City of Colusa
EPA ID: CA0610002 · 6,447 people served · 6 ZIP codes
Per EPA records, City of Colusa: 17 unresolved violations, 6,447 people in service area.
Data: EPA SDWIS Last verified: 2026-04-02
Compliance Trajectory
Stable · Risk tier: High · 95% chance of violation in next 12 months
Violations went from 6 (2021) to 9 (2024). Violation counts have remained relatively steady.
Service Area Map
Coverage area for City of Colusa Source: EPA SDWIS service area boundaries.
Service area boundary — Grade B
Service Area Demographics
The City of Colusa serves a community with a median household income of $79,375 and an estimated 21,742 residents across its service area. Approximately 69% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
Environmental Justice Note: 50% of the population in this service area is classified as disadvantaged under EPA's EJScreen criteria. Communities with higher disadvantaged populations often face disproportionate environmental and health burdens, including aging water infrastructure and limited resources for remediation.
💧 Where Does Your Water Come From?
City of Colusa's water is pumped from underground aquifers. Groundwater is naturally filtered through rock and soil, but it can be vulnerable to PFAS contamination, nitrates from agriculture, and industrial chemicals that seep into the water table.
About 1% of homes in Colusa County, California rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Infrastructure Risk
Detected Contaminants
How City of Colusa compares to EPA limits
What This Means For You
Barium at 16 mg/L exceeds the EPA maximum of 2 mg/L.
Consumer Confidence Report Rule at 3 mg/L exceeds the EPA maximum of mg/L.
Stage 2 DBP Rule at 2 mg/L exceeds the EPA maximum of mg/L.
Stage 1 DBP Rule at 1 mg/L exceeds the EPA maximum of mg/L.
Comparable Water Systems
Similar-sized systems in California
Estimated Remediation Costs
Average estimated costs across ZIP codes served by this system
Based on national averages for common remediation projects. Actual costs vary by property. Only issues flagged by EPA, FEMA, or state data for each ZIP code are included.
System Overview
City of Colusa (EPA ID: CA0610002) is a community water system in California that serves approximately 6,447 people from groundwater sources.
This system provides water to 6 ZIP codes across 6 communities.
Average Home Safety Score: B (76/100)
Based on water quality violations, lead levels, and radon risk across all ZIP codes served by this system.
Violation History
Recent Violations
| Date | Contaminant | Type | Status |
|---|---|---|---|
| July 2, 2025 | Stage 2 DBP Rule | Monitoring | Unresolved |
| June 1, 2025 | Consumer Confidence Report Rule | Monitoring | Unresolved |
| October 17, 2024 | Stage 2 DBP Rule | Health-based | Unresolved |
| October 17, 2024 | Stage 2 DBP Rule | Monitoring | Unresolved |
| October 1, 2024 | Barium | Health-based | Unresolved |
| July 1, 2024 | Barium | Health-based | Unresolved |
| April 1, 2024 | Barium | Health-based | Unresolved |
| January 1, 2024 | Consumer Confidence Report Rule | Monitoring | Resolved |
| January 1, 2024 | Barium | Health-based | Unresolved |
| October 1, 2023 | Stage 1 DBP Rule | Monitoring | Resolved |
| October 1, 2023 | Barium | Health-based | Unresolved |
| July 1, 2023 | Barium | Health-based | Unresolved |
| April 1, 2023 | Barium | Health-based | Unresolved |
| January 1, 2023 | Barium | Health-based | Unresolved |
Contaminants Detected
The following contaminants have been flagged in EPA records for this water system:
| Contaminant | Category | Violations | Health-Based |
|---|---|---|---|
| Barium | Inorganic | 16 | Yes |
| Consumer Confidence Report Rule | Reporting Failure | 3 | No |
| Stage 2 DBP Rule | Treatment Failure | 2 | Yes |
| Stage 1 DBP Rule | Treatment Failure | 1 | No |
Lead & Copper
EPA Lead and Copper Rule sampling data for ZIP codes served by this system:
| ZIP Code | Lead Level | Exceeds Limit | Sample Date |
|---|---|---|---|
| 95950 | 0.00978 mg/L | No | N/A |
| 95932 | 0.0068 mg/L | No | N/A |
| 95912 | 0.0011 mg/L | No | N/A |
| 95955 | 0.00098 mg/L | No | N/A |
Radon Risk in Service Area
Dominant radon zone for ZIP codes served by this system: Zone 3 (Low Risk)
Need help with your water quality?
