S.D. Codified Laws § 11-2-65.1
Any county zoning ordinance provision setting a time limit for commencement or completion of a special permitted use, conditional use, or variance granted under this chapter is tolled to allow commencement within a period of two years following completion of any final appeal of the county zoning decision. Any county zoning ordinance provision to the contrary is invalid or unenforceable and the special permitted use, conditional use, or variance shall be allowed if actual construction as approved is commenced within this period and any provision addressing timely completion shall commence only upon such actual construction. The authority constitutes a lawful use, lot, or occupancy of land or premises existing at the time of the adoption of a zoning ordinance amendment or replacement within this period or while an appeal is pending regardless of the commencement of actual construction, so that the approved use shall be allowed if upheld on final appeal.
For purposes of this section, the term, actual construction, means that construction materials are being permanently placed and the construction work is proceeding without undue delay.
SDCL 11-2-65.1