Mashantucket Pequot Water System water quality
Ledyard, CT · serves 22,171 people (119 connections) · Groundwater under influence of surface water · Native American · EPA ID 010106001
Data: U.S. EPA · How we read the data · How we check it
Summary
PFAS above the 2024 federal limits. Systems have until 2029 to meet the PFAS limits.
Is it an emergency? No: PFAS limits are about years of exposure, not a glass of water, and nothing in EPA's data calls for you to stop drinking the water today. If your utility ever issues a boil-water or do-not-drink notice, follow it.
- PFAS
- Above limitPFOA above the federal limit in EPA's 2023–2025 testing (PFOA 5.28 ppt vs a limit of 4 ppt, where ppt = parts per trillion).
- Lead
- Below action level1 ppb (parts per billion) at the 90th percentile: 9 in 10 homes sampled were at or below it. Action level 15 ppb, falling to 10 ppb in Nov 2027. Monitoring period ending Dec 2025. Your home's pipes can make yours higher.
- Violations
- Resolved2 health-based violations since 2016, most recently Oct 2018.
- Pregnant, or mixing baby formula with tap water? Babies drink more water for their size, so PFAS exposure matters more for them. Consider bottled water or a filter certified for PFAS for formula, and ask your doctor. Health effects.
- To lower your PFAS exposure now, a home filter certified for PFAS reduction works (reverse osmosis, or activated carbon certified to NSF/ANSI 53 or 58). Filters for these results.
- Built before 1986, or not sure what your service line is made of? Check your service line and test your tap. Utility data can't show your pipes.
- Tested your own tap? Compare your result with these numbers. Moving? Compare this system with another.
- Read Mashantucket Pequot Water System's annual water quality report (Consumer Confidence Report). It lists every regulated contaminant tested and is usually on the utility's website or mailed with your bill, and you can also request it at (860) 396-6740. EPA: how to find it.
PFAS (“forever chemicals”)
EPA UCMR 5: 1 entry point tested Aug 2023 to May 2024. "Average" is the highest entry-point average (non-detects counted as zero), the way EPA compares UCMR 5 results to the limits. ppt = parts per trillion. These results do not determine compliance.
| Contaminant | Highest average |
|---|---|
| PFOA Above limit Limit 4 ppt | 5.28 ppt 1.32× the limit |
| PFOS Not detected Limit 4 ppt | – |
| PFHxS Not detected Limit 10 ppt | – |
| PFNA Not detected Limit 10 ppt | – |
| HFPO-DA (GenX) Not detected Limit 10 ppt | – |
| Hazard Index (a combined score for PFHxS, PFNA, GenX and PFBS, where above 1 is over the limit) Detected, below limit Limit 1 | 0.0013 |
| PFBS Detected, below limit Guideline 2,000 ppt | 2.65 ppt |
| PFBA Detected, below limit Guideline 6,000 ppt | 4.75 ppt |
| PFHxA Detected, below limit Guideline 3,000 ppt | 7.2 ppt |
| PFPeA Detected, no limit | 14.8 ppt |
| PFHpA Detected, no limit | 2.6 ppt |
For context: the PFOA average is higher than at 70% of the Connecticut systems EPA tested.
29 PFAS tested, 6 detected at least once. "Not detected" means below EPA's reporting limit (about 2 to 20 ppt depending on the chemical), not proven zero. PFAS not listed were not detected. The limits for PFHxS, PFNA, GenX and the Hazard Index were proposed for rescission in May 2026. That proposal is not final. Systems have until 2029 to meet the limits.
Lithium
Not detected in 4 samples (reporting limit 9 ppb). About lithium.
