Massachusetts lake · state assessment record
Cambridge Reservoir
Assessment decisions reported by Massachusetts to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2026 reporting cycle, a cycle that is open for public comment.
- 531
- Assessed acres
- Lake, Freshwater
- Water type
This waterbody in one line
Cambridge Reservoir, a lake in Massachusetts, is assessed as not supporting one or more designated uses, with one listed impairment cause in the state's most recent Integrated Report cycle (2026), a cycle that is open for public comment. By assessed acreage it sits among the largest 10% by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (one listed cause vs 23,610 assessed lakes). Aquatic life is assessed as not supporting.
- Not Supporting
- overall status
- P91
- Assessed size nationally
- P20
- 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 Cambridge Reservoir 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: assessed size
The number that most separates Cambridge Reservoir nationally is assessed size: 531 acres, larger than 91% of the 38,628 lake-type units with an area on file.
The uses disagree
This record splits: Not Supporting on aquatic life, Fully Supporting on recreation. The divergence is inside the designated-use matrix, not a single all-or-nothing label.
Cambridge Reservoir: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Cambridge Reservoir. Read the listed causes and any cleanup actions filed beside them before treating the overall status tile as a finished restoration story.
Overall status: not supporting
The filer's overall status for Cambridge Reservoir is Not Supporting. That tile summarizes the assessment unit; the designated-use rows and cause list are the evidence behind it.
Typical cause-list length
1 listed cause is a middle-tercile list length among assessed lake-type units. Look to IR category and use outcomes for the distinctive reading.
According to the U.S. Environmental Protection Agency's ATTAINS program, Massachusetts carries 1,191 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Cambridge Reservoir 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. For the definitive verdicts on this record, Massachusetts filed the assessment basis as Monitored Data. Those are EPA's own words, not PlainLakes' summary of them.
| Designated use | Group | Verdict |
|---|---|---|
| Aesthetic | Other | Fully Supporting |
| Fish, Other Aquatic Life and Wildlife | Aquatic-life or related | Not Supporting |
| Primary Contact Recreation | Recreation | Fully Supporting |
| Secondary Contact Recreation | Recreation | Fully Supporting |
| Fish Consumption | Fish-consumption or fishery | Not Assessed |
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 |
|---|---|---|---|
| Chloride | Fish, Other Aquatic Life and Wildlife | 2016 | 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.
- Chloride
- Contaminated Groundwater (confirmed) Highway/Road/Bridge Runoff (Non-Construction Related) (confirmed) Impervious Surface/Parking Lot Runoff (confirmed) Salt Storage Sites (confirmed) Upstream Source (confirmed)
Reading the record
Where Cambridge Reservoir sits among peers
19% of Massachusetts's lakes assessed this deeply also came out mixed
Massachusetts ruled definitively on 4 designated uses at Cambridge Reservoir and found 1 of 4 not supported. The dataset shows 159 Massachusetts lakes judged to that same depth.
Massachusetts's assessed lakes are most often judged on 1 use; this one was judged on 4.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 15 | 14 | 11 | 0 | 0 |
| Mixed | Not possible | 5 | 19 | 31 (this record) | 12 |
| None supported | 283 | 60 | 91 | 128 | 49 |
Ringed cell: Cambridge Reservoir. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Cambridge Reservoir is one of 1,191 lake-type waterbodies reported to EPA from Massachusetts, and one of 678 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 531 assessed acres it ranks 3,582nd 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 3,581 lakes with a larger one.
Still unfiled
The state has not yet filed a definitive fish-consumption verdict for this record; that field populates when it reports it in a future Integrated Report cycle.
In context
Where Cambridge Reservoir 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
531 Top 9% larger than 91% 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
1 Longer than most more listed causes than 49% 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 Cambridge Reservoir. Hover or tap any bar for its full count and share.
In context
Massachusetts context
ATTAINS carries 1,191 lake-type waterbodies in Massachusetts, 678 assessed as not supporting at least one use and 40 fully supporting. Among the 678 indexed units there, Cambridge Reservoir ranks 380th by listed-cause count (one listed cause) and 20th by assessed size among the 678 with an area filed; it sits in the not-supporting set (678 statewide) . Its listed causes (Chloride) sit outside Massachusetts's top-five list, which is led by Mercury in Fish Tissue.
| Other large assessed lakes in Massachusetts | Assessed acres |
|---|---|
| Quabbin Reservoir Not Supporting | 24,010 |
| Wachusett Reservoir Not Supporting | 3,962 |
| Assawompset Pond Not Assessed | 2,034 |
| North Watuppa Pond Not Supporting | 1,728 |
| Long Pond Not Supporting | 1,728 |
| South Watuppa Pond Not Supporting | 1,473 |
Peers near Cambridge Reservoir's size or cause load
Similar assessed acres
Nearest filed extents (531 acres here).
- Island Lake (Crescent Lake NWR) · 531 acres · NE
- Swepco Lake · 531 acres · AR
- Northeast Emeralda Marsh Conservation Area · 531 acres · FL
- Sunset Lake · 531 acres · MI
Similar cause load
Nearest listed-cause counts (1 here). Peers already in the acreage column are omitted.
- Aaron · 1 causes · MN
- Abbotts Creek (including Lexington-Thomasville Water Supply Reservoir at normal reservoir elevation, Tom-A-Lex Lake) · 1 causes · NC
- Abeniki Lake · 1 causes · NH
- Academy Brook II Dam · 1 causes · NH
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 MA72014. 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.