Data & Methodology — Imperial County

Full contaminant data, sample history, and sourcing for Imperial County. For readers who want to go beyond the summary.

Contaminant Data — All Analytes

1515 well testing events on record, covering 25 analytes. Data spans 1917 to 2024.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. CA Avg
Boron 2 2007–2009 100%
146% of limit ↑ 781% above
Chloride 1423 1917–2023 100%
68% of limit ↑ 125% above
Sulfate 1297 1917–2023 100%
44% of limit ↑ 118% above
Arsenic 98 1958–2023 97%
34% of limit ~ typical
Radon 5 2007–2013 100%
11% of limit ↓ 88% below
Iron 884 1917–2023 67%
8% of limit ↓ 94% below
Manganese 761 1955–2023 68%
4% of limit ↓ 99% below
Lead 48 1963–2023 35%
1% of limit ↓ 92% below
Fluoride 1123 1933–2023 100%
22% of limit ↑ 220% above
Nitrate 691 1917–2023 94%
13% of limit ↓ 45% below
PFOS municipal 39 2022–2025 0%
— —
HFPO-DA (GenX) municipal 39 2022–2025 0%
— —
Nitrite 526 1991–2023 28%
1% of limit ~ typical
Perchlorate 2 2007–2009 50%
6% of limit ~ typical
PFOA municipal 39 2022–2025 0%
— —
Uranium 38 2007–2023 100%
11% of limit ↑ 99% above
Chromium (total) 2 2007–2009 100%
2% of limit ↓ 38% below
1,2,3-Trichloropropane 2 2007–2009 0%
— —
PFHxS municipal 39 2022–2025 0%
— —
PFNA municipal 39 2022–2025 0%
— —
Tds 2 2007–2009 100%
— ↑ 349% above
Hardness 1312 1917–2023 100%
— ↓ 66% below
Sodium 1109 1933–2023 100%
— ↑ 80% above
PFBS municipal 39 2022–2025 0%
— —
pH 1405 1933–2023 100%
— ~ typical

Distribution shows the share of samples in each concentration band relative to the EPA Maximum Contaminant Level (MCL): Low = below half the MCL, Moderate = between half and the MCL, High = above the MCL. Analytes without an MCL (e.g. sodium, pH) show — in the limit columns. State average is based on county median values across CA.

Compare your result with Imperial County

Of the 98 arsenic tests on record for Imperial County (1958–2023), 3% found none, and half were below 3.25 µg/L.

Of the 1423 chloride tests on record for Imperial County (1917–2023), 0% found none, and half were below 169 mg/L.

Of the 1123 fluoride tests on record for Imperial County (1933–2023), 0% found none, and half were below 890 µg/L.

Of the 884 iron tests on record for Imperial County (1917–2023), 33% found none, and half were below 10.8 µg/L.

Of the 48 lead tests on record for Imperial County (1963–2023), 65% found none.

Of the 761 manganese tests on record for Imperial County (1955–2023), 32% found none, and half were below 0.66 µg/L.

Of the 691 nitrate tests on record for Imperial County (1917–2023), 6% found none, and half were below 1.25 mg/L.

Of the 1297 sulfate tests on record for Imperial County (1917–2023), 0% found none, and half were below 110 mg/L.

Of the 38 uranium tests on record for Imperial County (2007–2023), 0% found none, and half were below 3.25 µg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Chloride 1423 samples
  • Sulfate 1297 samples
  • Arsenic 98 samples
  • Iron 884 samples
  • Manganese 761 samples
  • Lead 48 samples
  • Fluoride 1123 samples
  • Nitrate 691 samples
  • PFOS 39 samples
  • HFPO-DA (GenX) 39 samples
  • Nitrite 526 samples
  • PFOA 39 samples
  • Uranium 38 samples
  • PFHxS 39 samples
  • PFNA 39 samples
  • Hardness 1312 samples
  • Sodium 1109 samples
  • PFBS 39 samples
  • pH 1405 samples

Limited data (<15 samples) — interpret with caution

  • Boron 2 samples
  • Radon 5 samples
  • Perchlorate 2 samples
  • Chromium (total) 2 samples
  • 1,2,3-Trichloropropane 2 samples
  • Tds 2 samples

Public vs. Private Water in Imperial County

79 Active public water systems
186,298 Residents on public water
7% Households on private wells

Public water systems in Imperial County are regulated by the EPA and must test and report contaminant levels. Private well owners are responsible for their own testing — there is no routine monitoring of private wells by any government agency.

CDC Health Outcome Correlations

Where contaminants detected in Imperial County have established associations with specific health outcomes, we cross-reference CDC PLACES county-level prevalence data. This is a contextual signal, not a causal claim.

Contaminant Associated Condition Imperial County Prevalence CA Average Source Year
Arsenic Cancer prevalence 4.6% 6.2% 2020
Arsenic Kidney disease rate 3.6% 3.0% 2020
Lead Heart disease rate 6.5% 6.3% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Imperial County CDC PLACES data →

Data Sources

This report aggregates data from the following public databases:

Methodology

Raw records are downloaded from the Water Quality Portal and normalized to µg/L (ppb). Records are deduplicated by sample ID and date, and certified outliers are excluded. Analyte names are mapped to EPA canonical forms. Detection rates, distribution bands, and MCL comparisons are computed from the normalized dataset.

Distribution bands use the EPA Maximum Contaminant Level as the threshold: concentrations below 50% of the MCL are classed as Low, between 50% and 100% as Moderate, and above 100% as High. For analytes without an MCL (sodium, hardness, pH), distribution is not computed.

State comparison uses the median of county median values across all counties in CA with at least one sample for that analyte.

Last updated: 2026-09-10

Full methodology →