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PFAS in drinking water: Tribal water systems, EPA Region 1

EPA's UCMR 5 data lists water systems on tribal lands by EPA region (Region 1) rather than by state.

EPA UCMR 5 results for 2 public water systems. 1 had at least one PFAS detected; 1 had a highest single PFOA or PFOS result above 4.0 ppt.

UCMR 5 is a one-time EPA monitoring program, not a compliance determination. The values shown are the highest single sample result at any of the system's sampling points; one result above 4.0 ppt does not mean the system violates the PFAS rule, which is judged on running annual averages under separate compliance monitoring. Results describe the public water system, not an individual home.

Water system	Serves	PFOA max (ppt)	PFOS max (ppt)	PFAS detected
Mashantucket Pequot Water System 010106001		7.4	ND	6
Mohegan Tribal Utility Authority 010109005		ND	ND	0

ND = not detected (below the 4 ppt UCMR 5 reporting level). Values are the highest single sample result, not an annual average.

Source: EPA UCMR 5 final occurrence data (EPA page last updated 2026-08-28; samples collected January 2023 – December 2025) ↗.

PFAS disclaimer: PFAS results are copied from EPA's UCMR 5 dataset and describe samples taken at a public water system's entry points between 2023 and 2025, not water at any specific address. Levels may have changed since sampling (for example, after new treatment). “Not detected” means below EPA's UCMR 5 minimum reporting level, not zero. This is not a compliance determination or a water test. Contact your water utility for current information.