County water report

Fairfax County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Fairfax County, Virginia.

Water grade

Water score

86.0

State rank

#13

of 95

Health violations

EPA SDWIS, 5-year lookback

Watershed impaired

55.1%

178 water bodies assessed

Monitoring sites

288

81,734 recent measurements

Live streamflow

82%

DIFFICULT RUN NEAR GREAT FALLS, VA

Water at a glance

Key Water Indicators for Fairfax County

EPA SDWIS

Safety Grade

Score: 86.0 / 100

EPA SDWIS

Active Violations

5-year health-based lookback

EPA ATTAINS

Watershed Health

55% impaired

178 bodies assessed

USGS NWIS

Streamflow Snapshot

82% of mean

DIFFICULT RUN NEAR GREAT FALLS, VA

EPA WQP

Monitoring Sites

288

81,734 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

86.0/100

Health violations

Health-based violations

Violations per 100K served

0.0

Population-normalized SDWIS rate

Data center water stress

Fairfax County has 50 facilities in the DCWSI dataset.

ByCounty's DCWSI ranks this county #1 nationally by combining its water score with mapped data center density.

DCWSI

91.1

0-100 index

Facility count

98.8 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

+36.0

Compared with US county median

Named operators

AWS

Mapped facilities

8100 Boone Boulevard
Digital Realty
OSM
AMAZON DATA SERVICES INC - DCA-64
SPRINGFIELD · Amazon Data Services
EPA ECHO
AMAZON DATA SERVICES INC - IAD-134/135/136
CHANTILLY · Amazon Data Services
EPA ECHO
AMAZON DATA SERVICES INC - IAD-165/166/167/168/613
HERNDON · Amazon Data Services
EPA ECHO
AMAZON DATA SERVICES INC - IAD-500/501
HERNDON · Amazon Data Services
EPA ECHO
AMAZON DATA SERVICES, INC. IAD-1 IAD-9
CHANTILLY · Amazon Data Services
EPA ECHO

44 more mapped facilities included in the county score.

See the Fairfax County data-center report Review methodology

Data Center Water Budget Calculator

Estimate daily water use for a hypothetical facility in Fairfax County.

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayHigh Impact

Your facility would use 241.0% of this county's industrial water baseline. Verify water rights and long-term drought projections before committing.

241.0% of county industrial baseline

Based on USGS 2020 water-use data and EPA-standard cooling intensity constants. Not a substitute for site-specific water rights analysis.

Editorial analysis

Understanding Fairfax County’s Water

Drinking Water Quality Overview

EPA SDWIS

Fairfax County earns an A grade for drinking water quality, scoring 86.0 out of 100. EPA's Safe Drinking Water Information System (SDWIS) records zero health-based violations over the past five years — a strong compliance signal for a heavily urbanized county.

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 substantial 55.1% of assessed waterways are impaired (98 of 178 water bodies) across Fairfax County's watersheds. The leading impairment causes are escherichia coli (e. coli) and benthic macroinvertebrates bioassessments. Impairment does not mean tap water is unsafe — it measures ambient waterway conditions upstream of treatment, not finished drinking water.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T14:15:00.000-04:00) puts DIFFICULT RUN at 52.0 cfs — running somewhat below its historical average at 82% of mean. Streamflow is a leading indicator of drought stress, sediment load, and dilution capacity: low flows concentrate pollutants and warm water temperatures, stressing aquatic life and, in surface-water-dependent systems, the source water quality for treatment plants.

Monitoring Network

EPA WQP

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. Fairfax County has extensive coverage with 288 active monitoring sites with 81,734 recent measurements on record. Predominant monitoring categories include physical and nutrient. 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 Fairfax County

Water Verdict

Fairfax County receives an excellent water quality assessment with a grade of A and a score of 86.0 out of 100. The water supply meets or exceeds federal safety standards, and residents can generally drink tap water with confidence.

Violation Context

Fairfax County has recorded zero health-based violations, indicating no recent health-based violations in the reporting period. The violation rate is zero per 100,000 people served, which is the best possible outcome.

Consumer Guidance

The EPA compliance record for Fairfax County shows no recent health-based violations. Fairfax County's drinking-water compliance score is 86.0 out of 100. Watershed monitoring does show E. coli in local surface water — a reminder that treated drinking water and source-water quality are measured separately. Reviewing your utility's annual Consumer Confidence Report each July confirms that treatment is keeping pace with any upstream pressures. With 288 active water-quality monitoring sites in Fairfax County, data coverage is strong. A pipeline streamflow snapshot from the DIFFICULT RUN gauge is also available on this page.

