Data & Methodology — Washington County

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

Contaminant Data — All Analytes

25 well testing events on record, covering 20 analytes. Data spans 1954 to 2025.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. VT Avg
Radon 738 — 100%
360% of limit ~ typical
Manganese 1441 1971–1980 100%
6% of limit ↓ 99% below
Iron 1254 1971–1980 100%
17% of limit ↓ 92% below
Lead 3916 — 89%
13% of limit ↓ 81% below
PFOS municipal 18 2023–2024 6%
115% of limit ~ typical
Chloride 2318 1971–1980 100%
1% of limit ↓ 88% below
Arsenic 2760 — 57%
10% of limit ↓ 81% below
Nitrate 2985 1971 100%
2% of limit ↓ 24% below
Uranium 2262 — 89%
3% of limit ↓ 59% below
Fluoride 2791 1971–1980 100%
3% of limit ~ typical
HFPO-DA (GenX) municipal 18 2023–2024 0%
— —
Nitrite 2898 — 100%
2% of limit ~ typical
PFHxS municipal 18 2023–2024 0%
— —
PFNA municipal 18 2023–2024 0%
— —
PFOA municipal 18 2023–2024 0%
— —
Sulfate 62 1971–1980 100%
6% of limit ~ typical
Hardness 990 1971–1980 100%
— ~ typical
PFBS municipal 18 2023–2024 0%
— —
pH 780 1971–1980 100%
— ~ typical
Sodium 1224 1971–1980 100%
— ↓ 60% 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 VT.

Compare your result with Washington County

Of the 2760 arsenic tests on record for Washington County, 43% found none, and half were below 1 µg/L.

Of the 2318 chloride tests on record for Washington County (1971–1980), 0% found none, and half were below 2.5 mg/L.

Of the 2791 fluoride tests on record for Washington County (1971–1980), 0% found none, and half were below 110 µg/L.

Of the 1254 iron tests on record for Washington County (1971–1980), 0% found none, and half were below 50 µg/L.

Of the 3916 lead tests on record for Washington County, 11% found none, and half were below 2 µg/L.

Of the 1441 manganese tests on record for Washington County (1971–1980), 0% found none, and half were below 3 µg/L.

Of the 2985 nitrate tests on record for Washington County (1971), 0% found none, and half were below 250 µg/L.

Of the 62 sulfate tests on record for Washington County (1971–1980), 0% found none, and half were below 16 mg/L.

Of the 2262 uranium tests on record for Washington County, 11% found none, and half were below 1 µg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Radon 738 samples
  • Manganese 1441 samples
  • Iron 1254 samples
  • Lead 3916 samples
  • Chloride 2318 samples
  • Arsenic 2760 samples
  • Nitrate 2985 samples
  • Uranium 2262 samples
  • Fluoride 2791 samples
  • Nitrite 2898 samples
  • Sulfate 62 samples
  • Hardness 990 samples
  • pH 780 samples
  • Sodium 1224 samples

No private-well PFAS data for Washington County

We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Washington County. PFAS has been detected in local public water systems (UCMR 5 data) — indicated by the "municipal" badge in the table above — but this does not directly indicate private well contamination. PFAS testing for private wells requires a dedicated lab panel (~$300–$500). If you are near a military base, airport, or industrial site, consider testing proactively. Learn more about PFAS →

Public vs. Private Water in Washington County

125 Active public water systems
61,286 Residents on public water
37% Households on private wells

Public water systems in Washington 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 Washington 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 Washington County Prevalence VT Average Source Year
Arsenic Cancer prevalence 7.9% 7.0% 2020
Arsenic Kidney disease rate 2.9% 2.8% 2020
Lead Heart disease rate 5.1% 6.3% 2020

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

Last updated: 2026-07-31

Full methodology →