S.D. Codified Laws § 11-2-60
In lieu of appointing the board of adjustment provided by § 11-2-49, the board of county commissioners having adopted and in effect a zoning ordinance may act as and perform all the duties and exercise the powers of the board of adjustment. When acting as the board of adjustment, the chair of the board of county commissioners is chair of the board of adjustment. The concurring vote of at least two-thirds of the members of the board is necessary to reverse any order, requirement, decision, or determination of any administrative official, or to decide in favor of the appellant on any matter upon which it is required to pass under any zoning ordinance, or to effect any variation in the ordinance. Any initial conditional use determinations of the board shall be determined by the vote set forth in § 11-2-17.3.
SDCL 11-2-60