Regional Context

Fairfax County has better water quality than the average county in Virginia. Its water score is 28.3 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 Fairfax County's water environment

Watershed Impairment Causes (EPA ATTAINS)

1
E. coli (bacteria)
Impairment cause per EPA Clean Water Act §303(d) assessment
2
Benthic Macroinvertebrates Bioassessments
Impairment cause per EPA Clean Water Act §303(d) assessment
3
Pcbs in Fish Tissue
Impairment cause per EPA Clean Water Act §303(d) assessment

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Fairfax County

EPA How's My Waterway

Interactive watershed health data for Fairfax County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Fairfax County

Consumer Confidence Reports (VA)

Annual water quality reports from utilities in Virginia

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

55.1%

98 of 178 assessed

Moderate concern

Top Impairment Causes

1
ESCHERICHIA COLI (E. COLI)
2
BENTHIC MACROINVERTEBRATES BIOASSESSMENTS
3
PCBS IN FISH TISSUE

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

288

Active in the past 5 years

Measurements Recorded

82K

81,734 total readings

Most Measured

Physical
Nutrient
Inorganics, Major, Non-metals

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).

Live USGS Streamgage

River & Stream Conditions

Current Discharge

52.0cfs

May 14, 6:15 PM UTC

vs Long-Term Average

82%

Below typical

Primary Streamgage

DIFFICULT RUN NEAR GREAT FALLS, VA

USGS site: 01646000
Drainage area: 57.8 sq mi
Long-term mean: 63.4 cfs

One representative streamgage (the one with the largest drainage area in the county). Many counties have multiple gauges; this view summarizes the primary one. The long-term mean is the full-record annual average; the percent-of-typical value compares the latest reading against that average.

Free tool

Estimate Your Water Costs

Water Cost Estimate

Household size

3 people · ~225 gal/day

Filter type

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for Fairfax 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.

Try the full calculator →

Fairfax County has good water quality

Learn about water restrictions and conservation in your area.

Water Restrictions →

Frequently Asked Questions

What is the water quality in Fairfax County, Virginia?

Fairfax County, Virginia has a drinking-water quality grade of A with a score of 86.0/100, based on EPA SDWIS compliance data. The county has 0 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 Fairfax County?

Fairfax County has 0 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). Zero violations is an excellent record indicating consistent compliance with federal drinking water standards.

How healthy are the watersheds in Fairfax County?

EPA ATTAINS assessments under Clean Water Act §303(d) indicate 55.1% of Fairfax County's 178 assessed water bodies are classified as impaired (98 impaired). The top reported causes are ESCHERICHIA COLI (E. COLI), BENTHIC MACROINVERTEBRATES BIOASSESSMENTS, PCBS IN FISH TISSUE. 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 Fairfax County?

EPA's Water Quality Portal records 81,734 measurements from 288 monitoring sites in Fairfax County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, Inorganics, Major, Non-metals. 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.

What's happening with rivers in Fairfax County right now?

Fairfax County's primary USGS streamgage on the DIFFICULT RUN has a pipeline snapshot of 52 cubic feet per second — 82% of the long-term mean of 63.38 cfs. Flow is within typical range for this gauge. For the latest gauge feed, visit waterdata.usgs.gov.

How does Fairfax County water compare to the Virginia average?

Fairfax County's SDWIS water quality score of 86.0/100 is higher than the Virginia state average of 57.7. The average water quality grade across Virginia is D, based on data from 95 counties with available SDWIS data.

Is tap water safe to drink in Fairfax County?

Based on EPA SDWIS data, Fairfax County has a water quality grade of A (86.0/100). 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 Fairfax County have clean drinking water?

Fairfax County has 0 health-based drinking water violations according to EPA records. With a water quality score of 86.0/100 and grade A, the county's drinking water meets EPA standards with no recorded health violations. 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 Fairfax County rank for water quality in Virginia?

Fairfax County ranks #13 out of 95 counties in Virginia by SDWIS water quality score (1 = best). With a score of 86.0/100, it falls in the top 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

Albemarle County

Virginia

86.0

Water score

Amelia County

Virginia

86.0

Water score

Appomattox County

Virginia

86.0

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.

Live streamflow from the USGS National Water Information System (NWIS), continuous discharge measurements from the largest-drainage gauge in each county, compared against the full-record long-term annual mean.

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 May 14, 2026Reviewed by Evan Brooks, Data Editor

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