O'Fallon Park Lake
St. Louis city County, MissouriView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- Limited data
O'Fallon Park Lake in St. Louis city County, Missouri is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 1.6 ft visibility. Phosphorus: 335 µg/L. Chlorophyll-a (algae): 2 µg/L.
- Clarity
- 1.6 ft
- Phosphorus
- 335 µg/L
- Chlorophyll-a
- 2 µg/L
Stays via Stay22
Stays near O'Fallon Park Lake
Compare lakeside cabins, hotels, and vacation rentals near O'Fallon Park Lake in St. Louis city County, Missouri — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near O'Fallon Park Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Missouri’s top lakes →
Watch O'Fallon Park Lake’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Why O'Fallon Park Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For O'Fallon Park Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity, phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by Missouri DNR and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
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. Grade methodology: LakeQuality methodology.
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for O'Fallon Park Lake
These readings exist but are not enough for an A–F grade — see why.
Very murky, less than 1.6 ft of visibility. Phosphorus 335 µg/L. Chlorophyll-a 2 µg/L. TSI 65.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | 335 µg/L | Not graded |
| Chlorophyll-a (Algae) | 2 µg/L | Not graded |
| Trophic State Index (TSI) | 65 | Eutrophic |
High nutrients, frequent algae, reduced clarity
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.
Graded lakes near O'Fallon Park Lake
O'Fallon Park Lake has no grade, but these lakes within a short drive do.
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. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for O'Fallon Park Lake?
- O'Fallon Park Lake in St. Louis city County, Missouri is not rated for water quality — its monitoring record does not meet the evidence bar. 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?
- The letter is 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 Missouri Lake Rankings
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)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Regulated discharger data from EPA ECHO (ICIS-NPDES)