Drinking water quality · 2025
· Verified
What's in Contra Costa Water District, CA tap water
105 contaminants were measured in the Contra Costa Water District, CA water system's 2025 annual report. Each is shown below against its federal limit — 4 sit at or above that limit.
- Reporting year
- 2025
- Contaminants measured
- 105
- Over federal limit
- 4
- Approaching the limit
- 0
- Worst contaminant
- Odor
- Service area
- CA
4.5× the limit
state-level CCR
At or above the federal limit
- OdorPhysical & aggregate · Average13.4 TONlimit 3 TON · 4.5× the limit
- IronMetals · Average468.3333333333333 UG/Llimit 300 UG/L · 1.6× the limit
- TurbidityPhysical & aggregate · Average7.720000000000001 NTUlimit 5 NTU · 1.5× the limit
- ColorPhysical & aggregate · Average17.5 UNITSlimit 15 UNITS · 1.2× the limit
Where your water comes from · EPA SDWIS
Contra Costa Water District, CA's drinking water comes from surface water, drawn from 10 sources.
Source
10surface water
- CANAL AT CLYDE
- MALLARD RESERVOIR
- MARTINEZ RESERVOIR
- CONTRA COSTA CANAL
- + 6 more
Treatment
1treatment plant
- BOLLMAN WATER TREATMENT PLANT
Distribution
0storage units
Also buys water from RANDALL-BOLD WATER TREATMENT PLANT, EAST BAY MUD.
Source: EPA SDWIS facilities inventory. Methodology.
Historical readings · EPA Six-Year Review (2012–2019)
3 contaminants historically over EPA limits in Contra Costa Water District, 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) |
|---|---|---|---|
GROSS BETA worst: 2015 | 65 mrem/yr 16.3× | 4 mrem/yr | '14'15'16'19 |
ARSENIC worst: 2015 | 0.017 mg/L 1.7× above national p90 | 0.01 mg/L | '12'13'14'15'16'17'18'19 |
BROMATE worst: 2014 | 0.016 mg/L 1.6× | 0.01 mg/L | '13'14'15'17'18'19 |
SELENIUM worst: 2014 | 0.038 mg/L within | 0.05 mg/L | '14'15 |
DICHLOROMETHANE worst: 2017 | 0.0034 mg/L within | 0.005 mg/L | '17 |
TTHM worst: 2014 | 0.044 mg/L within | 0.08 mg/L | '12'13'14'15'16'17'18'19 |
NITRITE worst: 2012 | 0.52 mg/L within | 1 mg/L | '12'18 |
NITRATE worst: 2012 | 4.86 mg/L within | 10 mg/L | '12'13'14'15'16'17'18'19 |
CADMIUM worst: 2017 | 0.0016 mg/L within near national p90 | 0.005 mg/L | '15'17 |
CHROMIUM worst: 2012 | 0.03 mg/L within 3.0× the national p90 | 0.1 mg/L | '12'19 |
FLUORIDE worst: 2012 | 0.9 mg/L within | 4 mg/L | '12'13'14'15'16'19 |
HAA5 worst: 2019 | 0.012 mg/L within | 0.06 mg/L | '12'13'14'15'16'17'18'19 |
NITRATE NITRITE worst: 2019 | 1.1 mg/L within | 10 mg/L | '18'19 |
BARIUM worst: 2012 | 0.16 mg/L within near national p90 | 2 mg/L | '12'13'14'15'16'17'18'19 |
DEHP worst: 2019 | 0.00039 mg/L within | 0.006 mg/L | '19 |
ASBESTOS worst: 2013 | 0.2 MFL within below national p90 | 7 MFL | '13'15 |
CYANIDE worst: 2019 | 0.0016 mg/L within below national p90 | 0.2 mg/L | '18'19 |
DEHA worst: 2019 | 0.00021 mg/L within | 0.4 mg/L | '19 |
URANIUM worst: 2019 | 0.00139 ug/L within below national p90 | 30 ug/L | '19 |
COPPER worst: 2018 | 0.04 mg/L below national p90 | — | '18'19 |
LEAD worst: 2019 | 0.0028 mg/L | — | '19 |
DBAA worst: 2012 | 0.002 mg/L | — | '12'13'14'15'16'17'18'19 |
DCAA worst: 2013 | 0.003 mg/L | — | '13'14'15'16'17'18'19 |
MBAA worst: 2014 | 0.001 mg/L | — | '14'16 |
TCAA worst: 2013 | 0.001 mg/L | — | '13'17'19 |
BROMODICHLOROMETHANE worst: 2012 | 0.0068 mg/L | — | '12'13'14'15'16'17'18'19 |
BROMOFORM worst: 2012 | 0.0065 mg/L | — | '12'13'14'15'16'17'18'19 |
CHLOROFORM worst: 2012 | 0.0078 mg/L | — | '12'13'14'15'16'17'18'19 |
DIBROMOCHLOROMETHANE worst: 2012 | 0.0063 mg/L | — | '12'13'14'15'16'17'18'19 |
