Full contaminant data, sample history, and sourcing for Brazos County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
473 well testing events on record, covering
18 analytes.
Data spans 1956 to 1982.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. TX Avg
Iron
313
1924–2020
81%
67% of limit
↓ 57% below
Chloride
75
1956–1980
100%
28% of limit
↓ 23% below
Manganese
98
1972–2020
89%
19% of limit
↓ 70% below
Sulfate
75
1956–1980
100%
13% of limit
↓ 54% below
Nitrate
95
1963–2012
80%
4% of limit
↓ 82% below
Fluoride
388
1937–2020
99%
8% of limit
↓ 69% below
Arsenic
90
1987–2020
6%
25% of limit
↓ 35% below
HFPO-DA (GenX)
municipal
27
2023–2025
0%
—
—
Lead
90
1987–2020
12%
13% of limit
↓ 25% below
PFHxS
municipal
27
2023–2025
0%
—
—
PFNA
municipal
27
2023–2025
0%
—
—
PFOA
municipal
27
2023–2025
0%
—
—
PFOS
municipal
27
2023–2025
0%
—
—
Uranium
20
2009–2020
0%
—
—
Sodium
75
1956–1980
100%
—
↑ 38% above
pH
71
1963–1980
100%
—
~ typical
PFBS
municipal
27
2023–2025
7%
—
~ typical
Hardness
75
1956–1980
100%
—
↓ 64% below
Distribution shows the share of samples in each concentration band relative to the EPA Maximum Contaminant Level (MCL): Low = below half the MCL, Moderate = between half and the MCL, High = above the MCL. Analytes without an MCL (e.g. sodium, pH) show — in the limit columns. State average is based on county median values across TX.
Compare your result with Brazos County
Of the 90 arsenic tests on record for Brazos County (1987–2020),
94% found none.
Of the 75 chloride tests on record for Brazos County (1956–1980),
0% found none, and half were below 69 mg/L.
Of the 388 fluoride tests on record for Brazos County (1937–2020),
1% found none, and half were below 300 µg/L.
Of the 313 iron tests on record for Brazos County (1924–2020),
19% found none, and half were below 100 µg/L.
Of the 90 lead tests on record for Brazos County (1987–2020),
88% found none.
Of the 98 manganese tests on record for Brazos County (1972–2020),
11% found none, and half were below 7.77 µg/L.
Of the 95 nitrate tests on record for Brazos County (1963–2012),
20% found none, and half were below 100 µg/L.
Of the 75 sulfate tests on record for Brazos County (1956–1980),
0% found none, and half were below 33 mg/L.
Of the 20 uranium tests on record for Brazos County (2009–2020),
100% found none.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Iron 313 samples
Chloride 75 samples
Manganese 98 samples
Sulfate 75 samples
Nitrate 95 samples
Fluoride 388 samples
Arsenic 90 samples
Lead 90 samples
Uranium 20 samples
Sodium 75 samples
pH 71 samples
Hardness 75 samples
No private-well PFAS data for Brazos County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Brazos County.
PFAS testing for private wells requires a dedicated lab panel (~$300–$500). If you are near a military base, airport, or industrial site, consider testing proactively. Learn more about PFAS →
CDC Health Outcome Correlations
Where contaminants detected in Brazos County have established associations with specific health outcomes, we cross-reference CDC PLACES county-level prevalence data. This is a contextual signal, not a causal claim.
This report aggregates data from the following public databases:
Water Quality Portal (WQP) — groundwater sample results for Brazos County from EPA, USGS, and state agencies. Browse WQP data →
EPA Safe Drinking Water Information System (SDWIS) — public water system inventory used to estimate the share of residents on private wells. Browse SDWIS →
Census ACS 5-Year Estimates — well and cistern household counts (variable DP04_0074E) used to calculate the private-well percentage for Brazos County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Brazos County, which informs which contaminants are geologically likely. USGS Aquifer Atlas →
EPA UCMR 5 (2023–2025) — PFAS occurrence data from public water systems, used as a proxy indicator for aquifer PFAS exposure. Rows marked "municipal" in the table above come from this source. About UCMR 5 →
EPA Toxics Release Inventory (TRI) — industrial facility chemical releases near Brazos County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Brazos County, used in contamination risk scoring. Superfund site search →
CDC PLACES — county-level health outcome prevalence (kidney disease, cancer, heart disease) correlated with detected contaminants. About CDC PLACES →
Methodology
Raw records are downloaded from the Water Quality Portal and normalized to µg/L (ppb). Records are deduplicated by sample ID and date, and certified outliers are excluded. Analyte names are mapped to EPA canonical forms. Detection rates, distribution bands, and MCL comparisons are computed from the normalized dataset.
Distribution bands use the EPA Maximum Contaminant Level as the threshold: concentrations below 50% of the MCL are classed as Low, between 50% and 100% as Moderate, and above 100% as High. For analytes without an MCL (sodium, hardness, pH), distribution is not computed.
State comparison uses the median of county median values across all counties in TX with at least one sample for that analyte.