Oregon reservoir · state assessment record
Cottage Grove Lake
Assessment decisions reported by Oregon to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2012 reporting cycle. Both cleanup plans below were established by EPA rather than by Oregon.
- 1,026
- Assessed acres
- Lake / Reservoir / Pond
- Water type
- 776.8 ft
- Water Surface Elevation (provisional)
This waterbody in one line
Cottage Grove Lake, a reservoir in Oregon, is assessed as not supporting one or more designated uses, with 2 listed impairment causes in the state's most recent Integrated Report cycle (2012). By assessed acreage it sits among the largest 10% 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. Oregon assesses fishing as not supported; it reported no verdict on fish consumption itself. A USGS gauge tracks its water surface elevation daily.
- Not Supporting
- overall status
- P94
- 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.
Reading Cottage Grove Lake's filed record
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 Cottage Grove Lake nationally is assessed size: 1,026 acres, larger than 94% of the 38,628 lake-type units with an area on file.
Every ruled-on use is not supporting
On the uses this filer ruled on, fish consumption, aquatic life, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Cottage Grove Lake: Category 4A reading
Category 4A means a TMDL (or equivalent) is already approved for the impairment on Cottage Grove Lake. 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.
Overall status: not supporting
The filer's overall status for Cottage Grove Lake is Not Supporting. That tile summarizes the assessment unit; the designated-use rows and cause list are the evidence behind it.
According to the U.S. Environmental Protection Agency's ATTAINS program, Oregon carries 1,431 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Cottage Grove Lake 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.
| Designated use | Group | Verdict |
|---|---|---|
| Fish and Aquatic Life | Aquatic-life or related | Not Supporting |
| Fishing | Fish-consumption or fishery | Not Supporting |
| Private Domestic Water Supply | Drinking-water supply designation | Not Supporting |
| Public Domestic Water Supply | Drinking-water supply designation | Not Supporting |
| Aesthetic Quality | Other | Not Assessed |
| Boating | Recreation | Not Assessed |
| Hydropower | Other | Not Assessed |
| Industrial Water Supply | Other | Not Assessed |
| Irrigation | Other | Not Assessed |
| Livestock Watering | Other | Not Assessed |
| Water Contact Recreation | Recreation | Not Assessed |
| Wildlife and Hunting | Other | Not Assessed |
The record
Listed impairment causes
Causes the state listed as impairing designated uses of this reservoir, with the cycle each was first listed and the Clean Water Act action recorded against it.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| Mercury | Fish and Aquatic Life | 2012 | TMDL established by EPA |
| Methylmercury | Fishing, Private Domestic Water Supply, Public Domestic Water Supply | 2012 | TMDL established by EPA |
Reading the record
Cottage Grove Lake: Category 4A reading
4A Category 4A: impaired, TMDL completed
Oregon 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
Cottage Grove Lake is one of 1,431 lake-type waterbodies reported to EPA from Oregon, and one of 167 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 1,026 assessed acres it ranks 2,218th 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 2,217 lakes with a larger one.
Water level
A USGS gauge tracks this reservoir's water surface elevation daily, and the latest reading is 4.05 ft below the reading 30 days earlier, against a 365-day observed range of 38.1 ft. The state has not yet filed a definitive recreation verdict for this record; that field populates when it reports it in a future Integrated Report cycle.
Water level: 365-day record
Daily water surface elevation values, feet above the National Geodetic Vertical Datum of 1929 (NGVD 29), from USGS gauge 14153000 (Cottage Grove Lake Nr Cottage Grove, or), shown weekly. Readings are daily-batch snapshots, not real-time conditions. Each daily value is a single reading taken at 24:00, not a daily mean. It is the only daily statistic USGS files for this gauge.
- Latest reading
- 776.8 ft 4.050000000000068ft vs 30 days earlier
- 2026-08-15 · Provisional, subject to USGS revision
Water level: 365-day record
Subscribe to water level updates for Cottage Grove Lake (RSS)
53 of the 364 daily values in this window (15%) are provisional and subject to USGS revision; USGS has approved this gauge's record through 2026-06-22.
Full gauge record: USGS monitoring location 14153000
In context
Where Cottage Grove Lake 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
1,026 Top 6% larger than 94% 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 Cottage Grove Lake. Hover or tap any bar for its full count and share.
In context
Oregon context
ATTAINS carries 1,431 lake-type waterbodies in Oregon, 165 assessed as not supporting at least one use and 14 fully supporting. Among the 167 indexed units there, Cottage Grove Lake ranks 70th by listed-cause count (2 listed causes) and 65th by assessed size among the 167 with an area filed; it sits in the not-supporting set (165 statewide) . Its listed causes include Methylmercury, which also appears among Oregon's most-filed impairment causes (led by Temperature). It also lists Mercury, outside that top-five list.
| Other large assessed lakes in Oregon | Assessed acres |
|---|---|
| Goose Lake Not reported | 93,152 |
| Malheur Slough Not Supporting | 73,544 |
| Upper Klamath Lake Not Supporting | 62,130 |
| Columbia River Not Supporting | 55,630 |
| Lake Abert Not Assessed | 44,751 |
| Summer Lake Not reported | 31,606 |
Peers near Cottage Grove Lake's size or cause load
Similar assessed acres
Nearest filed extents (1,026 acres here).
- Lake Bogue Homo · 1,026 acres · MS
- Lake Concordia · 1,025 acres · LA
- Coddle Creek, including water supply reservoir for Concord) · 1,027 acres · NC
- Upper Eau Claire Lake · 1,024 acres · WI
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
- The listing here is on a fishery use, not on fish consumption, and this state reported no consumption verdict for this reservoir. Your state fish-advisory program is the source for whether the catch is safe to eat. Consumption status guide
- Water levels shown are daily snapshots. Seasonal drawdown and datum conventions matter when comparing levels. How to read level data
- 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 OR_LK_1709000203_02_100706. 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.