Norwalk - City, Water Dept.

PFAS monitoring results for a public water system in California

CA1910191UCMR 5EPA monitoring data
5.2Highest PFOA result, ppt
26Highest PFOS result, ppt
0.76Highest Hazard Index
600Results
PWSID
CA1910191
State
California
System type
community water system (CWS)
Population served
20,283
City
Norwalk
Counties
Los Angeles County
Primary source water
surface water (purchased)
UCMR 5 sampling
2024-02-27 to 2024-11-20 · 6 entry point(s) · water types: GW;SW
Service-area boundary
authoritative

PFOS ≥ 3 × its limit highest single result
PFOS ≥ 3 × 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.

Water purchased from

Seller results are the seller's own entry-point samples, not measurements of this system's water. This system's own samples (below) may reflect purchased water, its own sources, or both.

Compared with EPA's 2024 values

Highest single resultWorst entry-point average*Limit
PFOA (ppt)5.25.154
PFOS (ppt)26254
Hazard Index0.760.7451.0†

“<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 California guidance levels

Highest single resultWorst entry-point average*California
PFHxS (ppt)7.67.453 (guidance)
PFOA (ppt)5.25.154 (guidance)
PFOS (ppt)26254 (guidance)
PFBS (ppt)00500 (guidance)
PFHxA (ppt)001,000 (guidance)

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 2024-02-27 to 2024-11-20 · 6 entry point(s) · water types: GW;SW · 20 sampling visits. PFAS in ppt (ng/L).

DateEntry pointEventPFOAPFOSHIOther detections
2024-02-27Cabrillo (SW)SE1<4<40lithium 57 µg/L
2024-02-27City of Cerritos (SW)SE1<4<40lithium 56 µg/L
2024-02-27City of Santa Fe Springs (SW)SE1<4<40lithium 57 µg/L
2024-02-27Leffingwell Well 4 (GW)SE15.2240.71PFBA 5.6
2024-02-27MWD Intertie (SW)SE1<4<40lithium 56 µg/L
2024-02-27Taddy Well 5 (GW)SE14.7200.76none
2024-05-20Cabrillo (SW)SE2<4<40lithium 58 µg/L
2024-05-20City of Cerritos (SW)SE2<4<40lithium 59 µg/L
2024-05-20City of Santa Fe Springs (SW)SE2<4<40lithium 58 µg/L
2024-05-20MWD Intertie (SW)SE2<4<40lithium 58 µg/L
2024-08-26Cabrillo (SW)SE3<4<40lithium 43 µg/L
2024-08-26City of Cerritos (SW)SE3<4<40lithium 43 µg/L
2024-08-26City of Santa Fe Springs (SW)SE3<4<40lithium 39 µg/L
2024-08-26Leffingwell Well 4 (GW)SE25.1260.73PFBA 5.5, PFPeA 3.4
2024-08-26MWD Intertie (SW)SE3<4<40lithium 43 µg/L
2024-08-26Taddy Well 5 (GW)SE24.9220.73none
2024-11-20Cabrillo (SW)SE4<4<40lithium 26 µg/L
2024-11-20City of Cerritos (SW)SE4<4<40lithium 25 µg/L
2024-11-20City of Santa Fe Springs (SW)SE4<4<40lithium 21 µg/L
2024-11-20MWD Intertie (SW)SE4<4<40lithium 25 µg/L

“<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.

