Fairfield Lake is a 18-acre highly nutrient-loaded hypereutrophic lake in Wayne County, Illinois. Water quality is graded F based on 2 sampling years through 2022. Water clarity is declining over recent sampling years. Compared to the 2 other monitored lakes in Wayne County, Fairfield Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois DNR, last sampled 2022-10-24. Grade methodology: LakeGrade methodology.
Watch Fairfield Lake water quality
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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 1.3 ft of visibility. Phosphorus level: 114 µg/L. Trophic State Index: 73.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.3 ft | F |
| Phosphorus | 114 µg/L | F |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 73 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 18 acres |
Where to stay near Fairfield Lake
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Fishing Fairfield Lake
Water Quality Trend: → Stable
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -2 m/yr | 2 |
| Phosphorus | ↑ Improving | -18 µg/L/yr | 2 |
Water Temperature
Fairfield Lake averages about 82°F at the surface in summer, usually warmest in Jul (about 86°F) and coldest in Nov (about 59°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 91 field readings (2012–2022) via the EPA Water Quality Portal. See the full Fairfield Lake water temperature breakdown →
Location
County Ranking
Ranked #3 of 3 lakes in Wayne County
Cleaner Lakes Within 30 Miles
Fairfield Lake holds Grade F. 3 nearby lakes hold higher grades.
- COlney East Fork LakeRichland County · 28.3 mi · Two grade letters higher (F → C)
- DWayne City LakeWayne County · 18.9 mi · Higher grade (F → D)
- DVernor LakeRichland County · 28 mi · Higher grade (F → D)
Nearby Lakes in Wayne County
Explore Fairfield Lake across LakeGrade
Species activity outlook by water temperature and season
Where to stay at Illinois's top lakes, each with its grade
Very high nutrients, dense algae, poor clarity
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Other Grade F Lakes in Illinois
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More records, surveys & data sources
Reservoir Info (USACE NID)
Fairfield Lake is a man-made reservoir impounded by the Fairfield Side Channel Reservoir Dam (completed 1979), built primarily for water supply on the TRIB LITTLE WABASH R; earth-type dam, 16 ft tall and 1,850 ft long.
- Surface area
- 18 ac
- Normal storage
- 274.66 ac-ft
- Max storage
- 328.66 ac-ft
- Drainage area
- 0.03 sq mi
- Hazard class
- Low
- Owner
- CITY OF FAIRFIELD
Source: USACE National Inventory of Dams, NID ID IL50585 · Operator website · Matched by proximity (0.21 km)
EPA Impairment Status
Fairfield Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit IL_RCZJ · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Fairfield Lake under Clean Water Act (NPDES) discharge permits.
- Fairfield Wtp, City OfFairfield · 0.3 mi away · NPDES IL0046248
- Fairfield Water Treatment Plant, City OfFairfield · 4.1 mi away · NPDES IL0079375
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)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-10-24
Monitoring stations: 1