Data & Methodology — Prince William County

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

Contaminant Data — All Analytes

729 well testing events on record, covering 20 analytes. Data spans 1951 to 2026.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. VA Avg
PFOS municipal 23 2023–2025 39%
130% of limit ~ typical
Manganese 128 1990–2015 77%
56% of limit ↓ 55% below
PFOA municipal 23 2023–2025 26%
160% of limit ~ typical
Iron 156 1968–2015 90%
4% of limit ↓ 96% below
Sulfate 156 1968–2015 89%
3% of limit ↓ 62% below
Nitrate 105 1968–2015 76%
5% of limit ↑ 30% above
Chloride 156 1968–2015 100%
3% of limit ~ typical
Radon 95 1990–2014 100%
11% of limit ~ typical
Nitrite 98 1975–2015 33%
0% of limit ↓ 45% below
Lead 120 1975–2015 10%
1% of limit ~ typical
HFPO-DA (GenX) municipal 23 2023–2025 0%
— —
Fluoride 156 1968–2015 62%
2% of limit ↓ 57% below
PFNA municipal 23 2023–2025 0%
— —
Uranium 38 1994–2015 74%
0% of limit ↓ 22% below
Arsenic 70 1975–2015 36%
10% of limit ↑ 233% above
PFHxS municipal 23 2023–2025 9%
30% of limit ~ typical
Hardness 156 1968–2015 99%
— ~ typical
PFBS municipal 23 2023–2025 30%
— ↑ 25% above
pH 201 1968–2015 100%
— ~ typical
Sodium 156 1968–2015 100%
— ↓ 32% 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 VA.

Compare your result with Prince William County

Of the 70 arsenic tests on record for Prince William County (1975–2015), 64% found none.

Of the 156 chloride tests on record for Prince William County (1968–2015), 0% found none, and half were below 7.67 mg/L.

Of the 156 fluoride tests on record for Prince William County (1968–2015), 38% found none, and half were below 90 µg/L.

Of the 156 iron tests on record for Prince William County (1968–2015), 10% found none, and half were below 10 µg/L.

Of the 120 lead tests on record for Prince William County (1975–2015), 90% found none.

Of the 128 manganese tests on record for Prince William County (1990–2015), 23% found none, and half were below 8 µg/L.

Of the 105 nitrate tests on record for Prince William County (1968–2015), 24% found none, and half were below 280 µg/L.

Of the 156 sulfate tests on record for Prince William County (1968–2015), 11% found none, and half were below 5.45 mg/L.

Of the 38 uranium tests on record for Prince William County (1994–2015), 26% found none, and half were below 24.5 ng/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 128 samples
  • Iron 156 samples
  • Sulfate 156 samples
  • Nitrate 105 samples
  • Chloride 156 samples
  • Radon 95 samples
  • Nitrite 98 samples
  • Lead 120 samples
  • Fluoride 156 samples
  • Uranium 38 samples
  • Arsenic 70 samples
  • Hardness 156 samples
  • pH 201 samples
  • Sodium 156 samples

No private-well PFAS data for Prince William County

We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Prince William 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 Prince William County

45 Active public water systems
416,494 Residents on public water
22% Households on private wells

Public water systems in Prince William 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 Prince William 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 Prince William County Prevalence VA Average Source Year
Lead Heart disease rate 4.8% 6.7% 2020
Nitrate Cancer prevalence 5.5% 6.7% 2020

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

Last updated: 2026-08-04

Full methodology →