San Mateo County public water systems

Status classification

Share of listed systems, followed by the count, reported population, and funding in each status.

Failing11%

At-Risk17%

Not At-Risk61%

Failing

At-Risk

Potentially At-Risk

Not At-Risk

Not Assessed

Systems

4

6

2

22

2

Population

3,201

23,395

1,557

541,977

208,437

Funding since 2017

$0

Key figures

36

public water systems

778,567

reported population

33%

serve 500 people or fewer

$0

reported funding since 2017

System locations

Points show reported system locations. They do not represent service-area boundaries.

Each point represents one system record. Nearby or overlapping points can conceal multiple systems.

Summary

San Mateo County has 36 public water systems in the SAFER dataset. Of these, 10 (28%) are classified as Failing or At-Risk.

Those systems report serving 26,596 people. The county profile is also shaped by small systems: 12 systems serve 500 people or fewer.

2 systems are listed as Not Assessed, serving 208,437 people, so Not Assessed should not be read as a low-risk classification.

Reported funding since 2017 totals $0 across 0 systems. Technical assistance funding totals $984K.

System counts and reported population

Not Assessed systems make up 6% of listed systems and 27% of reported population. That population sits in a few large systems outside the SAFER assessment’s scope, which generally have more capacity, so this reflects scope rather than hidden risk.

Risk profile

Risk in San Mateo County is distributed across four dimensions. Accessibility contributes the largest share of the combined weighted risk score at 44%. Across all individual indicators, Total net annual income appears most often, affecting 18 of 34 assessed systems.

Water Quality

of combined weighted risk

State 32% · ▼ 12 pts

Most common flagWater quality trends toward MCL

Accessibility

of combined weighted risk

State 36% · ▲ 8 pts

Most common flagNo intertie

Affordability

of combined weighted risk

State 17% · ▼ 5 pts

Most common flagHousehold socioeconomic burden

TMF Capacity

of combined weighted risk

State 15% · ▲ 10 pts

Most common flagTotal net annual income

Water Quality

Water Quality accounts for 19% of the county’s combined weighted risk score. Water quality trends toward MCL appears in 10 of 34 assessed systems. Past presence on Failing list is next, appearing in 8 of 34 assessed systems.

Each indicator was assessed for 34 systems.

Accessibility

Accessibility accounts for 44% of the county’s combined weighted risk score. No intertie appears in 15 of 34 assessed systems. Limited water sources is next, appearing in 10 of 34 assessed systems.

Indicator denominators range from 18 to 34 assessed systems.

Affordability

Affordability accounts for 12% of the county’s combined weighted risk score. Household socioeconomic burden appears in 8 of 34 assessed systems. Extreme water bill is next, appearing in 6 of 34 assessed systems.

Each indicator was assessed for 34 systems.

TMF Capacity

TMF Capacity accounts for 24% of the county’s combined weighted risk score. Total net annual income appears in 18 of 34 assessed systems. Operating ratio is next, appearing in 10 of 34 assessed systems.

Indicator denominators range from 31 to 34 assessed systems.

Patterns and context

The countywide totals hide important differences among systems. The panels below show how SAFER status varies by system size and service-area economic status, what conditions appear among Failing systems, and how reported funding is distributed across the 36 systems in San Mateo County.

Status by system size

SAFER status within each population group

Among systems serving 500 people or fewer, 8 of 12 are Failing or At-Risk. This size group has the county’s highest concentration of high-concern classifications.

Economic context

Orange shows Failing or At-Risk systems within each service-area group

DAC and SDAC service areas contain 4 of 36 listed systems. Within those two groups, 3 systems are Failing or At-Risk.

Conditions among Failing systems

A system can appear under more than one condition

Frequently listed primary analytes

Total Haloacetic Acids (Haa5)1
Tthm1

Among 4 Failing systems, 2 report secondary MCL violation. The most frequently listed primary analytes are Total Haloacetic Acids (Haa5) and Tthm.

Reported funding

Totals since 2017 and number of systems reporting funding

No funding since 2017 is reported for systems in this county.

Key takeaways

28%

of systems are Failing or At-Risk

That represents 10 systems reporting service to 26,596 people. That is below the statewide average of 33%.

44%

of weighted risk comes from Accessibility

The most widespread individual flag is total net annual income, found in 18 of 34 assessed systems. Statewide, Accessibility accounts for 36% of weighted risk.

33%

of systems serve 500 people or fewer

Small systems account for 12 of the county’s 36 listed systems. That is below the statewide average of 61%.