Drinking water quality · 2025
· Verified
What's in Golden State Water Company - Los Osos, CA tap water
66 contaminants were measured in the Golden State Water Company - Los Osos, CA water system's 2025 annual report. Each is shown below against its federal limit — 1 sit at or above that limit.
- Reporting year
- 2025
- Contaminants measured
- 66
- Over federal limit
- 1
- Approaching the limit
- 0
- Worst contaminant
- Manganese
- Service area
- CA
PFAS — EPA UCMR5 (2023–2025)
1 PFAS compound approaching EPA limits in Golden State Water Company - Los Osos, CA
The EPA finalized the first-ever federal drinking-water limits for six PFAS compounds in April 2024. These numbers come straight from EPA's UCMR5 lab dataset — every U.S. system serving more than 3,300 people tested every PFAS sample at an entry point to its distribution system. PFAS not listed below were either tested and not detected, or not yet sampled.
PFHxS (Perfluorohexane sulfonic acid)
● Approaching limit (88%)near national p90 (12.049999999999997 ng/L across detecting U.S. systems)
PFPeA
● Detected (no federal limit)below national p90 (15.95999999999999 ng/L across detecting U.S. systems)
PFHxA
● Detected (no federal limit)below national p90 (12.190000000000003 ng/L across detecting U.S. systems)
Lithium
● Detected (no federal limit)below national p90 (76.59999999999991 mg/L across detecting U.S. systems)
PFBS
● Detected (no federal limit)below national p90 (13.909999999999979 ng/L across detecting U.S. systems)
Where your water comes from · EPA SDWIS
Golden State Water Company - Los Osos, CA's drinking water comes from ground water, drawn from 6 sources.
Source
- LOS OLIVOS · 2
- CABRILLO WELL
- SOUTH BAY
- ROSINA WELL
- + 1 more
Treatment
- LOS OLIVOS RESV NITRATE BLEND INFLUENT
- SOUTH BAY WELL 01 - TRT CL
- ROSINA WELL - TRT CL
- + 6 more
Distribution
Historical readings · EPA Six-Year Review (2012–2019)
2 contaminants historically over EPA limits in Golden State Water Company - Los Osos, CA
Every U.S. public water system reports compliance-monitoring data to EPA. The Six-Year Review releases the 2012–2019 window as a single dataset — here's what your system reported, year by year. Values shown are the highest detection per analyte per year, compared to the federal MCL.
| Contaminant | Worst detection | EPA limit | Years (2012–2019) |
|---|---|---|---|
NITRATE worst: 2017 | 24 mg/L 2.4× | 10 mg/L | '12'13'14'15'16'17'18'19 |
NITRATE NITRITE worst: 2017 | 21 mg/L 2.1× | 10 mg/L | '17'18 |
CHROMIUM worst: 2015 | 0.015 mg/L within above national p90 | 0.1 mg/L | '15 |
RADIUM 226 228 worst: 2018 | 0.62 pCi/L within below national p90 | 5 pCi/L | '18 |
DICHLOROMETHANE worst: 2017 | 0.0005 mg/L within | 0.005 mg/L | '17 |
HAA5 worst: 2014 | 0.0046 mg/L within | 0.06 mg/L | '14 |
BARIUM worst: 2016 | 0.14 mg/L within near national p90 | 2 mg/L | '12'15'16'19 |
FLUORIDE worst: 2012 | 0.25 mg/L within | 4 mg/L | '12'15'16'18'19 |
TTHM worst: 2016 | 0.0028 mg/L within | 0.08 mg/L | '16'19 |
MCAA worst: 2014 | 0.0046 mg/L | — | '14 |
BROMOFORM worst: 2016 | 0.0013 mg/L | — | '16 |
DIBROMOCHLOROMETHANE worst: 2016 | 0.0015 mg/L | — | '16'19 |
Metals
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| ManganeseA naturally occurring metal from soil and rock. | 95.66666666666667 UG/LAverageSource water | 50 UG/LMCL | At or above the limit |
| Chromium, HexavalentHexavalent chromium ('chromium-6') — the more toxic form of chromium. | 6.6000000000000005 UG/LAverageEntry point | 10 UG/LMCL | Within the limit |
| IronA naturally occurring metal common in groundwater. | 63.361111111111114 UG/LAverageSource water | 300 UG/LMCL | Within the limit |
Physical & aggregate
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| TurbidityA measure of cloudiness from suspended particles in the water. | 3.6333333333333333 NTUAverageSource water | 5 NTUMCL | Within the limit |
| Total Dissolved SolidsTotal dissolved solids — the combined content of all dissolved minerals and salts. | 453.59375 MG/LAverageSource water | 1000 MG/LMCL | Within the limit |
| ColorA measure of visible tint in the water. | Not detected UNITSHighest single sampleSource water | 15 UNITSMCL | None detected |
| OdorA measure of detectable smell in the water. | Not detected TONHighest single sampleSource water | 3 TONMCL | None detected |
Inorganic chemicals
Radionuclides
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| Combined RadiumCombined radium-226 and radium-228 — naturally occurring radioactive elements. | 0.32616666666666666 PCI/LAverageSource water | 5 PCI/LMCL | Within the limit |
