Chemical and radiological sample results

MS0730010 , Lake Arrowhead

19 of the 57 analytes this system has been tested for have been detected at least once, across 284 samples on record.

The other 38 were tested for and never found. An analyte is counted here if any result on record measured it, so this covers the whole history and not the samples listed below.

Across all 284 samples on record, detections range from November 5, 2003 to April 2, 2025. These figures cover the whole record; the list of samples further down is narrowed.

What counts as a non-detect is defined in the help: Less than Indicator. This system’s violations.

What has been detected, ever

Every analyte measured above its reporting level at any point in this system’s record, most often detected first. This is not limited to the samples listed below.

Every analyte ever detected for Lake Arrowhead, with how many results found it and when it was first and last detected. Covers the whole record, not only the samples listed below.
Analyte	Kind	Detected in	First detected	Last detected
Copper, Free 1022	Inorganic Chemical	82 of 83 results	Sep 27, 2004	Aug 28, 2023
Lead 1030	Inorganic Chemical	41 of 83 results	Sep 27, 2004	Sep 9, 2020
Barium 1010	Inorganic Chemical	29 of 29 results	Nov 5, 2003	Apr 2, 2025
Fluoride 1025	Inorganic Chemical	24 of 29 results	Nov 5, 2003	Apr 2, 2025
Nitrate 1040	Inorganic Chemical	19 of 64 results	Jun 16, 2004	Apr 17, 2024
Nitrate-Nitrite 1038	Inorganic Chemical	16 of 64 results	Apr 2, 2012	Apr 17, 2024
Nickel 1036	Inorganic Chemical	14 of 29 results	May 29, 2013	Apr 2, 2025
Chromium 1020	Inorganic Chemical	12 of 29 results	Nov 16, 2004	Dec 13, 2016
Gross Alpha, Incl. Radon & U 4002	Radionuclide	10 of 15 results	Mar 12, 2012	Oct 12, 2012
Sodium 1052	Inorganic Chemical	6 of 6 results	Sep 16, 2019	Mar 28, 2023
Combined Radium (-226 & -228) 4010	Radionuclide	5 of 15 results	Mar 12, 2012	Oct 12, 2012
Radium-228 4030	Radionuclide	5 of 15 results	Mar 12, 2012	Oct 12, 2012
Nitrite 1041	Inorganic Chemical	4 of 64 results	Dec 6, 2004	Apr 17, 2024
Sulfate 1055	Inorganic Chemical	4 of 4 results	Nov 5, 2003	Mar 29, 2004
TTHM 2950	Organic Chemical	2 of 7 results	Sep 20, 2007	Jul 15, 2010
Selenium 1045	Inorganic Chemical	2 of 29 results	Mar 29, 2004	Nov 16, 2004
Total Haloacetic Acids (Haa5) 2456	Organic Chemical	1 of 7 results	Jul 15, 2010	Jul 15, 2010
Toluene 2991	Organic Chemical	1 of 28 results	Sep 22, 2004	Sep 22, 2004
Cadmium 1015	Inorganic Chemical	1 of 29 results	Nov 5, 2003	Nov 5, 2003

Showing samples collected between September 25, 2024 and September 25, 2026. That is this page’s default, not a limit on what the agency records.

Show every sample on record

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The most recent samples, result by result

The table below lists 11–15 of 15 samples, newest first — collected February 25, 2025 to April 2, 2025. The summary above covers all 15.

43 results from the 5 samples listed here: 6 detected, 37 not detected. A sample is analysed for many analytes at once, so one sample appears on as many rows as it had results.

We withheld the location of 1 sampling point below. The location on record identifies a private home, and we do not publish those. That is our decision, not the agency’s. The sampling point, its type and every result taken there are published unchanged.

