Not safe for swimming (10 of 11 assessed stretches)
Is it safe to swim here?
North Carolina · waterway · Upper Dan basin
South Mayo River: what state assessments show
Not safe for swimming. Fish here are under a consumption advisory. Does not support healthy aquatic life.
Official state determinations under the Clean Water Act — about the waterway, not measurements taken today.
South Mayo River in the Upper Dan basin is tracked by the state as 11 separately assessed stretches (most recent cycle: 2022). Below is every designated-use determination on record — and what hasn't been assessed.
Designated uses
Fish here are under a consumption advisory (3 of 11 assessed stretches)
Can I eat fish caught here?
Does not support healthy aquatic life (1 of 11 assessed stretches)
Can fish and aquatic insects live here?
Never assessed — condition unknown
Can this water be used as a drinking-water supply?
A use the state didn't report is omitted rather than shown as passing. "Never assessed" means unknown — never clean.
Listed causes
- escherichia coli (e. coli) (pathogens)
- temperature
- mercury in fish tissue (mercury)
A listed cause names what the assessment found in the water. It is not an attribution to any specific facility or source.
Assessed stretches
The state tracks this waterway as 11 assessment units — a stretch can fail a standard while another meets it.
Assessment unit IDs (11)
VAW-L43R_SMR02A02 · VAW-L43R_SMR03A02 · VAW-L43R_SMR03B02 · VAW-L43R_SMR04A00 · VAW-L43R_SMR05A00 · VAW-L43R_SMR06A00 · VAW-L43R_SMR07A00 · VAW-L45R_SMR01A00 · VAW-L45R_SMR02A00 · VAW-L45R_SMR03A00 · VAW-L45R_SMR04A14
What the record doesn’t establish
- What today's water looks like — assessments are determinations made on multi-year cycles, not live measurements.
Common questions
Is it safe to swim in South Mayo River?
The state has determined South Mayo River is not considered safe for swimming (10 of 11 assessed stretches). That is an official Clean Water Act determination about the waterway, not a measurement taken today.
Can you eat fish caught in South Mayo River?
The state has determined fish caught in South Mayo River are under a consumption advisory (3 of 11 assessed stretches) — it doesn't meet standards for eating the fish caught in it.
Why is South Mayo River listed as impaired?
State assessments list: escherichia coli (e. coli), temperature, mercury in fish tissue. A listed cause names the problem the assessment found — it does not attribute it to any specific source.
Sources
| Dataset | Agency version | Retrieved |
|---|---|---|
| EPA/state ATTAINS waterway assessments | ATTAINS_Assessment ArcGIS snapshot (gispub.epa.gov) | 2026-08-15 |
| ATTAINS waterway geometry | ATTAINS_Assessment ArcGIS lines + areas (gispub.epa.gov) | 2026-08-16 |
| USGS watershed boundaries | USGS WBD via National Map MapServer | 2026-08-15 |
Records lag their agencies' refresh cycles — a recent change may not appear yet. Absence from a dataset is absence of a record, never evidence that water is clean.
Also in the Upper Dan basin
Go deeper
Search an address near South Mayo River to see how it connects — what drains toward it, monitoring-station samples, and permitted operations in its watershed.
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