Lagoon systems: wastewater treatment plants in Colorado
69 plants · 50% of the state · 49 MGD reported by 61 plants
Klarifi identifies 69 publicly owned wastewater treatment plants with lagoon systems in Colorado, 50% of the 137 plants in the state (49 MGD reported by 61 plants). The largest is Persigo Wastewater Treatment Plant in Grand Junction at 11.4 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 Colorado
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Persigo Wastewater Treatment Plant | Grand Junction | 11.4 | CO0040053 | Dec 2022 | 1 |
| 2 | Greeley WWTP | Greeley | 9.4 | COL040258 | Dec 2030 | 13 |
| 3 | Town Of Windsor Sewarage Treatment Plant | Windsor | 2.85 | CO0020320 | May 2020 | 0 |
| 4 | Arapahoe County Water And Waste Water Authority | Englewood | 2.53 | COE015000 | Aug 2020 | 0 |
| 5 | Steamboat Springs WWTP | Steamboat Springs | 2.22 | CO0020834 | Dec 2021 | 27 |
| 6 | Hill-N-Park STP | Greeley | 1.79 | CO0047287 | Dec 2023 | 5 |
| 7 | Golden City Of | Jefferson County | 1.73 | CO0042170 | Sep 2017 | 0 |
| 8 | Sterling City Of | Sterling | 1.64 | CO0026247 | Feb 2017 | 9 |
| 9 | Aspen Consolidated Sanitation District | Aspen | 1.4 | CO0026387 | Apr 2031 | 10 |
| 10 | Clifton #2 West WWTP | Clifton | 1.3 | CO0033791 | Mar 2020 | 0 |
| 11 | Woodmen Hills Metro Dist WWTF | Peyton | 1.16 | CO0047091 | Jan 2020 | 0 |
| 12 | Regional WWTF | Alamosa | 1.09 | CO0044458 | Oct 2019 | 4 |
| 13 | Pinery WWTF | Parker | 1.04 | CO0041092 | Oct 2016 | 2 |
| 14 | City Of Trinidad | Trinidad | 1.02 | CO0031232 | Apr 2020 | 0 |
| 15 | Lake City Area STP | Lake City | 0.72 | COG081214 | May 2028 | 33 |
| 16 | Las Animas WWTP | Las Animas | 0.71 | CO0040690 | Jan 2026 | 73 |
| 17 | Buena Vista Sanitation District WWTF | Buena Vista | 0.62 | CO0045748 | Oct 2020 | 1 |
| 18 | Milliken Sanitation District | Milliken | 0.53 | CO0042528 | Jul 2020 | 2 |
| 19 | Rocky Ford Sewage Lagoons | Rocky Ford | 0.52 | CO0023850 | Jul 2020 | 63 |
| 20 | West Montrose Sanitation Dist WWTF | Montrose | 0.42 | CO0030449 | Apr 2024 | 0 |
| 21 | Leadville Sanitation District | Leadville | 0.37 | CO0021164 | Dec 2025 | 41 |
| 22 | Hayden Town Of | Hayden | 0.33 | CO0040959 | Dec 2019 | 9 |
| 23 | Monte Vista City Of | Monte Vista | 0.32 | CO0023132 | Feb 2020 | 74 |
| 24 | Hotchkiss WWTP | Hotchkiss | 0.27 | CO0044903 | Jul 2018 | 4 |
| 25 | Palisade WWTF | Palisade | 0.24 | CO0000012 | Sep 2018 | 59 |
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 Colorado
Lagoon systems in other states
Lagoon systems in Colorado: 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.