CA / Half Moon Bay
CA · Tap water records
Half Moon Bay tap water, in plain English
Here is what the EPA's own data shows about tap water in Half Moon Bay. According to EPA SDWIS data retrieved June 2026, Half Moon Bay is served by 1 active community water system, together reported to serve about 18,940 people.
As of June 2026, EPA records show 15 violations across the community water system(s) serving Half Moon Bay, going back to the earliest EPA record. None were health-based; the records are monitoring or reporting violations (a required test or report was late or missed). Each is listed by system below, with its status.
What the EPA has on record, by system
Coastside County Water District
18,940 served · surface water · PWSID CA4110011 - Monitoring Gross Alpha Particle Activity: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 6 times between July 2001 and October 2001. All have since returned to compliance, per EPA records.
- Monitoring Nitrate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 6 times between July 2001 and October 2001. All have since returned to compliance, per EPA records.
- Monitoring Coliform (TCR): a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in February 1996. All have since returned to compliance, per EPA records.
What this means
A health-based violation means a contaminant was recorded above the limit the EPA tracks for it. A monitoring or reporting violation means a required test or report was late or missed — not that a contaminant was measured above a limit. “Returned to compliance” means the EPA recorded the issue as resolved.
This page summarizes the EPA's own records and does not assess whether your water is safe to drink. For the most current details, you can verify every record directly with the EPA, and contact your water system with questions.
Source: U.S. EPA Envirofacts SDWIS, retrieved June 2026. Records cover the EPA's full reporting history for these systems. Verify at EPA ECHO.