Mamanasco Lake
Mamanasco Lake in Fairfield County, Connecticut is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 42 µg/L. Chlorophyll-a (algae): 15.1 µg/L. Surface area: 87 acres.
- Area
- 87 acres
- Public access
- Yes
Why Mamanasco Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: 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 Mamanasco Lake, 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 your state environmental agency and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Mamanasco Lake is a 87-acre lake in Fairfield County, Connecticut. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2023-06-15. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Mamanasco Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
No clarity data. Phosphorus level: 42 µg/L. Chlorophyll-a: 15.1 µg/L. Trophic State Index: 58.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 42 µg/L | Not graded |
| Chlorophyll-a (Algae) | 15.1 µg/L | Not graded |
| Trophic State Index (TSI) | 58 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Mamanasco Lake
Compare lakeside cabins, hotels, and vacation rentals near Mamanasco Lake in Fairfield County, Connecticut — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Mamanasco Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 87 acres |
| Public Access | Yes |
No bathymetric survey has been published for Mamanasco Lake, so its depth is not documented here.
Recreation & Access
- Mamanasco LakePublic
Named access points from the USGS National Boat Ramps inventory, snapped within 5 km. More lakes with boat ramps
Fishing Mamanasco Lake
Reservoir Info (USACE NID)
Mamanasco Lake is a man-made reservoir impounded by the Mamanasco Lake Dam (completed 1870), built primarily for recreation on the Titicus River Trib; earth-type dam, 6 ft tall and 120 ft long.
- Surface area
- 87 ac
- Normal storage
- 435 ac-ft
- Max storage
- 435 ac-ft
- Drainage area
- 0.59 sq mi
- Hazard class
- Significant
- Owner
- Camp, Jr.
Source: USACE National Inventory of Dams, NID ID CT00220 · Operator website
EPA Impairment Status
Mamanasco Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit CT8104-00-2-L5_01 · Official waterbody report · Matched by proximity (0.06 km)
Graded lakes near Mamanasco Lake
Mamanasco Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Fairfield County
Frequently asked questions about Mamanasco Lake
Where is Mamanasco Lake?
- Mamanasco Lake is a lake in Fairfield County, Connecticut. LakeQuality has not rated this lake (UNRATED) — there is not enough recent sampling to assign a letter.
What is the water quality grade for Mamanasco Lake?
- Mamanasco Lake in Fairfield County, Connecticut is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 42 µg/L. Chlorophyll-a (algae): 15.1 µg/L. Surface area: 87 acres.
Is Mamanasco Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Mamanasco Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Algae concentration (chlorophyll-a) is 15.1 µg/L. Always check local health department advisories before swimming.
Are there boat ramps on Mamanasco Lake?
- Mamanasco Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Mamanasco Lake. Public access is listed as yes.
Explore Mamanasco Lake across LakeGrade
More Connecticut Lake Rankings
Other Lakes in Connecticut
Eutrophic Lakes in Connecticut
Where this data comes from
4 measurements from 1 monitoring station, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- Connecticut Department Of Energy And Environmental Protection
CT_DEP01_WQX4 samples · 2023
Analytical methods
- Total Phosphorus After Block Digestion
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- Nitrate-Nitrite Nitrogen by Colorimetry
- Turbidity by Nephelometry
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
Impairment status from EPA ATTAINS 303(d) database
Named boat-access points from the USGS National Boat Ramps inventory