S.D. Codified Laws § 1-26-30.1
The failure of any agency to make and file a decision within a period of thirty days after any matter has been finally submitted to it, entitles a person authorized to appeal from the record then existing as if the decision had been made adversely to him in whole or in part, unless within such time the agency shall make and serve upon all the parties to the record, an order extending such time for an additional period of not to exceed sixty days, which order shall state the grounds or reasons why such extension is necessary. At the expiration of the thirty days or the time to which extended by such order, such person may present to the agency a proposed decision, and if the same is not adopted within five days after presentation for filing, such person may appeal the same as if such proposed decision had been denied. This section does not apply to contested cases determined by the Public Utilities Commission.
SDCL 1-26-30.1