Impaired Lakes in Massachusetts
66 of 103 measured Massachusetts lakes (64%) are officially listed as impaired under Clean Water Act §303(d) in the most recent EPA ATTAINS reporting cycle. 17 have an approved TMDL restoration plan.
Top Causes of Impairment in Massachusetts
Reading the Massachusetts impairment landscape
64% of Massachusetts's tracked lakes — 66 of 103 — appear on the EPA Clean Water Act §303(d) impaired-waters list. At that share, impairment is the default state rather than an exception: the majority of lakes are flagged for at least one pollutant exceeding water-quality standards. Trip-planning for clean water in Massachusetts typically requires checking impairment status as a first filter, not as an edge case.
The leading impairment cause in Massachusetts is Algal growth. Each impairment category carries its own use-restriction implications — some affect fish consumption, some affect swimming, some affect aquatic-life habitat. Click through to the specific lake records below for the pollutant list and the TMDL (Total Maximum Daily Load) status, which determines whether a cleanup plan is in place.
Impaired-waters listings come from the state environmental agency's §303(d) submission to EPA, refreshed on a roughly 2-year cycle. A listed lake stays on the list until either a TMDL is established and the cleanup completes, or subsequent monitoring shows the pollutant concentrations no longer exceed water-quality standards. The list below reflects the most recent available Massachusetts submission to the EPA Assessment, Total Maximum Daily Load Tracking and Implementation System (ATTAINS) dataset.
All 66 EPA-Listed Impaired Lakes in Massachusetts
| Lake | County | Causes | TMDL |
|---|---|---|---|
| Long Pond | Worcester | Mercury, Nuisance exotic species | — |
| Bare Hill Pond | Worcester | Algal growth, Mercury, Noxious aquatic plants +1 more | ✓ |
| Arcadia Lake | Hampshire | Algal growth, Nuisance exotic species, Nutrients (phosphorus, nitrogen) | — |
| Benton Pond | Berkshire | Nuisance exotic species | — |
| Wrights Reservoir | Worcester | Mercury | ✓ |
| Ashley Lake | Berkshire | Mercury | — |
| Quacumquasit Pond | Worcester | Algal growth, Mercury, Nuisance exotic species | ✓ |
| Hamilton Reservoir | Hampden | Nuisance exotic species | — |
| Atkins Reservoir | Franklin | Mercury | — |
| Tully Pond | Franklin | Algal growth | — |
| Damon Pond | Hampshire | Mercury | — |
| Lake Pearl | Norfolk | Nuisance exotic species, Oxygen depletion (low DO) | ✓ |
| Fall Brook Reservoir | Worcester | Mercury | — |
| Walden Pond | Essex | Mercury | — |
| Wachusett Lake | Worcester | Mercury | — |
| Ponkapoag Pond | Norfolk | Algal growth, Mercury, Nuisance exotic species | ✓ |
| Crystal Lake | Worcester | Mercury | — |
| Crystal Lake | Essex | Mercury | — |
| Fort Pond | Worcester | Oxygen depletion (low DO) | — |
| Lower Crow Hill Pond | Worcester | Nuisance exotic species | — |
| Sudbury Reservoir | Worcester | Mercury, Noxious aquatic plants, Nuisance exotic species | ✓ |
| Marys Pond | Plymouth | Mercury | — |
| Ezekiel Pond | Plymouth | Mercury | — |
| Island Pond | Plymouth | Mercury | — |
| Wankinco River Lake | Plymouth | Pathogens (E. coli, fecal) | ✓ |
| Mashpee Pond | Barnstable | Mercury, Oxygen depletion (low DO) | ✓ |
| Stillwater Pond | Barnstable | Habitat alterations, Turbidity | — |
| Fresh Pond | Plymouth | Habitat alterations, Mercury | — |
| Chebacco Lake | Essex | Algal growth, Mercury, Nuisance exotic species | ✓ |
| Buckley-Dunton Lake | Berkshire | Mercury | ✓ |
| East Brimfield Reservoir | Worcester | Mercury, Nuisance exotic species | ✓ |
| Metacomet Lake | Hampshire | Algal growth, Nuisance exotic species, Oxygen depletion (low DO) | — |
| Windsor Lake | Berkshire | Algal growth | — |
| Sargent Pond | Worcester | Mercury, Nuisance exotic species | — |
| Field Pond | Essex | Algal growth, Nuisance exotic species | — |
| Nabnasset Pond | Middlesex | Algal growth, Mercury, Nuisance exotic species | ✓ |
| Cambridge Reservoir | Middlesex | Salinity / chlorides | — |
| Hinckleys Pond | Barnstable | Algal growth | — |
| Halfway Pond | Plymouth | Algal growth, Mercury | — |
| Watson Pond | Bristol | Algal growth, Nutrients (phosphorus, nitrogen), Oxygen depletion (low DO) +2 more | — |
| Congamond Lakes | Hartford | Nuisance exotic species, Nutrients (phosphorus, nitrogen), Oxygen depletion (low DO) | — |
| Pequot Pond | Hampden | Algal growth, Noxious aquatic plants, Nuisance exotic species +3 more | — |
| Robbins Pond | Worcester | Algal growth | — |
| Little Chauncy Pond | Worcester | Algal growth, Mercury, Nuisance exotic species | — |
| Heart Pond | Middlesex | Mercury, Noxious aquatic plants, Nuisance exotic species +1 more | — |
| Boons Pond | Middlesex | Algal growth, Mercury, Nuisance exotic species | ✓ |
| Cleveland Pond | Plymouth | Algal growth, Mercury | — |
