Gwa Northern Water System
Gwa Northern Water System (EPA ID GU0000006) in Mangilao, GU supplies groundwater (wells) to about 139,207 people: no health-based violations since 2016, latest lead result 1.7 ppb, PFAS 135 ppt.
No health-based violations reported since 2016.
90th-percentile lead in the latest round (Jan 2023). Lead comes mostly from household plumbing and service lines, so individual homes can be higher.
Highest PFOA or PFOS result in EPA’s 2023–2025 testing was at or above 4.0 ppt, EPA’s 2024 maximum contaminant level for each. 8 PFAS compounds detected.
Service area
EPA service-area boundary (state-supplied or EPA-modeled)System facts
Health-based violations
No health-based violations reported since 2016.
Lead
90th-percentile lead per sampling round (90% of the homes sampled were at or below this level). Black line: EPA’s 15 ppb action level; under the Lead and Copper Rule Improvements the action level becomes 10 ppb from 2027.
PFAS
| Compound | Highest result | Samples with detection | EPA limit |
|---|---|---|---|
| PFOS | 135 ppt | 37 of 121 | 4 ppt MCL |
| PFHxS | 80 ppt | 80 of 121 | — |
| PFPeA | 47.5 ppt | 66 of 121 | — |
| PFHxA | 37.1 ppt | 56 of 121 | — |
| PFBS | 34.9 ppt | 43 of 121 | — |
| PFHpA | 18.5 ppt | 22 of 121 | — |
| PFOA | 18.3 ppt | 9 of 121 | 4 ppt MCL |
| PFBA | 18.1 ppt | 8 of 121 | — |
| PFNA | not detected | 0 of 121 | — |
| PFDA | not detected | 0 of 121 | — |
| HFPO-DA (GenX) | not detected | 0 of 121 | — |
EPA Fifth Unregulated Contaminant Monitoring Rule (UCMR 5), samples 2023–2025; ppt = parts per trillion (ng/L). The 4.0 ppt maximum contaminant levels for PFOA and PFOS were set by EPA in 2024; water systems have until the end of the decade to comply.
What this is — and isn’t. These are records your water utility and state reported to the EPA, and the EPA’s radon map for your county. They describe the system and the area, not the water from your own tap or the air in your home. For that, read your utility’s annual Consumer Confidence Report and test: lead and radon tests are inexpensive.
Questions
Has Gwa Northern Water System had drinking water violations?
No health-based violations reported since 2016.
What is the lead level in Gwa Northern Water System water?
The latest 90th-percentile lead result (Jan 2023) was 1.7 ppb. EPA’s action level is 15 ppb (10 ppb from 2027).
Does Gwa Northern Water System have PFAS in its water?
Highest PFOA or PFOS result in EPA’s 2023–2025 testing was at or above 4.0 ppt, EPA’s 2024 maximum contaminant level for each. 8 PFAS compounds detected.