Lake Helena Center Deep
Lewis and Clark County, MontanaView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- Impaired · Metals (other than mercury)
- Limited data
Lake Helena Center Deep in Lewis and Clark County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 5.6 ft visibility.
- Clarity
- 5.6 ft
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Stays near Lake Helena Center Deep
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Watch Lake Helena Center Deep’s letter
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Why Lake Helena Center Deep has no grade
Lake Helena Center Deep has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Lake Helena Center Deep is Not Rated — not an F. Its 5.6-foot median from 5 readings collected 2026 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by Montana DEQ and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Lake Helena Center Deep is a lake in Lewis and Clark County, Montana.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2026-06-16. Grade methodology: LakeQuality methodology.
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Lake Helena Center Deep is listed impaired under Clean Water Act §303(d) (IR 4A) for metals (other than mercury), nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Water quality measurements for Lake Helena Center Deep
These readings exist but are not enough for an A–F grade — see why.
Murky, only visible to about 5.6 ft. TSI 52.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.6 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 52 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Fishing Lake Helena Center Deep
EPA Impairment Status
Lake Helena Center Deep is officially listed as impaired under Clean Water Act §303(d) in the 2021 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MT41I007_010 · Official waterbody report · Matched by proximity (0.47 km)
Graded lakes near Lake Helena Center Deep
Lake Helena Center Deep has no grade, but these lakes within a short drive do.
Nearby Lakes in Lewis and Clark County
Frequently asked questions about Lake Helena Center Deep
Where is Lake Helena Center Deep?
- Lake Helena Center Deep is a lake in Lewis and Clark County, Montana. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Lake Helena Center Deep?
- Lake Helena Center Deep in Lewis and Clark County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 5.6 ft visibility.
Is Lake Helena Center Deep safe to swim in?
- The letter is not a swimming clearance. Lake Helena Center Deep is listed impaired under Clean Water Act §303(d) (IR 4A) for metals (other than mercury), nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Explore Lake Helena Center Deep across LakeQuality
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Where this data comes from
5 measurements from 1 monitoring station, 2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Montana DEQ WQPB
MDEQ_WQ_WQX5 samples · 2026
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database