"By definition, an ERS is a site located outside a prime target area to which all or portions of a civilian or military headquarters may be moved. The ERS location must provide adequate protection from blast, heat, fire, and radiation. Although no area of the United States is safe from fallout, prevailing winds and target locations provide areas with a higher probability of reduced radiological hazard in the event of a nuclear attack. In that the danger zone for heat and fire are smaller than the danger zone for blast over-pressures, the effects of nuclear blast over-pressures are used as the primary consideration to identify safe distances from targets. The hazard zone, of course, depends upon the size of the explosion. For planning purposes, a location which limits the maximum over-pressure to 1.0 p.s.i. was used. For a 1 MT surface burst, the less than 1.0 p.s.i. over-pressure zone starts at approximately 7.0 miles from point of impact. For a 5 MT surface burst the distance is approximately 13 miles and for a 25 MT surface burst the distance is approximately 22 miles". (USACE, Planning and Operations Guidelines, Annex B: ERS, 1985, pp. B-3, B-4) )