Riverhead Water District

PFAS monitoring results for a public water system in New York

NY5103705UCMR 5EPA monitoring data
4Highest PFOA result, ppt
5.2Highest PFOS result, ppt
0Highest Hazard Index
600Results
PWSID
NY5103705
State
New York
System type
community water system (CWS)
Population served
35,000
City
Riverhead
Counties
Suffolk County
Primary source water
groundwater
UCMR 5 sampling
2023-06-14 to 2024-05-03 · 10 entry point(s) · water types: GW
Service-area boundary
authoritative

PFOS 1–3 × its limit highest single result
PFOS below its limit worst entry-point average

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.

Compared with EPA's 2024 values

Highest single resultWorst entry-point average*Limit
PFOA (ppt)424
PFOS (ppt)5.22.64
Hazard Index001.0†

“<MRL” = every result for the compound was below its reporting limit. * Mean of all samples at each entry point with non-detects = 0 (EPA compliance convention; the Hazard Index also uses non-detects = 0); a screening comparison, not a formal running annual average. † Rescission proposed May 2026. PFOA/PFOS MCL 4 ppt (2024 NPDWR, in effect). PFHxS, PFNA, HFPO-DA (10 ppt each) and the Hazard Index (1.0) are 2024 NPDWR values; EPA proposed rescinding them on 18 May 2026 (comment period closed 20 Jul 2026).

Compared with New York standards

Highest single resultWorst entry-point average*New York
PFOA (ppt)4210
PFOS (ppt)5.22.610

Sum standards add the listed compounds within each sample (non-detects = 0). State compliance is normally judged on averages over time; these are screening comparisons.

Sampling history

Sampled 2023-06-14 to 2024-05-03 · 10 entry point(s) · water types: GW · 27 sampling visits. PFAS in ppt (ng/L).

DateEntry pointEventPFOAPFOSHIOther detections
2023-06-14Well 16-1 TP (GW)SE1<4<40none
2023-06-14Well 1A (GW)SE1<4<40none
2023-06-14Well 3A (GW)SE1<4<40none
2023-06-20Well 11-1 & 11-2 TP (GW)SE1<4<40none
2023-06-20Well 15-1, 15-2 & 15-3 Treatment TP Plant (GW)SE1<4<40none
2023-06-20Well 2 (GW)SE1<4<40none
2023-06-20Well 4-1 & 4-2 TP (GW)SE1<4<40none
2023-06-20Well 5-1 & 5-2 TP (GW)SE145.20PFHxA 3.3, PFPeA 3.2
2023-06-20Well 7-2 & 7-3 TP (GW)SE1<4<40none
2023-06-20Well17-1 TP (GW)SE1<4<40none
2023-07-06Well 16-1 TP (GW)SE1n/an/an/anone
2023-07-17Well17-1 TP (GW)SE1n/an/an/anone
2023-07-31Well 15-1, 15-2 & 15-3 Treatment TP Plant (GW)SE1n/an/an/anone
2023-12-01Well 11-1 & 11-2 TP (GW)SE2<4<40none
2023-12-01Well 1A (GW)SE2<4<40none
2023-12-01Well 4-1 & 4-2 TP (GW)SE2<4<40none
2023-12-01Well 5-1 & 5-2 TP (GW)SE2<4<40none
2023-12-06Well 2 (GW)SE2<4<40none
2023-12-06Well 7-2 & 7-3 TP (GW)SE2<4<40none
2023-12-06Well17-1 TP (GW)SE2<4<40none
2023-12-08Well 3A (GW)SE2<4<40none
2023-12-15Well 15-1, 15-2 & 15-3 Treatment TP Plant (GW)SE2<4<40none
2024-01-17Well 11-1 & 11-2 TP (GW)SE2n/an/an/anone
2024-01-17Well 16-1 TP (GW)SE2<4<40none
2024-01-17Well 1A (GW)SE2n/an/an/anone
2024-01-17Well 4-1 & 4-2 TP (GW)SE2n/an/an/anone
2024-05-03Well 5-1 & 5-2 TP (GW)SE2n/an/an/anone

“<4” = not detected at the reporting limit shown; “n/a” = not analyzed in that sample. Highlighted = at or above the 4 ppt MCL. HI computed per sample with non-detects as 0. Other detections lists every other quantified compound (lithium in µg/L).

