Full contaminant data, sample history, and sourcing for Grimes County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
395 well testing events on record, covering
20 analytes.
Data spans 1927 to 2013.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. TX Avg
Radon
1
2013
100%
493% of limit
↑ 1270% above
Manganese
57
1946–2021
79%
88% of limit
↑ 36% above
Iron
231
1942–2021
86%
67% of limit
↓ 57% below
Sulfate
150
1927–2013
99%
14% of limit
↓ 50% below
Chloride
150
1927–2013
100%
48% of limit
↑ 34% above
Nitrate
158
1927–2013
97%
4% of limit
↓ 82% below
Arsenic
53
1987–2021
21%
69% of limit
↑ 81% above
Fluoride
372
1942–2021
97%
8% of limit
↓ 69% below
HFPO-DA (GenX)
municipal
6
2023
0%
—
—
Lead
53
1987–2021
6%
8% of limit
↓ 54% below
Nitrite
1
2013
0%
—
—
PFHxS
municipal
6
2023
0%
—
—
PFNA
municipal
6
2023
0%
—
—
PFOA
municipal
6
2023
0%
—
—
PFOS
municipal
6
2023
0%
—
—
Uranium
11
2009–2021
0%
—
—
Hardness
148
1927–2013
100%
—
~ typical
PFBS
municipal
6
2023
0%
—
—
pH
138
1942–2013
100%
—
~ typical
Sodium
145
1927–2013
100%
—
~ typical
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 Grimes County
Of the 53 arsenic tests on record for Grimes County (1987–2021),
79% found none.
Of the 150 chloride tests on record for Grimes County (1927–2013),
0% found none, and half were below 120 mg/L.
Of the 372 fluoride tests on record for Grimes County (1942–2021),
3% found none, and half were below 300 µg/L.
Of the 231 iron tests on record for Grimes County (1942–2021),
14% found none, and half were below 120 µg/L.
Of the 53 lead tests on record for Grimes County (1987–2021),
94% found none.
Of the 57 manganese tests on record for Grimes County (1946–2021),
21% found none, and half were below 33.5 µg/L.
Of the 158 nitrate tests on record for Grimes County (1927–2013),
3% found none, and half were below 400 µg/L.
Of the 150 sulfate tests on record for Grimes County (1927–2013),
1% found none, and half were below 36 mg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Manganese 57 samples
Iron 231 samples
Sulfate 150 samples
Chloride 150 samples
Nitrate 158 samples
Arsenic 53 samples
Fluoride 372 samples
Lead 53 samples
Hardness 148 samples
pH 138 samples
Sodium 145 samples
Limited data (<15 samples) — interpret with caution
Radon 1 sample
Nitrite 1 sample
Uranium 11 samples
No private-well PFAS data for Grimes County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Grimes 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 →
Public vs. Private Water in Grimes County
29Active public water systems
26,364Residents on public water
6%Households on private wells
Public water systems in Grimes County are regulated by the EPA and must test and report contaminant levels. Private well owners are responsible for their own testing — there is no routine monitoring of private wells by any government agency.
CDC Health Outcome Correlations
Where contaminants detected in Grimes 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 Grimes 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 Grimes County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Grimes 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 Grimes County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Grimes 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.