Sentinel Gap Water Assn
EPA ID: WA5376620 · 226 people served · 1 ZIP code
Compared to the national average for mid-size utilities, Sentinel Gap Water Assn sits well above the baseline — five years of EPA monitoring show no violations, no MCL exceedances, and no enforcement actions for the full service territory of 226 people.
Data: EPA SDWIS Last verified: 2026-04-02
Service Area Map
Coverage area for Sentinel Gap Water Assn Source: EPA SDWIS service area boundaries.
Service area boundary
Service Area Demographics
The Sentinel Gap Water Assn serves a community with a median household income of $62,851 and an estimated 8,098 residents across its service area.
Environmental Justice Note: 63% 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?
Sentinel Gap Water Assn'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 Grant County, Washington rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Infrastructure Risk
Comparable Water Systems
Similar-sized systems in Washington
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
Sentinel Gap Water Assn (EPA ID: WA5376620) is a community water system in Washington that serves approximately 226 people from groundwater sources.
This system serves ZIP code 99349 in Mattawa.
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
- 99349 — Mattawa
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for Sentinel Gap Water Assn (WA5376620) on EPA.gov.
Frequently Asked Questions
Is Sentinel Gap Water Assn water safe to drink?
Based on EPA records, Sentinel Gap Water Assn has no recorded violations in the past 5 years — a positive indicator of water quality management.
How many people does Sentinel Gap Water Assn serve?
Sentinel Gap Water Assn serves approximately 226 people across 1 ZIP code in Washington.
Where does Sentinel Gap Water Assn get its water?
The primary water source is groundwater.