PWSID CA0710003 · Source: EPA Six-Year Review 4 (2012–2019). Values are the highest detection in each calendar year; non-detect years are omitted. Year tags above show every year with a detection.
Physical & aggregate
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| OdorA measure of detectable smell in the water. | 13.4 TONAverageEntry point | 3 TONMCL | At or above the limit |
| TurbidityA measure of cloudiness from suspended particles in the water. | 7.720000000000001 NTUAverageSource water | 5 NTUMCL | At or above the limit |
| ColorA measure of visible tint in the water. | 17.5 UNITSAverageSource water | 15 UNITSMCL | At or above the limit |
| Total Dissolved SolidsTotal dissolved solids — the combined content of all dissolved minerals and salts. | 169.2 MG/LAverageSource water | 1000 MG/LMCL | Within the limit |
| Specific ConductanceA measure of how well water conducts electricity, which tracks dissolved mineral content. | 249.6 UMHO/CMAverageSource water | 1600 UMHO/CMMCL | Within the limit |
| AlkalinityA measure of the water's capacity to neutralize acids. | 50.733333333333334 MG/LAverageSource water | None set | Detected — no federal limit |
| HardnessA measure of dissolved calcium and magnesium minerals. | 81.17999999999999 MG/LAverageSource water | None set | Detected — no federal limit |
| pHA measure of how acidic or basic the water is. | 8.412 PHAverageEntry point | None set | Detected — no federal limit |
Metals
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| IronA naturally occurring metal common in groundwater. | 468.3333333333333 UG/LAverageSource water | 300 UG/LMCL | At or above the limit |
| ManganeseA naturally occurring metal from soil and rock. | 24.8 UG/LAverageEntry point | 50 UG/LMCL | Within the limit |
| AluminumA common element sometimes used as a treatment coagulant. | 292.5 UG/LAverageSource water | 1000 UG/LMCL | Within the limit |
| Chromium, HexavalentHexavalent chromium ('chromium-6') — the more toxic form of chromium. | 0.2 UG/LAverageEntry point | 10 UG/LMCL | Within the limit |
| Antimony | Not detected UG/LHighest single sampleEntry point | 6 UG/LMCL | None detected |
| Beryllium | Not detected UG/LHighest single sampleSource water | 4 UG/LMCL | None detected |
| MercuryA toxic metal from erosion of natural deposits and industrial runoff. | Not detected UG/LHighest single sampleEntry point | 2 UG/LMCL | None detected |
| NickelA metal from natural deposits and industrial discharge. | Not detected UG/LHighest single sampleEntry point | 100 UG/LMCL | None detected |
| Strontium | Not detected PCI/LHighest single sampleEntry point | 8 PCI/LMCL | None detected |
| Thallium | Not detected UG/LHighest single sampleEntry point | 2 UG/LMCL | None detected |
| ZincA naturally occurring metal that can also enter water from corroding pipes. | Not detected UG/LHighest single sampleSource water | 5000 UG/LMCL | None detected |
| BoronA naturally occurring element from rock and soil. | 82 UG/LAverageEntry point | None set | Detected — no federal limit |
| CalciumA naturally occurring mineral that contributes to water hardness. | 11.554545454545455 MG/LAverageSource water | None set | Detected — no federal limit |
| MagnesiumA naturally occurring mineral that contributes to water hardness. | 9.466666666666667 MG/LAverageSource water | None set | Detected — no federal limit |
| PotassiumA naturally occurring mineral from rock and soil. | 2.2983333333333333 MG/LAverageSource water | None set | Detected — no federal limit |
| SodiumA naturally occurring salt component. | 36.4 MG/LAverageEntry point | None set | Detected — no federal limit |
Radionuclides
