waterbycounty
EPA SDWIS

Washington County Water Quality

Washington County, Oregon

Water Grade

B

Water Score

67.7

Violations

12

State Rank

#8

of 36 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

B

Based on EPA compliance history and violation data

Water Score

67.7/100

Higher = better quality

Health Violations

12

Health-based violations

Violation Rate

2.1%

Systems with violations

Water Advisory: Washington County

Water Verdict

Washington County receives a fair water quality assessment with a grade of B and a score of 67.7 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

Washington County has recorded 12 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 2.1 violations per 1,000 residents, this rate is relatively low compared to many U.S. counties.

Consumer Guidance

Tap water in Washington County is generally safe to drink based on available data. Residents should still review their utility's annual Consumer Confidence Report for transparency on detected contaminants. With 12 recorded health violations, staying informed about utility communications and boil-water notices is especially important. For long-term peace of mind, request your utility's latest Consumer Confidence Report and consider independent water testing if you have specific health concerns.

Regional Context

Washington County has better water quality than the average county in Oregon. Its water score is 23.1 points higher than the state average, indicating stronger water system performance relative to neighboring counties.

Past 5 years

Water Quality Monitoring

Monitoring Sites

78

Active in the past 5 years

Measurements Recorded

202K

201,896 total readings

Most Measured

  • Physical
  • Nutrient
  • Organics, Pesticide

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

233cfs

May 14, 6:30 PM UTC

vs Long-Term Average

24%

Well below typical

Primary Streamgage

TUALATIN RIVER AT HWY 219 NEAR HILLSBORO, OR

USGS site
14206241
Drainage area
462 sq mi
Long-term mean
971 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; "% of typical" compares the latest reading against that average.

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Frequently Asked Questions

What is the water quality in Washington County, Oregon?
Washington County, Oregon has a drinking-water quality grade of B with a score of 67.7/100, based on EPA SDWIS compliance data. The county has 12 health-based drinking water violations over the past 5 years. Watershed health, monitoring records, and live streamflow are reported separately on this page.
Are there any water violations in Washington County?
Washington County has 12 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 Washington County?
EPA's Water Quality Portal records 201,896 measurements from 78 monitoring sites in Washington County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, Organics, Pesticide. 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 Washington County right now?
Washington County's primary USGS streamgage on the TUALATIN RIVER is currently reading 233 cubic feet per second — 24% of the long-term mean of 970.95 cfs. This is well below typical — often a signal of drought stress on source water. For genuine real-time data, visit waterdata.usgs.gov.
How does Washington County water compare to the Oregon average?
Washington County's SDWIS water quality score of 67.7/100 is higher than the Oregon state average of 44.6. The average water quality grade across Oregon is D, based on data from 36 counties with available SDWIS data.
Is tap water safe to drink in Washington County?
Based on EPA SDWIS data, Washington County has a water quality grade of B (67.7/100). 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).
Why does Washington County have so many water violations?
Washington County has 12 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 Washington County rank for water quality in Oregon?
Washington County ranks #8 out of 36 counties in Oregon by SDWIS water quality score (1 = best). With a score of 67.7/100, 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

Multnomah County

Oregon

B

66.8

Water score

Deschutes County

Oregon

C

60.1

Water score

Linn County

Oregon

C

53.8

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 Logan Johnson, Founder & Data EditorUpdated Reviewed by Logan Johnson, Founder & Data Editor

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