S.D. Codified Laws § 31-13-43
If the board of supervisors by resolution so provides, any portion of the cost may be paid by the township out of its general funds appropriated for that purpose and the proper deduction shall be made of the cost to be so paid before the cost to be assessed is distributed to the several lots as required. The sum determined to be paid may be a fixed amount or fraction of the total cost of the improvement, or of a specified portion thereof on which the construction is substantially uniform. Such amount or fraction may be additional to any amounts assumed by the township in accordance with the provisions of §§ 31-13-47 to 31-13-49, inclusive, or the costs referred to in those sections may be paid therefrom, as determined by the resolution.
SDCL 31-13-43