Lagoon systems: wastewater treatment plants in South Dakota
107 plants · 89% of the state · 15 MGD reported by 14 plants
Klarifi identifies 107 publicly owned wastewater treatment plants with lagoon systems in South Dakota, 89% of the 120 plants in the state (15 MGD reported by 14 plants). The largest is Rapid City Water Reclamation Facility in Rapid City at 10.62 MGD.
Lagoon systems treat wastewater in large earthen ponds over weeks of retention time, with or without mechanical aeration. They serve thousands of small towns because they are cheap to run, but they struggle with ammonia and nutrient limits, fill with sludge over decades and are the plants most often converted or upgraded when a permit is renewed.
The largest lagoons in South Dakota
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Rapid City Water Reclamation Facility | Rapid City | 10.62 | SD0023574 | Jun 2022 | 4 |
| 2 | Vermillion, City Of | Vermillion | 1.42 | SD0020061 | Sep 2017 | 2 |
| 3 | Harrisburg - City Of | Harrisburg, City Of | 0.47 | SD0023728 | Jun 2031 | 0 |
| 4 | Oacoma, Town Of | Oacoma | 0.37 | SD0020737 | Dec 2027 | 5 |
| 5 | Volga, City Of | Volga, City Of | 0.34 | SD0021920 | Dec 2028 | 34 |
| 6 | Whitewood Water | Whitewood | 0.3 | SD0021466 | Feb 2023 | 4 |
| 7 | Hartford, City Of | Hartford | 0.29 | SD0021750 | Dec 2024 | 117 |
| 8 | Summerset, City Of | Summerset | 0.22 | SD0027758 | Apr 2031 | 0 |
| 9 | Dell Rapids, City Of | Dell Rapids | 0.2 | SD0022101 | Sep 2019 | 1 |
| 10 | Beresford, City Of | Beresford | 0.19 | SD0020079 | May 2031 | 5 |
| 11 | Lennox, City Of | Lennox | 0.18 | SD0021768 | Dec 2027 | 3 |
| 12 | Iroquois, City Of | Iroquois | 0.14 | SDG922438 | Aug 2026 | 33 |
| 13 | Springfield, City Of | Springfield | 0.1 | SD0028647 | Sep 2029 | 120 |
| 14 | Roslyn, Town Of | Roslyn | 0.07 | SD0022802 | Dec 2028 | 3 |
| 15 | Andover, Town Of | Andover | — | SDG921504 | Aug 2026 | 112 |
| 16 | Arlington, City Of | Arlington | — | SD0020753 | Jun 2024 | 2 |
| 17 | Armour, City Of | Armour | — | SD0020222 | Apr 2026 | 19 |
| 18 | Ashton, Town Of | Ashton | — | SD0022276 | Sep 2024 | 0 |
| 19 | Avon, City Of | Avon, City Of | — | SD0022730 | Apr 2026 | 120 |
| 20 | Belle Fourche WTP | Belle Fourche | — | SD0021628 | Apr 2028 | — |
| 21 | Big Bend Lagoon System | Fort Thompson | — | SDG589201 | Mar 2027 | — |
| 22 | Black Pipe, Community Of | Rosebud | — | SDG589602 | Mar 2027 | 0 |
| 23 | Blunt- City Of | Blunt | — | SD0025020 | Dec 2027 | 1 |
| 24 | Bonesteel- City Of | Bonesteel | — | SDG920842 | Aug 2026 | 2 |
| 25 | Bridgewater, City Of | Bridgewater | — | SD0021512 | Jan 2027 | 32 |
Contacts and project signals for every plant on this list
Klarifi adds verified decision-maker contacts, permit limits, discharge monitoring data and the capital projects planned in each city, filterable by technology, size and compliance record.
Other technologies in South Dakota
Lagoon systems in other states
Lagoon systems in South Dakota: questions
Sources and methodology
Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.
Data refreshed September 11, 2026.