S.D. Codified Laws § 49-1-9
Such Public Utilities Commission may in all cases conduct its proceedings, when not otherwise particularly prescribed by law, in such manner and places as will best conduce to the proper dispatch of business and to the ends of justice.
A majority of the commissioners shall constitute a quorum for the transaction of business, but no commissioner shall participate in any hearing or proceeding in which he has any conflict of interest or if he is temporarily incapacitated. If a commissioner determines that he is incapacitated or disqualified from participating for any reason in any hearing or proceeding, he shall certify that determination to the Governor, or if the character of the incapacity of any commissioner is such that he is unable to certify his incapacity to the Governor, the commission may make such certification. In the event of any such certification, the Governor shall then appoint an elected constitutional officer, other than the attorney general, to act as a member of the commission in place of the disqualified or incapacitated commissioner for the purpose of such hearing or proceeding only.
SDCL 49-1-9