Mansfield Hollow Lake
Tolland County, Connecticut450 acresView mapDirections
CT DEEP publishes the water-quality measurements for Mansfield Hollow Lake. Here is what has been measured.
- Public access
- Limited data
Mansfield Hollow Lake in Tolland County, Connecticut has water-quality measurements published by CT DEEP, shown here as reported. Water clarity: 7.5 ft visibility. Surface area: 450 acres.
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. Methodology: how these readings are compared.
What Mansfield Hollow Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Mansfield Hollow Lake is safe to swim in today is a call for the Connecticut Department of Energy and Environmental Protection and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Mansfield Hollow Lake
These are the measurements CT DEEP publishes for Mansfield Hollow Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 7.5 ft. TSI 48.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 7.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 48 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Mansfield Hollow Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
450 acres
Public access
Yes
Listed by CT DEEP
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 in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
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Stays near Mansfield Hollow Lake
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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
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. Its water-quality measurements are published by CT DEEP and shown on this page as reported.
What is the water quality of Mansfield Hollow Lake?
- Mansfield Hollow Lake in Tolland County, Connecticut has water-quality measurements published by CT DEEP, shown here as reported. Water clarity: 7.5 ft visibility. Surface area: 450 acres.
Is Mansfield Hollow Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
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.
Can I fish at Mansfield Hollow Lake?
- Mansfield Hollow Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Connecticut's fish and wildlife agency, so check its current regulations before you go.
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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)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Named boat-access points from the USGS National Boat Ramps inventory