| Ames Long Pond | Bristol | Algal growth, Noxious aquatic plants, Nuisance exotic species +2 more | — |
| Horn Pond | Middlesex | Algal growth, Habitat alterations, Nutrients (phosphorus, nitrogen) +2 more | — |
| Nashawannuck Pond | Hampshire | Noxious aquatic plants, Nutrients (phosphorus, nitrogen) | — |
| Bartlett Pond | Worcester | Algal growth, Noxious aquatic plants, Nuisance exotic species | — |
| Furnace Pond | Plymouth | Algal growth, Oxygen depletion (low DO) | — |
| Cooks Pond | Plymouth | Algal growth, Nuisance exotic species | — |
| South Watuppa Pond | Bristol | Algal growth | — |
| Wedge Pond | Middlesex | Algal growth, Nutrients (phosphorus, nitrogen), Oxygen depletion (low DO) | — |
| Spy Pond | Middlesex | Algal growth, Noxious aquatic plants, Nuisance exotic species +3 more | — |
| Wachusett Reservoir | Worcester | Algal growth, Mercury, Nuisance exotic species | ✓ |
| Lake Quannapowitt | Middlesex | Algal growth, Habitat alterations, Pesticides +1 more | — |
| Upper Mystic Lake | Middlesex | Algal growth, Nutrients (phosphorus, nitrogen), Oxygen depletion (low DO) +1 more | — |
| Sherman Reservoir | Franklin | Mercury | — |
| Santuit Pond | Barnstable | Algal growth, Biotoxins, Habitat alterations +3 more | — |
| Silver Lake | Plymouth | Habitat alterations, Hydrologic alteration, Oxygen depletion (low DO) | — |
| Stetson Pond | Plymouth | Algal growth, Noxious aquatic plants, Nuisance exotic species +2 more | ✓ |
| Webster Lake | Worcester | Algal growth, Nuisance exotic species, Oxygen depletion (low DO) | — |
| Lake Quinsigamond | Worcester | Algal growth, Noxious aquatic plants, Nuisance exotic species +2 more | ✓ |
| Indian Lake | Worcester | Algal growth, Nuisance exotic species, Nutrients (phosphorus, nitrogen) +1 more | ✓ |
Frequently Asked Questions
How many lakes are impaired in Massachusetts?
66 of 103 measured Massachusetts lakes (64%) are listed as impaired in the most recent EPA ATTAINS reporting cycle. Of those, 46 are on the federal Clean Water Act §303(d) list and 17 have an approved Total Maximum Daily Load (TMDL) restoration plan.
What does Clean Water Act §303(d) mean?
Section 303(d) of the federal Clean Water Act requires every state to identify waters that don't meet water quality standards even after pollution control measures. Each listed water must then have a Total Maximum Daily Load (TMDL) developed — a plan that caps how much of each pollutant can enter the waterbody. The "303(d) list" is the impaired-waters list. The EPA reviews each state's list every two years.
What are the top causes of impairment in Massachusetts?
The most common causes flagged across Massachusetts's impaired lakes are: Algal growth (34 lakes); Mercury (31 lakes); Nuisance exotic species (30 lakes); Oxygen depletion (low DO) (17 lakes); Nutrients (phosphorus, nitrogen) (13 lakes); Noxious aquatic plants (10 lakes). Mercury is widespread in fish tissue across the upper Midwest from atmospheric deposition. Nutrient impairment (phosphorus, nitrogen) typically reflects agricultural runoff and urban stormwater.
Can I swim in an impaired lake?
It depends on the cause of impairment. A lake impaired for "mercury in fish tissue" is generally safe to swim in — the warning is about long-term consumption of fish. A lake impaired for "pathogens" (E. coli) or "algal growth" may pose a swimming risk and often has a separate beach advisory. Check the cause categories listed for each lake below, and consult your state health department's beach monitoring program for current advisories.
Where does this impairment data come from?
Every impairment record on this page comes from the EPA's ATTAINS (Assessment and TMDL Tracking and Implementation System) public dataset, the federal repository of state-reported water quality assessments. EPA ATTAINS is published as GeoParquet files on the EPA Office of Water S3 bucket and refreshed several times per year. Causes and use-support codes follow EPA's standard taxonomy.
More on impaired waters
What it means when a lake is listed as impaired, why mercury is the most common reason, and why a listed lake can still be clear water with favourable readings.
Why states issue fish-consumption advisories, which contaminants — mercury, PCBs, PFAS — drive them, and how to eat the fish you catch more safely.
How phosphorus and nutrient runoff drive algae growth and turn lakes green, where the nutrients come from, and what it means for a lake’s readings.
Which lakes are actually improving: multi-year EPA monitoring trends, the named recoveries still in progress, and what it takes to move the readings.
Data source
Impairment data from the EPA ATTAINS (Assessment and TMDL Tracking and Implementation System) public dataset. Assessment unit IDs are matched to LakeQuality lakes by name and proximity; some lakes may not appear here if their ATTAINS name doesn't match our naming convention. For an official query, consult .