Tap Water Results

Colorado PFAS results from EPA's final data

Report published Nov 14, 2026 · EPA UCMR 5 final data file of Oct 15, 2026 (samples collected 2023–2025) · Method · National results →

4 Colorado water systems serving 101,207 people had PFAS above a 2024 federal limit in EPA's final round of nationwide PFAS testing: 3% of the 158 Colorado systems tested, compared with 11% nationally.

158
systems tested (serving 6.3 million people)
37
had at least one PFAS detected
4
had an average above a federal limit
101,207
people served by those systems

Highest PFOA or PFOS averages in Colorado

  1. Snake River Water District Keystone · PFOS
    17.5 ppt
  2. Widefield Water & Sanitation District Security-Widefield · PFOS
    11.8 ppt
  3. City of Brighton Brighton · PFOS
    7.97 ppt
  4. Todd Creek Village Metropolitan District Thornton · PFOS
    5.38 ppt
  5. Town of Mountain Village Mountain Village · PFOS
    3.75 ppt
  6. City of Thornton Thornton · PFOA
    3.4 ppt
  7. Cherokee Metropolitan District Black Forest · PFOA
    3.05 ppt
  8. Arapahoe County WWWA Centennial · PFOA
    2.3 ppt
  9. City of Gunnison Gunnison · PFOS
    2.1 ppt
  10. City of Rocky Ford Rocky Ford · PFOS
    2.05 ppt
  11. Cottonwood Water & Sanitation District Parker · PFOA
    2 ppt
  12. Stonegate Metropolitan District Centennial · PFOA
    1.4 ppt
  13. Parker Water & Sanitation District Parker · PFOA
    1.2 ppt
  14. Little Thompson Water District Loveland · PFOA
    1.2 ppt
  15. City of Englewood Englewood · PFOA
    1 ppt
The 15 Colorado systems with the highest PFOA or PFOS entry-point average (whichever is higher) in EPA's 2023–2025 testing, in parts per trillion.
Chart data as a table
Systemppt
Snake River Water District · Keystone · PFOS17.5
Widefield Water & Sanitation District · Security-Widefield · PFOS11.8
City of Brighton · Brighton · PFOS7.97
Todd Creek Village Metropolitan District · Thornton · PFOS5.38
Town of Mountain Village · Mountain Village · PFOS3.75
City of Thornton · Thornton · PFOA3.4
Cherokee Metropolitan District · Black Forest · PFOA3.05
Arapahoe County WWWA · Centennial · PFOA2.3
City of Gunnison · Gunnison · PFOS2.1
City of Rocky Ford · Rocky Ford · PFOS2.05
Cottonwood Water & Sanitation District · Parker · PFOA2
Stonegate Metropolitan District · Centennial · PFOA1.4
Parker Water & Sanitation District · Parker · PFOA1.2
Little Thompson Water District · Loveland · PFOA1.2
City of Englewood · Englewood · PFOA1

Largest systems above a limit

#SystemPeople servedAbove the limit forPFOA avgPFOS avg
1City of Brighton
Brighton
Above: PFOS
56,304PFOS2.5 ppt7.97 ppt
2Widefield Water & Sanitation District
Security-Widefield
Above: PFOA, PFOS, PFHxS, Hazard Index
27,640PFOA, PFOS, PFHxS, Hazard Index10.3 ppt11.8 ppt
3Snake River Water District
Keystone
Above: PFOS
9,900PFOS2.9 ppt17.5 ppt
4Todd Creek Village Metropolitan District
Thornton
Above: PFOS
7,363PFOS–5.38 ppt

Which limits were exceeded

PFASFederal limitSystems above itPeople served
PFOA
27,640 people
4 ppt127,640
PFOS
101,207 people
4 ppt4101,207
PFHxS
27,640 people
10 ppt127,640
PFNA10 ppt00
GenX (HFPO-DA)10 ppt00
Hazard Index
27,640 people
1127,640

"–" in the table above means not detected. A system can be above more than one limit. EPA proposed in May 2026 to rescind the PFHxS, PFNA, GenX and Hazard Index limits. That proposal is not final.

Data and how to cite it

Suggested citation:

Tap Water Results, "Colorado PFAS results from EPA's final UCMR 5 data" (published Nov 14, 2026, EPA data file of Oct 15, 2026). https://tapwaterresults.com/pfas/colorado/

You're welcome to quote and republish these figures with a link back. Questions from reporters: see contact.

Method

For each system we average each entry point's UCMR 5 results (non-detects count as zero, complete sets of samples only) and compare the highest entry-point average with the 2024 federal limit, using EPA's rounding. This is how EPA compares UCMR 5 results to the limits in its own data summary, and our national counts match EPA's published table within 2% (how we check). Results are monitoring data from 2023–2025, not compliance determinations, and treatment installed since then is not reflected. Full method.

Questions

How many Colorado water systems have PFAS above the limit?

4 of the 158 Colorado community water systems EPA tested in 2023–2025 (3%) had at least one entry-point average above a 2024 federal PFAS limit. They serve 101,207 people. Nationally the share is 11%.

Are these systems violating the law?

Not yet. Systems have until 2029 to meet the 2024 limits, and EPA has proposed moving the PFOA and PFOS deadline to 2031 and rescinding the other limits. EPA's UCMR 5 results are monitoring data and do not determine compliance.

Which systems were tested?

EPA's UCMR 5 tested every community water system serving more than 3,300 people and a representative sample of smaller ones. Systems that were not tested have no federal result, which is not the same as having no PFAS.

All Colorado water systems → · National results → · PFAS results for every state →

Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.