Cabrillo facility 14332 · sample point 14332 · surface water

CompoundMRL2024-02-27
SE1
2024-05-20
SE2
2024-08-26
SE3
2024-11-20
SE4
11Cl-PF3OUdS5 ppt< 5< 5< 5< 5
4:2 FTS3 ppt< 3< 3< 3< 3
6:2 FTS5 ppt< 5< 5< 5< 5
8:2 FTS5 ppt< 5< 5< 5< 5
9Cl-PF3ONS2 ppt< 2< 2< 2< 2
ADONA3 ppt< 3< 3< 3< 3
HFPO-DA5 ppt< 5< 5< 5< 5
NEtFOSAA5 ppt< 5< 5< 5< 5
NFDHA20 ppt< 20< 20< 20< 20
NMeFOSAA6 ppt< 6< 6< 6< 6
PFBA5 ppt< 5< 5< 5< 5
PFBS3 ppt< 3< 3< 3< 3
PFDA3 ppt< 3< 3< 3< 3
PFDoA3 ppt< 3< 3< 3< 3
PFEESA3 ppt< 3< 3< 3< 3
PFHpA3 ppt< 3< 3< 3< 3
PFHpS3 ppt< 3< 3< 3< 3
PFHxA3 ppt< 3< 3< 3< 3
PFHxS3 ppt< 3< 3< 3< 3
PFMBA3 ppt< 3< 3< 3< 3
PFMPA4 ppt< 4< 4< 4< 4
PFNA4 ppt< 4< 4< 4< 4
PFOA4 ppt< 4< 4< 4< 4
PFOS4 ppt< 4< 4< 4< 4
PFPeA3 ppt< 3< 3< 3< 3
PFPeS4 ppt< 4< 4< 4< 4
PFTA8 ppt< 8< 8< 8< 8
PFTrDA7 ppt< 7< 7< 7< 7
PFUnA2 ppt< 2< 2< 2< 2
lithium9 µg/L57584326

City of Cerritos facility 91804 · sample point 1910191804 · surface water

CompoundMRL2024-02-27
SE1
2024-05-20
SE2
2024-08-26
SE3
2024-11-20
SE4
11Cl-PF3OUdS5 ppt< 5< 5< 5< 5
4:2 FTS3 ppt< 3< 3< 3< 3
6:2 FTS5 ppt< 5< 5< 5< 5
8:2 FTS5 ppt< 5< 5< 5< 5
9Cl-PF3ONS2 ppt< 2< 2< 2< 2
ADONA3 ppt< 3< 3< 3< 3
HFPO-DA5 ppt< 5< 5< 5< 5
NEtFOSAA5 ppt< 5< 5< 5< 5
NFDHA20 ppt< 20< 20< 20< 20
NMeFOSAA6 ppt< 6< 6< 6< 6
PFBA5 ppt< 5< 5< 5< 5
PFBS3 ppt< 3< 3< 3< 3
PFDA3 ppt< 3< 3< 3< 3
PFDoA3 ppt< 3< 3< 3< 3
PFEESA3 ppt< 3< 3< 3< 3
PFHpA3 ppt< 3< 3< 3< 3
PFHpS3 ppt< 3< 3< 3< 3
PFHxA3 ppt< 3< 3< 3< 3
PFHxS3 ppt< 3< 3< 3< 3
PFMBA3 ppt< 3< 3< 3< 3
PFMPA4 ppt< 4< 4< 4< 4
PFNA4 ppt< 4< 4< 4< 4
PFOA4 ppt< 4< 4< 4< 4
PFOS4 ppt< 4< 4< 4< 4
PFPeA3 ppt< 3< 3< 3< 3
PFPeS4 ppt< 4< 4< 4< 4
PFTA8 ppt< 8< 8< 8< 8
PFTrDA7 ppt< 7< 7< 7< 7
PFUnA2 ppt< 2< 2< 2< 2
lithium9 µg/L56594325

City of Santa Fe Springs facility 91805 · sample point 1910191805 · surface water

CompoundMRL2024-02-27
SE1
2024-05-20
SE2
2024-08-26
SE3
2024-11-20
SE4
11Cl-PF3OUdS5 ppt< 5< 5< 5< 5
4:2 FTS3 ppt< 3< 3< 3< 3
6:2 FTS5 ppt< 5< 5< 5< 5
8:2 FTS5 ppt< 5< 5< 5< 5
9Cl-PF3ONS2 ppt< 2< 2< 2< 2
ADONA3 ppt< 3< 3< 3< 3
HFPO-DA5 ppt< 5< 5< 5< 5
NEtFOSAA5 ppt< 5< 5< 5< 5
NFDHA20 ppt< 20< 20< 20< 20
NMeFOSAA6 ppt< 6< 6< 6< 6
PFBA5 ppt< 5< 5< 5< 5
PFBS3 ppt< 3< 3< 3< 3
PFDA3 ppt< 3< 3< 3< 3
PFDoA3 ppt< 3< 3< 3< 3
PFEESA3 ppt< 3< 3< 3< 3
PFHpA3 ppt< 3< 3< 3< 3
PFHpS3 ppt< 3< 3< 3< 3
PFHxA3 ppt< 3< 3< 3< 3
PFHxS3 ppt< 3< 3< 3< 3
PFMBA3 ppt< 3< 3< 3< 3
PFMPA4 ppt< 4< 4< 4< 4
PFNA4 ppt< 4< 4< 4< 4
PFOA4 ppt< 4< 4< 4< 4
PFOS4 ppt< 4< 4< 4< 4
PFPeA3 ppt< 3< 3< 3< 3
PFPeS4 ppt< 4< 4< 4< 4
PFTA8 ppt< 8< 8< 8< 8
PFTrDA7 ppt< 7< 7< 7< 7
PFUnA2 ppt< 2< 2< 2< 2
lithium9 µg/L57583921

