Thread Lake is a 80-acre productive, nutrient-rich eutrophic lake in Genesee County, Michigan. Water quality is graded F based on 1 sampling years through 2022. Overall water quality is improving over recent sampling years. Compared to the 8 other monitored lakes in Genesee County, Thread Lake ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, Michigan DNR, last sampled 2022-09-17. 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
Very murky, less than 1.8 ft of visibility. Trophic State Index: 69.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.8 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 69 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 80 acres |
Where to stay near Thread Lake
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Fishing Thread Lake
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.44 m/yr | 2 |
Location
County Ranking
Ranked #9 of 9 lakes in Genesee County
Cleaner Lakes Within 30 Miles
Thread Lake holds Grade F. 2 nearby lakes hold higher grades.
Nearby Lakes in Genesee County
Explore Thread Lake across LakeGrade
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Where to stay at Michigan's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
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Other Grade F Lakes in Michigan
Lapeer County · Clarity: 3 ft
Washtenaw County · Clarity: 3 ft
Washtenaw County · Clarity: 3 ft
Washtenaw County · Clarity: 3 ft
Jackson County · Clarity: 3 ft
Jackson County · Clarity: 2.8 ft
Eutrophic Lakes in Michigan
More records, surveys & data sources
Reservoir Info (USACE NID)
Thread Lake is a man-made reservoir impounded by the Thread Lake Dam (completed 1973), built primarily for recreation on the Thread Creek; gravity-type dam, 9 ft tall and 293 ft long.
- Surface area
- 80 ac
- Normal storage
- 320 ac-ft
- Max storage
- 1,250 ac-ft
- Drainage area
- 57.9 sq mi
- Hazard class
- Significant
- Owner
- City of Flint
Source: USACE National Inventory of Dams, NID ID MI00063 · Operator website
EPA Impairment Status
Thread Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MI040802040306-03 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
9 EPA-permitted facilities operate within about 5 miles of Thread Lake under Clean Water Act (NPDES) discharge permits. 7 facilities have a reported Clean Water Act violation in the past three years.
- Bendle Ps MS4-GeneseeBurton · 1.5 mi away · NPDES MI0060346Recent violation
- Burton MS4-GeneseeBurton · 2.9 mi away · NPDES MI0060093Recent violation
- Atherton Ps MS4-GeneseeBurton · 3 mi away · NPDES MI0060357Recent violation
- Grand Blanc Twp MS4-GeneseeGrand Blanc · 3.3 mi away · NPDES MI0060099Recent violation
- Genesee Co MS4Flint · 4.1 mi away · NPDES MI0060015Recent violation
- Bentley Ps MS4-GeneseeBurton · 4.2 mi away · NPDES MI0060350Recent violation
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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-09-17
Monitoring stations: 1