Well water in Cameron County, Texas
In Cameron County, 1% of 92 tested well samples exceeded the EPA limit for fluoride (4 mg/L), based on public data from Texas Water Development Board Groundwater Database and USGS Water Quality Portal.
129 individual samples from 99 wells, 1945 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 Cameron 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 1988 to 2025 | 12 | 42% | 17% | 0 | 28 | 10 ug/L EPA limit | |
| Fluoride 1952 to 2025 | 92 | 99% | 1% | 1.05 | 7 | 4 mg/L EPA limit | |
| Lead 1988 to 2025 | 12 | 0% | 0% | 0 | 0 | 15 ug/L EPA limit | |
| Copper 1988 to 2025 | 12 | 25% | 0% | 0 | 0.002 | 1.3 mg/L EPA limit | |
| Chloride 1945 to 2025 | 129 | 100% | no limit | 287 | 3,168 | 250 mg/L nuisance level | |
| Sodium 1945 to 2025 | 115 | 100% | no limit | 436 | 2,700 | 20 mg/L health guideline | |
| Iron 1945 to 2025 | 21 | 62% | no limit | 210 | 6,130 | 300 ug/L nuisance level | |
| Manganese 1988 to 2025 | 12 | 83% | no limit | 51.2 | 383 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Gross alpha (4), Radium (226 + 228) (6), Uranium (5), Nitrate (4), E. coli (1), Radon (1).
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What this means
The contaminants most often above their limit here are arsenic (17% of 12 samples) and fluoride (1% of 92 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 Cameron County
- Volatile organic compounds (VOCs)375 leaking underground storage tank sites on record locally.
- Metals panel1 hazardous waste site on record locally.
- Arsenic17% of 12 local samples were above the limit.
- Fluoride1% of 92 local samples were above the limit.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 400 pCi/L.
- Gross alphaAbove the limit in 1 of 4 local samples; too few to quote a rate.
- ChlorideDetected in 100% of local samples.
- NitrateRecommended for every private well, especially near farms or septic systems.
Contamination sources on record in Cameron County
TCEQ records 375 leaking underground storage tank sites and 1 hazardous waste site in Cameron County, among 402 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.
- 375
- 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.
- 26
- 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
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Chloride
- Point-of-use reverse osmosis; Distillation
- Iron
- Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
- Manganese
- Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
Get your Cameron County water tested at home
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Common questions
Is there arsenic in well water in Cameron County?
Arsenic was detected in 42% of 12 public well samples in Cameron 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 high is radon in well water in Cameron County?
The median radon level across 1 public samples in Cameron County was 400 pCi/L, with a high of 400 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Cameron 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: 421 samples in Cameron 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: 5 samples in Cameron 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: 402 regulated sites located in Cameron 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.