Name: Project Abacus: EPA UCMR 5 PFAS and lithium results for U.S. public water systems
Creator: Project Abacus

Project Abacus publishes EPA UCMR 5 PFAS results for 10,313 sampled public water systems (1,991,977 results, samples 2023-01-03 to 2026-06-17) and lists 66,457 systems in all, with per-state CSV downloads.

What the data are

EPA's Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) required public water systems to sample the water leaving their treatment plants and wells (entry points) for 29 PFAS and lithium. Project Abacus takes EPA's published UCMR 5 occurrence data and joins it to EPA's SDWIS records of every community and non-transient non-community water system. 10,313 systems were sampled; 3,595 had at least one PFAS result at or above EPA's reporting level.

These are monitoring results collected under EPA's Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) at entry points, where treated water enters the distribution system; they are not tap-water samples. They are not compliance determinations: compliance with EPA's 2024 PFAS limits is judged on running annual averages of compliance monitoring, required from 2029, so a single UCMR 5 result at or above a limit is not a violation. “< MRL” means the compound was not quantified at EPA's minimum reporting level; it does not mean zero.

Methods

Non-detects. A result reported as “< MRL” is below EPA's minimum reporting level for that compound; tables show it as “< MRL”, not as zero. Where a calculation needs a number — entry-point averages and the Hazard Index, as in the 2024 rule, and the lower bound of a mean — non-detects are set to 0, and the page says so. A system that was not tested is never shown as “not detected”.
Highest single result is the largest result for a compound at any of the system's entry points.
Entry-point average averages each entry point's samples with non-detects as 0, as the 2024 rule's compliance calculation does, and reports the worst entry point. It is a screening value, not a running annual average.
Hazard Index is computed per sample from PFHxS, PFNA, HFPO-DA and PFBS (with non-detects as 0) as in the 2024 rule.
Statistics. Left-censored Kaplan–Meier statistics follow Helsel (2005) and Helsel & Lee (2006, NADA for R). Each compound has a single reporting limit, so the Kaplan–Meier mean equals the mean with non-detects at the limit; pages show it as an upper bound with the lower bound (non-detects at 0).
Counties and service areas. County colors on the maps show the most elevated sampled system associated with the county; they do not describe the water at any address.

Downloads

One systems file and one results file per state or territory. The systems file has one row per listed system with its UCMR 5 summary; the results file has every UCMR 5 result for the sampled systems (gzip-compressed CSV). In the systems file, a *_max value of 0 means every result for that compound was below its reporting limit (not detected), not a measured zero; *_ep_avg and hi_* values use non-detects = 0; the summary columns are blank for systems not sampled. In the results file, sign is = for a quantified result and < for a result below the reporting limit given in mrl.

