Community Water System · PWS GU0000001
Gwa Southern Water System
Mangilao, Guam 96913 - drinking water served from surface water sources to 5,801 people, tracked in EPA SDWIS and UCMR5.
- 5,801
- People served
- 24
- EPA violations
- 7
- Health-based
- No PFAS
- UCMR5 result
The verdict
EPA records 24 drinking-water violations at Gwa Southern Water System, 29% of them health-based - below the Guam per-system average.
- 24
- Total EPA violations on record
- 29%
- Health-based (MCL / treatment failure)
- 5,801
- People served by this system
- 0
- PFAS compounds detected (UCMR5)
Water Quality Snapshot: Gwa Southern Water System
Gwa Southern Water System is a state-owned community water system that delivers drinking water to 5,801 residents in Mangilao, Guam (Guam County) through 1,900 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 24 total violations for this system , of which 7 (29%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. The most recent violation on record dates to 2018.
The most frequently cited contaminant at this system is Revised Total Coliform Rule, recorded in 4 violations (MCL, health-based). This system was sampled under EPA's UCMR5 PFAS monitoring program and no PFAS compounds were detected above the minimum reporting level.
Across Guam, EPA tracks 8 public water systems serving 327,417 people, with 203 cumulative violations and 94 health-based violations on record. About 100% of systems in the state carry at least one violation, and state-wide the average per system is 25.4 violations. Statewide, 3 of 5 UCMR5-tested systems have reported PFAS detections (60%).
Gwa Southern Water System's 24 violations sit below the Guam average.
All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.
System Details
- System Type
- Community
- Owner Type
- State
- Connections
- 1,900
- County
- Guam
- School/Daycare
- No
- MCL Violations
- 7
- Monitoring Violations
- 0
- Treatment Tech Violations
- 0
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Revised Total Coliform Rule | MCL | 4 | 2018 |
| Total Haloacetic Acids (HAA5) | MCL | 3 | 2012 |
PFAS Testing Results (UCMR5)
Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 0 of 87 samples detected PFAS.
| Contaminant | Date | Result | MRL | Status |
|---|---|---|---|---|
| ADONA | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| NEtFOSAA | 4/7/2025 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFTrDA | 4/7/2025 | <7.00 ppt | 7.00 ppt | Not Detected |
| PFTA | 4/7/2025 | <8.00 ppt | 8.00 ppt | Not Detected |
| PFHpS | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFPeS | 4/7/2025 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFEESA | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFPeA | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFMPA | 4/7/2025 | <4.00 ppt | 4.00 ppt | Not Detected |
| 8:2 FTS | 4/7/2025 | <5.00 ppt | 5.00 ppt | Not Detected |
| 4:2 FTS | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| 6:2 FTS | 4/7/2025 | <5.00 ppt | 5.00 ppt | Not Detected |
| NMeFOSAA | 4/7/2025 | <6.00 ppt | 6.00 ppt | Not Detected |
| HFPO-DA | 4/7/2025 | <5.00 ppt | 5.00 ppt | Not Detected |
| NFDHA | 4/7/2025 | <20.00 ppt | 20.00 ppt | Not Detected |
| 9Cl-PF3ONS | 4/7/2025 | <2.00 ppt | 2.00 ppt | Not Detected |
| 11Cl-PF3OUdS | 4/7/2025 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFUnA | 4/7/2025 | <2.00 ppt | 2.00 ppt | Not Detected |
| PFHxA | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDoA | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDA | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFOA | 4/7/2025 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOS | 4/7/2025 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFNA | 4/7/2025 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHxS | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpA | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFBS | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFBA | 4/7/2025 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFMBA | 4/7/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFEESA | 10/27/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFBS | 10/27/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpA | 10/27/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxS | 10/27/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFNA | 10/27/2025 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFMBA | 10/27/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFPeS | 10/27/2025 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOS | 10/27/2025 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHpS | 10/27/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFTA | 10/27/2025 | <8.00 ppt | 8.00 ppt | Not Detected |
| PFTrDA | 10/27/2025 | <7.00 ppt | 7.00 ppt | Not Detected |
| NEtFOSAA | 10/27/2025 | <5.00 ppt | 5.00 ppt | Not Detected |
| NMeFOSAA | 10/27/2025 | <6.00 ppt | 6.00 ppt | Not Detected |
| PFOA | 10/27/2025 | <4.00 ppt | 4.00 ppt | Not Detected |
| 9Cl-PF3ONS | 10/27/2025 | <2.00 ppt | 2.00 ppt | Not Detected |
| PFDA | 10/27/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDoA | 10/27/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| NFDHA | 10/27/2025 | <20.00 ppt | 20.00 ppt | Not Detected |
| PFPeA | 10/27/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxA | 10/27/2025 | <3.00 ppt | 3.00 ppt | Not Detected |
| 11Cl-PF3OUdS | 10/27/2025 | <5.00 ppt | 5.00 ppt | Not Detected |
Verify This Water System
The figures above are aggregated from EPA's public databases. To verify the underlying records, or to file a complaint, request a Consumer Confidence Report, or check current monitoring status, go directly to the federal and state regulators that enforce the Safe Drinking Water Act for Gwa Southern Water System.
EPA SDWIS, Federal Reports
EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:
View PWS ID GU0000001 on SDWISSource: EPA SDWIS Federal Reports Search
Guam Drinking Water Authority
Guam's primacy agency administers the Safe Drinking Water Act locally. Search EPA SDWIS for the current state contact, or use the state's public health or environment department portal.
Find GU regulator via EPA SDWISViolation Timeline
Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.
| Year (latest) | Contaminant | Category | Count | EPA Record |
|---|---|---|---|---|
| 2018 | Revised Total Coliform Rule | MCL | 4 | SDWIS / GU0000001 / 8000 |
| 2012 | Total Haloacetic Acids (HAA5) | MCL | 3 | SDWIS / GU0000001 / 2456 |
How Gwa Southern Water System Compares
Cross-reference this system's record against state averages and the federal MCL framework for context.
| Metric | Gwa Southern Water System | Guam avg | Federal benchmark |
|---|---|---|---|
| Total violations | 24 | 25.4 | SDWA compliance, any non-zero count is a recorded breach |
| Health-based violations | 7 | 11.8 | Indicates a contaminant exceeded a federal MCL |
| PFAS detection | None | 60% | EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt |
| Population served | 5,801 | 40,927 | Sizing context for compliance burden |
Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across 8 regulated public water systems in Guam.
Federal MCL reference, Safe Drinking Water Act thresholds ▼
| Contaminant | Federal MCL / Action Level | Note |
|---|---|---|
| Lead | 0 mg/L (Action Level: 0.015 mg/L) | Lead and Copper Rule treatment technique |
| Arsenic | 0.010 mg/L (10 ppb) | Health-based MCL since 2006 |
| Total Coliform | Treatment technique (RTCR) | Indicator organism, monitoring trigger |
| PFOA / PFOS (PFAS) | 4.0 ppt each (final 2024 rule) | Compliance deadline 2029 (EPA proposed extending to 2031, not yet final as of May 2026) |
| Nitrate (as N) | 10 mg/L | Acute health risk for infants |
Frequently Asked Questions
Is Gwa Southern Water System water safe to drink? ▼
How many people does Gwa Southern Water System serve? ▼
What type of violations does Gwa Southern Water System have? ▼
Has PFAS been detected in Gwa Southern Water System water? ▼
What water source does Gwa Southern Water System use? ▼
Where does this data come from? ▼
Read our methodology - how this data is sourced, computed, and verified.
Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This system's figures are rendered directly from EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.