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EPA SDWIS

Lassen County Water Quality

Lassen County, California

Water Grade

C

Water Score

54.6

Violations

2

State Rank

#19

of 58 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

C

Based on EPA compliance history and violation data

Water Score

54.6/100

Higher = better quality

Health Violations

2

Health-based violations

Violation Rate

10.7%

Systems with violations

Water Advisory: Lassen County

Water Verdict

Lassen County receives a below-average water quality assessment with a grade of C and a score of 54.6 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

Lassen County has recorded 2 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 10.7 violations per 1,000 residents, this rate is high and signals significant water quality management issues.

Consumer Guidance

Tap water in Lassen County meets baseline standards, but residents who are immunocompromised or have young children may want to use an NSF-certified water filter as a precaution. With 2 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

Lassen County has better water quality than the average county in California. Its water score is 10 points higher than the state average, indicating stronger water system performance relative to neighboring counties.

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

22.9%

16 of 70 assessed

Some impairment

Top Impairment Causes

  • 1

    PATHOGENS

  • 2

    NITROGEN

  • 3

    TOTAL DISSOLVED SOLIDS (TDS)

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

34

Active in the past 5 years

Measurements Recorded

4.2K

4,168 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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Frequently Asked Questions

What is the water quality in Lassen County, California?
Lassen County, California has a drinking-water quality grade of C with a score of 54.6/100, based on EPA SDWIS compliance data. The county has 2 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 Lassen County?
Lassen County has 2 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 Lassen County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 22.9% of Lassen County's 70 assessed water bodies are classified as impaired (16 impaired). The top reported causes are PATHOGENS, NITROGEN, TOTAL DISSOLVED SOLIDS (TDS). 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 Lassen County?
EPA's Water Quality Portal records 4,168 measurements from 34 monitoring sites in Lassen 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 Lassen County water compare to the California average?
Lassen County's SDWIS water quality score of 54.6/100 is higher than the California state average of 44.6. The average water quality grade across California is D, based on data from 58 counties with available SDWIS data.
Is tap water safe to drink in Lassen County?
Based on EPA SDWIS data, Lassen County has a water quality grade of C (54.6/100). 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 Lassen County have clean drinking water?
Lassen County has 2 health-based drinking water violations according to EPA records. With a water quality score of 54.6/100 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 Lassen County rank for water quality in California?
Lassen County ranks #19 out of 58 counties in California by SDWIS water quality score (1 = best). With a score of 54.6/100, 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

San Diego County

California

C

54.6

Water score

Humboldt County

California

C

54.8

Water score

Fresno County

California

C

52.5

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

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