Data & Methodology — Guadalupe County

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

Contaminant Data — All Analytes

304 well testing events on record, covering 20 analytes. Data spans 1936 to 2023.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. TX Avg
Iron 124 1944–2020 80%
200% of limit ↑ 30% above
Nitrate 100 1957–2015 93%
10% of limit ↓ 55% below
Manganese 26 1962–2020 81%
24% of limit ↓ 63% below
Chloride 148 1936–2015 100%
46% of limit ↑ 29% above
Sulfate 123 1936–2015 100%
28% of limit ~ typical
Arsenic 25 1992–2020 24%
68% of limit ↑ 78% above
PFOS municipal 52 2023–2025 2%
110% of limit ~ typical
Fluoride 206 1940–2020 97%
10% of limit ↓ 58% below
HFPO-DA (GenX) municipal 52 2023–2025 0%
— —
Lead 25 1992–2020 28%
1% of limit ↓ 94% below
Nitrite 8 2008–2015 62%
0% of limit ↓ 71% below
PFHxS municipal 52 2023–2025 0%
— —
PFNA municipal 52 2023–2025 0%
— —
PFOA municipal 52 2023–2025 0%
— —
Radon 3 2008 100%
6% of limit ↓ 83% below
Uranium 10 2008–2020 20%
11% of limit ↓ 30% below
Hardness 114 1936–2015 100%
— ↑ 34% above
PFBS municipal 52 2023–2025 0%
— —
pH 129 1940–2015 100%
— ~ typical
Sodium 114 1936–2015 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 TX.

Compare your result with Guadalupe County

Of the 25 arsenic tests on record for Guadalupe County (1992–2020), 76% found none.

Of the 148 chloride tests on record for Guadalupe County (1936–2015), 0% found none, and half were below 115 mg/L.

Of the 206 fluoride tests on record for Guadalupe County (1940–2020), 3% found none, and half were below 350 µg/L.

Of the 124 iron tests on record for Guadalupe County (1944–2020), 20% found none, and half were below 93 µg/L.

Of the 25 lead tests on record for Guadalupe County (1992–2020), 72% found none.

Of the 26 manganese tests on record for Guadalupe County (1962–2020), 19% found none, and half were below 9.65 µg/L.

Of the 100 nitrate tests on record for Guadalupe County (1957–2015), 7% found none, and half were below 700 µg/L.

Of the 123 sulfate tests on record for Guadalupe County (1936–2015), 0% found none, and half were below 71 mg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Iron 124 samples
  • Nitrate 100 samples
  • Manganese 26 samples
  • Chloride 148 samples
  • Sulfate 123 samples
  • Arsenic 25 samples
  • Fluoride 206 samples
  • Lead 25 samples
  • Hardness 114 samples
  • pH 129 samples
  • Sodium 114 samples

Limited data (<15 samples) — interpret with caution

  • Nitrite 8 samples
  • Radon 3 samples
  • Uranium 10 samples

No private-well PFAS data for Guadalupe County

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

17 Active public water systems
207,597 Residents on public water
5% Households on private wells

Public water systems in Guadalupe 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 Guadalupe 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 Guadalupe County Prevalence TX Average Source Year
Arsenic Cancer prevalence 5.4% 6.1% 2020
Arsenic Kidney disease rate 2.7% 3.3% 2020

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