All results by entry point

600 results. Each column is one sampling visit (date and UCMR 5 sample event). A number is a measured concentration; “< 4” = below the minimum reporting level shown; “–” = not analyzed in that visit. PFAS in ppt (ng/L); lithium in µg/L.

Well 11-1 & 11-2 TP facility 17707 · sample point T17707T122918 · groundwater

CompoundMRL2023-06-20
SE1
2023-12-01
SE2
2024-01-17
SE2
11Cl-PF3OUdS5 ppt< 5< 5–
4:2 FTS3 ppt< 3< 3–
6:2 FTS5 ppt< 5< 5–
8:2 FTS5 ppt< 5< 5–
9Cl-PF3ONS2 ppt< 2< 2–
ADONA3 ppt< 3< 3–
HFPO-DA5 ppt< 5< 5–
NEtFOSAA5 ppt< 5–< 5
NFDHA20 ppt< 20< 20–
NMeFOSAA6 ppt< 6–< 6
PFBA5 ppt< 5< 5–
PFBS3 ppt< 3< 3–
PFDA3 ppt< 3< 3–
PFDoA3 ppt< 3< 3–
PFEESA3 ppt< 3< 3–
PFHpA3 ppt< 3< 3–
PFHpS3 ppt< 3< 3–
PFHxA3 ppt< 3< 3–
PFHxS3 ppt< 3< 3–
PFMBA3 ppt< 3< 3–
PFMPA4 ppt< 4< 4–
PFNA4 ppt< 4< 4–
PFOA4 ppt< 4< 4–
PFOS4 ppt< 4< 4–
PFPeA3 ppt< 3< 3–
PFPeS4 ppt< 4< 4–
PFTA8 ppt< 8–< 8
PFTrDA7 ppt< 7–< 7
PFUnA2 ppt< 2< 2–
lithium9 µg/L< 9< 9–

Well 15-1, 15-2 & 15-3 Treatment TP Plant facility 12965 · sample point T129656 · groundwater

CompoundMRL2023-06-20
SE1
2023-07-31
SE1
2023-12-15
SE2
11Cl-PF3OUdS5 ppt< 5–< 5
4:2 FTS3 ppt< 3–< 3
6:2 FTS5 ppt< 5–< 5
8:2 FTS5 ppt< 5–< 5
9Cl-PF3ONS2 ppt< 2–< 2
ADONA3 ppt< 3–< 3
HFPO-DA5 ppt< 5–< 5
NEtFOSAA5 ppt–< 5< 5
NFDHA20 ppt< 20–< 20
NMeFOSAA6 ppt–< 6< 6
PFBA5 ppt< 5–< 5
PFBS3 ppt< 3–< 3
PFDA3 ppt< 3–< 3
PFDoA3 ppt< 3–< 3
PFEESA3 ppt< 3–< 3
PFHpA3 ppt< 3–< 3
PFHpS3 ppt< 3–< 3
PFHxA3 ppt< 3–< 3
PFHxS3 ppt< 3–< 3
PFMBA3 ppt< 3–< 3
PFMPA4 ppt< 4–< 4
PFNA4 ppt< 4–< 4
PFOA4 ppt< 4–< 4
PFOS4 ppt< 4–< 4
PFPeA3 ppt< 3–< 3
PFPeS4 ppt< 4–< 4
PFTA8 ppt–< 8< 8
PFTrDA7 ppt–< 7< 7
PFUnA2 ppt< 2–< 2
lithium9 µg/L< 9–< 9

Well 16-1 TP facility 12945 · sample point T129453 · groundwater

CompoundMRL2023-06-14
SE1
2023-07-06
SE1
2024-01-17
SE2
11Cl-PF3OUdS5 ppt< 5–< 5
4:2 FTS3 ppt< 3–< 3
6:2 FTS5 ppt< 5–< 5
8:2 FTS5 ppt< 5–< 5
9Cl-PF3ONS2 ppt< 2–< 2
ADONA3 ppt< 3–< 3
HFPO-DA5 ppt< 5–< 5
NEtFOSAA5 ppt–< 5< 5
NFDHA20 ppt< 20–< 20
NMeFOSAA6 ppt–< 6< 6
PFBA5 ppt< 5–< 5
PFBS3 ppt< 3–< 3
PFDA3 ppt< 3–< 3
PFDoA3 ppt< 3–< 3
PFEESA3 ppt< 3–< 3
PFHpA3 ppt< 3–< 3
PFHpS3 ppt< 3–< 3
PFHxA3 ppt< 3–< 3
PFHxS3 ppt< 3–< 3
PFMBA3 ppt< 3–< 3
PFMPA4 ppt< 4–< 4
PFNA4 ppt< 4–< 4
PFOA4 ppt< 4–< 4
PFOS4 ppt< 4–< 4
PFPeA3 ppt< 3–< 3
PFPeS4 ppt< 4–< 4
PFTA8 ppt–< 8< 8
PFTrDA7 ppt–< 7< 7
PFUnA2 ppt< 2–< 2
lithium9 µg/L< 9–< 9

