Maine lake · state assessment record
Threemile P
Assessment decisions reported by Maine to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2016 reporting cycle.
- 1,162
- Assessed acres
- Lake, Freshwater
- Water type
This waterbody in one line
Threemile P, a lake in Maine, is assessed as not supporting one or more designated uses, with 2 listed impairment causes in the state's most recent Integrated Report cycle (2016). By assessed acreage it sits among the largest 5% by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (2 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as not supporting. Fish consumption is assessed as fully supporting.
- Not Supporting
- overall status
- P95
- Assessed size nationally
- P10
- Shorter cause list
- Not 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 Threemile P 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 Maine, cause-list rank is the local separator: Threemile P is 12 of 302 indexed units by listed-cause count, toward the top of that state's filed lists.
Large assessed unit
At 1,162 acres, Threemile P clears the upper tercile of assessed lake-type units with an area on file (2,045 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 recreation, aquatic life, Fully Supporting on fish consumption. The divergence is inside the designated-use matrix, not a single all-or-nothing label.
Threemile P: Category 4A reading
Category 4A means a TMDL (or equivalent) is already approved for the impairment on Threemile P. The remaining work is implementation and tracking, read the cleanup-standing and cause rows for what the state already committed to address.
Longer than most cause lists
2 listed causes puts this unit above 80% 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.
According to the U.S. Environmental Protection Agency's ATTAINS program, Maine carries 339 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Threemile P 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. Maine filed 2014 as the year this waterbody was last monitored. Maine filed its own confidence on the 10 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 |
|---|---|---|
| Agricultural Supply | Other | Fully Supporting Filer confidence: Good |
| Drinking Water Supply After Disinfection | Drinking-water supply designation | Fully Supporting Filer confidence: Good |
| Fish Consumption | Fish-consumption or fishery | Fully Supporting Filer confidence: Good |
| Fish and Other Aquatic Life | Aquatic-life or related | Not Supporting Filer confidence: Good |
| Fishing | Fish-consumption or fishery | Fully Supporting Filer confidence: Good |
| Hydroelectric Power Generation | Other | Fully Supporting Filer confidence: Good |
| Industrial Process and Cooling Water Supply | Other | Fully Supporting Filer confidence: Good |
| Navigation | Other | Fully Supporting Filer confidence: Good |
| Primary Contact Recreation | Recreation | Not Supporting Filer confidence: Good |
| Secondary Contact Recreation | Recreation | Fully 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 |
|---|---|---|---|
| Phosphorus, Total | Fish and Other Aquatic Life; Primary Contact Recreation | 2000 | TMDL approved |
| Secchi Disk Transparency | Fish and Other Aquatic Life; Primary Contact Recreation | 2000 | TMDL approved |
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.
- Phosphorus, Total
- Crop Production (Non-Irrigated) (suspected) Rural (Residential Areas) (suspected)
- Secchi Disk Transparency
- Crop Production (Non-Irrigated) (suspected) Rural (Residential Areas) (suspected)
Reading the record
Threemile P: Category 4A reading
4A Category 4A: impaired, TMDL completed
Maine filed this assessment unit as Category 4A: impaired, with a pollutant-budget TMDL already completed under 303(d). The listing remains an impairment finding; the plan is on file rather than still awaiting write-up.
Scale and rank
Threemile P is one of 339 lake-type waterbodies reported to EPA from Maine, and one of 302 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 1,162 assessed acres it ranks 2,046th 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 2,045 lakes with a larger one.
In context
Where Threemile P 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
1,162 Top 5% larger than 95% 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
2 Longer than most more listed causes than 80% 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 Threemile P. Hover or tap any bar for its full count and share.
In context
Maine context
ATTAINS carries 339 lake-type waterbodies in Maine, 31 assessed as not supporting at least one use and 272 fully supporting. Among the 302 indexed units there, Threemile P ranks 12th by listed-cause count (2 listed causes) and 145th by assessed size among the 302 with an area filed; it sits in the not-supporting set (31 statewide) . Its listed causes include Phosphorus, Total; and Secchi Disk Transparency, which also appear among Maine's most-filed impairment causes (led by Phosphorus, Total).
| Other large assessed lakes in Maine | Assessed acres |
|---|---|
| Moosehead Lake Fully Supporting | 79,454 |
| Sebago Lake Fully Supporting | 45,624 |
| Spednick Lake Fully Supporting | 35,904 |
| Chesuncook Lake Fully Supporting | 34,926 |
| Mooselookmeguntic Lake Fully Supporting | 32,243 |
| West Grand Lake Fully Supporting | 31,174 |
Peers near Threemile P's size or cause load
Similar assessed acres
Nearest filed extents (1,162 acres here).
- Marengo Bend-Portion within the Louisiana state line · 1,162 acres · LA
- Brandy Branch Reservoir · 1,163 acres · TX
- Beaver Dam Lake · 1,163 acres · WI
- Lake Norris · 1,161 acres · FL
Similar cause load
Nearest listed-cause counts (2 here). Peers already in the acreage column are omitted.
- 12th St. Beach · 2 causes · IL
- 31st St. Beach · 2 causes · IL
- 49th St. Beach · 2 causes · IL
- 57th St. Beach · 2 causes · IL
What to do with this record
- Assessment verdicts are cycle-based, not real-time. For fish-consumption decisions, your state advisory program is the binding source. 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 ME0103000312_5416L. 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.