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| Gross AlphaGross alpha particle activity — a combined measure of alpha-emitting radioactive substances. | 1.9769999999999999 PCI/LAverageSource water | 15 PCI/LMCL | Within the limit |
| Combined RadiumCombined radium-226 and radium-228 — naturally occurring radioactive elements. | 0.304 PCI/LAverageEntry point | 5 PCI/LMCL | Within the limit |
| RadonA naturally occurring radioactive gas that can dissolve into groundwater. | Not detected PCI/LHighest single sampleEntry point | None set | None detected |
Inorganic chemicals
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| ChlorideA naturally occurring salt compound. | 34.166666666666664 MG/LAverageSource water | 500 MG/LMCL | Within the limit |
| SulfateA naturally occurring mineral from rock and soil. | 26 MG/LAverageEntry point | 500 MG/LMCL | Within the limit |
| Ammonia | 0.13599999999999998 MG/LAverageEntry point | None set | Detected — no federal limit |
| BromideA naturally occurring salt found in source water. | 0.10333333333333333 MG/LAverageSource water | None set | Detected — no federal limit |
Disinfection byproducts
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| PerchlorateA chemical used in rocket fuel and fireworks that can also form during disinfection. | Not detected UG/LHighest single sampleSource water | 6 UG/LMCL | None detected |
Other
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| Carbofuran | Not detected UG/LHighest single sampleSource water | 18 UG/LMCL | None detected |
| Carbon Tetrachloride | Not detected UG/LHighest single sampleSource water | 0.5 UG/LMCL | None detected |
| Chlordane | Not detected UG/LHighest single sampleSource water | 0.1 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 |
| Dichloroethane 12 | Not detected UG/LHighest single sampleEntry point | 0.5 UG/LMCL | None detected |
| Dichloroethylene 11 | Not detected UG/LHighest single sampleEntry point | 6 UG/LMCL | None detected |
| Dichloropropane 12 | Not detected UG/LHighest single sampleEntry point | 5 UG/LMCL | None detected |
| Dinoseb | Not detected UG/LHighest single sampleSource water | 7 UG/LMCL | None detected |
| Diquat | Not detected UG/LHighest single sampleEntry point | 20 UG/LMCL | None detected |
| Edb | Not detected UG/LHighest single sampleEntry point | 0.05 UG/LMCL | None detected |
| Endothall | Not detected UG/LHighest single sampleEntry point | 100 UG/LMCL | None detected |
| Endrin | Not detected UG/LHighest single sampleEntry point | 2 UG/LMCL | None detected |
| Glyphosate | Not detected UG/LHighest single sampleEntry point | 700 UG/LMCL | None detected |
| Heptachlor | Not detected UG/LHighest single sampleSource water | 0.01 UG/LMCL | None detected |
| Heptachlor Epoxide | Not detected UG/LHighest single sampleSource water | 0.01 UG/LMCL | None detected |
| Hexachlorobenzene | Not detected UG/LHighest single sampleSource water | 1 UG/LMCL | None detected |
| Hexachlorocyclopentadiene | Not detected UG/LHighest single sampleEntry point | 50 UG/LMCL | None detected |
| Methoxychlor | Not detected UG/LHighest single sampleSource water | 30 UG/LMCL | None detected |
| O Dichlorobenzene | Not detected UG/LHighest single sampleSource water | 600 UG/LMCL | None detected |
| Oxamyl | Not detected UG/LHighest single sampleSource water | 50 UG/LMCL | None detected |
| P Dichlorobenzene | Not detected UG/LHighest single sampleEntry point | 5 UG/LMCL | None detected |
| Pcb Total | Not detected UG/LHighest single sampleSource water | 0.5 UG/LMCL | None detected |
| Pce | Not detected UG/LHighest single sampleEntry point | 5 UG/LMCL | None detected |
