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Federal water data

County water report

Nassau County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Nassau County, Florida.

Water grade

B

Water score

62.6

State rank

#30

of 66

Health violations

3

EPA SDWIS, 5-year lookback

Watershed impaired

27.9%

204 water bodies assessed

Monitoring sites

112

40,422 recent measurements

Live streamflow

No gauge

Primary USGS station not mapped

Water at a glance

Key Water Indicators for Nassau County

EPA SDWIS

Safety Grade

B

Score: 62.6 / 100

EPA SDWIS

Active Violations

3

5-year health-based lookback

EPA ATTAINS

Watershed Health

28% impaired

204 bodies assessed

USGS NWIS

Streamflow Snapshot

No gauge

Primary USGS gauge not mapped

EPA WQP

Monitoring Sites

112

40,422 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

B

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

62.6/100

Health violations

3

Health-based violations

Violations per 100K served

4.9

Population-normalized SDWIS rate

Editorial analysis

Understanding Nassau County’s Water

Drinking Water Quality Overview

EPA SDWIS

Nassau County earns a B grade for drinking water quality, scoring 62.6 out of 100. Over the past five years, EPA SDWIS records 3 health-based violations — a small cluster that warrants attention.

Watershed Conditions

EPA ATTAINS

Under the Clean Water Act §303(d), EPA ATTAINS tracks whether waterways meet quality standards for drinking, recreation, and aquatic life (reporting cycle: 2022). A notable 27.9% of assessed waterways carry an impairment designation (57 of 204 water bodies) across Nassau County's watersheds. The leading impairment causes are mercury in fish tissue and iron. Impairment does not mean tap water is unsafe — it measures ambient waterway conditions upstream of treatment, not finished drinking water.

Monitoring Network

EPA WQP

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. Nassau County has extensive coverage with 112 active monitoring sites with 40,422 recent measurements on record. Predominant monitoring categories include physical and inorganics, minor, metals. More monitoring sites generally indicate greater scientific attention to local water conditions — and provide the baseline data that regulators use to set future impairment listings.

Editorial advisory

What the data suggests for Nassau County

Water Verdict

Nassau County, Florida receives a fair water quality assessment with a grade of B and a score of 62.6 out of 100. The water supply meets baseline federal standards, but there may be periods of elevated contaminant levels or infrastructure concerns worth monitoring. Separately, EPA ATTAINS assessments cover 204 water bodies in the county's watershed, with 27.9% listed as impaired under the Clean Water Act — a source-water measure that is tracked independently of tap-water compliance.

Violation Context

EPA SDWIS records for Nassau County, Florida show 3 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 4.9 violations per 100,000 people served, this rate is moderate and suggests recurring water quality challenges. This compliance record sits alongside an unusually deep monitoring archive: 40,422 water-quality results have been logged across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Tap water in Nassau County scores well above average for drinking-water safety. Nassau County's drinking-water compliance score is 62.6 out of 100. With 3 recorded health violations, the water supply is generally reliable. The violation rate for Nassau County is 4.9 per 100,000 people served. Households with infants, pregnant individuals, or immunocompromised members may want to use an NSF 53-certified pitcher filter as a low-cost precaution. Mercury in Fish Tissue is the leading impairment cause in Nassau County's watershed. With 112 active water-quality monitoring sites in Nassau County, data coverage is strong.

Regional Context

Nassau County has better water quality than the average county in Florida. Its water score is 6.6 points higher than the state average, indicating stronger water system performance relative to neighboring counties.

Advisory text summarizes county-level public records and is not a replacement for your utility's current Consumer Confidence Report or direct local notices.

Contaminants & Resources

Key issues flagged in Nassau County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Mercury (fish tissue)

    Impairment cause per EPA Clean Water Act §303(d) assessment

  • 2

    Iron

    Impairment cause per EPA Clean Water Act §303(d) assessment

  • 3

    pH imbalance

    Impairment cause per EPA Clean Water Act §303(d) assessment

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Nassau County

EPA How's My Waterway

Interactive watershed health data for Nassau County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Nassau County

Consumer Confidence Reports (FL)

Annual water quality reports from utilities in Florida

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

27.9%

57 of 204 assessed

Some impairment

Top Impairment Causes

  • 1

    MERCURY IN FISH TISSUE

  • 2

    IRON

  • 3

    PH

Source: EPA ATTAINS · Reporting cycle 2022

Impairment is determined under the Clean Water Act §303(d): a water body is impaired when it fails to meet state-defined quality standards for designated uses (drinking, recreation, aquatic life). Assessment coverage varies by state; counties without assessed water bodies are not shown.

