Data & Methodology — Hillsborough County Well Water

Contaminant Data — All Analytes

9267 well testing events on record, covering 23 analytes. Data spans 1923 to 2024.

Contaminant	Samples	Years	Detection Rate	vs. Limit	vs. FL Avg
Radon	75	1995–2012	100%	20% of limit	↓ 31% below
PFOS municipal	55	2023–2025	49%	135% of limit	↓ 36% below
Iron	2677	1923–2025	96%	80% of limit	↓ 60% below
Sulfate	3364	1923–2025	99%	21% of limit	↓ 21% below
Chloride	8617	1923–2025	100%	10% of limit	↓ 79% below
PFOA municipal	55	2023–2025	20%	192% of limit	↑ 35% above
Arsenic	843	1969–2024	79%	10% of limit	↓ 23% below
Manganese	1676	1942–2025	95%	11% of limit	↓ 57% below
Lead	901	1969–2024	28%	1% of limit	↓ 58% below
PFHxS municipal	55	2023–2025	31%	40% of limit	↓ 22% below
Nitrate	1215	1930–2023	84%	0% of limit	↓ 94% below
Fluoride	1980	1953–2025	92%	7% of limit	~ typical
Nitrite	1205	1969–2024	50%	1% of limit	~ typical
Uranium	128	1979–2012	82%	1% of limit	~ typical
HFPO-DA (GenX) municipal	55	2023–2025	0%	—	—
PFNA municipal	55	2023–2025	0%	—	—
pH	3217	1942–2025	100%	—	~ typical
Sodium	3135	1953–2025	100%	—	↓ 86% below
E. coli	46	2002–2025	100%	—	~ typical
Fecal Coliform	66	1923–2021	60%	—	~ typical
PFBS municipal	55	2023–2025	56%	—	~ typical
Hardness	2949	1923–2012	100%	—	↓ 23% below
Total Coliform	112	1923–2025	79%	—	~ 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 FL.

Data Coverage & Gaps

Well-sampled analytes (15+ samples)

Radon 75 samples
Iron 2677 samples
Sulfate 3364 samples
Chloride 8617 samples
Arsenic 843 samples
Manganese 1676 samples
Lead 901 samples
Nitrate 1215 samples
Fluoride 1980 samples
Nitrite 1205 samples
Uranium 128 samples
pH 3217 samples
Sodium 3135 samples
E. coli 46 samples
Fecal Coliform 66 samples
Hardness 2949 samples
Total Coliform 112 samples

No private-well PFAS data for Hillsborough County

We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Hillsborough County. PFAS has been detected in local public water systems (UCMR 5 data) — indicated by the "municipal" badge in the table above — but this does not directly indicate private well contamination. 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 Hillsborough County

722 Active public water systems

1,743,513 Residents on public water

Public water systems in Hillsborough 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 Hillsborough 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.

Contaminant	Associated Condition	Hillsborough County Prevalence	FL Average	Source Year
Arsenic	Cancer prevalence	5.9%	6.8%	2020
Arsenic	Kidney disease rate	3.0%	3.4%	2020
Lead	Heart disease rate	6.3%	7.7%	2020

Data Sources

This report aggregates data from the following public databases:

Water Quality Portal (WQP) — groundwater sample results for Hillsborough 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 Hillsborough County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Hillsborough 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 Hillsborough County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Hillsborough 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 FL with at least one sample for that analyte.

Last updated: 2026-08-12

Full methodology →