The board of county commissioners may exempt any officer, board, department commission, or commissions from the requirements of section 06-11-03: above and may exempt any building, structure or additions thereto from said requirements by means of a letter signed by the chairman of the board of county commissioners, wherein they find that such incorporation of fallout shelter will create an additional net cost in the construction of such structure in excess of one percent (1%) of the estimated cost thereof without a shelter so incorporated, or that other factors as they may determine in their discretion make unnecessary or impracticable a fallout shelter in such building or structures. (Ord. 70-001, 12-29-69, eff. 12-29-69)