These standards shall not be construed to prevent the construction, reconstruction, alteration or demolition of any building, structure, earthwork or component thereof of a recognized historic, cultural or archaeological resource which has been officially certified as being imminently dangerous to life or public health. Nor shall these standards be construed to prevent the ordinary maintenance or repair or proper restoration, according to the United States Department of the Interior's Standards for Rehabilitation and Guidelines for Rehabilitating Historic Buildings, of any building, structure, site or earthwork, or component thereof, of a recognized historic, cultural or archaeological resource which does not involve a significant adverse change to the resource.