Drinking water quality · 2026
· Verified
What's in Contra Costa Water District, CA tap water
97 contaminants were measured in the Contra Costa Water District, CA water system's 2026 annual report. Each is shown below against its federal limit — 4 sit at or above that limit.
- Reporting year
- 2026
- Contaminants measured
- 97
- Over federal limit
- 4
- Approaching the limit
- 0
- Worst contaminant
- Turbidity
- Service area
- CA
4.2× the limit
state-level CCR
At or above the federal 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 |
|---|---|---|---|
| TurbidityA measure of cloudiness from suspended particles in the water. | 21 NTUAverageSource water | 5 NTUMCL | At or above the limit |
| ColorA measure of visible tint in the water. | 50 UNITSAverageSource water | 15 UNITSMCL | At or above the limit |
| OdorA measure of detectable smell in the water. | 8 TONAverageSource water | 3 TONMCL | At or above the limit |
| Specific ConductanceA measure of how well water conducts electricity, which tracks dissolved mineral content. | 261 UMHO/CMAverageSource water | 1600 UMHO/CMMCL | Within the limit |
| Total Dissolved SolidsTotal dissolved solids — the combined content of all dissolved minerals and salts. | 150 MG/LAverageSource water | 1000 MG/LMCL | Within the limit |
| AlkalinityA measure of the water's capacity to neutralize acids. | 39 MG/LAverageSource water | None set | Detected — no federal limit |
| HardnessA measure of dissolved calcium and magnesium minerals. | 65 MG/LAverageSource water | None set | Detected — no federal limit |
| pHA measure of how acidic or basic the water is. | 7.51 PHAverageSource water | None set | Detected — no federal limit |
Metals
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| IronA naturally occurring metal common in groundwater. | 899 UG/LAverageSource water | 300 UG/LMCL | At or above the limit |
| AluminumA common element sometimes used as a treatment coagulant. | 776 UG/LAverageSource water | 1000 UG/LMCL | Within the limit |
| ManganeseA naturally occurring metal from soil and rock. | 22.8 UG/LAverageSource water | 50 UG/LMCL | Within the limit |
| Chromium, HexavalentHexavalent chromium ('chromium-6') — the more toxic form of chromium. | 0.089 UG/LAverageSource water | 10 UG/LMCL | Within the limit |
| Antimony | Not detected UG/LHighest single sampleSource water | 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 sampleSource water | 2 UG/LMCL | None detected |
| NickelA metal from natural deposits and industrial discharge. | Not detected UG/LHighest single sampleSource water | 100 UG/LMCL | None detected |
| Strontium | Not detected PCI/LHighest single sampleSource water | 8 PCI/LMCL | None detected |
| Thallium | Not detected UG/LHighest single sampleSource water | 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 |
| CalciumA naturally occurring mineral that contributes to water hardness. | 16.45 MG/LAverageEntry point | None set | Detected — no federal limit |
| MagnesiumA naturally occurring mineral that contributes to water hardness. | 10.212499999999999 MG/LAverageEntry point | None set | Detected — no federal limit |
| PotassiumA naturally occurring mineral from rock and soil. | 2.49 MG/LAverageSource water | None set | Detected — no federal limit |
| SodiumA naturally occurring salt component. | 50.65 MG/LAverageEntry point | None set | Detected — no federal limit |
Inorganic chemicals
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| ChlorideA naturally occurring salt compound. | 35 MG/LAverageSource water | 500 MG/LMCL | Within the limit |
| SulfateA naturally occurring mineral from rock and soil. | 11 MG/LAverageSource water | 500 MG/LMCL | Within the limit |
| Ammonia | Not detected MG/LHighest single sampleSource water | None set | None detected |
| BromideA naturally occurring salt found in source water. | 0.1 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 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 |
| Dinoseb | Not detected UG/LHighest single sampleSource water | 7 UG/LMCL | None detected |
| Diquat | Not detected UG/LHighest single sampleSource water | 20 UG/LMCL | None detected |
| Edb | Not detected UG/LHighest single sampleSource water | 0.05 UG/LMCL | None detected |
| Endothall | Not detected UG/LHighest single sampleSource water | 100 UG/LMCL | None detected |
| Endrin | Not detected UG/LHighest single sampleSource water | 2 UG/LMCL | None detected |
| Glyphosate | Not detected UG/LHighest single sampleSource water | 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 sampleSource water | 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 sampleSource water | 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 sampleSource water | 5 UG/LMCL | None detected |
| Pentachlorophenol | Not detected UG/LHighest single sampleSource water | 1 UG/LMCL | None detected |
| Picloram | Not detected UG/LHighest single sampleSource water | 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 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 |
| Twofourd | Not detected UG/LHighest single sampleSource water | 70 UG/LMCL | None detected |
| Vinyl Chloride | Not detected UG/LHighest single sampleSource water | 0.5 UG/LMCL | None detected |
| Mcaa | 1.2237500000000001 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 sampleSource water | 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 sampleSource water | 0.2 UG/LMCL | None detected |
| Dalapon | Not detected UG/LHighest single sampleSource water | 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 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 |
Source: Contra Costa Water District, CA's 2026 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 2026?
The 2026 Consumer Confidence Report for the Contra Costa Water District, CA water utility lists 4 contaminants at or above the federal limit: Turbidity, Color, Iron, and Odor. 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?
97 contaminants were measured in Contra Costa Water District, CA's 2026 Consumer Confidence Report, spanning other, metals, and vocs & pesticides. 79 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 2026 report sit at or above the federal limit: Turbidity (4.2× the limit); Color (3.3× the limit); Iron (3.0× the limit); Odor (2.7× 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 2026 report is Turbidity, at 4.2× 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 2026 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 2026 report; a new report will replace it once the utility publishes its next annual update.
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