Is Colusa, CA Tap Water Safe to Drink?
Graded C- — but Manganese was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
59/100
waterverge.com Colusa, CA — Water Quality Report
Colusa's drinking water received a grade of C- (59 out of 100), indicating poor water quality. The city's 6 water systems serve approximately 10,524 residents using groundwater.
Lead levels were measured at 6.6 ppb (90th percentile), which is within EPA limits but above recommended levels. UCMR 5 testing detected 1 PFAS compound in the water supply.
The system has 352 violations on record, including 6 health-based violations. 25 remain unresolved.
What to know about Colusa's water
Colusa ranks #571 out of 694 cities in California for water quality, placing it among the lowest-rated in the state.
Colusa relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
PFAS compounds were detected in testing, though levels remain within current EPA limits. Residents seeking extra precaution may consider an activated carbon or reverse osmosis filter.
While lead levels are within EPA limits, they are above the recommended 5 ppb threshold that health organizations consider ideal. A point-of-use filter adds an extra layer of protection.
The system has seen 8 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
Water quality score
See methodology →Is Colusa, CA water safe to drink?
Colusa's drinking water has significant quality concerns based on EPA testing data. With a grade of C- (59/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 6 water systems serve approximately 10,524 residents using groundwater (wells).
Recent water quality updates for Colusa
A timeline of significant water quality events, violations, and data updates.
Detected at levels within current EPA limits. PFAS persist indefinitely in the environment.
Latest EPA compliance and testing data incorporated into Colusa's water quality assessment. Grade: C- (59/100).
1 health-based. Contaminants: LEAD AND COPPER RULE REVISIONS.
Federal disaster declaration (FEMA DR-4683). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-3591). Flood event — may have impacted local water infrastructure.
Contaminants: Revised Total Coliform Rule.
Key contaminant findings
Based on the most recent EPA sampling data for Colusa's water supply.
Within EPA limits but above the American Academy of Pediatrics recommended level of 1 ppb. An NSF 53-certified filter provides additional protection.
Detected but within current EPA limits. PFAS do not break down in the environment and can accumulate in the body over time. An activated carbon filter can reduce exposure.
Violation history
Colusa's water system has 352 total violations on record, including 6 health-based violations. 25 remain unresolved. 8 violations were issued in the last 5 years.
Flood & environmental risk
Colusa County has experienced 8 federally declared disasters since 1964. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include Sacramento R A Colusa.
Where does Colusa's water come from?
Colusa's drinking water comes from groundwater (wells), supplied by 6 water systems serving approximately 10,524 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Sacramento R A Colusa (river).
What Colusa residents can do
Recommended: Activated carbon or reverse osmosis filter. This addresses the specific contaminants found in Colusa's water.
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Run cold water for 30 seconds before drinking, especially in the morning. Lead and copper leach from household plumbing when water sits in pipes.
Colusa's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Forever chemicals overview
National PFAS report →Violation summary
Violations & advisories
Top industrial polluters within 10 miles of Colusa
Industrial polluters nearby
Reported releases to surface water by facilities near Colusa, ranked by pounds discharged annually.
