Mo. Rev. Stat. § 260.455

Within sixty days after June 27, 1983, the department shall notify by certified mail the owner of all or any part of each site or area to be included in the registry required by section 260.440 by mailing notice to the owner's last known address. Thereafter, thirty days before any site is added to the registry, the department shall notify the owner of all or any part of such site by certified mail of the proposed addition to the registry by mailing notice to each such owner at the owner's last known address.