CONTFTIDENTTAL One other public shelter design that has been given serious consideration by research agencies is the deep underground community redoubt, described as: . built at a depth of 200 to 400 ft in a network or honeycombfashion so as to provide a capacity of on the order of 20,000 each. They will almost necessarily be built on a large scale to spread the heavy initial cost involved in penetrating to such depths. These shelters will be assumed to be capable of supportinglife for a period of a week or 10 days in almost complete isolation from the surface, being provided with food, water, air, sanitation, and fuel. They would be constructed by mining techniques, and either interconnected or provided with multiple entrances and exits. They are assumed to be vulnerable only within 1.5 crater radii of gz. For the deep shelters geological conditions may sometimes create problems, but it is believed that the freedom to select, within certain limits, both site and depth may minimize these (as compared with, e.g., mining or subway tunneling, which are in the nature of the case more constrained as to locus). The chief problems that may arise are excessive wetness, weak soil structure in certain strata (sand, mud,orfill), and rock pressure. Remedies for all these exist, but of course may seriously increase costs of construction.” Original Seren surfac a.eel aed erieYanik en pnae EOan nn 7 in ed geen, tame oe yah pean Fig. 44 -- srt Public Shelter (Showing Vertical Section) The cost of such a shelter system is estimated at $500 per occupant where the number of occupant spaces is in excess of 20,000 and $625 per occupant where the numberof spaces is less than 20,000.” For sheltering the entire population this would be the most expensive shelter program of all. Furthermore such a shelter system would havelittle or no auxiliary value, such as the large dome-type shelters could have (as auditoriums, skating rinks, public garages, etc.). The community redoubt, however, does offer maximum protection, and included in its total cost are the costs of entryways serving every % sq mile, which meansthat this shelter might be accessible during the 1cpm period. The shelter of the Cleveland Twist Drill Company is of special interest since it has actually been built and is completely stocked. Hence its cost, $300,000, is based on ex-, perience rather than builders’ estimates. The only other public shelter that has been constructed in this country (by the Cincinnati Milling Machine Co.) was built above grade at relatively high cost ($425 per occupant). It is believed the cost of the below-grade shelter may be more applicable in estimating the costs of the shelter types considered here. Among home-type shelters (discounting the below-grade 90-in. pipe shelter, which did not seem to offer good protection in Nevada tests), one type seems to offer unusually cheap protection. The Portland Cement Association has designed a house with a rein- forced-concrete floor that is designed to prevent the wood-frame structure from collapsing | i 62 ORO—R-17 (App B)