S.D. Codified Laws § 6-3-2
The agreement referred to in § 6-3-1 shall be set forth in writing, approved by resolutions of the governing bodies of the participating political subdivisions and executed by their officers thereunto duly authorized, and shall state the purposes for which the building or improvement shall be used, the estimated cost thereof, the estimated amount of such cost to be borne by each subdivision, the proportion and method of allocating the expenses of operation and maintenance of such building or improvement, and the disposition to be made of any revenues to be derived therefrom; and copies of such written agreement shall be filed and kept of public record by the recording officers of each participating subdivision. Such agreement may be amended or supplemented from time to time by action of the governing bodies of the participating subdivisions, and all such amendments or supplements shall be filed with the recording officers of the respective subdivisions.
SDCL 6-3-2