Leffingwell Well 4 facility 91802 · sample point 1910191802 · groundwater

CompoundMRL2024-02-27
SE1
2024-08-26
SE2
PFBA5 ppt5.65.5
PFHxS3 ppt7.17.3
PFOA4 ppt5.25.1
PFOS4 ppt2426
PFPeA3 ppt< 33.4
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
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
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

MWD Intertie facility 91803 · sample point 1910191803 · surface water

CompoundMRL2024-02-27
SE1
2024-05-20
SE2
2024-08-26
SE3
2024-11-20
SE4
11Cl-PF3OUdS5 ppt< 5< 5< 5< 5
4:2 FTS3 ppt< 3< 3< 3< 3
6:2 FTS5 ppt< 5< 5< 5< 5
8:2 FTS5 ppt< 5< 5< 5< 5
9Cl-PF3ONS2 ppt< 2< 2< 2< 2
ADONA3 ppt< 3< 3< 3< 3
HFPO-DA5 ppt< 5< 5< 5< 5
NEtFOSAA5 ppt< 5< 5< 5< 5
NFDHA20 ppt< 20< 20< 20< 20
NMeFOSAA6 ppt< 6< 6< 6< 6
PFBA5 ppt< 5< 5< 5< 5
PFBS3 ppt< 3< 3< 3< 3
PFDA3 ppt< 3< 3< 3< 3
PFDoA3 ppt< 3< 3< 3< 3
PFEESA3 ppt< 3< 3< 3< 3
PFHpA3 ppt< 3< 3< 3< 3
PFHpS3 ppt< 3< 3< 3< 3
PFHxA3 ppt< 3< 3< 3< 3
PFHxS3 ppt< 3< 3< 3< 3
PFMBA3 ppt< 3< 3< 3< 3
PFMPA4 ppt< 4< 4< 4< 4
PFNA4 ppt< 4< 4< 4< 4
PFOA4 ppt< 4< 4< 4< 4
PFOS4 ppt< 4< 4< 4< 4
PFPeA3 ppt< 3< 3< 3< 3
PFPeS4 ppt< 4< 4< 4< 4
PFTA8 ppt< 8< 8< 8< 8
PFTrDA7 ppt< 7< 7< 7< 7
PFUnA2 ppt< 2< 2< 2< 2
lithium9 µg/L56584325

Taddy Well 5 facility 91801 · sample point 1910186801 · groundwater

CompoundMRL2024-02-27
SE1
2024-08-26
SE2
PFHxS3 ppt7.67.3
PFOA4 ppt4.74.9
PFOS4 ppt2022
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
PFMBA3 ppt< 3< 3
PFMPA4 ppt< 4< 4
PFNA4 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
lithium2080%59
2024-05-20
36.2–3843575858
PFHxS2020%7.6
2024-02-27
1.47–3.87<MRL<MRL7.37.3
PFOA2020%5.2
2024-02-27
0.99–4.2<MRL<MRL4.95.1
PFOS2020%26
2024-08-26
4.6–7.8<MRL<MRL2224
PFBA2010%5.6
2024-02-27
0.56–5.05<MRL<MRL<MRL5.5
PFPeA205%3.4
2024-08-26
0.17–3.02<MRL<MRL<MRL<MRL

Never detected (24): 11Cl-PF3OUdS, 4:2 FTS, 6:2 FTS, 8:2 FTS, 9Cl-PF3ONS, ADONA, HFPO-DA, NEtFOSAA, NFDHA, NMeFOSAA, PFBS, PFDA, PFDoA, PFEESA, PFHpA, PFHpS, PFHxA, PFMBA, PFMPA, PFNA, PFPeS, PFTA, PFTrDA, PFUnA.

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 2023-01-09 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 90f0922cd84f · 2026-10-18T04:12Z · UCMR 5 release Jul2026 · SDWIS 2026Q3. Data and methods.