Third Connecticut Lake
Coos County, New Hampshire231 acresView mapDirections
No nutrient or algae sampling on record from NHDES for this lake.
- Impaired · Mercury
- 100 ft max depth
Third Connecticut Lake in Coos County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Maximum depth: 100 ft. Surface area: 231 acres.
Third Connecticut Lake is a 231-acre lake in Coos County, New Hampshire with a maximum depth of 100 feet (42-foot average).
Source: EPA Water Quality Portal sampling records, your state environmental agency. Methodology: how these readings are compared.
What Third Connecticut Lake is good for
From access and monitoring records, not editorial picks.
- Deep water100 ft surveyed max depth
Swimming conditions
No readingNot rated
Nutrient and algae readings are not a swimming clearance. Third Connecticut Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pH / acidity. Check local advisories before you swim.
Whether Third Connecticut Lake is safe to swim in today is a call for the New Hampshire Department of Environmental Services and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Third Connecticut Lake
These are the measurements NHDES publishes for Third Connecticut Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. TSI undefined.
Ask about Third Connecticut Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
100 ft
Average depth
42 ft
Surface area
231 acres
Shoreline
3.2 mi
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Stays near Third Connecticut Lake
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Fishing Third Connecticut Lake
EPA Impairment Status
Third Connecticut Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK801010101-02 · Official waterbody report
Nearby Lakes in Coos County
Frequently asked questions about Third Connecticut Lake
Where is Third Connecticut Lake?
- Third Connecticut Lake is a lake in Coos County, New Hampshire. Its water-quality measurements are published by NHDES and shown on this page as reported.
What is the water quality of Third Connecticut Lake?
- Third Connecticut Lake in Coos County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Maximum depth: 100 ft. Surface area: 231 acres.
Is Third Connecticut Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Third Connecticut Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pH / acidity. Check local advisories before you swim.
How deep is Third Connecticut Lake?
- Third Connecticut Lake has a maximum depth of 100 feet and an average depth of 42 feet. The lake covers 231 acres.
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Where this data comes from
Measurements for Third Connecticut Lake come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database