Well 1A facility 10834 · sample point T10834 · groundwater

CompoundMRL2023-06-14
SE1
2023-12-01
SE2
2024-01-17
SE2
11Cl-PF3OUdS5 ppt< 5< 5–
4:2 FTS3 ppt< 3< 3–
6:2 FTS5 ppt< 5< 5–
8:2 FTS5 ppt< 5< 5–
9Cl-PF3ONS2 ppt< 2< 2–
ADONA3 ppt< 3< 3–
HFPO-DA5 ppt< 5< 5–
NEtFOSAA5 ppt< 5–< 5
NFDHA20 ppt< 20< 20–
NMeFOSAA6 ppt< 6–< 6
PFBA5 ppt< 5< 5–
PFBS3 ppt< 3< 3–
PFDA3 ppt< 3< 3–
PFDoA3 ppt< 3< 3–
PFEESA3 ppt< 3< 3–
PFHpA3 ppt< 3< 3–
PFHpS3 ppt< 3< 3–
PFHxA3 ppt< 3< 3–
PFHxS3 ppt< 3< 3–
PFMBA3 ppt< 3< 3–
PFMPA4 ppt< 4< 4–
PFNA4 ppt< 4< 4–
PFOA4 ppt< 4< 4–
PFOS4 ppt< 4< 4–
PFPeA3 ppt< 3< 3–
PFPeS4 ppt< 4< 4–
PFTA8 ppt< 8–< 8
PFTrDA7 ppt< 7–< 7
PFUnA2 ppt< 2< 2–
lithium9 µg/L< 9< 9–

Well 2 facility 07261 · sample point T07261 · groundwater

CompoundMRL2023-06-20
SE1
2023-12-06
SE2
11Cl-PF3OUdS5 ppt< 5< 5
4:2 FTS3 ppt< 3< 3
6:2 FTS5 ppt< 5< 5
8:2 FTS5 ppt< 5< 5
9Cl-PF3ONS2 ppt< 2< 2
ADONA3 ppt< 3< 3
HFPO-DA5 ppt< 5< 5
NEtFOSAA5 ppt< 5< 5
NFDHA20 ppt< 20< 20
NMeFOSAA6 ppt< 6< 6
PFBA5 ppt< 5< 5
PFBS3 ppt< 3< 3
PFDA3 ppt< 3< 3
PFDoA3 ppt< 3< 3
PFEESA3 ppt< 3< 3
PFHpA3 ppt< 3< 3
PFHpS3 ppt< 3< 3
PFHxA3 ppt< 3< 3
PFHxS3 ppt< 3< 3
PFMBA3 ppt< 3< 3
PFMPA4 ppt< 4< 4
PFNA4 ppt< 4< 4
PFOA4 ppt< 4< 4
PFOS4 ppt< 4< 4
PFPeA3 ppt< 3< 3
PFPeS4 ppt< 4< 4
PFTA8 ppt< 8< 8
PFTrDA7 ppt< 7< 7
PFUnA2 ppt< 2< 2
lithium9 µg/L< 9< 9