Chemical and radiological sample results for Lake Arrowhead, every result from 11 to 15 of 15 samples shown, newest first. Not detected means the amount was below the level the laboratory can reliably report, which is given beside it.
Result	Analyte	Monitoring period
Collected Apr 2, 2025 11:30 Sampling point TF102 Treatment Plant T102 Sample type Routine Lab sample IN-250403-036 Laboratory MSDH Lab
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:30, sampling point TF102	Arsenic 1005 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
0.0168 mg/l , sample collected Apr 2, 2025 11:30, sampling point TF102	Barium 1010 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:30, sampling point TF102	Cadmium 1015 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:30, sampling point TF102	Chromium 1020 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
0.321 mg/l , sample collected Apr 2, 2025 11:30, sampling point TF102	Fluoride 1025 EPA method QC 10-109-12-2-A	Jan 1, 2023 – Dec 31, 2025
0.0006 mg/l , sample collected Apr 2, 2025 11:30, sampling point TF102	Nickel 1036 EPA method 200.8	Not recorded
Not detected below 0.0025 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:30, sampling point TF102	Selenium 1045 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:30, sampling point TF102	Antimony, Total 1074 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:30, sampling point TF102	Beryllium, Total 1075 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:30, sampling point TF102	Thallium, Total 1085 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Collected Apr 2, 2025 11:40 Sampling point TF101 Treatment Plant T101 Sample type Routine Lab sample IN-250403-035 Laboratory MSDH Lab
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:40, sampling point TF101	Arsenic 1005 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
0.0169 mg/l , sample collected Apr 2, 2025 11:40, sampling point TF101	Barium 1010 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:40, sampling point TF101	Cadmium 1015 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:40, sampling point TF101	Chromium 1020 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
0.275 mg/l , sample collected Apr 2, 2025 11:40, sampling point TF101	Fluoride 1025 EPA method QC 10-109-12-2-A	Jan 1, 2023 – Dec 31, 2025
0.0007 mg/l , sample collected Apr 2, 2025 11:40, sampling point TF101	Nickel 1036 EPA method 200.8	Not recorded
Not detected below 0.0025 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:40, sampling point TF101	Selenium 1045 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:40, sampling point TF101	Antimony, Total 1074 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:40, sampling point TF101	Beryllium, Total 1075 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Apr 2, 2025 11:40, sampling point TF101	Thallium, Total 1085 EPA method 200.8	Jan 1, 2023 – Dec 31, 2025
Collected Mar 11, 2025 11:40 Sampling point TF101 Treatment Plant T101 Sample type Routine Lab sample VO-250312-015 Laboratory MSDH Lab
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	1,2,4-Trichlorobenzene 2378 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Cis-1,2-Dichloroethylene 2380 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Xylenes, Total 2955 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Dichloromethane 2964 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	O-Dichlorobenzene 2968 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	P-Dichlorobenzene 2969 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Vinyl Chloride 2976 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	1,1-Dichloroethylene 2977 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Trans-1,2-Dichloroethylene 2979 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	1,2-Dichloroethane 2980 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	1,1,1-Trichloroethane 2981 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Carbon Tetrachloride 2982 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	1,2-Dichloropropane 2983 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Trichloroethylene 2984 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	1,1,2-Trichloroethane 2985 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Tetrachloroethylene 2987 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Chlorobenzene 2989 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Benzene 2990 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Toluene 2991 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Ethylbenzene 2992 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Mar 11, 2025 11:40, sampling point TF101	Styrene 2996 EPA method 524.2	Jan 1, 2025 – Dec 31, 2025
Collected Feb 25, 2025 11:50 Sampling point SM1 Location withheld Sample type Routine Lab sample TH-250226-005 Laboratory MSDH Lab
Not detected below 1 ug/l Minimum Reporting Level , sample collected Feb 25, 2025 11:50, sampling point SM1	TTHM 2950 EPA method 524.2	Jan 1, 2023 – Dec 31, 2025
Collected Feb 25, 2025 11:50 Sampling point SM1 Location withheld Sample type Routine Lab sample HA-250226-005 Laboratory MSDH Lab
Not detected below 1 ug/l Minimum Reporting Level , sample collected Feb 25, 2025 11:50, sampling point SM1	Total Haloacetic Acids (Haa5) 2456 EPA method 552.2	Jan 1, 2023 – Dec 31, 2025

