Tolland County Lake Quality
Connecticut, 13 lakes, average grade B (Good)
Tolland County has 13 graded lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. With an average grade of B, Tolland County sits comfortably above the Connecticut median.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Crystal Lake (B); the most-stressed is Coventry Lake (C).
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Quick Answers for Tolland County
Planning a trip? Check special fishing regulations for Crystal Lake — or check the official Connecticut fishing regulations.
All Lakes in Tolland County
13 lakes · 4 graded, 9 not rated4 graded lakes · 9 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | BCrystal LakeTolland | B | No recent samples | 13 µg/L | 2.1 µg/L | No recent samples | Not recorded |
| 2 | BHalls PondTolland | B | No recent samples | 15.5 µg/L | 3.5 µg/L | No recent samples | Not recorded |
| 3 | BMashapaug PondTolland | B | No recent samples | 8 µg/L | 1.6 µg/L | No recent samples | Not recorded |
| 4 | CCoventry LakeTolland | C | No recent samples | 18 µg/L | 2.9 µg/L | No recent samples | Not recorded |
| NRAndover LakeTolland | NR | 10.2 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBigelow PondTolland | NR | 12.3 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBolton LakeTolland | NR | 8.5 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBreakneck PondTolland | NR | No recent samples | 25.5 µg/L | 6.7 µg/L | No recent samples | Not recorded | |
| NRHurds LakeTolland | NR | 4.8 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMansfield Hollow LakeTolland | NR | 7.5 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMorey PondTolland | NR | 10.1 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRSomersville PondTolland | NR | 4.1 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRWangumbaug LakeTolland | NR | 11.5 ft | No recent samples | No recent samples | No recent samples | Not recorded |
NR = not rated: the monitoring record does not meet the evidence bar for a grade. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
Lake Match
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Six questions — swimming, fishing, quiet, cabins, drive time — and a shortlist of graded lakes that fit, with the water quality behind each one.
Other Counties in Connecticut
See how Tolland County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 49 states and 2 Canadian provinces.
Source: EPA National Aquatic Resource Surveys, 2026.