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
LATHAM POOL PRODUCTS INC-CA WILLIAMS, CA95987 | — | — | 7.9 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Flood & disaster history
Colusa County has experienced 8 federally declared disasters since 1964. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Recommended water filters
Based on contaminants detected in Colusa's water supply, we recommend the following filter types.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 6.6 | 15 | ppb | Inorganic | Safe |
| 11Cl-PF3OUdS | ND | HI | µg/L | PFAS | Not Detected |
| 4:2 FTS | ND | HI | µg/L | PFAS | Not Detected |
| 6:2 FTS 6:2 FTSPFAS A fluorotelomer sulfonate commonly found at sites contaminated with aqueous film-forming foam (AFFF) used in firefighting. Health EffectsPotential liver toxicity and endocrine disruption. Less studied but identified as a contaminant of concern. EPA LimitNo individual MCL (not yet regulated) Common SourcesFirefighting foam (AFFF), airports, military bases, and industrial facilities. | ND | HI | µg/L | PFAS | Not Detected |
| 8:2 FTS | ND | HI | µg/L | PFAS | Not Detected |
| 9Cl-PF3ONS | ND | HI | µg/L | PFAS | Not Detected |
| ADONA | ND | HI | µg/L | PFAS | Not Detected |
| HFPO-DA HFPO-DA (GenX)PFAS A replacement for PFOA in manufacturing, marketed as safer but still a persistent "forever chemical." Also known as GenX. Health EffectsLiver and kidney effects, reproductive toxicity, immune system effects, and potential cancer risk. EPA Limit10 ppt MCL Common SourcesFluoropolymer manufacturing (used as PFOA replacement), industrial wastewater discharge. | ND | 0.01 | µg/L | PFAS | Not Detected |
| lithium LithiumInorganic A naturally occurring alkali metal found in groundwater. Monitored under UCMR 5 to assess occurrence in drinking water. Health EffectsKidney effects at high doses. Low-level exposure effects under study; some research suggests neurological effects. EPA LimitNo MCL (monitoring only under UCMR 5) Common SourcesNatural mineral deposits, geothermal water, and industrial discharge. | 41.900 | HI | µg/L | PFAS | Detected |
| NEtFOSAA | ND | HI | µg/L | PFAS | Not Detected |
| NFDHA | ND | HI | µg/L | PFAS | Not Detected |
| NMeFOSAA | ND | HI | µg/L | PFAS | Not Detected |
| PFBA PFBAPFAS One of the shortest-chain PFAS compounds. Very mobile in water and difficult to remove with standard filtration. Health EffectsThyroid effects, potential developmental toxicity. Shorter half-life in body than long-chain PFAS. EPA LimitNo individual MCL (not yet regulated) Common SourcesDegradation of longer-chain PFAS, industrial discharge, and firefighting foam. | ND | HI | µg/L | PFAS | Not Detected |
| PFBS PFBSPFAS A short-chain PFAS used as a replacement for PFOS. While it clears the body faster than long-chain PFAS, it still persists in the environment. Health EffectsThyroid effects, reproductive and developmental toxicity, kidney effects. EPA LimitPart of Hazard Index (1.0) Common SourcesIndustrial discharge, firefighting foam, and as a replacement chemical in manufacturing. | ND | HI | µg/L | PFAS | Not Detected |
| PFDA | ND | HI | µg/L | PFAS | Not Detected |
| PFDoA | ND | HI | µg/L | PFAS | Not Detected |
| PFEESA | ND | HI | µg/L | PFAS | Not Detected |
| PFHpA PFHpAPFAS A medium-chain PFAS compound found in various environmental samples. Less studied than PFOA/PFOS but still considered a contaminant of concern. Health EffectsLiver effects, potential developmental toxicity, and endocrine disruption. EPA LimitPart of Hazard Index (1.0) Common SourcesDegradation of longer-chain PFAS, industrial discharge, and contaminated water sources. | ND | HI | µg/L | PFAS | Not Detected |
| PFHpS | ND | HI | µg/L | PFAS | Not Detected |
| PFHxA PFHxAPFAS A short-chain PFAS replacement chemical widely used after manufacturers phased out longer-chain PFAS. Very commonly detected in water. Health EffectsLiver and kidney effects, potential thyroid disruption. Considered less toxic than long-chain PFAS but still persistent. EPA LimitNo individual MCL (not yet regulated) Common SourcesIndustrial processes, firefighting foam (AFFF), food packaging, and textile treatment. | ND | HI | µg/L | PFAS | Not Detected |
| PFHxS PFHxSPFAS A medium-chain PFAS found in firefighting foam and consumer products. It has a long half-life in the human body, similar to long-chain PFAS. Health EffectsImmune system effects, thyroid disruption, and potential reproductive and developmental harm. EPA LimitPart of Hazard Index (1.0) Common SourcesFirefighting foam (AFFF), waterproof textiles, food packaging, and industrial discharge. | ND | HI | µg/L | PFAS | Not Detected |
| PFMBA | ND | HI | µg/L | PFAS | Not Detected |
| PFMPA | ND | HI | µg/L | PFAS | Not Detected |
| PFNA PFNAPFAS A long-chain PFAS compound used in manufacturing fluoropolymers. It bioaccumulates in the body and is very persistent in the environment. Health EffectsDevelopmental effects, liver toxicity, immune suppression, and potential cancer risk. EPA LimitPart of Hazard Index (1.0) Common SourcesFluoropolymer manufacturing, industrial emissions, and contaminated water sources. | ND | HI | µg/L | PFAS | Not Detected |
