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Colusa County, CA Water Quality

Water quality data for 8 public water systems serving Colusa County, California — based on EPA SDWIS enforcement records, lead testing results, and health-based violation history.

📅 2026 Report 🔄 Data updated 2026 Q2 📍 8 water systems · 8 cities
✅
Excellent — All Systems Performing Well

Water quality across the county is outstanding with minimal violations and very low lead levels.

A

Colusa County Earns a A

Colusa County: 8 communities across 8 water systems. 100.0% have no open violations.

  • Median lead where detected: 5.00 ppb
  • 5 communities with a lead detection, 3 reporting none detected
  • 0 communities with PFAS above the federal limit
  • 0 with significant inspection deficiencies
  • 100.0% of communities have no open violations
5 ppb
Median Lead Level
County-wide, 90th percentile
8
Water Systems
Active CWS & NTNCWS
100%
Violation-Free
No active violations on record
How we grade counties: MyWaterIQ uses EPA SDWIS enforcement data — actual MCL violations and lead test results — not the aspirational MCLG targets used by some sites. A grade reflects real compliance history, not theoretical risk. Learn more →

Cities by Water Quality

⭐ Best Performing
  • Williams
    Not detected
    No federal limits exceeded on record
    A
  • Arbuckle
    Not detected
    No federal limits exceeded on record
    B
  • Maxwell
    0.98 ppb
    No federal limits exceeded on record
    B
  • Princeton
    1.30 ppb
    No federal limits exceeded on record
    B
  • Stonyford
    Not detected
    No federal limits exceeded on record
    B
⚠ Needs Attention
  • Grimes
    5.77 ppb
    39 health-based violations since 2015
    B
  • Colusa
    6.80 ppb
    Lead at 6.80 ppb, above a third of the action level
    A
  • Lodoga
    5.00 ppb
    Lead at 5.00 ppb, above a third of the action level
    B
  • Williams
    Not detected
    No federal limits exceeded on record
    A
  • Arbuckle
    Not detected
    No federal limits exceeded on record
    B
County Lead Level — Median 5 ppb
Based on most recent 90th percentile lead tests across all reporting systems
0 ppb5 ppb10 ppb15 ppb
County median: 5 ppb — 33.3% of the federal action level
Systems by Lead Level
Under 5 ppb
2
5 – 10 ppb
3
No Data
3

All Cities in Colusa County

Colusa 6.80 ppb A
Williams Not detected A
Arbuckle Not detected B
Maxwell 0.98 ppb B
Grimes 5.77 ppb B
Princeton 1.30 ppb B
Stonyford Not detected B
Lodoga 5.00 ppb B
Showing 8 cities
No active violations Active violations

About Colusa County Drinking Water

Colusa County is served by 8 water systems covering 8 communities. No community here has an open violation on record.

Of the communities reporting lead results, 5 recorded a detection, with a median of 5.00 ppb — 33% of the federal action level. 3 reported none detected, which means below the laboratory limit rather than an absence of lead.

No community here has PFAS above the federal limit on record. State inspectors recorded no significant deficiencies.

Frequently Asked Questions

Is Colusa County tap water safe to drink?▼
No community in Colusa County has an open violation on record. No community has PFAS above the federal limit on record.
What is the lead level in Colusa County?▼
Among communities with a detection the median is 5.00 ppb, 33% of the 15 ppb action level. 3 reported none detected and 0 reported no result.
How many water systems serve Colusa County?▼
8 community water systems serve 8 communities here.
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