Great Oaks Wc Inc.
EPA ID: CA4310022 · 110,088 people served · 7 ZIP codes
ZipCheckup's reading of EPA SDWIS for Great Oaks Wc Inc. (CA4310022): no EPA violations recorded in the last five years. For the full five-year period covered by EPA monitoring, Great Oaks Wc Inc. has supplied tap water to 110,088 residents with no violations of any type on record.
Data: EPA SDWIS
Service Area Map
Coverage area for Great Oaks Wc Inc. Source: EPA SDWIS service area boundaries.
Service area boundary
Service Area Demographics
The Great Oaks Wc Inc. serves a community with a median household income of $164,129 and an estimated 251,499 residents across its service area. Approximately 67% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
💧 Where Does Your Water Come From?
Great Oaks Wc Inc.'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.
Superfund Proximity Note: This service area ranks in the 80th percentile nationally for proximity to Superfund (NPL) sites. Groundwater sources near contaminated sites may face elevated risk from industrial chemicals.
Infrastructure Risk
PFAS Detected in Service Area
PFAS ("forever chemicals") have been detected in water serving this system's area. 28 detections recorded. 7 exceed federal EPA limits (4 ppt for PFOA/PFOS).
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
Great Oaks Wc Inc. (EPA ID: CA4310022) is a community water system in California that serves approximately 110,088 people from groundwater sources.
This system provides water to 7 ZIP codes across 1 community.
Violation History
Lead & Copper
EPA Lead and Copper Rule evidence attributed directly to this water system:
| Lead Level | Exceeds Action Level | Sample Date |
|---|---|---|
| 0 mg/L | No | N/A |
No copper action-level exceedance record appears for this PWSID in the accepted LCR snapshot. This does not establish a clean copper measurement.
Radon Risk in Service Area
Dominant radon zone for ZIP codes served by this system: Zone 2 (Moderate Risk)
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
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.
- 95111 - San Jose
- 95119 - San Jose
- 95120 - San Jose
- 95123 - San Jose
- 95136 - San Jose
- 95138 - San Jose
- 95139 - San Jose
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for Great Oaks Wc Inc. (CA4310022) on EPA.gov.
Frequently Asked Questions
Is Great Oaks Wc Inc. water safe to drink?
The accepted 2026Q2 ECHO snapshot contains zero violation records for Great Oaks Wc Inc. in the inclusive 2021-2026 record-year window. This is a compliance-record finding, not a guarantee about water at a specific tap.
How many people does Great Oaks Wc Inc. serve?
Great Oaks Wc Inc. serves approximately 110,088 people across 7 ZIP codes in California.
Where does Great Oaks Wc Inc. get its water?
The primary water source is groundwater.
Federal UCMR5 PFAS Monitoring: Detected
This water system was tested under the federal EPA Unregulated Contaminant Monitoring Rule (UCMR5). PFAS compounds were detected below the current state-enforceable MCL.
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 →
Frequently Asked Questions
How to cite this page
ZipCheckup. (n.d.). Great Oaks Wc Inc., CA: Serves 110K People. https://zipcheckup.com/water-system/ca4310022/
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