Well water in Matagorda County, Texas
In Matagorda County, 15% of 34 tested well samples exceeded the EPA limit for gross alpha (15 pCi/L), based on public data from Texas Water Development Board Groundwater Database and USGS Water Quality Portal.
140 individual samples from 76 wells, 1960 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 Matagorda 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 1988 to 2021 | 34 | 68% | 15% | 5.05 | 28 | 15 pCi/L EPA limit | |
| Arsenic 1988 to 2025 | 53 | 34% | 2% | 0 | 11.7 | 10 ug/L EPA limit | |
| Fluoride 1960 to 2025 | 140 | 100% | 0% | 0.6 | 3.07 | 4 mg/L EPA limit | |
| Copper 1988 to 2025 | 53 | 38% | 0% | 0 | 0.006 | 1.3 mg/L EPA limit | |
| Lead 1988 to 2025 | 52 | 6% | 0% | 0 | 1.66 | 15 ug/L EPA limit | |
| Nitrate 1966 to 2025 | 52 | 35% | 0% | 0 | 3.22 | 10 mg/L EPA limit | |
| Radium (226 + 228) 2009 to 2013 | 40 | 20% | 0% | 0 | 2 | 5 pCi/L EPA limit | |
| Uranium 2005 to 2025 | 33 | 58% | 0% | 1.99 | 7.86 | 30 ug/L EPA limit | |
| Sodium 1960 to 2025 | 136 | 100% | no limit | 175 | 790 | 20 mg/L health guideline | |
| Chloride 1960 to 2025 | 134 | 100% | no limit | 173 | 1,890 | 250 mg/L nuisance level | |
| Manganese 1965 to 2025 | 76 | 88% | no limit | 50 | 560 | 300 ug/L health guideline | |
| Iron 1965 to 2025 | 72 | 64% | no limit | 66.0 | 3,900 | 300 ug/L nuisance level |
Sampled fewer than 10 times, too few to summarize: E. coli (1), Radon (1).
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What this means
The contaminants most often above their limit here are gross alpha (15% of 34 samples) and arsenic (2% of 53 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, Manganese, and Iron 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 Matagorda County
- Volatile organic compounds (VOCs)105 leaking underground storage tank sites on record locally.
- Metals panel1 hazardous waste site on record locally.
- Gross alpha15% of 34 local samples were above the limit.
- Arsenic2% of 53 local samples were above the limit.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 490 pCi/L.
- FluorideDetected in 100% of local samples.
- ChlorideDetected in 100% of local samples.
- NitrateRecommended for every private well, especially near farms or septic systems.
Contamination sources on record in Matagorda County
TCEQ records 105 leaking underground storage tank sites and 1 hazardous waste site in Matagorda County, among 119 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.
- 105
- 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.
- 13
- 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
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Chloride
- Point-of-use reverse osmosis; Distillation
- Manganese
- Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
Get your Matagorda County water tested at home
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Common questions
Is there arsenic in well water in Matagorda County?
Arsenic was detected in 34% of 53 public well samples in Matagorda County, and 2% 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 high is radon in well water in Matagorda County?
The median radon level across 1 public samples in Matagorda County was 490 pCi/L, with a high of 490 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Matagorda 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: 861 samples in Matagorda 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: 16 samples in Matagorda 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: 119 regulated sites located in Matagorda 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.