| Gross AlphaGross alpha particle activity — a combined measure of alpha-emitting radioactive substances. | Not detected PCI/LHighest single sampleSource water | 15 PCI/LMCL | None detected |
| UraniumA naturally occurring radioactive metal from erosion of natural deposits. | Not detected PCI/LHighest single sampleSource water | 20 PCI/LMCL | None detected |
Other
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| Carbon Tetrachloride | Not detected UG/LHighest single sampleSource water | 0.5 UG/LMCL | None detected |
| Chlorobenzene | Not detected UG/LHighest single sampleSource water | 70 UG/LMCL | None detected |
| Cis Dichloroethylene 12 | Not detected UG/LHighest single sampleSource water | 6 UG/LMCL | None detected |
| Dbaa | Not detected UG/LHighest single sampleDistribution | None set | None detected |
| Dcaa | Not detected UG/LHighest single sampleDistribution | None set | None detected |
| Dichloroethane 12 | Not detected UG/LHighest single sampleSource water | 0.5 UG/LMCL | None detected |
| Dichloroethylene 11 | Not detected UG/LHighest single sampleSource water | 6 UG/LMCL | None detected |
| Dichloropropane 12 | Not detected UG/LHighest single sampleSource water | 5 UG/LMCL | None detected |
| Mbaa | Not detected UG/LHighest single sampleDistribution | None set | None detected |
| O Dichlorobenzene | Not detected UG/LHighest single sampleSource water | 600 UG/LMCL | None detected |
| P Dichlorobenzene | Not detected UG/LHighest single sampleSource water | 5 UG/LMCL | None detected |
| Pce | Not detected UG/LHighest single sampleSource water | 5 UG/LMCL | None detected |
| Styrene | Not detected UG/LHighest single sampleSource water | 100 UG/LMCL | None detected |
| Tcaa | Not detected UG/LHighest single sampleDistribution | None set | None detected |
| Tce | Not detected UG/LHighest single sampleSource water | 5 UG/LMCL | None detected |
| Trans Dichloroethylene 12 | Not detected UG/LHighest single sampleSource water | 10 UG/LMCL | None detected |
| Trichlorobenzene 124 | Not detected UG/LHighest single sampleSource water | 5 UG/LMCL | None detected |
| Trichloroethane 111 | Not detected UG/LHighest single sampleSource water | 200 UG/LMCL | None detected |
| Trichloroethane 112 | Not detected UG/LHighest single sampleSource water | 5 UG/LMCL | None detected |
| Vinyl Chloride | Not detected UG/LHighest single sampleSource water | 0.5 UG/LMCL | None detected |
PFAS ("forever chemicals")
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid, a chlorinated PFAS compound. | Not detected NG/LHighest single sampleSource water | None set | None detected |
| 4,8-Dioxa-3H-perfluorononanoic acid (ADONA)ADONA, a newer-generation PFAS replacement compound. | Not detected NG/LHighest single sampleSource water | None set | None detected |
| 4:2 Fluorotelomer sulfonic acid (4:2 FTS)4:2 fluorotelomer sulfonic acid, a PFAS-related compound. | Not detected NG/LHighest single sampleEntry point | None set | None detected |
| 6:2 Fluorotelomer sulfonic acid (6:2 FTS)6:2 fluorotelomer sulfonic acid, a PFAS-related compound. | Not detected NG/LHighest single sampleEntry point | None set | None detected |
| 8:2 Fluorotelomer sulfonic acid (8:2 FTS)8:2 fluorotelomer sulfonic acid, a PFAS-related compound. | Not detected NG/LHighest single sampleSource water | None set | None detected |
| 9-Chlorohexadecafluoro-3-oxanonane-1-sulfonic acid (9Cl-PF3ONS)9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid, a chlorinated PFAS compound. | Not detected NG/LHighest single sampleEntry point | None set | None detected |
| Hexafluoropropylene oxide dimer acidHFPO-DA ('GenX chemicals'), a newer-generation PFAS replacement compound. | Not detected NG/LHighest single sampleSource water | None set | None detected |
| Perfluoro-3-methoxypropanoic acid (PFMPA)Perfluoro-3-methoxypropanoic acid, a PFAS-related compound. | Not detected NG/LHighest single sampleSource water | None set | None detected |
| Perfluoro-4-methoxybutanoic acid (PFMBA)Perfluoro-4-methoxybutanoic acid, a PFAS-related compound. | Not detected NG/LHighest single sampleSource water | None set | None detected |
| Perfluoro(2-ethoxyethane)sulfonic acid (PFEESA)Perfluoro(2-ethoxyethane)sulfonic acid, a PFAS-related compound. | Not detected NG/LHighest single sampleSource water | None set | None detected |
| Perfluorodecanoic acid (PFDA)Perfluorodecanoic acid, a longer-chain PFAS 'forever chemical.' | Not detected NG/LHighest single sampleSource water | None set | None detected |
