Connecticut lake · state assessment record
Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield)
Assessment decisions reported by Connecticut to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2014 reporting cycle.
- 1,595
- Assessed acres
- Lake, Freshwater
- Water type
This waterbody in one line
Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield), a lake in Connecticut, is assessed as not supporting one or more designated uses, with 6 listed impairment causes in the state's most recent Integrated Report cycle (2014). By assessed acreage it sits among the largest 5% by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (6 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as fully supporting. Fish consumption is assessed as not supporting.
- Not Supporting
- overall status
- P96
- Assessed size nationally
- P1
- Shorter cause list
- Fully Supporting
- aquatic life
Assessment verdicts are the state agency's decisions as reported to EPA ATTAINS; PlainLakes renders them without modification.
A composite of this record's EPA ATTAINS designated-use verdicts, filed impairment count, and assessment currency, weighted and benchmarked against the national corpus of assessed active waterbodies. This is a water-quality standing, not a human-recreation or property-value judgment, and dimensions with no filed verdict drop out rather than count against the score.
Where Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield) stands in the filed register
Paragraphs are selected by this unit's percentiles and use matrix: different lakes lead with different dimensions. Figures are ATTAINS / portal register arithmetic, not advice.
The signature stat: in-state cause rank
Inside Connecticut, cause-list rank is the local separator: Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield) is 1 of 97 indexed units by listed-cause count, toward the top of that state's filed lists.
Longer than most cause lists
6 listed causes puts this unit above 99% of assessed lake-type records by list length. Treat that as a coding-and-sampling signal: states that split pollutants finely mint longer lists without proving worse water.
Large assessed unit
At 1,595 acres, Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield) clears the upper tercile of assessed lake-type units with an area on file (1,613 still larger). Size comparisons use the portal's deduplicated lake ranking population, not raw ATTAINS row counts.
A split ruling across uses
This record splits: Not Supporting on fish consumption, recreation, Fully Supporting on aquatic life. The divergence is inside the designated-use matrix, not a single all-or-nothing label.
Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield): Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield). Read the listed causes and any cleanup actions filed beside them before treating the overall status tile as a finished restoration story.
According to the U.S. Environmental Protection Agency's ATTAINS program, Connecticut carries 182 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield) without modification. See our methodology for reporting-unit limits and gauge linking rules.
The record
Designated-use assessments
Fully Supporting and Not Supporting are the state's definitive verdicts; other entries mean the use was not conclusively assessed in this cycle. Connecticut filed its own confidence on the 3 definitive verdicts it rated: Good. That rating is the filer's, in EPA's own field, and EPA publishes no definition of the four words it offers.
| Designated use | Group | Verdict |
|---|---|---|
| Fish Consumption | Fish-consumption or fishery | Not Supporting Filer confidence: Good |
| Habitat for Fish, Other Aquatic Life and Wildlife | Aquatic-life or related | Fully Supporting Filer confidence: Good |
| Recreation | Recreation | Not Supporting Filer confidence: Good |
The record
Listed impairment causes
Causes the state listed as impairing designated uses of this lake, with the cycle each was first listed and the Clean Water Act action recorded against it.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| Algae | Recreation | 1998 | TMDL priority: Low |
| Chlorophyll-a | Recreation | 1998 | TMDL priority: Low |
| Floating Debris | Recreation | 1998 | TMDL priority: Low |
| Nutrients | Recreation | 1998 | TMDL priority: Low |
| Polychlorinated Biphenyls (PCBs) | Fish Consumption | 1998 | Action recorded (type not published) |
| Taste | Recreation | 1998 | TMDL priority: Low |
Probable sources named by the state
Each source below is listed under the cause the state filed it against, and carries the word the state filed with it — confirmed, or suspected.
- Algae
- Agriculture (suspected) Municipal Point Source Discharges (suspected) Non-Point Source (suspected) Unspecified Urban Stormwater (suspected)
- Chlorophyll-a
- Agriculture (suspected) Municipal Point Source Discharges (suspected) Non-Point Source (suspected) Unspecified Urban Stormwater (suspected)
- Floating Debris
- Non-Point Source (suspected) Unspecified Urban Stormwater (suspected)
- Nutrients
- Agriculture (suspected) Municipal Point Source Discharges (suspected) Non-Point Source (suspected) Unspecified Urban Stormwater (suspected)
- Polychlorinated Biphenyls (PCBs)
- Contaminated Sediments (suspected) Industrial Point Source Discharge (suspected) Sources Outside State Jurisdiction or Borders (suspected)
- Taste
- Agriculture (suspected) Municipal Point Source Discharges (suspected) Non-Point Source (suspected) Unspecified Urban Stormwater (suspected)
Reading the record
Where Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield) sits among peers
5 of 6 Connecticut lakes assessed this deeply also came out mixed
Connecticut ruled definitively on 3 designated uses at Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield) and found 2 of 3 not supported. The dataset shows 6 Connecticut lakes judged to that same depth.
