(1)Where any building or part thereof abutting on a public street is within a street alignment defined under section 350, the Secretary may, whoever, it is proposed-(a)to rebuild such building or take it down to an extent exceeding one half thereof above the ground level, such half to be measured in pubic metre; or(b)to remove, reconstruct or make any addition to any portion of such building, which is within a street alignment;in any order which is issued concerning the rebuilding, alteration or repair of such building, require such building to set back to be the street alignment.