| PFOA PFOAPFAS A long-chain PFAS ("forever chemical") once widely used in nonstick coatings and firefighting foam. It persists in the body and environment for years. Health EffectsLinked to kidney and testicular cancer, thyroid disease, elevated cholesterol, and reproductive issues. EPA Limit4.0 ppt MCL Common SourcesIndustrial discharge, firefighting foam (AFFF), nonstick cookware manufacturing, and contaminated groundwater. | ND | 0.004 | µg/L | PFAS | Not Detected |
| PFOS PFOSPFAS A long-chain PFAS compound historically used in stain-resistant coatings and firefighting foam. One of the most studied and persistent PFAS chemicals. Health EffectsLiver damage, immune system suppression, thyroid disruption, increased cholesterol, and potential cancer risk. EPA Limit4.0 ppt MCL Common SourcesFirefighting foam (AFFF), industrial sites, stain-resistant fabric treatments, and contaminated groundwater. | ND | 0.004 | µg/L | PFAS | Not Detected |
| PFPeA PFPeAPFAS A short-chain PFAS compound commonly detected in drinking water. One of the most frequently found PFAS in UCMR 5 monitoring. Health EffectsLess studied than PFOA/PFOS. Potential liver and thyroid effects. Research is ongoing. EPA LimitNo individual MCL (not yet regulated) Common SourcesIndustrial discharge, firefighting foam degradation, and consumer products. | ND | HI | µg/L | PFAS | Not Detected |
| PFPeS | ND | HI | µg/L | PFAS | Not Detected |
| PFTA | ND | HI | µg/L | PFAS | Not Detected |
| PFTrDA | ND | HI | µg/L | PFAS | Not Detected |
| PFUnA | ND | HI | µg/L | PFAS | Not Detected |
Lead level trend (90th percentile)
See how Colusa compares by contaminant
Explore where Colusa ranks among all California cities for specific contaminants.
Water source & infrastructure
Where Colusa's water comes from
Colusa's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by local government ownership and serves approximately 10,524 people through 6 water systems.
Water bodies near Colusa
Colusa is located near 1 notable water body. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Colusa
| System Name | PWSID | Population | Source |
|---|---|---|---|
| CITY OF COLUSA | CA0610002 | 6,447 | GW |
| Colusa Southern System | 090605047 | 3,474 | GW |
| COLUSA CO. SERVICE AREA #2-STONYFORD | CA0600005 | 250 | GW |
| COLUSA CO. SERVICE AREA #1-CENTURY RANCH | CA0600012 | 246 | SW |
| Colusa Northern System | 090605046 | 67 | GW |
| CEDAR CREEK MOBILEHOME PARK | CA4500063 | 40 | GW |
How Colusa compares
Full California rankings →Colusa's score of 59/100 is on par with the average of 57/100 among major California cities. It outscores 5 of 10 nearby cities.
Nearby cities
View California rankings →ZIP codes served by Colusa
The water systems serving Colusa cover 1 ZIP code. Select any ZIP to see which water systems serve that area.
About Colusa, CA
Wikipedia →Colusa is a city in and the county seat of Colusa County, California, located in the Sacramento Valley region of the Central Valley. The population was 6,411 at the 2020 census, up from 5,971 at the 2010 census. Colusa originates from the local Coru Native American tribe, who in the 1840s lived on the opposite side of the Sacramento River.
Learn more about your water
Guides and resources related to Colusa's water quality findings.
Explore water quality across Colusa
Frequently asked questions
Is Colusa, CA tap water safe to drink?
Colusa's water quality earned a grade of C- (59/100). Significant issues have been found. A water filter is strongly recommended. The city ranks #571 out of 694 cities tested in California.
What contaminants are in Colusa's water?
Lead was measured at 6.6 ppb (90th percentile). 1 PFAS compound was detected. 352 violations are on record.
How is Colusa's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Colusa?
While lead levels are within EPA limits, a filter adds extra protection. PFAS compounds have been detected. A filter with activated carbon can help reduce exposure.
Where does Colusa's water come from?
Colusa's water is sourced from Groundwater. The city has 6 water systems serving approximately 10,524 residents.
What health violations has Colusa's water system had?
Colusa has 6 health-based violations on record. The most recent violation was recorded in October 2024. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 25 violations remain unresolved.
Is Colusa's groundwater at risk of contamination?
Colusa uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 352 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Colusa's water compare to other cities?
Colusa ranks #571 out of 694 cities in California (better than 18% of state cities) and #12227 out of 15744 cities nationally (22th percentile). The grade of C- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.