Well water in Martin County, Texas
In Martin County, 67% of 81 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.
89 individual samples from 46 wells, 1936 to 2024. 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 Martin 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 | |
|---|---|---|---|---|---|---|---|
| Arsenic 1984 to 2024 | 81 | 86% | 67% | 15.1 | 240 | 10 ug/L EPA limit | |
| Nitrate 1990 to 2024 | 71 | 100% | 52% | 11.4 | 34.8 | 10 mg/L EPA limit | |
| Gross alpha 2008 to 2016 | 19 | 79% | 42% | 12.4 | 117 | 15 pCi/L EPA limit | |
| Fluoride 1975 to 2024 | 82 | 100% | 41% | 3.28 | 10.1 | 4 mg/L EPA limit | |
| Uranium 2001 to 2024 | 26 | 100% | 23% | 15.6 | 245 | 30 ug/L EPA limit | |
| Copper 1988 to 2024 | 53 | 83% | 0% | 0.003 | 0.412 | 1.3 mg/L EPA limit | |
| Lead 1996 to 2024 | 52 | 6% | 0% | 0 | 5.61 | 15 ug/L EPA limit | |
| Radium (226 + 228) 2008 to 2016 | 40 | 60% | 0% | 0.295 | 3.7 | 5 pCi/L EPA limit | |
| Chloride 1936 to 2024 | 89 | 100% | no limit | 285 | 2,400 | 250 mg/L nuisance level | |
| Sodium 1975 to 2024 | 85 | 100% | no limit | 215 | 1,249 | 20 mg/L health guideline | |
| Iron 1988 to 2024 | 65 | 51% | no limit | 8 | 12,800 | 300 ug/L nuisance level | |
| Manganese 1996 to 2024 | 53 | 55% | no limit | 0.638 | 125 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: E. coli (2), Radon (5).
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What this means
The contaminants most often above their limit here are arsenic (67% of 81 samples), nitrate (52% of 71 samples), and gross alpha (42% of 19 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, Iron, 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 Martin County
- Volatile organic compounds (VOCs)7 leaking underground storage tank sites on record locally.
- Arsenic67% of 81 local samples were above the limit.
- Nitrate52% of 71 local samples were above the limit.
- Gross alpha42% of 19 local samples were above the limit.
- Fluoride41% of 82 local samples were above the limit.
- Uranium23% of 26 local samples were above the limit.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 730 pCi/L.
Contamination sources on record in Martin County
TCEQ records 7 leaking underground storage tank sites in Martin County, among 9 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.
- 7
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 2
- lined landfills and transfer facilities
Treatment that fits the local profile
- Arsenic
- Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
- Nitrate
- Point-of-use reverse osmosis; Anion exchange; Distillation
- Gross alpha
- Point-of-use reverse osmosis; Water softener (cation exchange) for radium; Anion exchange for uranium
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Uranium
- Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
Get your Martin 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 Martin County.
Common questions
Is there arsenic in well water in Martin County?
Arsenic was detected in 86% of 81 public well samples in Martin County, and 67% 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 Martin County?
The median radon level across 5 public samples in Martin County was 730 pCi/L, with a high of 810 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Martin 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: 706 samples in Martin 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: 17 samples in Martin 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: 9 regulated sites located in Martin 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.