| Perfluorododecanoic acid (PFDoA)Perfluorododecanoic acid, a longer-chain PFAS 'forever chemical.' | Not detected NG/LHighest single sampleSource water | None set | None detected |
| Perfluoroheptanesulfonic acid (PFHpS)Perfluoroheptanesulfonic acid, a PFAS 'forever chemical.' | Not detected NG/LHighest single sampleSource water | None set | None detected |
| Perfluorononanoic acidPerfluorononanoic acid, a PFAS 'forever chemical.' | Not detected NG/LHighest single sampleSource water | None set | None detected |
| Perfluoroundecanoic acid (PFUnA)Perfluoroundecanoic acid, a longer-chain PFAS 'forever chemical.' | Not detected NG/LHighest single sampleEntry point | None set | None detected |
| Perfluoroheptanoic acidPerfluoroheptanoic acid, a PFAS 'forever chemical.' | 1.2846153846153845 NG/LAverageSource water | None set | Detected — no federal limit |
| Perfluoropentanesulfonic acid (PFPeS)Perfluoropentanesulfonic acid, a PFAS 'forever chemical.' | 1.7999999999999998 NG/LAverageSource water | None set | Detected — no federal limit |
| PFBAPerfluorobutanoic acid, a shorter-chain PFAS 'forever chemical.' | 1.0769230769230769 NG/LAverageSource water | None set | Detected — no federal limit |
VOCs & pesticides
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| Benzene | Not detected UG/LHighest single sampleSource water | 1 UG/LMCL | None detected |
| Ethylbenzene | Not detected UG/LHighest single sampleSource water | 300 UG/LMCL | None detected |
| Toluene | Not detected UG/LHighest single sampleSource water | 150 UG/LMCL | None detected |
| XylenesA group of industrial solvents found in gasoline and paint. | Not detected UG/LHighest single sampleSource water | 1750 UG/LMCL | None detected |
Disinfection byproducts
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| BromodichloromethaneA trihalomethane disinfection byproduct. | 1.1 UG/LAverageDistribution | None set | Detected — no federal limit |
| ChloroformA trihalomethane formed when chlorine reacts with organic matter in water. | 0.54 UG/LAverageDistribution | None set | Detected — no federal limit |
People also ask about Golden State Water Company - Los Osos, CA's water
+Is Golden State Water Company - Los Osos, CA tap water safe to drink in 2025?
The 2025 Consumer Confidence Report for the Golden State Water Company - Los Osos, CA water utility lists 1 contaminant at or above the federal limit: Manganese. Whether that means the water is "unsafe" depends on which contaminant, how long the exposure, and individual health factors. The table on this page shows the measured value, the federal threshold, and the regulated statistic used for compliance.
+What contaminants are in Golden State Water Company - Los Osos, CA tap water?
66 contaminants were measured in Golden State Water Company - Los Osos, CA's 2025 Consumer Confidence Report, spanning other, pfas ("forever chemicals"), and disinfection byproducts. 37 have an enforceable federal limit; the rest are detected but unregulated. Every measured value, in the utility's own units, is on this page.
+Which contaminants exceed federal limits in Golden State Water Company - Los Osos, CA tap water?
One contaminant in Golden State Water Company - Los Osos, CA's 2025 report sits at or above the federal limit: Manganese (1.9× the limit). The EPA enforces these limits against the regulated reporting statistic — typically a running annual average or 90th percentile — not a one-off sample spike.
+What is the worst contaminant in Golden State Water Company - Los Osos, CA tap water?
The contaminant with the highest measured value relative to its federal limit in the 2025 report is Manganese, at 1.9× the federal threshold. It belongs to the metals family of contaminants.
+Where does the data on this page come from?
Every value is transcribed from Golden State Water Company - Los Osos, CA's 2025 Consumer Confidence Report — the annual drinking-water report every U.S. public water utility is required by federal law to publish. The original source document is archived and viewable on this site. A water-quality report covers an entire service area, not a single address.
+How often is Golden State Water Company - Los Osos, CA's water quality data updated?
Each U.S. public water utility publishes one Consumer Confidence Report per year, covering the prior calendar year's measurements. This page reflects the 2025 report; a new report will replace it once the utility publishes its next annual update.