State	File	Contents	Size
Alabama	AL_systems.csv	one row per listed public water system with its UCMR 5 summary	0.10 MB
Alabama	AL_results.csv.gz	every UCMR 5 result for the sampled systems	0.27 MB
Alaska	AK_systems.csv	one row per listed public water system with its UCMR 5 summary	0.09 MB
Alaska	AK_results.csv.gz	every UCMR 5 result for the sampled systems	0.02 MB
Arizona	AZ_systems.csv	one row per listed public water system with its UCMR 5 summary	0.18 MB
Arizona	AZ_results.csv.gz	every UCMR 5 result for the sampled systems	0.23 MB
Arkansas	AR_systems.csv	one row per listed public water system with its UCMR 5 summary	0.11 MB
Arkansas	AR_results.csv.gz	every UCMR 5 result for the sampled systems	0.09 MB
California	CA_systems.csv	one row per listed public water system with its UCMR 5 summary	0.70 MB
California	CA_results.csv.gz	every UCMR 5 result for the sampled systems	1.03 MB
Colorado	CO_systems.csv	one row per listed public water system with its UCMR 5 summary	0.19 MB
Colorado	CO_results.csv.gz	every UCMR 5 result for the sampled systems	0.13 MB
Connecticut	CT_systems.csv	one row per listed public water system with its UCMR 5 summary	0.15 MB
Connecticut	CT_results.csv.gz	every UCMR 5 result for the sampled systems	0.06 MB
Delaware	DE_systems.csv	one row per listed public water system with its UCMR 5 summary	0.04 MB
Delaware	DE_results.csv.gz	every UCMR 5 result for the sampled systems	0.04 MB
District of Columbia	DC_systems.csv	one row per listed public water system with its UCMR 5 summary	0.00 MB
District of Columbia	DC_results.csv.gz	every UCMR 5 result for the sampled systems	0.00 MB
Florida	FL_systems.csv	one row per listed public water system with its UCMR 5 summary	0.38 MB
Florida	FL_results.csv.gz	every UCMR 5 result for the sampled systems	0.27 MB
Georgia	GA_systems.csv	one row per listed public water system with its UCMR 5 summary	0.29 MB
Georgia	GA_results.csv.gz	every UCMR 5 result for the sampled systems	0.21 MB
Hawaii	HI_systems.csv	one row per listed public water system with its UCMR 5 summary	0.02 MB
Hawaii	HI_results.csv.gz	every UCMR 5 result for the sampled systems	0.05 MB
Idaho	ID_systems.csv	one row per listed public water system with its UCMR 5 summary	0.15 MB
Idaho	ID_results.csv.gz	every UCMR 5 result for the sampled systems	0.08 MB
Illinois	IL_systems.csv	one row per listed public water system with its UCMR 5 summary	0.34 MB
Illinois	IL_results.csv.gz	every UCMR 5 result for the sampled systems	0.28 MB
Indiana	IN_systems.csv	one row per listed public water system with its UCMR 5 summary	0.22 MB
Indiana	IN_results.csv.gz	every UCMR 5 result for the sampled systems	0.11 MB
Iowa	IA_systems.csv	one row per listed public water system with its UCMR 5 summary	0.18 MB
Iowa	IA_results.csv.gz	every UCMR 5 result for the sampled systems	0.08 MB
Kansas	KS_systems.csv	one row per listed public water system with its UCMR 5 summary	0.13 MB
Kansas	KS_results.csv.gz	every UCMR 5 result for the sampled systems	0.07 MB
Kentucky	KY_systems.csv	one row per listed public water system with its UCMR 5 summary	0.08 MB
Kentucky	KY_results.csv.gz	every UCMR 5 result for the sampled systems	0.15 MB
Louisiana	LA_systems.csv	one row per listed public water system with its UCMR 5 summary	0.17 MB
Louisiana	LA_results.csv.gz	every UCMR 5 result for the sampled systems	0.18 MB
Maine	ME_systems.csv	one row per listed public water system with its UCMR 5 summary	0.11 MB
Maine	ME_results.csv.gz	every UCMR 5 result for the sampled systems	0.02 MB
Maryland	MD_systems.csv	one row per listed public water system with its UCMR 5 summary	0.16 MB
Maryland	MD_results.csv.gz	every UCMR 5 result for the sampled systems	0.07 MB
Massachusetts	MA_systems.csv	one row per listed public water system with its UCMR 5 summary	0.14 MB
Massachusetts	MA_results.csv.gz	every UCMR 5 result for the sampled systems	0.21 MB
Michigan	MI_systems.csv	one row per listed public water system with its UCMR 5 summary	0.43 MB
Michigan	MI_results.csv.gz	every UCMR 5 result for the sampled systems	0.18 MB
Minnesota	MN_systems.csv	one row per listed public water system with its UCMR 5 summary	0.22 MB
Minnesota	MN_results.csv.gz	every UCMR 5 result for the sampled systems	0.13 MB
Mississippi	MS_systems.csv	one row per listed public water system with its UCMR 5 summary	0.17 MB
Mississippi	MS_results.csv.gz	every UCMR 5 result for the sampled systems	0.20 MB
Missouri	MO_systems.csv	one row per listed public water system with its UCMR 5 summary	0.25 MB
Missouri	MO_results.csv.gz	every UCMR 5 result for the sampled systems	0.20 MB
Montana	MT_systems.csv	one row per listed public water system with its UCMR 5 summary	0.17 MB
Montana	MT_results.csv.gz	every UCMR 5 result for the sampled systems	0.04 MB
Nebraska	NE_systems.csv	one row per listed public water system with its UCMR 5 summary	0.11 MB
Nebraska	NE_results.csv.gz	every UCMR 5 result for the sampled systems	0.05 MB
Nevada	NV_systems.csv	one row per listed public water system with its UCMR 5 summary	0.06 MB
Nevada	NV_results.csv.gz	every UCMR 5 result for the sampled systems	0.08 MB
New Hampshire	NH_systems.csv	one row per listed public water system with its UCMR 5 summary	0.17 MB
New Hampshire	NH_results.csv.gz	every UCMR 5 result for the sampled systems	0.04 MB