Lead and copper
Latest 90th percentile: 1 ppb lead (Jan 2023 – Dec 2025). Below action level
Highest since 2016: 4 ppb (Dec 2016).
| Monitoring period | Lead (90th pct.) |
|---|---|
| Jan 2023 – Dec 2025 | 1 ppb |
| Jan 2020 – Dec 2022 | 3.9 ppb |
| Jan 2017 – Dec 2019 | 2.3 ppb |
Earlier results (5)
| Jan 2014 – Dec 2016 | 4 ppb |
| Jan 2011 – Dec 2013 | < 1 ppb |
| Jan 2010 – Dec 2010 | 1 ppb |
| Jul 2007 – Dec 2007 | 1 ppb |
| Jul 2004 – Dec 2004 | 4 ppb |
Lead comes from pipes and fixtures, not the source water, so it varies home to home. The 90th percentile means 9 in 10 sampled homes were at or below it. More on lead.
Violations
| When | What happened |
|---|---|
| Jul 2018 – Oct 2018 2 times | The running annual average for TTHM was above the legal limit. EPA record: TTHM · Maximum Contaminant Level Violation, Average · measured 0.084 mg/l (limit 0.080 mg/L) Resolved |
Health-based violations mean a contaminant exceeded a limit or a required treatment step was missed. Monitoring and reporting violations mean required tests or reports were late or missing, so the water's quality during that time is unknown. The total includes every violation in EPA's records, most of them paperwork.
Earlier EPA testing (2013–2020)
| Contaminant | Highest | Guideline |
|---|---|---|
| Manganese | 15.7 ppb | 300 ppb |
| Chlorate | 470 ppb | 210 ppb |
| Strontium | 0.27 ppm | 1.5 ppm |
| Cobalt | 1.5 ppb | 70 ppb |
| Vanadium | 0.2 ppb | 21 ppb |
| Chromium-6 | 0.17 ppb | – |
Where it serves
Ledyard
ZIP codes the system reported serving: 06338, 06339
Nearby utilities
- Norwich Public Utilities Norwich · 9 mi · PFAS above limit
- East Lyme Water & Sewer Commission East Lyme · 12 mi · PFAS above limit
- Colchester Sewer & Water Commission Colchester · 19 mi · PFAS above limit
- University of Connecticut – Main Campus Water System Mansfield · 27 mi · PFAS above limit
- Connecticut Water Company – Crystal System Killingly · 29 mi · PFAS above limit
- Putnam Water Pollution Control Authority Putnam · 34 mi · PFAS above limit
Questions
Is Mashantucket Pequot Water System water safe to drink?
Mashantucket Pequot Water System had 2 health-based violations since 2016, all since resolved. EPA testing found PFAS above the 2024 federal limits, which systems must meet by 2029. Federal data can't tell you about your own pipes: lead comes from service lines and plumbing, so test your tap if your home was built before 1986. For the official word, read the utility's annual Consumer Confidence Report.
Does Mashantucket Pequot Water System water have PFAS?
Yes. EPA's 2023–2025 testing of Mashantucket Pequot Water System found 6 PFAS at least once. The highest entry-point averages were above the federal limit for PFOA: PFOA 5.28 ppt (limit 4 ppt for PFOA and PFOS, 10 ppt for the others).
What is the lead level in Mashantucket Pequot Water System water?
The most recent 90th-percentile lead result for Mashantucket Pequot Water System is 1 ppb, for the period ending Dec 2025. The federal action level is 15 ppb, falling to 10 ppb in November 2027. The 90th percentile means 9 in 10 homes sampled were at or below this number. Individual homes can be higher.
Check these numbers yourself
Every figure on this page comes from public EPA records. You don't have to take our word for it:
- EPA's own report for 010106001: violations, enforcement and inspections, straight from EPA.
- EPA UCMR 5 data: the PFAS and lithium results (search the file for PWSID 010106001).
- EPA SDWIS download: the lead results, population and violation records we use.
- The utility's annual water quality report (Consumer Confidence Report): ask Mashantucket Pequot Water System at (860) 396-6740, or see EPA's guide to finding it.
Found something that doesn't match? Tell us and we'll check it against EPA's records. How we check our data.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.