The order to show cause shall be returnable not less than five days after service is completed and shall provide for personal service of a copy thereof and the papers upon which it is based on the operator of the facility and upon the owner or owners of the land and/or owners of the land and/or structure on or in which the facility is located. If any such operator or owner cannot with due diligence be served personally within the county where the property is located and within the time fixed in such order, then service may be made on such person by posting a copy thereof in a conspicuous place within the facility in question, and by sending a copy thereof by registered mail, return receipt requested, to such owner at the last address registered to him with the office, or in the absence of such registration, to the address set forth in the last recorded deed with respect to such facility. Service shall be deemed complete on filing proof of service thereof in the office of the county clerk, or the clerk of the city of New York, as the case may be.
N.Y. Mental Hyg. Law § 31.28