Well 3A facility 15117 · sample point T15117 · groundwater

CompoundMRL2023-06-14
SE1
2023-12-08
SE2
11Cl-PF3OUdS5 ppt< 5< 5
4:2 FTS3 ppt< 3< 3
6:2 FTS5 ppt< 5< 5
8:2 FTS5 ppt< 5< 5
9Cl-PF3ONS2 ppt< 2< 2
ADONA3 ppt< 3< 3
HFPO-DA5 ppt< 5< 5
NEtFOSAA5 ppt< 5< 5
NFDHA20 ppt< 20< 20
NMeFOSAA6 ppt< 6< 6
PFBA5 ppt< 5< 5
PFBS3 ppt< 3< 3
PFDA3 ppt< 3< 3
PFDoA3 ppt< 3< 3
PFEESA3 ppt< 3< 3
PFHpA3 ppt< 3< 3
PFHpS3 ppt< 3< 3
PFHxA3 ppt< 3< 3
PFHxS3 ppt< 3< 3
PFMBA3 ppt< 3< 3
PFMPA4 ppt< 4< 4
PFNA4 ppt< 4< 4
PFOA4 ppt< 4< 4
PFOS4 ppt< 4< 4
PFPeA3 ppt< 3< 3
PFPeS4 ppt< 4< 4
PFTA8 ppt< 8< 8
PFTrDA7 ppt< 7< 7
PFUnA2 ppt< 2< 2
lithium9 µg/L< 9< 9

Well 4-1 & 4-2 TP facility 78329 · sample point 1 · groundwater

CompoundMRL2023-06-20
SE1
2023-12-01
SE2
2024-01-17
SE2
11Cl-PF3OUdS5 ppt< 5< 5–
4:2 FTS3 ppt< 3< 3–
6:2 FTS5 ppt< 5< 5–
8:2 FTS5 ppt< 5< 5–
9Cl-PF3ONS2 ppt< 2< 2–
ADONA3 ppt< 3< 3–
HFPO-DA5 ppt< 5< 5–
NEtFOSAA5 ppt< 5–< 5
NFDHA20 ppt< 20< 20–
NMeFOSAA6 ppt< 6–< 6
PFBA5 ppt< 5< 5–
PFBS3 ppt< 3< 3–
PFDA3 ppt< 3< 3–
PFDoA3 ppt< 3< 3–
PFEESA3 ppt< 3< 3–
PFHpA3 ppt< 3< 3–
PFHpS3 ppt< 3< 3–
PFHxA3 ppt< 3< 3–
PFHxS3 ppt< 3< 3–
PFMBA3 ppt< 3< 3–
PFMPA4 ppt< 4< 4–
PFNA4 ppt< 4< 4–
PFOA4 ppt< 4< 4–
PFOS4 ppt< 4< 4–
PFPeA3 ppt< 3< 3–
PFPeS4 ppt< 4< 4–
PFTA8 ppt< 8–< 8
PFTrDA7 ppt< 7–< 7
PFUnA2 ppt< 2< 2–
lithium9 µg/L< 9< 9–

Well 5-1 & 5-2 TP facility 78331 · sample point 1 · groundwater

CompoundMRL2023-06-20
SE1
2023-12-01
SE2
2024-05-03
SE2
PFHxA3 ppt3.3< 3–
PFOA4 ppt4< 4–
PFOS4 ppt5.2< 4–
PFPeA3 ppt3.2< 3–
11Cl-PF3OUdS5 ppt< 5< 5–
4:2 FTS3 ppt< 3< 3–
6:2 FTS5 ppt< 5< 5–
8:2 FTS5 ppt< 5< 5–
9Cl-PF3ONS2 ppt< 2< 2–
ADONA3 ppt< 3< 3–
HFPO-DA5 ppt< 5< 5–
NEtFOSAA5 ppt< 5–< 5
NFDHA20 ppt< 20< 20–
NMeFOSAA6 ppt< 6–< 6
PFBA5 ppt< 5< 5–
PFBS3 ppt< 3< 3–
PFDA3 ppt< 3< 3–
PFDoA3 ppt< 3< 3–
PFEESA3 ppt< 3< 3–
PFHpA3 ppt< 3< 3–
PFHpS3 ppt< 3< 3–
PFHxS3 ppt< 3< 3–
PFMBA3 ppt< 3< 3–
PFMPA4 ppt< 4< 4–
PFNA4 ppt< 4< 4–
PFPeS4 ppt< 4< 4–
PFTA8 ppt< 8–< 8
PFTrDA7 ppt< 7–< 7
PFUnA2 ppt< 2< 2–
lithium9 µg/L< 9< 9–

