation routes connecting dispersed nuclei with one another and with the central part of the city should be selected. These routes will be pri- ORO-R-17 (App B) 86 CONFIDENTIAL