Collected
Apr 2, 2025 11:30

Sampling point
TF102 Treatment Plant T102

Sample type
Routine

Lab sample
IN-250403-036

Laboratory
MSDH Lab
- Arsenic 1005 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Barium 1010 EPA method 200.8
  
  Result
  0.0168 mg/l
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Cadmium 1015 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Chromium 1020 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Fluoride 1025 EPA method QC 10-109-12-2-A
  
  Result
  0.321 mg/l
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Nickel 1036 EPA method 200.8
  
  Result
  0.0006 mg/l
  
  Monitoring period
  Not recorded
- Selenium 1045 EPA method 200.8
  
  Result
  Not detected below 0.0025 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Antimony, Total 1074 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Beryllium, Total 1075 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Thallium, Total 1085 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
Collected
Apr 2, 2025 11:40

Sampling point
TF101 Treatment Plant T101

Sample type
Routine

Lab sample
IN-250403-035

Laboratory
MSDH Lab
- Arsenic 1005 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Barium 1010 EPA method 200.8
  
  Result
  0.0169 mg/l
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Cadmium 1015 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Chromium 1020 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Fluoride 1025 EPA method QC 10-109-12-2-A
  
  Result
  0.275 mg/l
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Nickel 1036 EPA method 200.8
  
  Result
  0.0007 mg/l
  
  Monitoring period
  Not recorded
- Selenium 1045 EPA method 200.8
  
  Result
  Not detected below 0.0025 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Antimony, Total 1074 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Beryllium, Total 1075 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
- Thallium, Total 1085 EPA method 200.8
  
  Result
  Not detected below 0.0005 mg/l Minimum Reporting Level
  
  Monitoring period
  Jan 1, 2023 – Dec 31, 2025
Collected
Mar 11, 2025 11:40

Sampling point
TF101 Treatment Plant T101

Sample type
Routine

Lab sample
VO-250312-015

Laboratory
MSDH Lab

Monitoring period
Jan 1, 2025 – Dec 31, 2025
- 1,2,4-Trichlorobenzene 2378 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Cis-1,2-Dichloroethylene 2380 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Xylenes, Total 2955 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Dichloromethane 2964 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- O-Dichlorobenzene 2968 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- P-Dichlorobenzene 2969 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Vinyl Chloride 2976 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- 1,1-Dichloroethylene 2977 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Trans-1,2-Dichloroethylene 2979 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- 1,2-Dichloroethane 2980 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- 1,1,1-Trichloroethane 2981 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Carbon Tetrachloride 2982 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- 1,2-Dichloropropane 2983 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Trichloroethylene 2984 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- 1,1,2-Trichloroethane 2985 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Tetrachloroethylene 2987 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Chlorobenzene 2989 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Benzene 2990 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Toluene 2991 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Ethylbenzene 2992 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
- Styrene 2996 EPA method 524.2
  
  Result
  Not detected below 0.5 ug/l Minimum Reporting Level
Collected
Feb 25, 2025 11:50

Sampling point
SM1 Location withheld

Sample type
Routine

Lab sample
TH-250226-005

Laboratory
MSDH Lab

Monitoring period
Jan 1, 2023 – Dec 31, 2025
- TTHM 2950 EPA method 524.2
  
  Result
  Not detected below 1 ug/l Minimum Reporting Level
Collected
Feb 25, 2025 11:50

Sampling point
SM1 Location withheld

Sample type
Routine

Lab sample
HA-250226-005

Laboratory
MSDH Lab

Monitoring period
Jan 1, 2023 – Dec 31, 2025
- Total Haloacetic Acids (Haa5) 2456 EPA method 552.2
  
  Result
  Not detected below 1 ug/l Minimum Reporting Level

Routine (5).