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County water report

Mason County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Mason County, Washington.

Water grade

C

Water score

62.2

State rank

#21

of 39

Health violations

3

EPA SDWIS, 5-year lookback

Watershed impaired

Not reported

EPA ATTAINS coverage varies by state

Monitoring sites

250

34,637 recent measurements

Live streamflow

48%

SKOKOMISH RIVER NEAR POTLATCH, WA

Water at a glance

Key Water Indicators for Mason County

EPA SDWIS

Safety Grade

C

Score: 62.2 / 100

EPA SDWIS

Active Violations

3

5-year health-based lookback

EPA ATTAINS

Watershed Health

Not reported

Coverage varies by state

USGS NWIS

Streamflow Snapshot

48% of mean

SKOKOMISH RIVER NEAR POTLATCH, WA

EPA WQP

Monitoring Sites

250

34,637 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

C

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

62.2/100

Health violations

3

Health-based violations

Violations per 100K served

5.1

Population-normalized SDWIS rate

Editorial analysis

Understanding Mason County’s Water

Drinking Water Quality Overview

EPA SDWIS

Mason County's drinking water earned a C grade, scoring 62.2 out of 100. Over the past five years, EPA SDWIS records 3 health-based violations — a small cluster that warrants attention.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T11:30:00.000-07:00) puts SKOKOMISH RIVER at 594.0 cfs — well below its long-term average at 48% of mean — low-flow conditions worth noting for water-dependent ecosystems. 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. Mason County has extensive coverage with 250 active monitoring sites with 34,637 recent measurements on record. Predominant monitoring categories include physical and microbiological. 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 Mason County

Water Verdict

Mason County receives a fair water quality assessment with a grade of C and a score of 62.2 out of 100. The water supply meets baseline federal standards, but there may be periods of elevated contaminant levels or infrastructure concerns worth monitoring.

Violation Context

Mason County has recorded 3 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 5.1 violations per 100,000 people served, this rate is moderate and suggests recurring water quality challenges.

Consumer Guidance

Tap water in Mason County meets baseline standards but the compliance record shows room for improvement, with a Grade C rating. Mason County's drinking-water compliance score is 62.2 out of 100. The violation rate for Mason County is 5.1 per 100,000 people served. Residents who are immunocompromised, pregnant, or have young children may benefit from using an NSF 53-certified filter. Contacting your local utility for the current Consumer Confidence Report will confirm which specific violations were recorded and whether they have been resolved. With 250 active water-quality monitoring sites in Mason County, data coverage is strong. A pipeline streamflow snapshot from the SKOKOMISH RIVER gauge is also available on this page.

Regional Context

Mason County has water quality close to the average county in Washington. Its water score is within 2.9 points of the state average, meaning its overall water system performance is broadly representative of Washington as a whole.

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 Mason County's water environment

Official EPA Resources for Mason County

EPA How's My Waterway

Interactive watershed health data for Mason County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Mason County

Consumer Confidence Reports (WA)

Annual water quality reports from utilities in Washington

Past 5 years

Water Quality Monitoring

Monitoring Sites

250

Active in the past 5 years

Measurements Recorded

35K

34,637 total readings

Most Measured

  • Physical
  • Microbiological
  • 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).

Live USGS Streamgage

River & Stream Conditions

Current Discharge

594cfs

May 14, 6:30 PM UTC

vs Long-Term Average

48%

Well below typical

Primary Streamgage

SKOKOMISH RIVER NEAR POTLATCH, WA

USGS site
12061500
Drainage area
227 sq mi
Long-term mean
1,228 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

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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 Mason 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 Mason County, Washington?
Mason County, Washington has a drinking-water quality grade of C with a score of 62.2/100, 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 Mason County?
Mason 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 much water-quality monitoring happens in Mason County?
EPA's Water Quality Portal records 34,637 measurements from 250 monitoring sites in Mason County over the past five years. The most frequently measured characteristic groups are Physical, Microbiological, 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.
What's happening with rivers in Mason County right now?
Mason County's primary USGS streamgage on the SKOKOMISH RIVER has a pipeline snapshot of 594 cubic feet per second — 48% of the long-term mean of 1,227.81 cfs. This is well below typical — often a signal of drought stress on source water. For the latest gauge feed, visit waterdata.usgs.gov.
How does Mason County water compare to the Washington average?
Mason County's SDWIS water quality score of 62.2/100 is higher than the Washington state average of 59.3. The average water quality grade across Washington is D, based on data from 39 counties with available SDWIS data.
Is tap water safe to drink in Mason County?
Based on EPA SDWIS data, Mason County has a water quality grade of C (62.2/100). This indicates moderate compliance. Some violations have been recorded but overall standards are maintained. 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 Mason County have clean drinking water?
Mason County has 3 health-based drinking water violations according to EPA records. With a water quality score of 62.2/100 and grade C, 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 Mason County rank for water quality in Washington?
Mason County ranks #21 out of 39 counties in Washington by SDWIS water quality score (1 = best). With a score of 62.2/100, 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

Yakima County

Washington

B

62.8

Water score

Clallam County

Washington

B

63.0

Water score

Spokane County

Washington

B

63.8

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.

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 Reviewed by Evan Brooks, Data Editor

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