S.D. Codified Laws § 31-13-18
Whenever it shall appear by an affidavit filed by a patron of the mail route with the county auditor that a certain described secondary road in any township of the county is regularly used as part of a United States mail route, and is, in certain designated places, in urgent need of repairs to put such road in reasonably suitable condition for travel, or is, in certain designated places, likely to be made impassable by reason of the weeds along such highway not being cut, as provided by law, so as to prevent the forming of snowdrifts, or is in other respects not being suitably maintained as provided by law, and that the board of supervisors of the proper township has been notified of the condition complained of and has refused or neglected to attend thereto, it shall be the duty of the county auditor to cause copies of such affidavit to be served upon the clerk of the proper township and upon the chairman of the board of supervisors thereof, together with a notice that unless the repairs or maintenance referred to in the affidavit are attended to forthwith by such board and a certificate that the same has been done delivered to the county auditor, that such repairs or maintenance will be executed by the county at the expense of the township as in this chapter provided. Such copy and notice may be served by registered or certified mail.
SDCL 31-13-18