EPA system CA3310037 · California

Corona, City of: Lithium at or above EPA's 10 ppb health reference level

System ID CA3310037; community water system; California; source: purchased surface water; serves 168,575 people via 44,981 connections; status: active

In focus168,575people served, EPA registry

Public records. Clearer context.

Corona, City of is a local-government-owned community water system in California serving about 168,575 people, matched to 5 ZIP codes.

PFAS treatment declared to EPA: Granular activated carbon (38 of 54 sampling events) · PFAS found before UCMR 5: Yes, at 54 of 54 sampling events

PFAS and lithium: what EPA's national survey found

EPA tested this water for 30 substances and found 5. Lithium reached 55.1 ppb; EPA's health reference level, which is guidance and not a limit, is 10 ppb.

Between September 2023 and September 2024, EPA's UCMR 5 program tested 1,620 samples from 15 sampling locations for 30 contaminants (29 PFAS plus lithium). 5 were detected above the reporting level in at least one sample. Lithium reached 55.1 ppb in a single sample, at or above the health reference level of 10 ppb, which is non-regulatory.

Sampling-point average: mean of a location's two (ground water) or four (surface water) UCMR 5 results with non-detects counted as zero, EPA's method for comparing UCMR 5 data to the PFAS MCLs. EPA rounds to the reference value's significant digits before deciding whether an average is "greater than" an MCL (PFOA/PFOS averages count as above 4.0 ng/L only from 4.05 ng/L; lithium results count as above the 10 ppb reference only from 15 ppb). This site does not apply that rounding: "at or above" here means the measured value is numerically at or above the reference.

Utility-reported context (UCMR 5 questionnaire, aggregated across sampling events): PFAS previously found at this system: yes at 54 of 54 sampling events; potential PFAS sources nearby: not known at 54 of 54 sampling events; PFAS treatment in place: granular activated carbon at 38 of 54 sampling events, no PFAS treatment at 16 of 54 sampling events.

Lead and copper at customer taps

In the latest completed monitoring period, ending Dec 31, 2023, 9 in 10 sampled homes had lead at or below 3.7 ppb, below the 15 ppb action level that triggers utility action. None of the 20 periods on record reached it.

In the most recent completed lead monitoring period, ending Dec 31, 2023, the 90th-percentile lead result at customer taps was 3.7 ppb, below the action level of 15 ppb (20 monitoring periods on record, none at the action level). The 90th percentile is the value that 9 in 10 sampled homes were at or below. Values are in parts per billion (ppb).

Drinking water violations since Sep 3, 2016

EPA lists 68 violations since Sep 3, 2016. None is health-based. All concern missed monitoring, reporting or public notices, not the water itself.

EPA's SDWIS database lists 68 violations recorded since Sep 3, 2016: 68 for monitoring or reporting, none health-based.

Sanitary surveys and site visits

Most recent state inspection: Oct 9, 2025 (sanitary survey); 2 visits since Sep 3, 2021.

What you can do about these results

ZIP codes served

Sources

Data vintage: EPA UCMR 5 occurrence data, samples collected 2023-01-03 – 2026-06-17, final release, August 2026 (file dated Aug 28, 2026); EPA SDWIS via ECHO, 2026Q2 extract (file dated Jul 9, 2026); EPA service-area boundaries v3.0; Census 2020 ZCTAs. Page generated 2026-09-03.

• EPA ECHO detailed facility report
• EPA UCMR 5 Data Finder
• EPA service-area boundary: modeled, 41.1 sq mi