Tilles Park Reservoir
St. Louis 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
Tilles Park Reservoir in St. Louis County, Missouri is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 434.5 µg/L. Chlorophyll-a (algae): 66.5 µg/L.
- Phosphorus
- 434.5 µg/L
- Chlorophyll-a
- 66.5 µg/L
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Stays near Tilles Park Reservoir
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Watch Tilles Park Reservoir’s letter
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Why Tilles Park Reservoir 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 Tilles Park Reservoir, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded phosphorus and algae (chlorophyll-a), but not water clarity.
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.
Tilles Park Reservoir is a lake in St. Louis County, Missouri.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2022-06-05. 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 Tilles Park Reservoir
These readings exist but are not enough for an A–F grade — see why.
No clarity data. Phosphorus 434.5 µg/L. Chlorophyll-a 66.5 µg/L. TSI 82.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 434.5 µg/L | Not graded |
| Chlorophyll-a (Algae) | 66.5 µg/L | Not graded |
| Trophic State Index (TSI) | 82 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Fishing Tilles Park Reservoir
Regulated Pollution Sources Nearby
24 EPA-permitted facilities operate within about 5 miles of Tilles Park Reservoir under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Rock Hill Quarries Company Demo LandfillSt. Louis · 0.5 mi away · NPDES MO0138371Recent violation
- Mo Petroleum ProductsOverland · 4.3 mi away · NPDES MO0126357Recent violation
- Rock Hill Fire DepartmentRock Hill · 1 mi away · NPDES MONX00802
- Rock Hill Public Works DepartmentRock Hill · 1.1 mi away · NPDES MONX00799
- Service Center Webster GrovesWebster Groves · 1.3 mi away · NPDES MONX00061
- Specgx LlcWebster Groves · 1.5 mi away · NPDES MONX00257
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 Tilles Park Reservoir
Tilles Park Reservoir has no grade, but these lakes within a short drive do.
Nearby Lakes in St. Louis County
Frequently asked questions about Tilles Park Reservoir
Where is Tilles Park Reservoir?
- Tilles Park Reservoir is a lake in St. Louis 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 Tilles Park Reservoir?
- Tilles Park Reservoir in St. Louis County, Missouri is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 434.5 µg/L. Chlorophyll-a (algae): 66.5 µg/L.
Is Tilles Park Reservoir safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
Explore Tilles Park Reservoir across LakeQuality
Planning a trip around Gateway Arch?
Tilles Park Reservoir is about 9 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
Hypereutrophic Lakes in Missouri
Where this data comes from
6 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Univ. of Missouri, Columbia
UMC6 samples · 2022
Analytical methods
- 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)