County water report

Thurston County Water Report

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

Water grade

Water score

50.8

State rank

#29

of 39

Health violations

EPA SDWIS, 5-year lookback

Watershed impaired

Not reported

EPA ATTAINS coverage varies by state

Monitoring sites

838

100,252 recent measurements

Live streamflow

26%

CHEHALIS RIVER NEAR GRAND MOUND, WA

Water at a glance

Key Water Indicators for Thurston County

EPA SDWIS

Safety Grade

Score: 50.8 / 100

EPA SDWIS

Active Violations

5-year health-based lookback

EPA ATTAINS

Watershed Health

Not reported

Coverage varies by state

USGS NWIS

Streamflow Snapshot

26% of mean

CHEHALIS RIVER NEAR GRAND MOUND, WA

EPA WQP

Monitoring Sites

838

100,252 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.

50.8/100

Health violations

Health-based violations

Violations per 100K served

15.0

Population-normalized SDWIS rate

Data center water stress

Thurston County has 1 facility in the DCWSI dataset.

ByCounty's DCWSI ranks this county #1536 nationally by combining its water score with mapped data center density.

DCWSI

30.5

0-100 index

Facility count

0.0 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

+0.8

Compared with US county median

Mapped facilities

Wave Broadband Tahoma Terra Facility
Facility details limited
OSM

See the Thurston County data-center report Review methodology

Data Center Water Budget Calculator

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

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayHigh Impact

Your facility would use 88.4% of this county's industrial water baseline. Verify water rights and long-term drought projections before committing.

88.4% of county industrial baseline0.10 Mgal/day remaining headroom

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 Thurston County’s Water

Drinking Water Quality Overview

EPA SDWIS

Thurston County's drinking water earned a C grade, scoring 50.8 out of 100. Over the past five years, EPA SDWIS records 55 health-based violations — a pattern that public water utilities are required to disclose and correct.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T12:00:00.000-07:00) puts CHEHALIS RIVER at 727.0 cfs — well below its long-term average at 26% 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. Thurston County has extensive coverage with 838 active monitoring sites with 100,252 recent measurements on record. Predominant monitoring categories include physical and organics, other. 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 Thurston County

Water Verdict

Thurston County receives a below-average water quality assessment with a grade of C and a score of 50.8 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

Thurston County has recorded 55 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 15.0 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Tap water in Thurston County meets baseline standards but the compliance record shows room for improvement, with a Grade C rating. Thurston County's drinking-water compliance score is 50.8 out of 100. The violation rate for Thurston County is 15.0 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 838 active water-quality monitoring sites in Thurston County, data coverage is strong. A pipeline streamflow snapshot from the CHEHALIS RIVER gauge is also available on this page.

Regional Context

Thurston County has poorer water quality than the average county in Washington. Its water score is 8.5 points lower than the state average, suggesting more challenges with contamination control or infrastructure than 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 Thurston County's water environment

Official EPA Resources for Thurston County

EPA How's My Waterway

Interactive watershed health data for Thurston County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Thurston County

Consumer Confidence Reports (WA)

Annual water quality reports from utilities in Washington

Past 5 years

Water Quality Monitoring

Monitoring Sites

838

Active in the past 5 years

Measurements Recorded

100K

100,252 total readings

Most Measured

Physical
Organics, Other
Microbiological

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

727cfs

May 14, 7:00 PM UTC

vs Long-Term Average

26%

Well below typical

Primary Streamgage

CHEHALIS RIVER NEAR GRAND MOUND, WA

USGS site: 12027500
Drainage area: 895 sq mi
Long-term mean: 2,829 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 Thurston County:D — Poor

Elevated violations or significant watershed impairment.

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 Thurston County, Washington?

Thurston County, Washington has a drinking-water quality grade of C with a score of 50.8/100, based on EPA SDWIS compliance data. The county has 55 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 Thurston County?

Thurston County has 55 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 Thurston County?

EPA's Water Quality Portal records 100,252 measurements from 838 monitoring sites in Thurston County over the past five years. The most frequently measured characteristic groups are Physical, Organics, Other, Microbiological. 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 Thurston County right now?

Thurston County's primary USGS streamgage on the CHEHALIS RIVER has a pipeline snapshot of 727 cubic feet per second — 26% of the long-term mean of 2,829.34 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 Thurston County water compare to the Washington average?

Thurston County's SDWIS water quality score of 50.8/100 is lower 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 Thurston County?

Based on EPA SDWIS data, Thurston County has a water quality grade of C (50.8/100). 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).

Why does Thurston County have so many water violations?

Thurston County has 55 health-based drinking water violations on record from the EPA SDWIS database. A higher violation count can result from aging infrastructure, underfunded water utilities, agricultural runoff contamination, or industrial pollution. Counties with more water systems may also see more violations simply due to scale. Residents concerned about water quality should consider independent water testing and home filtration systems.

How does Thurston County rank for water quality in Washington?

Thurston County ranks #29 out of 39 counties in Washington by SDWIS water quality score (1 = best). With a score of 50.8/100, it falls in the bottom 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

Lewis County

Washington

49.9

Water score

Okanogan County

Washington

49.7

Water score

Walla Walla County

Washington

53.3

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 May 14, 2026Reviewed by Evan Brooks, Data Editor

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