Data & Methodology — Sacramento County

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

Contaminant Data — All Analytes

801 well testing events on record, covering 27 analytes. Data spans 1931 to 2020.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. CA Avg
Manganese 396 1958–2022 60%
40% of limit ↓ 87% below
Arsenic 368 1958–2022 99%
37% of limit ~ typical
Iron 395 1969–2022 46%
10% of limit ↓ 92% below
PFOS municipal 554 2022–2025 6%
172% of limit ~ typical
Boron 38 2017–2022 97%
2% of limit ↓ 86% below
PFOA municipal 554 2022–2025 5%
149% of limit ~ typical
Chloride 557 1955–2022 100%
6% of limit ↓ 80% below
PFHxS municipal 554 2022–2025 6%
42% of limit ↓ 25% below
Uranium 205 1995–2022 89%
3% of limit ↓ 47% below
Fluoride 401 1955–2022 84%
4% of limit ↓ 42% below
Lead 199 1958–2022 31%
1% of limit ↓ 94% below
Nitrate 285 1955–2022 85%
20% of limit ~ typical
Sulfate 451 1955–2022 82%
4% of limit ↓ 80% below
Nitrite 228 1991–2022 12%
1% of limit ↓ 51% below
HFPO-DA (GenX) municipal 554 2022–2025 0%
— —
Chromium (total) 39 2004–2022 79%
5% of limit ↑ 78% above
1,2,3-Trichloropropane 40 2004–2022 0%
— —
Perchlorate 37 2017–2022 65%
6% of limit ~ typical
PFNA municipal 554 2022–2025 0%
— —
Radon 22 1995–2005 100%
8% of limit ↓ 92% below
Tds 39 2004–2022 100%
— ↓ 44% below
PFBS municipal 554 2022–2025 2%
— ~ typical
Sodium 552 1955–2022 100%
— ↓ 72% below
Hardness 556 1955–2022 100%
— ↓ 53% below
E. coli 33 2002–2022 2%
— ~ typical
pH 615 1955–2023 100%
— ~ typical
Total Coliform 33 2002–2022 7%
— ~ 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 Sacramento County

Of the 368 arsenic tests on record for Sacramento County (1958–2022), 1% found none, and half were below 3.65 µg/L.

Of the 557 chloride tests on record for Sacramento County (1955–2022), 0% found none, and half were below 15 mg/L.

Of the 39 chromium (total) tests on record for Sacramento County (2004–2022), 21% found none, and half were below 3.6 µg/L.

Of the 401 fluoride tests on record for Sacramento County (1955–2022), 16% found none, and half were below 130 µg/L.

Of the 395 iron tests on record for Sacramento County (1969–2022), 54% found none.

Of the 199 lead tests on record for Sacramento County (1958–2022), 69% found none.

Of the 396 manganese tests on record for Sacramento County (1958–2022), 40% found none, and half were below 0.6 µg/L.

Of the 285 nitrate tests on record for Sacramento County (1955–2022), 15% found none, and half were below 1.63 mg/L.

Of the 451 sulfate tests on record for Sacramento County (1955–2022), 18% found none, and half were below 6.92 mg/L.

Of the 39 tds tests on record for Sacramento County (2004–2022), 0% found none, and half were below 222 mg/L.

Of the 205 uranium tests on record for Sacramento County (1995–2022), 11% found none, and half were below 0.373 µg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 396 samples
  • Arsenic 368 samples
  • Iron 395 samples
  • PFOS 554 samples
  • Boron 38 samples
  • PFOA 554 samples
  • Chloride 557 samples
  • PFHxS 554 samples
  • Uranium 205 samples
  • Fluoride 401 samples
  • Lead 199 samples
  • Nitrate 285 samples
  • Sulfate 451 samples
  • Nitrite 228 samples
  • HFPO-DA (GenX) 554 samples
  • Chromium (total) 39 samples
  • 1,2,3-Trichloropropane 40 samples
  • Perchlorate 37 samples
  • PFNA 554 samples
  • Radon 22 samples
  • Tds 39 samples
  • PFBS 554 samples
  • Sodium 552 samples
  • Hardness 556 samples
  • E. coli 33 samples
  • pH 615 samples
  • Total Coliform 33 samples

Public vs. Private Water in Sacramento County

164 Active public water systems
1,693,284 Residents on public water
4% Households on private wells

Public water systems in Sacramento 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 Sacramento 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 Sacramento County Prevalence CA Average Source Year
Arsenic Cancer prevalence 5.9% 6.2% 2020
Arsenic Kidney disease rate 2.9% 3.0% 2020

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