New Jersey	NJ_systems.csv	one row per listed public water system with its UCMR 5 summary	0.20 MB
New Jersey	NJ_results.csv.gz	every UCMR 5 result for the sampled systems	0.26 MB
New Mexico	NM_systems.csv	one row per listed public water system with its UCMR 5 summary	0.12 MB
New Mexico	NM_results.csv.gz	every UCMR 5 result for the sampled systems	0.08 MB
New York	NY_systems.csv	one row per listed public water system with its UCMR 5 summary	0.45 MB
New York	NY_results.csv.gz	every UCMR 5 result for the sampled systems	0.32 MB
North Carolina	NC_systems.csv	one row per listed public water system with its UCMR 5 summary	0.35 MB
North Carolina	NC_results.csv.gz	every UCMR 5 result for the sampled systems	0.29 MB
North Dakota	ND_systems.csv	one row per listed public water system with its UCMR 5 summary	0.05 MB
North Dakota	ND_results.csv.gz	every UCMR 5 result for the sampled systems	0.02 MB
Ohio	OH_systems.csv	one row per listed public water system with its UCMR 5 summary	0.27 MB
Ohio	OH_results.csv.gz	every UCMR 5 result for the sampled systems	0.15 MB
Oklahoma	OK_systems.csv	one row per listed public water system with its UCMR 5 summary	0.15 MB
Oklahoma	OK_results.csv.gz	every UCMR 5 result for the sampled systems	0.14 MB
Oregon	OR_systems.csv	one row per listed public water system with its UCMR 5 summary	0.19 MB
Oregon	OR_results.csv.gz	every UCMR 5 result for the sampled systems	0.09 MB
Pennsylvania	PA_systems.csv	one row per listed public water system with its UCMR 5 summary	0.46 MB
Pennsylvania	PA_results.csv.gz	every UCMR 5 result for the sampled systems	0.33 MB
Rhode Island	RI_systems.csv	one row per listed public water system with its UCMR 5 summary	0.03 MB
Rhode Island	RI_results.csv.gz	every UCMR 5 result for the sampled systems	0.02 MB
South Carolina	SC_systems.csv	one row per listed public water system with its UCMR 5 summary	0.11 MB
South Carolina	SC_results.csv.gz	every UCMR 5 result for the sampled systems	0.14 MB
South Dakota	SD_systems.csv	one row per listed public water system with its UCMR 5 summary	0.08 MB
South Dakota	SD_results.csv.gz	every UCMR 5 result for the sampled systems	0.03 MB
Tennessee	TN_systems.csv	one row per listed public water system with its UCMR 5 summary	0.09 MB
Tennessee	TN_results.csv.gz	every UCMR 5 result for the sampled systems	0.17 MB
Texas	TX_systems.csv	one row per listed public water system with its UCMR 5 summary	0.89 MB
Texas	TX_results.csv.gz	every UCMR 5 result for the sampled systems	0.96 MB
Utah	UT_systems.csv	one row per listed public water system with its UCMR 5 summary	0.09 MB
Utah	UT_results.csv.gz	every UCMR 5 result for the sampled systems	0.14 MB
Vermont	VT_systems.csv	one row per listed public water system with its UCMR 5 summary	0.10 MB
Vermont	VT_results.csv.gz	every UCMR 5 result for the sampled systems	0.02 MB
Virginia	VA_systems.csv	one row per listed public water system with its UCMR 5 summary	0.24 MB
Virginia	VA_results.csv.gz	every UCMR 5 result for the sampled systems	0.12 MB
Washington	WA_systems.csv	one row per listed public water system with its UCMR 5 summary	0.42 MB
Washington	WA_results.csv.gz	every UCMR 5 result for the sampled systems	0.25 MB
West Virginia	WV_systems.csv	one row per listed public water system with its UCMR 5 summary	0.08 MB
West Virginia	WV_results.csv.gz	every UCMR 5 result for the sampled systems	0.05 MB
Wisconsin	WI_systems.csv	one row per listed public water system with its UCMR 5 summary	0.30 MB
Wisconsin	WI_results.csv.gz	every UCMR 5 result for the sampled systems	0.16 MB
Wyoming	WY_systems.csv	one row per listed public water system with its UCMR 5 summary	0.06 MB
Wyoming	WY_results.csv.gz	every UCMR 5 result for the sampled systems	0.02 MB
Puerto Rico	PR_systems.csv	one row per listed public water system with its UCMR 5 summary	0.07 MB
Puerto Rico	PR_results.csv.gz	every UCMR 5 result for the sampled systems	0.09 MB
U.S. Virgin Islands	VI_systems.csv	one row per listed public water system with its UCMR 5 summary	0.03 MB
U.S. Virgin Islands	VI_results.csv.gz	every UCMR 5 result for the sampled systems	0.00 MB
American Samoa	AS_systems.csv	one row per listed public water system with its UCMR 5 summary	0.00 MB
American Samoa	AS_results.csv.gz	every UCMR 5 result for the sampled systems	0.01 MB
Guam	GU_systems.csv	one row per listed public water system with its UCMR 5 summary	0.00 MB
Guam	GU_results.csv.gz	every UCMR 5 result for the sampled systems	0.02 MB
Northern Mariana Islands	MP_systems.csv	one row per listed public water system with its UCMR 5 summary	0.01 MB
Northern Mariana Islands	MP_results.csv.gz	every UCMR 5 result for the sampled systems	0.00 MB

Reports

Sources

U.S. EPA, Occurrence Data from the Unregulated Contaminant Monitoring Rule: EPA UCMR 5 occurrence data text files (UCMR5_All.txt; samples 2023-01-03 to 2026-06-17, all jurisdictions; data summary dated Jul 2026).
EPA SDWIS via ECHO SDWA downloads, quarter 2026Q3
EPA Public Water System Service Areas v3 (Mar 2026)
US Census Bureau cartographic boundary counties 1:500k, 2024
EPA/USGS NHDPlus V2 (medium resolution) flowlines, Strahler order 2+
Helsel, D.R. (2005). Nondetects and Data Analysis. Wiley. Helsel, D.R. & Lee, L. (2006). NADA for R (ASA workshop).