Well water in San Patricio County, Texas
In San Patricio County, 17% of 30 tested well samples exceeded the EPA limit for arsenic (10 ug/L), based on public data from Texas Water Development Board Groundwater Database and USGS Water Quality Portal.
148 individual samples from 108 wells, 1938 to 2025. Data refreshed September 9, 2026.
TWDB samples an ambient monitoring network of wells on a rotation, so these describe aquifers, not a survey of homeowners' tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside San Patricio County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Samples | Detected | Above limit | Median | Highest | Limit | |
|---|---|---|---|---|---|---|---|
| Gross alpha 1992 to 2025 | 18 | 56% | 33% | 4.2 | 174 | 15 pCi/L EPA limit | |
| Uranium 2006 to 2025 | 12 | 75% | 33% | 3.36 | 211 | 30 ug/L EPA limit | |
| Arsenic 1992 to 2025 | 30 | 47% | 17% | 0 | 27 | 10 ug/L EPA limit | |
| Fluoride 1938 to 2025 | 84 | 100% | 1% | 1 | 4.65 | 4 mg/L EPA limit | |
| Nitrate 1992 to 2025 | 32 | 69% | 0% | 0.065 | 4.14 | 10 mg/L EPA limit | |
| Lead 1992 to 2025 | 30 | 3% | 0% | 0 | 2.45 | 15 ug/L EPA limit | |
| Copper 1992 to 2025 | 30 | 57% | 0% | 0.003 | 0.052 | 1.3 mg/L EPA limit | |
| Chloride 1938 to 2025 | 148 | 100% | no limit | 525 | 3,350 | 250 mg/L nuisance level | |
| Sodium 1938 to 2025 | 123 | 100% | no limit | 459 | 1,750 | 20 mg/L health guideline | |
| Iron 1992 to 2025 | 32 | 44% | no limit | 0 | 913 | 300 ug/L nuisance level | |
| Manganese 1992 to 2025 | 30 | 73% | no limit | 8 | 139 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Radium (226 + 228) (4).
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What this means
The contaminants most often above their limit here are gross alpha (33% of 18 samples), uranium (33% of 12 samples), and arsenic (17% of 30 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.
Chloride and Manganese are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in San Patricio County
- Volatile organic compounds (VOCs)128 leaking underground storage tank sites on record locally.
- Metals panel1 hazardous waste site on record locally.
- Gross alpha33% of 18 local samples were above the limit.
- Uranium33% of 12 local samples were above the limit.
- Arsenic17% of 30 local samples were above the limit.
- Fluoride1% of 84 local samples were above the limit.
- Coliform bacteriaRecommended for every private well, every year.
- ChlorideDetected in 100% of local samples.
- NitrateRecommended for every private well, especially near farms or septic systems.
Contamination sources on record in San Patricio County
TCEQ records 128 leaking underground storage tank sites and 1 hazardous waste site in San Patricio County, among 141 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.
- 128
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 1
- hazardous waste siteSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 12
- lined landfills and transfer facilities
Treatment that fits the local profile
- Gross alpha
- Point-of-use reverse osmosis; Water softener (cation exchange) for radium; Anion exchange for uranium
- Uranium
- Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Copper
- Neutralizing filter to raise pH; Point-of-use reverse osmosis
Get your San Patricio County water tested at home
A licensed local water treatment company tests your tap water in your home, walks you through the numbers, and quotes treatment only if something needs fixing. Free, about 30 minutes, no obligation. Tell us what you need and we match you with a company that serves San Patricio County.
Common questions
Is there arsenic in well water in San Patricio County?
Arsenic was detected in 47% of 30 public well samples in San Patricio County, and 17% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How often should I test a private well in San Patricio County?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Sources
- Texas Water Development Board Groundwater Database: 572 samples in San Patricio County. Water quality samples from the Texas Water Development Board Groundwater Database, collected by TWDB, groundwater conservation districts and cooperators. Retrieved September 9, 2026.
- USGS Water Quality Portal: 1 samples in San Patricio County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- TCEQ regulated sites: 141 regulated sites located in San Patricio County. Leaking petroleum storage tank sites, state Superfund sites and municipal solid waste landfills from the Texas Commission on Environmental Quality. Retrieved September 9, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.