First Connecticut Lake-Deep Spot
Coos County, New HampshireView mapDirections
NHDES publishes the water-quality measurements for First Connecticut Lake-Deep Spot. Here is what has been measured.
- Impaired · Mercury
- Public access
- Limited data
First Connecticut Lake-Deep Spot in Coos County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 7.4 µg/L.
First Connecticut Lake-Deep Spot is a lake in Coos County, New Hampshire. Limited fish-species data available. Public access is available.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-08-14. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. First Connecticut Lake-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether First Connecticut Lake-Deep Spot 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 First Connecticut Lake-Deep Spot
These are the measurements NHDES publishes for First Connecticut Lake-Deep Spot, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 7.4 µg/L. TSI 33.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 7.4µg/L | Measured, not scored 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. | 33 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about First Connecticut Lake-Deep Spot
Answers come straight from the public measurements and survey records on this page.
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Fishing First Connecticut Lake-Deep Spot
EPA Impairment Status
First Connecticut Lake-Deep Spot is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK801010102-02 · Official waterbody report
Nearby Lakes in Coos County
Frequently asked questions about First Connecticut Lake-Deep Spot
Where is First Connecticut Lake-Deep Spot?
- First Connecticut Lake-Deep Spot 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 First Connecticut Lake-Deep Spot?
- First Connecticut Lake-Deep Spot in Coos County, New Hampshire has water-quality measurements published by NHDES, shown here as reported. Phosphorus: 7.4 µg/L.
Is First Connecticut Lake-Deep Spot safe to swim in?
- Nutrient and algae readings are not a swimming clearance. First Connecticut Lake-Deep Spot is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Can I fish at First Connecticut Lake-Deep Spot?
- Public access to First Connecticut Lake-Deep Spot is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by New Hampshire's fish and wildlife agency, so check its current regulations before you go.
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Where this data comes from
5 measurements from 1 monitoring station, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
111133005 samples · 2025
Analytical methods
- 10-115-01-1 F ~ LACHAT; Total Phosphorus- Manual persulfate digest
Monitoring station identifiers (1)
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
Impairment status from EPA ATTAINS 303(d) database