Sandmound Mutual
EPA ID: CA0707556 · 100 people served · 1 ZIP code
Water monitoring history at Sandmound Mutual shows a clean slate — EPA tracking over the past five years turned up no violations, and 100 residents continue to receive fully compliant service.
Data: EPA SDWIS Last verified: 2026-04-02
Service Area Map
Coverage area for Sandmound Mutual Source: EPA SDWIS service area boundaries.
Service area boundary
Service Area Demographics
The Sandmound Mutual serves a community with a median household income of $78,393 and an estimated 2,144 residents across its service area. Approximately 71% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
💧 Where Does Your Water Come From?
Sandmound Mutual'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 Contra Costa County, California rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Superfund Proximity Note: This service area ranks in the 60th percentile nationally for proximity to Superfund (NPL) sites. Groundwater sources near contaminated sites may face elevated risk from industrial chemicals.
Infrastructure Risk
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
Sandmound Mutual (EPA ID: CA0707556) is a community water system in California that serves approximately 100 people from groundwater sources.
This system serves ZIP code 94511 in Bethel Island.
Violation History
Lead & Copper
No Lead and Copper Rule sampling data available for this water system.
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
- 94511 — Bethel Island
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for Sandmound Mutual (CA0707556) on EPA.gov.
Frequently Asked Questions
Is Sandmound Mutual water safe to drink?
Based on EPA records, Sandmound Mutual has no recorded violations in the past 5 years — a positive indicator of water quality management.
How many people does Sandmound Mutual serve?
Sandmound Mutual serves approximately 100 people across 1 ZIP code in California.
Where does Sandmound Mutual get its water?
The primary water source is groundwater.
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.