| Pentachlorophenol | Not detected UG/LHighest single sampleSource water | 1 UG/LMCL | None detected |
| Picloram | Not detected UG/LHighest single sampleEntry point | 500 UG/LMCL | None detected |
| Styrene | Not detected UG/LHighest single sampleSource water | 100 UG/LMCL | None detected |
| Tce | Not detected UG/LHighest single sampleSource water | 5 UG/LMCL | None detected |
| Toxaphene | Not detected UG/LHighest single sampleSource water | 3 UG/LMCL | None detected |
| Trans Dichloroethylene 12 | Not detected UG/LHighest single sampleEntry point | 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 |
| Twofourd | Not detected UG/LHighest single sampleEntry point | 70 UG/LMCL | None detected |
| Vinyl Chloride | Not detected UG/LHighest single sampleSource water | 0.5 UG/LMCL | None detected |
| Mcaa | 0.7915 UG/LAverageDistribution | None set | Detected — no federal limit |
VOCs & pesticides
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| AtrazineA widely used agricultural herbicide that reaches water through runoff. | Not detected UG/LHighest single sampleEntry point | 1 UG/LMCL | None detected |
| Benzene | Not detected UG/LHighest single sampleSource water | 1 UG/LMCL | None detected |
| Benzo(a)pyrene | Not detected UG/LHighest single sampleEntry point | 0.2 UG/LMCL | None detected |
| Dalapon | Not detected UG/LHighest single sampleEntry point | 200 UG/LMCL | None detected |
| Ethylbenzene | Not detected UG/LHighest single sampleSource water | 300 UG/LMCL | None detected |
| Simazine | Not detected UG/LHighest single sampleSource water | 4 UG/LMCL | None detected |
| Toluene | Not detected UG/LHighest single sampleEntry point | 150 UG/LMCL | None detected |
| XylenesA group of industrial solvents found in gasoline and paint. | Not detected UG/LHighest single sampleEntry point | 1750 UG/LMCL | None detected |
Source: Contra Costa Water District, CA's 2025 Consumer Confidence Report — the annual drinking-water report every U.S. utility is required to publish. The numbers on this page are the utility's own. A water-quality report covers an entire service area, not a single address.
People also ask about Contra Costa Water District, CA's water
+Is Contra Costa Water District, CA tap water safe to drink in 2025?
The 2025 Consumer Confidence Report for the Contra Costa Water District, CA water utility lists 4 contaminants at or above the federal limit: Odor, Iron, Turbidity, and Color. 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 Contra Costa Water District, CA tap water?
105 contaminants were measured in Contra Costa Water District, CA's 2025 Consumer Confidence Report, spanning other, metals, and inorganic chemicals. 85 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 Contra Costa Water District, CA tap water?
4 contaminants in Contra Costa Water District, CA's 2025 report sit at or above the federal limit: Odor (4.5× the limit); Iron (1.6× the limit); Turbidity (1.5× the limit); Color (1.2× 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 Contra Costa Water District, CA tap water?
The contaminant with the highest measured value relative to its federal limit in the 2025 report is Odor, at 4.5× the federal threshold. It belongs to the physical & aggregate family of contaminants.
+Where does the data on this page come from?
Every value is transcribed from Contra Costa Water District, 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 Contra Costa Water District, 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.
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