Well 7-2 & 7-3 TP facility 34272 · sample point T34272T105439 · groundwater

CompoundMRL2023-06-20
SE1
2023-12-06
SE2
11Cl-PF3OUdS5 ppt< 5< 5
4:2 FTS3 ppt< 3< 3
6:2 FTS5 ppt< 5< 5
8:2 FTS5 ppt< 5< 5
9Cl-PF3ONS2 ppt< 2< 2
ADONA3 ppt< 3< 3
HFPO-DA5 ppt< 5< 5
NEtFOSAA5 ppt< 5< 5
NFDHA20 ppt< 20< 20
NMeFOSAA6 ppt< 6< 6
PFBA5 ppt< 5< 5
PFBS3 ppt< 3< 3
PFDA3 ppt< 3< 3
PFDoA3 ppt< 3< 3
PFEESA3 ppt< 3< 3
PFHpA3 ppt< 3< 3
PFHpS3 ppt< 3< 3
PFHxA3 ppt< 3< 3
PFHxS3 ppt< 3< 3
PFMBA3 ppt< 3< 3
PFMPA4 ppt< 4< 4
PFNA4 ppt< 4< 4
PFOA4 ppt< 4< 4
PFOS4 ppt< 4< 4
PFPeA3 ppt< 3< 3
PFPeS4 ppt< 4< 4
PFTA8 ppt< 8< 8
PFTrDA7 ppt< 7< 7
PFUnA2 ppt< 2< 2
lithium9 µg/L< 9< 9

Well17-1 TP facility 13031 · sample point T130317 · groundwater

CompoundMRL2023-06-20
SE1
2023-07-17
SE1
2023-12-06
SE2
11Cl-PF3OUdS5 ppt< 5–< 5
4:2 FTS3 ppt< 3–< 3
6:2 FTS5 ppt< 5–< 5
8:2 FTS5 ppt< 5–< 5
9Cl-PF3ONS2 ppt< 2–< 2
ADONA3 ppt< 3–< 3
HFPO-DA5 ppt< 5–< 5
NEtFOSAA5 ppt–< 5< 5
NFDHA20 ppt< 20–< 20
NMeFOSAA6 ppt–< 6< 6
PFBA5 ppt< 5–< 5
PFBS3 ppt< 3–< 3
PFDA3 ppt< 3–< 3
PFDoA3 ppt< 3–< 3
PFEESA3 ppt< 3–< 3
PFHpA3 ppt< 3–< 3
PFHpS3 ppt< 3–< 3
PFHxA3 ppt< 3–< 3
PFHxS3 ppt< 3–< 3
PFMBA3 ppt< 3–< 3
PFMPA4 ppt< 4–< 4
PFNA4 ppt< 4–< 4
PFOA4 ppt< 4–< 4
PFOS4 ppt< 4–< 4
PFPeA3 ppt< 3–< 3
PFPeS4 ppt< 4–< 4
PFTA8 ppt–< 8< 8
PFTrDA7 ppt–< 7< 7
PFUnA2 ppt< 2–< 2
lithium9 µg/L< 9–< 9

Statistics by compound

CompoundResultsDetectedHighest (date)Mean boundsKM medianP75P90P95
PFHxA205%3.3
2023-06-20
0.17–3.02<MRL<MRL<MRL<MRL
PFOA205%4
2023-06-20
0.2–4<MRL<MRL<MRL<MRL
PFOS205%5.2
2023-06-20
0.26–4.06<MRL<MRL<MRL<MRL
PFPeA205%3.2
2023-06-20
0.16–3.01<MRL<MRL<MRL<MRL

Never detected (26): 11Cl-PF3OUdS, 4:2 FTS, 6:2 FTS, 8:2 FTS, 9Cl-PF3ONS, ADONA, HFPO-DA, NEtFOSAA, NFDHA, NMeFOSAA, PFBA, PFBS, PFDA, PFDoA, PFEESA, PFHpA, PFHpS, PFHxS, PFMBA, PFMPA, PFNA, PFPeS, PFTA, PFTrDA, PFUnA, lithium.

Left-censored Kaplan–Meier statistics (Helsel 2005; Helsel & Lee 2006, NADA for R). Units: ppt; lithium µg/L. Each compound has one reporting limit, so the Kaplan–Meier mean equals the upper mean bound (non-detects at the MRL); the lower bound sets non-detects to 0. “<MRL” = the percentile falls below the reporting limit and cannot be estimated. These describe this system's UCMR 5 samples, not population estimates.

Sources

  • EPA UCMR 5 occurrence data text files (UCMR5_All.txt; samples 2023-01-03 to 2026-06-17; 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+

Data build 171ad949e257 · 2026-10-18T04:10Z · UCMR 5 release Jul2026 · SDWIS 2026Q3. Data and methods.