Typical cost: Water test: typically $20–$50 (DIY kit) · Professional inspection: $150–$400
Find the Right Water FilterFree tip: Let cold water run for 2 minutes before drinking — this helps flush lead from your pipes.
ZIP Codes Served
Coverage: Service area ZIP codes sourced from EPA Community Water System Service Area Boundaries v3 (March 2026 release). These ZIPs reflect the actual deployment footprint recorded by CA or modeled from parcel and building-footprint data.
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for City of Colusa (CA0610002) on EPA.gov.
Frequently Asked Questions
Is City of Colusa water safe to drink?
City of Colusa has recorded 16 health-based violations in the past 5 years. While the system is required to treat water to meet federal standards, you may want to consider additional precautions such as a certified water filter.
How many people does City of Colusa serve?
City of Colusa serves approximately 6,447 people across 6 ZIP codes in California.
Where does City of Colusa get its water?
The primary water source is groundwater.
Water Source & Treatment
Where this water originates and how it's treated before reaching your tap.
Source: City of Colusa Consumer Confidence Report.
ZipCheckup is not affiliated with this water utility. Treatment and source data are sourced from the utility's published CCR filings.
Federal UCMR5 PFAS Monitoring: Tested Clean
This water system was tested under the federal EPA Unregulated Contaminant Monitoring Rule (UCMR5). No PFAS compounds were detected.
Current MCL reflects the lowest state-enforceable limit (NYS 10 ppt for PFOA/PFOS, effective August 2020). The federal final MCL of 4 ppt for PFOA/PFOS (EPA April 2024 rule) is not enforceable until April 2029. Detections above 4 ppt but below 10 ppt are below current MCL but above the future federal limit.
Source: U.S. EPA UCMR5 (Unregulated Contaminant Monitoring Rule, 5th cycle) — per-system federal sampling, 2023–2025. EPA UCMR5 monitoring program →
Lead Service Line Replacement Tracker
This water utility's lead service line (LSL) replacement program is tracked from public Consumer Confidence Report filings. Email signup notifies subscribers when the utility files an updated replacement plan or progress milestone.
City of Colusa
ZipCheckup is not affiliated with this water utility. LSL replacement-program data is sourced from public CCR filings published by the utility. Subscription notifications are based on automated parsing of subsequent CCR releases.
Learn more about Lead and Copper Rule replacement requirements →
Lead Service Line Inventory
Service line breakdown reported under the federal Lead and Copper Rule Improvements (LCRI) inventory requirement:
This system reports zero confirmed lead service lines in its inventory. Unknown-material counts may still warrant verification.
Federal LCRI rule (effective October 2024) requires every public water system to inventory its service lines and complete lead-line replacement within 10 years.
Source: EPA SDWIS Federal Service Line Inventory (Phase 2) · Submitted 2026
ZipCheckup is not affiliated with the utility or state agency. Inventory figures render verbatim from the public LCRI submission cited above; ZipCheckup does not perform inspections or replacements.
Frequently Asked Questions
What You Can Do
Test your water
Home test kits can detect lead, bacteria, and other contaminants at your tap. Find the right filter →
Check your specific ZIP code
Water quality can vary within a system. View nearest ZIP report →
Contact your utility
City of Colusa (EPA ID: CA0610002) — request the latest Consumer Confidence Report or ask about specific contaminants.