Mansfield Hollow Lake
Mansfield Hollow Lake in Tolland County, Connecticut is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 7.5 ft visibility. Surface area: 450 acres.
- Clarity
- 7.5 ft
- Area
- 450 acres
- Public access
- Yes
Why Mansfield Hollow 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 Mansfield Hollow Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
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.
Mansfield Hollow Lake is a 450-acre lake in Tolland 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 2022-09-26. Grade methodology: LakeGrade methodology.
Watch Mansfield Hollow Lake water quality
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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 Mansfield Hollow Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Moderate clarity, visible to about 7.5 ft. Trophic State Index: 48.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 7.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 48 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Mansfield Hollow Lake
Compare lakeside cabins, hotels, and vacation rentals near Mansfield Hollow Lake in Tolland 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 Mansfield Hollow Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 450 acres |
| Public Access | Yes |
No bathymetric survey has been published for Mansfield Hollow Lake, so its depth is not documented here.
Recreation & Access
- Mansfield Hollow DamPublic
Named access points from the USGS National Boat Ramps inventory, snapped within 5 km. More lakes with boat ramps
Fishing Mansfield Hollow Lake
Reservoir Info (USACE NID)
Mansfield Hollow Lake is a man-made reservoir impounded by the Mansfield Hollow Dam - Dike F (completed 1952), built primarily for flood risk reduction on the Nachaug River; gravity-type dam, 78 ft tall and 14,050 ft long.
- Surface area
- 450 ac
- Normal storage
- 2,800 ac-ft
- Max storage
- 76,000 ac-ft
- Drainage area
- 159 sq mi
- Hazard class
- High
- Owner
- USACE - New England District
Source: USACE National Inventory of Dams, NID ID CT00503 · Operator website
Graded lakes near Mansfield Hollow Lake
Mansfield Hollow Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Tolland County
Frequently asked questions about Mansfield Hollow Lake
Where is Mansfield Hollow Lake?
- Mansfield Hollow Lake is a lake in Tolland 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 Mansfield Hollow Lake?
- Mansfield Hollow Lake in Tolland County, Connecticut is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 7.5 ft visibility. Surface area: 450 acres.
Is Mansfield Hollow Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Mansfield Hollow Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
Are there boat ramps on Mansfield Hollow Lake?
- Mansfield Hollow Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Mansfield Hollow Dam. Public access is listed as yes.
Explore Mansfield Hollow Lake across LakeGrade
More Connecticut Lake Rankings
Other Lakes in Connecticut
Mesotrophic Lakes in Connecticut
Where this data comes from
30 measurements from 2 monitoring stations, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- North American Lake Management Society
NALMS22 samples · 2020–2022 - CT DEEP Volunteer Water Monitoring Program (Volunteer)
CTVOLMON8 samples · 2022
Monitoring station identifiers (2)
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
Named boat-access points from the USGS National Boat Ramps inventory