Tilles Park Reservoir is a highly nutrient-loaded hypereutrophic lake in St. Louis County, Missouri. Water quality is graded F based on 2 sampling years through 2022. Compared to the 8 other monitored lakes in St. Louis County, Tilles Park Reservoir ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2022-06-05. Grade methodology: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
No clarity data. Phosphorus level: 434.5 µg/L. Chlorophyll-a: 66.5 µg/L. Trophic State Index: 82.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | 434.5 µg/L | F |
| Chlorophyll-a (Algae) | 66.5 µg/L | F |
| Trophic State Index (TSI) | 82 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Tilles Park Reservoir
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Fishing Tilles Park Reservoir
Location
County Ranking
Ranked #9 of 9 lakes in St. Louis County
Cleaner Lakes Within 30 Miles
Tilles Park Reservoir holds Grade F. 5 nearby lakes hold higher grades.
- DBoathouse LakeSt. Louis city County · 6.7 mi · Higher grade (F → D)
- DO'Fallon Park LakeSt. Louis city County · 8.7 mi · Higher grade (F → D)
- DForest Park PondSt. Louis city County · 4.4 mi · Higher grade (F → D)
- DSimpson Park LakeSt. Louis County · 7 mi · Higher grade (F → D)
- DSimpson Park LakeSt. Louis County · 7.3 mi · Higher grade (F → D)
Nearby Lakes in St. Louis County
Explore Tilles Park Reservoir across LakeGrade
Species activity outlook by water temperature and season
Where to stay at Missouri's top lakes, each with its grade
Very high nutrients, dense algae, poor clarity
Missouri's cleanest and most-polluted lakes, ranked
More Missouri Lake Rankings
Other Grade F Lakes in Missouri
Jefferson County · Clarity: 1.3 ft
St. Charles County · Clarity: 2.3 ft
St. Charles County · Clarity: 2.6 ft
St. Francois County · Clarity: 1.1 ft
Audrain County · Clarity: 1.8 ft
Reynolds County · Clarity: 2.7 ft
Hypereutrophic Lakes in Missouri
More records, surveys & data sources
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.
Data Sources
Water quality data from the EPA Water Quality Portal
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-06-05
Monitoring stations: 1