S.D. Codified Laws § 46A-14-65

The managers may amend the general plan of improvements or adopt a supplemental plan of improvements by using, as applicable, the same provisions and procedures in §§ 46A-14-47 to 46A-14-58, inclusive, that were used to establish the initial plan of improvements. The managers may call a special election and submit to the eligible voters of the district the question of whether additional taxes or special assessment shall be levied for the purpose of raising money to cover increased costs resulting from an amended or supplemental plan of improvements which are over and above the initial plan of improvements.