Blue Pit Lake
Cerro Gordo County, IowaView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Mesotrophic
- #1 of 4 in the county
Blue Pit Lake in Cerro Gordo County, Iowa has a water quality grade of A (Excellent). Water clarity: 17.1 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 2.4 µg/L.
- Clarity
- 17.1 ft
- Typical in September
- 68°F
- Type
- Mesotrophic
- Trend
- ↑ Improving
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Watch Blue Pit Lake’s letter
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Blue Pit Lake is a mesotrophic lake in Cerro Gordo County, Iowa. Water quality is graded A based on 2 sampling years through 2022. Overall water quality is improving over recent sampling years. Compared to the 3 other monitored lakes in Cerro Gordo County, Blue Pit Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2022-09-12. Grade methodology: LakeQuality methodology.
What Blue Pit Lake is good for
From access and monitoring records, not editorial picks.
- Clear water17.1 ft of visibility
Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Crystal clear, you can see 17.1 ft down. Phosphorus 20 µg/L. Chlorophyll-a 2.4 µg/L. TSI 41. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 17.1 ft | Not graded |
| Phosphorus | 20 µg/L | Good |
| Chlorophyll-a (Algae) | 2.4 µg/L | Good |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Water Temperature
Blue Pit Lake typically sits around 68°F at the surface in September. Summer average is about 76°F. Usually warmest in Jul (about 80°F) and coldest in Sep (about 68°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 9 field readings (2018–2022) via the EPA Water Quality Portal. See the full Blue Pit Lake water temperature breakdown →
Fishing Blue Pit Lake
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.6 m/yr | 3 |
| Phosphorus | ↑ Improving | -20.1 µg/L/yr | 3 |
| Chlorophyll-a | ↑ Improving | -15.75 µg/L/yr | 3 |
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Blue Pit Lake under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Heidelberg Materials Us Cement Llc (Remediation Site)Mason City · 2.5 mi away · NPDES IA0072907Recent violation
- Heidelberg Materials Us Cement LlcMason City · 2.5 mi away · NPDES IA0001945Recent 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.
County Ranking
Ranked #1 of 4 lakes in Cerro Gordo County
Nearby Lakes in Cerro Gordo County
Frequently asked questions about Blue Pit Lake
Where is Blue Pit Lake?
- Blue Pit Lake is a lake in Cerro Gordo County, Iowa. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Blue Pit Lake?
- Blue Pit Lake in Cerro Gordo County, Iowa has a water quality grade of A (Excellent). Water clarity: 17.1 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 2.4 µg/L.
Is Blue Pit Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Blue Pit Lake?
- Blue Pit Lake typically sits around 68°F at the surface in September, from 9 EPA Water Quality Portal field readings (2018–2022). That is a typical value for the month, not a live reading.
Explore Blue Pit Lake across LakeQuality
More Iowa Lake Rankings
Other Grade A Lakes in Iowa
Mesotrophic Lakes in Iowa
Where this data comes from
36 measurements from 1 monitoring station, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX36 samples · 2020–2022
Analytical methods
- Unknown
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- ISU modification of APHA 2130-B
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)