O'Fallon Park Lake
St. Louis city County, MissouriView mapDirections
Missouri DNR publishes the water-quality measurements for O'Fallon Park Lake. Here is what has been measured.
- Limited data
O'Fallon Park Lake in St. Louis city County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 335 µg/L. Chlorophyll-a (algae): 2 µg/L.
O'Fallon Park Lake is a lake in St. Louis city County, Missouri.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2021-07-17. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether O'Fallon Park Lake is safe to swim in today is a call for the Missouri Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for O'Fallon Park Lake
These are the measurements Missouri DNR publishes for O'Fallon Park Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 1.6 ft of visibility. Phosphorus 335 µg/L. Chlorophyll-a 2 µg/L. TSI 65.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 335µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 2µg/L | Measured, not scored The green pigment in algae — a direct measure of how much algae is in the water. |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 65 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
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Fishing O'Fallon Park Lake
Regulated Pollution Sources Nearby
14 EPA-permitted facilities operate within about 5 miles of O'Fallon Park Lake under Clean Water Act (NPDES) discharge permits, including 2 classified by the EPA as major dischargers. 5 facilities have a reported Clean Water Act violation in the past three years.
- Msd Bissell Point WwtpSt Louis · 1.5 mi away · NPDES MO0025178MajorRecent violation
- Illinois American Water Company - Granite City WwtpGranite City · 2.3 mi away · NPDES IL0033481MajorRecent violation
- Illinois Department Of TransportationVenice · 2.2 mi away · NPDES IL0071765Recent violation
- Municipal River TerminalSt. Louis · 2.5 mi away · NPDES MO0113328Recent violation
- Venice Energy CenterVenice · 3 mi away · NPDES IL0000175Recent violation
- Stericycle St LouisSt. Louis · 0.7 mi away · NPDES MONX00148
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Nearby Lakes in St. Louis city County
Frequently asked questions about O'Fallon Park Lake
Where is O'Fallon Park Lake?
- O'Fallon Park Lake is a lake in St. Louis city County, Missouri. Its water-quality measurements are published by Missouri DNR and shown on this page as reported.
What is the water quality of O'Fallon Park Lake?
- O'Fallon Park Lake in St. Louis city County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 335 µg/L. Chlorophyll-a (algae): 2 µg/L.
Is O'Fallon Park Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Explore O'Fallon Park Lake across LakeQuality
Planning a trip around Gateway Arch?
O'Fallon Park Lake is about 4 miles from Gateway Arch National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Gateway Arch →More lakes in Missouri
Other Lakes in Missouri
Eutrophic Lakes in Missouri
Where this data comes from
3 measurements from 1 monitoring station, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Univ. of Missouri, Columbia
UMC3 samples · 2021
Analytical methods
- Depth, Secchi disk in meters
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Regulated discharger data from EPA ECHO (ICIS-NPDES)