Well water in Blanco County, Texas
In Blanco County, 3% of 36 tested well samples exceeded the EPA limit for radium (226 + 228) (5 pCi/L), based on public data from Texas Water Development Board Groundwater Database and USGS Water Quality Portal.
581 individual samples from 395 wells, 1938 to 2026. 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 Blanco 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 2026 | 23 | 35% | 4% | 0 | 17 | 15 pCi/L EPA limit | |
| Radium (226 + 228) 1994 to 2016 | 36 | 47% | 3% | 0 | 5.21 | 5 pCi/L EPA limit | |
| Nitrate 1988 to 2026 | 237 | 73% | 1% | 0.282 | 94 | 10 mg/L EPA limit | |
| Fluoride 1938 to 2026 | 414 | 98% | <1% | 0.6 | 7.8 | 4 mg/L EPA limit | |
| Arsenic 1988 to 2026 | 237 | 9% | 0% | 0 | 9.02 | 10 ug/L EPA limit | |
| Copper 1988 to 2026 | 237 | 68% | 0% | 0.002 | 0.336 | 1.3 mg/L EPA limit | |
| Lead 1994 to 2026 | 233 | 10% | 0% | 0 | 8.63 | 15 ug/L EPA limit | |
| Uranium 1996 to 2026 | 147 | 45% | 0% | 0 | 4.36 | 30 ug/L EPA limit | |
| Chloride 1938 to 2026 | 581 | 100% | no limit | 22 | 451 | 250 mg/L nuisance level | |
| Sodium 1938 to 2026 | 509 | 97% | no limit | 13.5 | 489 | 20 mg/L health guideline | |
| Iron 1967 to 2026 | 253 | 37% | no limit | 0 | 6,430 | 300 ug/L nuisance level | |
| Manganese 1988 to 2026 | 239 | 44% | no limit | 0 | 71.1 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: E. coli (1), Radon (7).
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What this means
The contaminants most often above their limit here are gross alpha (4% of 23 samples), radium (226 + 228) (3% of 36 samples), and nitrate (1% of 237 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 Blanco County
- Volatile organic compounds (VOCs)18 leaking underground storage tank sites on record locally.
- Gross alpha4% of 23 local samples were above the limit.
- Radium (226 + 228)3% of 36 local samples were above the limit.
- Nitrate1% of 237 local samples were above the limit.
- Fluoride<1% of 414 local samples were above the limit.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 180 pCi/L.
- ChlorideDetected in 100% of local samples.
Contamination sources on record in Blanco County
TCEQ records 18 leaking underground storage tank sites in Blanco County, among 21 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.
- 18
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 3
- 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
- Radium (226 + 228)
- Water softener (cation exchange); Point-of-use reverse osmosis
- Nitrate
- Point-of-use reverse osmosis; Anion exchange; Distillation
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Copper
- Neutralizing filter to raise pH; Point-of-use reverse osmosis
Get your Blanco 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 Blanco County.
Common questions
Is there arsenic in well water in Blanco County?
Arsenic was detected in 9% of 237 public well samples in Blanco 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 high is radon in well water in Blanco County?
The median radon level across 7 public samples in Blanco County was 180 pCi/L, with a high of 320 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Blanco 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: 3,143 samples in Blanco 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: 11 samples in Blanco 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: 21 regulated sites located in Blanco 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.