All 3 systems met the sampling requirement for a yearly average. Of those systems, 1 had at least one yearly average at or above a study benchmark and 2 did not.
EPA-based study benchmark: a fixed, unrounded research cutoff used to reproduce EPA’s January 2026 technical-assistance classification based on the April 2024 federal levels. It is not a current federal or state standard. The label does not determine compliance, household exposure, or health risk.
State rules: The labels on this page use fixed research cutoffs based on the April 2024 federal levels. Guam may use different current standards or guidance. These UCMR 5 results do not determine current federal or state compliance. Find the official Guam drinking-water program →
Find your water system
A ZIP code finds possible public water systems for an area; it cannot identify the supplier for a specific home. Confirm the provider using a water bill or utility record.
System counts in Guam
Each count shows how many included water systems had a yearly average at or above the named study benchmark.
| Study benchmark | Systems at or above benchmark | Water systems included | Percent |
|---|---|---|---|
| PFOA: 4.05 ppt study benchmark (reproduces EPA classification around 4 ppt) | 1 | 3 | 33.3% |
| PFOS: 4.05 ppt study benchmark (reproduces EPA classification around 4 ppt) | 1 | 3 | 33.3% |
| PFHxS: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 1 | 3 | 33.3% |
| PFNA: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 0 | 3 | 0.0% |
| HFPO-DA: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 0 | 3 | 0.0% |
| Hazard Index: 1.5 study benchmark with at least two detected components (reproduces EPA classification around 1) | 1 | 3 | 33.3% |
Community water systems with complete monitoring
“Complete monitoring” means at least one sampling location had every required sample needed to calculate a yearly average. It does not mean every location or home was tested. Each PWSID appears once, preventing double counting across ZIP associations.
| Public water system | PWSID | Population served | Primary source | Sampling locations | Study benchmark result |
|---|---|---|---|---|---|
| ANDERSEN AIR FORCE BASE WATER SYSTEM | GU0000009 | 7,700 | Ground water | 4 | Below all study benchmarks |
| GWA NORTHERN WATER SYSTEM | GU0000006 | 139,207 | Ground water | 58 | At or above a study benchmark |
| U.S. NAVY WATER SYSTEM | GU0000010 | 12,780 | Surface water | 6 | Below all study benchmarks |
What is included
Each active community water system with enough required samples for a yearly average is counted once, even if it is linked with several ZIP codes. Private wells are excluded, and UCMR 5 did not comprehensively monitor every small system.