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County Water Quality Report

San Mateo County, California

5 public water systems serving 425,645 residents

Data sources: EPA SDWIS EPA ECHO EWG Tap Water Database Utility CCRs ⓘ How did we get these ratings?
County average grade
C
74/100
Utilities rated 5
Population served 425,645
🇪🇺 Would fail EU standards 1 of 5

Top water quality concerns in San Mateo County

  • Haloacetic acids (HAA9) significantly above health guidelinein 5 of 5 utilities
  • Haloacetic acids (HAA5) significantly above health guidelinein 5 of 5 utilities
  • Total trihalomethanes (TTHMs) significantly above health guidelinein 3 of 5 utilities
  • Arsenic detectedin 1 of 5 utilities
  • Arsenic significantly above health guidelinein 1 of 5 utilities

All utilities in San Mateo County

Click any utility for full grade card, contaminant data, and treatment plant contact info.

B
81/100

CITY OF REDWOOD CITY

REDWOOD CITY · 92,819 residents

Top concern: Haloacetic acids (HAA9) significantly above health guideline

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B
79/100

CALIFORNIA WATER SERVICE - BEAR GULCH

SAN JOSE · 61,431 residents

Top concern: Haloacetic acids (HAA9) significantly above health guideline

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B
75/100

CALIFORNIA WATER SERVICE - SAN MATEO

SAN JOSE · 102,348 residents

Top concern: Haloacetic acids (HAA9) significantly above health guideline

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C
69/100

CITY OF DALY CITY

DALY CITY · 104,901 residents

Top concern: PFAS contamination

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C
65/100

CALIFORNIA WATER SERVICE-S SAN FRANCISCO

SAN JOSE · 64,146 residents

Top concern: Arsenic significantly above health guideline

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