Data & Methodology — Gonzales County

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

Contaminant Data — All Analytes

718 well testing events on record, covering 20 analytes. Data spans 1938 to 2021.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. TX Avg
Manganese 288 1940–2020 86%
55% of limit ~ typical
Iron 386 1940–2020 71%
69% of limit ↓ 55% below
Chloride 191 1938–2021 100%
40% of limit ~ typical
Sulfate 188 1938–2021 99%
16% of limit ↓ 43% below
Nitrate 219 1938–2021 82%
4% of limit ↓ 82% below
Fluoride 669 1928–2021 94%
8% of limit ↓ 69% below
Lead 226 1988–2020 12%
14% of limit ~ typical
Arsenic 231 1988–2020 8%
25% of limit ↓ 35% below
HFPO-DA (GenX) municipal 24 2023–2024 0%
— —
Nitrite 8 2008–2021 12%
0% of limit ↓ 71% below
PFHxS municipal 24 2023–2024 0%
— —
PFNA municipal 24 2023–2024 0%
— —
PFOA municipal 24 2023–2024 0%
— —
PFOS municipal 24 2023–2024 0%
— —
Radon 2 2008–2015 100%
16% of limit ↓ 56% below
Uranium 27 2008–2020 0%
— —
PFBS municipal 24 2023–2024 8%
— ~ typical
pH 186 1941–2021 100%
— ~ typical
Sodium 187 1938–2021 100%
— ↑ 51% above
Hardness 187 1938–2021 100%
— ↓ 49% 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 TX.

Compare your result with Gonzales County

Of the 231 arsenic tests on record for Gonzales County (1988–2020), 92% found none.

Of the 191 chloride tests on record for Gonzales County (1938–2021), 0% found none, and half were below 100 mg/L.

Of the 669 fluoride tests on record for Gonzales County (1928–2021), 6% found none, and half were below 300 µg/L.

Of the 386 iron tests on record for Gonzales County (1940–2020), 29% found none, and half were below 71.7 µg/L.

Of the 226 lead tests on record for Gonzales County (1988–2020), 88% found none.

Of the 288 manganese tests on record for Gonzales County (1940–2020), 14% found none, and half were below 11.3 µg/L.

Of the 219 nitrate tests on record for Gonzales County (1938–2021), 18% found none, and half were below 200 µg/L.

Of the 188 sulfate tests on record for Gonzales County (1938–2021), 1% found none, and half were below 40 mg/L.

Of the 27 uranium tests on record for Gonzales County (2008–2020), 100% found none.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 288 samples
  • Iron 386 samples
  • Chloride 191 samples
  • Sulfate 188 samples
  • Nitrate 219 samples
  • Fluoride 669 samples
  • Lead 226 samples
  • Arsenic 231 samples
  • Uranium 27 samples
  • pH 186 samples
  • Sodium 187 samples
  • Hardness 187 samples

Limited data (<15 samples) — interpret with caution

  • Nitrite 8 samples
  • Radon 2 samples

No private-well PFAS data for Gonzales County

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

7 Active public water systems
23,735 Residents on public water
6% Households on private wells

Public water systems in Gonzales 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 Gonzales 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 Gonzales County Prevalence TX Average Source Year
Lead Heart disease rate 6.6% 7.4% 2020
Arsenic Cancer prevalence 5.2% 6.1% 2020
Arsenic Kidney disease rate 3.1% 3.3% 2020

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

Last updated: 2026-08-04

Full methodology →