"....the policy of the Federal Civil Defense Administration....briefly....is this: First, that a survey be made, block by block, house by house, in all the more critical target areas, particularly within a community in those subareas which are industrial, institutinal, or commercial in nature. In other words where there is the greatest density of population during certain hours of the day. That survey will bring about an understanding of how many places, how many actual structures, can be used without any modification in order to afford at least fairly adequate shelter. Second, it will show those shelters which with some modification can be considered as fairly adequate. After we have discovered those areas and how many people can be sheltered, based on a rule of thumb of six square feet per person, we will arrive at our deficit; e will then recommed that new shelters be built for those people". (Wadsworth, The National Civil Defense Plan, 1952, 13).