Data & Methodology — Somerset County

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

Contaminant Data — All Analytes

160 well testing events on record, covering 20 analytes. Data spans 1925 to 2023.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. PA Avg
Manganese 78 1964–2023 95%
305% of limit ↓ 40% below
Iron 79 1964–2023 96%
233% of limit ↓ 60% below
Sulfate 87 1933–2023 98%
4% of limit ↓ 79% below
Lead 36 1964–2023 11%
0% of limit ↓ 95% below
Nitrite 55 1973–2023 13%
1% of limit ↓ 33% below
Arsenic 65 1972–2023 71%
3% of limit ↓ 91% below
Chloride 81 1933–2023 100%
2% of limit ↓ 82% below
Fluoride 43 1964–2023 60%
5% of limit ~ typical
HFPO-DA (GenX) municipal 63 2023–2025 0%
— —
Nitrate 77 1933–2023 61%
2% of limit ↓ 88% below
PFHxS municipal 44 2023–2025 0%
— —
PFNA municipal 44 2023–2025 0%
— —
PFOA municipal 100 2023–2025 1%
52% of limit ↓ 44% below
PFOS municipal 100 2023–2025 0%
— —
Radon 11 1996–2018 100%
13% of limit ↓ 90% below
Uranium 18 1996–2021 28%
1% of limit ↓ 42% below
Hardness 76 1933–2023 100%
— ↓ 53% below
PFBS municipal 63 2023–2025 0%
— —
pH 93 1964–2023 100%
— ~ typical
Sodium 63 1964–2023 100%
— ↓ 87% below

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 PA.

Compare your result with Somerset County

Of the 65 arsenic tests on record for Somerset County (1972–2023), 29% found none, and half were below 0.12 µg/L.

Of the 81 chloride tests on record for Somerset County (1933–2023), 0% found none, and half were below 4.78 mg/L.

Of the 43 fluoride tests on record for Somerset County (1964–2023), 40% found none, and half were below 100 µg/L.

Of the 79 iron tests on record for Somerset County (1964–2023), 4% found none, and half were below 620 µg/L.

Of the 36 lead tests on record for Somerset County (1964–2023), 89% found none.

Of the 78 manganese tests on record for Somerset County (1964–2023), 5% found none, and half were below 125 µg/L.

Of the 77 nitrate tests on record for Somerset County (1933–2023), 39% found none.

Of the 56 pfoa tests on record for Somerset County (2025), 98% found none.

Of the 56 pfos tests on record for Somerset County (2025), 100% found none.

Of the 87 sulfate tests on record for Somerset County (1933–2023), 2% found none, and half were below 9.05 mg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 78 samples
  • Iron 79 samples
  • Sulfate 87 samples
  • Lead 36 samples
  • Nitrite 55 samples
  • Arsenic 65 samples
  • Chloride 81 samples
  • Fluoride 43 samples
  • HFPO-DA (GenX) 63 samples
  • Nitrate 77 samples
  • PFOA 100 samples
  • PFOS 100 samples
  • Uranium 18 samples
  • Hardness 76 samples
  • PFBS 63 samples
  • pH 93 samples
  • Sodium 63 samples

Limited data (<15 samples) — interpret with caution

  • Radon 11 samples

Public vs. Private Water in Somerset County

108 Active public water systems
68,539 Residents on public water
41% Households on private wells

Public water systems in Somerset 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 Somerset 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 Somerset County Prevalence PA Average Source Year
Radon Cancer prevalence 6.1% 7.0% 2020
Lead Heart disease rate 6.5% 7.2% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Somerset 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 PA with at least one sample for that analyte.

Last updated: 2026-08-04

Full methodology →