Connecticut's assessed lakes are most often judged on 2 uses; this one was judged on 3.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 42 | 53 | 0 | 0 | 0 |
| Mixed | Not possible | 11 | 5 (this record) | 1 | 0 |
| None supported | 16 | 10 | 1 | 0 | 0 |
Ringed cell: Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield). Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield) is one of 182 lake-type waterbodies reported to EPA from Connecticut, and one of 97 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 1,595 assessed acres it ranks 1,614th by assessed size among the 38,628 lakes the dataset carries an area for, counting a state’s repeated filings of one water once, behind 1,613 lakes with a larger one.
In context
Where Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield) sits nationally
Assessed size among U.S. lakes
Distribution of assessed acreage across ATTAINS lakes filed with an area, counting a state’s repeated filings of one water once
1,595 Top 4% larger than 96% of 38,628 lakes
lakes the dataset carries an area for, counting a state’s repeated filings of one water once, bucketed by value
Source EPA ATTAINS · Reporting cycles 1987–2026
Listed causes vs waterbodies carrying a verdict
How many impairment causes U.S. waterbodies with a reported verdict carry
6 Longer than most more listed causes than 99% of 23,610 waterbodies carrying a verdict
named waterbodies carrying a verdict, bucketed by value
Source EPA ATTAINS · Reporting cycles 1987–2026
In both charts each bar is a band and taller bars hold more waterbodies; the dashed line and filled bar mark Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield). Hover or tap any bar for its full count and share.
In context
Connecticut context
ATTAINS carries 182 lake-type waterbodies in Connecticut, 44 assessed as not supporting at least one use and 95 fully supporting. Among the 97 indexed units there, Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield) ranks 1st by listed-cause count (6 listed causes) and 2nd by assessed size among the 97 with an area filed; it sits in the not-supporting set (44 statewide) . Its listed causes include Algae, Chlorophyll-a, Nutrients, and Polychlorinated Biphenyls (PCBs), which also appear among Connecticut's most-filed impairment causes (led by Algae). It also lists Floating Debris and Taste, outside that top-five list.
| Other large assessed lakes in Connecticut | Assessed acres |
|---|---|
| Candlewood, Lake (New Fairfield/Danbury/Sherman/New Milford) Fully Supporting | 5,086 |
| Bantam Lake (Litchfield/Morris) Not Supporting | 955 |
| Colebrook River (Reservoir) Lake (Colebrook) Not Assessed | 852 |
| Pachaug Pond (Griswold) Fully Supporting | 837 |
| Saugatuck Reservoir (Weston/Easton/Redding) Fully Supporting | 823 |
| Waramaug, Lake (Kent/Warren/Washington) Not Supporting | 641 |
Peers near Lillinonah, Lake (Newtown/Southbury/Bridgewater/Brookfield)'s size or cause load
Similar assessed acres
Nearest filed extents (1,595 acres here).
- Sacandaga Lake · 1,595 acres · NY
- Tallapoosa River (Yates Lake) · 1,596 acres · AL
- Wallowa Lake · 1,592 acres · OR
- Molunkus Stream · 1,591 acres · ME
Similar cause load
Nearest listed-cause counts (6 here). Peers already in the acreage column are omitted.
- Allegan Lake · 6 causes · MI
- Almonesson Creek · 6 causes · NJ
- Ambrose Brook (below Lake Nelson) · 6 causes · NJ
- Assunpink Ck (below Shipetaukin Ck) · 6 causes · NJ
What to do with this record
- The fish-consumption use is assessed as not supporting. Before eating fish from this lake, check your state fish-advisory program for species-specific meal limits. Consumption status guide
- Impairment listings follow the Clean Water Act 303(d) process; a listing is a regulatory finding, not a closure notice. 303(d) explained
PlainLakes renders state assessment decisions and federal gauge observations without modification. It does not issue advisories.
Assessment decisions on this page are rendered directly from state Integrated Report records in EPA's ATTAINS system; gauge figures are daily-value observations from the USGS National Water Information System, no number is typed in by an editor. Overall status, use verdicts, and causes are the state's reported decisions for assessment unit CT6000-00-5+L1_01. Counts and percentiles are computed across all lake-type records PlainLakes ingests from ATTAINS. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-08-17. Primary sources: EPA ATTAINS and USGS National Water Information System.