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This is a rebuild of Drinking Water Watch and not yet the official record. Use the agency’s current Drinking Water Watch for anything you need to rely on.

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.

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

No date range is applied: this list draws on every sample on record. Show the last two years only.

The most recent samples, result by result

The table below lists 21–30 of 284 samples, newest first — collected March 28, 2023 to October 25, 2023. The summary above covers all 284.

19 results from the 10 samples listed here: 7 detected, 12 not detected. Across the whole record it is 278 of 1,425. 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 5 sampling points 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 21 to 30 of 284 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
Oct 25, 2023 13:32
Sampling point
TF102 Treatment Plant T102
Sample type
Routine
Lab sample
NI-231026-022
Laboratory
MSDH Lab
Not detected below 0.1 mg/l Minimum Reporting Level , sample collected Oct 25, 2023 13:32, sampling point TF102 Nitrate-Nitrite 1038 EPA method QC10107041C Jan 1, 2023 – Dec 31, 2023
Not detected below 0.08 mg/l Minimum Reporting Level , sample collected Oct 25, 2023 13:32, sampling point TF102 Nitrate 1040 EPA method QC10107041C Jan 1, 2023 – Dec 31, 2023
Not detected below 0.02 mg/l Minimum Reporting Level , sample collected Oct 25, 2023 13:32, sampling point TF102 Nitrite 1041 EPA method QC10107041C Jan 1, 2023 – Dec 31, 2023
Collected
Oct 25, 2023 13:15
Sampling point
TF101 Treatment Plant T101
Sample type
Routine
Lab sample
NI-231026-021
Laboratory
MSDH Lab
Not detected below 0.1 mg/l Minimum Reporting Level , sample collected Oct 25, 2023 13:15, sampling point TF101 Nitrate-Nitrite 1038 EPA method QC10107041C Jan 1, 2023 – Dec 31, 2023
Not detected below 0.08 mg/l Minimum Reporting Level , sample collected Oct 25, 2023 13:15, sampling point TF101 Nitrate 1040 EPA method QC10107041C Jan 1, 2023 – Dec 31, 2023
Not detected below 0.02 mg/l Minimum Reporting Level , sample collected Oct 25, 2023 13:15, sampling point TF101 Nitrite 1041 EPA method QC10107041C Jan 1, 2023 – Dec 31, 2023
Collected
Aug 28, 2023 14:10
Sampling point
LC0006 Location withheld
Sample type
Routine
Lab sample
PB-230830-102
Laboratory
MSDH Lab
0.0032 mg/l , sample collected Aug 28, 2023 14:10, sampling point LC0006 Copper, Free 1022 EPA method 200.8 Jan 1, 2021 – Dec 31, 2023
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Aug 28, 2023 14:10, sampling point LC0006 Lead 1030 EPA method 200.8 Jan 1, 2021 – Dec 31, 2023
Collected
Aug 28, 2023 14:00
Sampling point
LC0001 Location withheld
Sample type
Routine
Lab sample
PB-230830-101
Laboratory
MSDH Lab
0.0038 mg/l , sample collected Aug 28, 2023 14:00, sampling point LC0001 Copper, Free 1022 EPA method 200.8 Jan 1, 2021 – Dec 31, 2023
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Aug 28, 2023 14:00, sampling point LC0001 Lead 1030 EPA method 200.8 Jan 1, 2021 – Dec 31, 2023
Collected
Aug 28, 2023 13:45
Sampling point
LC0007 Location withheld
Sample type
Routine
Lab sample
PB-230830-100
Laboratory
MSDH Lab
0.0094 mg/l , sample collected Aug 28, 2023 13:45, sampling point LC0007 Copper, Free 1022 EPA method 200.8 Jan 1, 2021 – Dec 31, 2023
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Aug 28, 2023 13:45, sampling point LC0007 Lead 1030 EPA method 200.8 Jan 1, 2021 – Dec 31, 2023
Collected
Aug 28, 2023 13:00
Sampling point
LC0003 Location withheld
Sample type
Routine
Lab sample
PB-230830-099
Laboratory
MSDH Lab
0.0033 mg/l , sample collected Aug 28, 2023 13:00, sampling point LC0003 Copper, Free 1022 EPA method 200.8 Jan 1, 2021 – Dec 31, 2023
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Aug 28, 2023 13:00, sampling point LC0003 Lead 1030 EPA method 200.8 Jan 1, 2021 – Dec 31, 2023
Collected
Aug 28, 2023 12:10
Sampling point
LC0008 Location withheld
Sample type
Routine
Lab sample
PB-230830-098
Laboratory
MSDH Lab
Not detected below 0.0005 mg/l Minimum Reporting Level , sample collected Aug 28, 2023 12:10, sampling point LC0008 Copper, Free 1022 EPA method 200.8 Jan 1, 2021 – Dec 31, 2023
Not detected below 0.5 ug/l Minimum Reporting Level , sample collected Aug 28, 2023 12:10, sampling point LC0008 Lead 1030 EPA method 200.8 Jan 1, 2021 – Dec 31, 2023
Collected
Mar 28, 2023 12:43
Sampling point
TF103 Treatment Plant T103
Sample type
Routine
Lab sample
NA-230329-005
Laboratory
MSDH Lab
56.4 mg/l , sample collected Mar 28, 2023 12:43, sampling point TF103 Sodium 1052 EPA method 200.7 Not recorded
Collected
Mar 28, 2023 12:23
Sampling point
TF102 Treatment Plant T102
Sample type
Routine
Lab sample
NA-230329-004
Laboratory
MSDH Lab
54.2 mg/l , sample collected Mar 28, 2023 12:23, sampling point TF102 Sodium 1052 EPA method 200.7 Not recorded
Collected
Mar 28, 2023 12:05
Sampling point
TF101 Treatment Plant T101
Sample type
Routine
Lab sample
NA-230329-003
Laboratory
MSDH Lab
52.1 mg/l , sample collected Mar 28, 2023 12:05, sampling point TF101 Sodium 1052 EPA method 200.7 Not recorded

Routine (10).