Is Lamar City Lk. South Arm Lake Polluted?
Yes — Lamar City Lk. South Arm Lake in Barton County, Missouri is on the EPA's Clean Water Act 303(d) impaired-waters list (2022 assessment cycle). It is cited for Nutrients (phosphorus, nitrogen). A formal cleanup plan — a Total Maximum Daily Load (TMDL) — has been written. "Impaired" is a legal designation, separate from the lake's A–F water-quality grade: it means at least one designated use (such as swimming, aquatic life, or fish consumption) does not meet state standards for the listed pollutant.
EPA 303(d) Listing
| On 303(d) impaired list | Listed impaired |
| Cleanup plan (TMDL) | Completed |
| Assessment cycle | 2022 |
| EPA IR category | 4A |
| Location | Barton County, Missouri |
Pollutants Cited
- Nutrients (phosphorus, nitrogen) — Excess phosphorus and nitrogen fuel algae growth and summer blooms. This is the classic agricultural-runoff and shoreline-development impairment, and the one most likely to affect swimming via blue-green algae.
Specific parameters in the EPA record: NUTRIENT/EUTROPHICATION BIOLOGICAL INDICATORS.
What this means for using Lamar City Lk. South Arm Lake
Because Lamar City Lk. South Arm Lake is listed for Nutrients (phosphorus, nitrogen), swimming can be affected — check for posted beach advisories, especially after heavy rain or during visible algae. An impairment listing does not mean the lake is closed — most impaired lakes remain open for boating and swimming. It means a specific pollutant exceeds a standard for a specific use. Lamar City Lk. South Arm Lake carries an overall water-quality grade of F, with algae (chlorophyll-a) at 39 µg/L and phosphorus at 80.4 µg/L — see the full breakdown on the lake report. The official EPA assessment is available in the ATTAINS waterbody report.