Past 5 years

Water Quality Monitoring

Monitoring Sites

112

Active in the past 5 years

Measurements Recorded

40K

40,422 total readings

Most Measured

  • Physical
  • Inorganics, Minor, Metals
  • Nutrient

Categories measured most frequently

Data from the EPA Water Quality Portal (WQP), aggregating monitoring records from federal, state, and tribal sources. Each measurement represents a single sample analyzed for a specific characteristic (e.g., E. coli, pH, dissolved oxygen, nitrogen).

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Water Cost Estimate

3

3 people  ·  ~225 gal/day

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for Nassau County:C — Moderate

Some violations or watershed impairment detected.

Estimates use the national average residential water rate ($0.0068/gal, EPA/AWWA 2023) and EPA WaterSense per-person consumption baseline (75 gal/person/day). Actual bills vary by utility, usage tier, and local infrastructure fees. For informational purposes only.

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Frequently Asked Questions

What is the water quality in Nassau County, Florida?
Nassau County, Florida has a drinking-water quality grade of B with a score of 62.6/100, based on EPA SDWIS compliance data. The county has 3 health-based drinking water violations over the past 5 years. Watershed health, monitoring records, and streamflow snapshots are reported separately on this page.
Are there any water violations in Nassau County?
Nassau County has 3 health-based drinking water violations recorded by the EPA over the past 5 years. Health-based violations indicate instances where contaminant levels exceeded EPA Maximum Contaminant Levels (MCLs). Violations may have been resolved — check with your local water utility for current status.
How healthy are the watersheds in Nassau County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 27.9% of Nassau County's 204 assessed water bodies are classified as impaired (57 impaired). The top reported causes are MERCURY IN FISH TISSUE, IRON, PH. Impairment means the water body fails to meet state quality standards for at least one designated use — drinking water source, recreation, aquatic life, or fish consumption. Note: watershed impairment doesn't always translate to tap-water issues; treatment plants can remove most regulated contaminants.
How much water-quality monitoring happens in Nassau County?
EPA's Water Quality Portal records 40,422 measurements from 112 monitoring sites in Nassau County over the past five years. The most frequently measured characteristic groups are Physical, Inorganics, Minor, Metals, Nutrient. Each measurement is a single sample analyzed for one characteristic (E. coli, pH, dissolved oxygen, etc.). High monitoring density means more scientific evidence behind any reported signal — it does not by itself indicate water quality.
How does Nassau County water compare to the Florida average?
Nassau County's SDWIS water quality score of 62.6/100 is higher than the Florida state average of 56.0. The average water quality grade across Florida is D, based on data from 66 counties with available SDWIS data.
Is tap water safe to drink in Nassau County?
Based on EPA SDWIS data, Nassau County has a water quality grade of B (62.6/100). This indicates good to excellent water quality with strong SDWIS compliance. The grade speaks to the public water system, not the watershed — for watershed-level concerns, see the Watershed Health zone. For the most up-to-date information, contact your local water utility or review your Consumer Confidence Report (CCR).
Does Nassau County have clean drinking water?
Nassau County has 3 health-based drinking water violations according to EPA records. With a water quality score of 62.6/100 and grade B, the county's drinking water has had some compliance issues but continues to be monitored. Note: drinking-water compliance speaks to the public water system, not necessarily to the watershed itself — check the Watershed Health zone for ATTAINS §303(d) data.
How does Nassau County rank for water quality in Florida?
Nassau County ranks #30 out of 66 counties in Florida by SDWIS water quality score (1 = best). With a score of 62.6/100, it falls in the middle third of counties statewide. The ranking reflects EPA SDWIS compliance only — not watershed impairment, monitoring density, or streamflow, which are tracked separately on this page.

Counties with Similar Water Quality

Volusia County

Florida

C

61.2

Water score

Lee County

Florida

B

64.2

Water score

Citrus County

Florida

C

60.8

Water score

Data Sources

Drinking-water compliance data from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. Scores reflect compliance history and health-based violation counts.

Watershed health and impaired-waterway data from the EPA ATTAINS Clean Water Act §303(d) assessments, state-reported and EPA-finalized.

Water-quality monitoring counts from the EPA Water Quality Portal (WQP), federated USGS, EPA, and state agency sampling records over a rolling 5-year window.

Disclaimer: This data is informational only. It is not health, legal, or professional advice. For concerns about your specific water supply, contact your local water utility.

By Evan Brooks, Data EditorUpdated Reviewed by Evan Brooks, Data Editor

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