Well water in Mason County, Texas
In Mason County, 18% of 50 tested well samples exceeded the EPA limit for nitrate (10 mg/L), based on public data from Texas Water Development Board Groundwater Database.
113 individual samples from 61 wells, 1939 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 Mason 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 | |
|---|---|---|---|---|---|---|---|
| Radium (226 + 228) 1987 to 2020 | 24 | 83% | 29% | 2.4 | 8.68 | 5 pCi/L EPA limit | |
| Nitrate 1989 to 2024 | 50 | 94% | 18% | 2.56 | 42.5 | 10 mg/L EPA limit | |
| Gross alpha 1987 to 2024 | 27 | 93% | 15% | 6.8 | 34 | 15 pCi/L EPA limit | |
| Fluoride 1939 to 2024 | 111 | 97% | 0% | 0.5 | 2.1 | 4 mg/L EPA limit | |
| Lead 1993 to 2024 | 46 | 28% | 0% | 0 | 7.34 | 15 ug/L EPA limit | |
| Arsenic 1993 to 2024 | 46 | 9% | 0% | 0 | 5.85 | 10 ug/L EPA limit | |
| Copper 1993 to 2024 | 46 | 72% | 0% | 0.003 | 0.025 | 1.3 mg/L EPA limit | |
| Uranium 2008 to 2024 | 14 | 79% | 0% | 2.16 | 3.76 | 30 ug/L EPA limit | |
| Chloride 1939 to 2024 | 113 | 100% | no limit | 37 | 332 | 250 mg/L nuisance level | |
| Sodium 1939 to 2024 | 111 | 100% | no limit | 27 | 144 | 20 mg/L health guideline | |
| Iron 1972 to 2024 | 63 | 35% | no limit | 0 | 22,000 | 300 ug/L nuisance level | |
| Manganese 1974 to 2024 | 48 | 25% | no limit | 0 | 265 | 300 ug/L health guideline |
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What this means
The contaminants most often above their limit here are radium (226 + 228) (29% of 24 samples), nitrate (18% of 50 samples), and gross alpha (15% of 27 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 is widespread in local groundwater. It is mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Mason County
- Volatile organic compounds (VOCs)10 leaking underground storage tank sites on record locally.
- Radium (226 + 228)29% of 24 local samples were above the limit.
- Nitrate18% of 50 local samples were above the limit.
- Gross alpha15% of 27 local samples were above the limit.
- Coliform bacteriaRecommended for every private well, every year.
- ChlorideDetected in 100% of local samples.
- FluorideDetected in 97% of local samples.
- CopperDetected in 72% of local samples.
Contamination sources on record in Mason County
TCEQ records 10 leaking underground storage tank sites in Mason County, among 11 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.
- 10
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 1
- lined landfill or transfer facility
Treatment that fits the local profile
- Radium (226 + 228)
- Water softener (cation exchange); Point-of-use reverse osmosis
- 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
- Copper
- Neutralizing filter to raise pH; Point-of-use reverse osmosis
Get your Mason 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 Mason County.
Common questions
Is there arsenic in well water in Mason County?
Arsenic was detected in 9% of 46 public well samples in Mason County, and 0% 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 Mason 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: 699 samples in Mason County. Water quality samples from the Texas Water Development Board Groundwater Database, collected by TWDB, groundwater conservation districts and cooperators. Retrieved September 9, 2026.
- TCEQ regulated sites: 11 regulated sites located in Mason 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.