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Public water system record

County Service Area 7

Serves La Honda, San Mateo County, CA · 300 people served

Federal records show 6 health-based violations and no monitoring/reporting issues for County Service Area 7 in the last ten years. The most serious issue in this window was a resolved Haloacetic Acids (HAA5) violation.

  • CA4100509
  • REDWOOD CITY
  • CA
  • 300 served

System profile

Source water Surface water
ZIP 94063
EPA system ID CA4100509

Verify this system on EPA ECHO →

Health-based violations, last 10 years
6
Resolved
6
Unresolved
0
Any acute record
No
Monitoring issues, last 10 years
0

Key facts

  • County Service Area 7 draws water from 1 surface water intake.
  • Highest measured level in the last 10 years: Total Trihalomethanes (TTHMs), 0.115 mg/L, federal limit 0.08 mg/L (1.4 times the limit), 2018.
  • Most recent formal enforcement: compliance order (no penalty) by California, July 2025.
  • Record on file since 1980, with 1 health-based violation before October 19, 2016.
  • Lead pipe inventory: 0 lead and 0 unknown out of 71 service lines.

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Health-based violations

Since October 2016

Violation data reflects EPA records through March 2026. For the most current status, visit the EPA ECHO database.

Contaminant Rule family Start date Status Acute
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.064 mg/L, federal limit 0.06 mg/L (1.1 times the limit)
 220 Jan 1, 2025 Resolved No
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.073 mg/L, federal limit 0.06 mg/L (1.2 times the limit)
 220 Jan 1, 2020 Resolved No
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.115 mg/L, federal limit 0.08 mg/L (1.4 times the limit)
 220 Apr 1, 2018 Resolved No
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1006 mg/L, federal limit 0.08 mg/L (1.3 times the limit)
 220 Jan 1, 2018 Resolved No
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0913 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
 220 Oct 1, 2017 Resolved No
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
 220 Jul 1, 2017 Resolved No

Full record since 1980

EPA's records for County Service Area 7 go back to 1980. Before October 19, 2016 they list 1 health-based violation (1 resolved) and 48 monitoring or reporting violations.

Violations that began in Health-based Monitoring and reporting
1980s 0 26
1990s 1 1
2000s 0 21
October 19, 2016 to 2019 4 0
2020s 2 0

Most recent health-based violation before October 19, 2016: Surface Water Treatment Rule, began January 1992, Resolved.

Show the health-based violation before October 19, 2016
Contaminant Start date Status
Surface Water Treatment Rule
Treatment technique failure
 Jan 1, 1992 Resolved

Enforcement actions

California regulators took 3 formal enforcement actions against County Service Area 7 between 2017 and 2025. The most recent was a compliance order (no penalty) in July 2025.

Date By Action Violations covered
Jul 11, 2025 California Compliance order (no penalty) 1 violation (1 health-based): Haloacetic Acids (HAA5)
May 1, 2020 California Compliance order (no penalty) 1 violation (1 health-based): Haloacetic Acids (HAA5)
Nov 2, 2017 California Compliance order (no penalty) 4 violations (4 health-based): Total Trihalomethanes (TTHMs)

What the violations mean

Total Trihalomethanes (TTHMs)

4 incidents

Disinfection byproduct levels exceeded the federal limit

Long-term TTHM exposure may increase bladder cancer risk

Haloacetic Acids (HAA5)

2 incidents

Haloacetic acid byproducts exceeded the federal limit

Long-term exposure to HAAs may increase cancer risk

Where the water comes from

County Service Area 7 draws water from 1 surface water intake.

Annual water quality report

County Service Area 7 must give its customers an annual water quality report (Consumer Confidence Report) by July 1, with the levels its tests found in the previous year.

Systems serving 500 or fewer people may meet the rule by telling customers the report is available on request, so you may need to ask County Service Area 7 for a copy.

Find a posted report with EPA's Consumer Confidence Report search

Testing your own water

To test the water at your tap, or a private well this record does not cover, use a laboratory certified for drinking water by California.

Certified drinking water labs by state EPA guidance for private wells