Data & Methodology — Orange County Well Water

Contaminant Data — All Analytes

3411 well testing events on record, covering 23 analytes. Data spans 1952 to 2024.

Contaminant	Samples	Years	Detection Rate	vs. Limit	vs. FL Avg
Iron	983	1956–2025	98%	23% of limit	↓ 88% below
Chloride	3308	1956–2025	100%	36% of limit	↓ 27% below
PFOS municipal	90	2023–2025	13%	196% of limit	~ typical
Sulfate	2425	1956–2025	98%	36% of limit	↑ 36% above
PFOA municipal	90	2023–2025	4%	125% of limit	~ typical
Manganese	376	1961–2025	96%	7% of limit	↓ 74% below
Arsenic	369	1978–2025	84%	5% of limit	↓ 62% below
Fluoride	2177	1956–2025	98%	5% of limit	↓ 30% below
HFPO-DA (GenX) municipal	90	2023–2025	0%	—	—
Radon	37	1999–2015	100%	9% of limit	↓ 68% below
Uranium	26	1999–2015	81%	1% of limit	↓ 43% below
Lead	368	1978–2025	78%	0% of limit	↓ 89% below
Nitrate	388	1956–2015	90%	0% of limit	↓ 86% below
PFHxS municipal	90	2023–2025	1%	40% of limit	↓ 22% below
PFNA municipal	90	2023–2025	0%	—	—
Nitrite	179	1969–2015	68%	0% of limit	↓ 96% below
pH	2423	1956–2025	100%	—	~ typical
Sodium	2423	1956–2025	100%	—	~ typical
Hardness	2163	1956–2023	100%	—	↑ 51% above
Total Coliform	26	1978–2025	97%	—	~ typical
E. coli	14	2015–2025	93%	—	~ typical
Fecal Coliform	12	1978–2021	100%	—	~ typical
PFBS municipal	90	2023–2025	10%	—	~ 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)

Iron 983 samples
Chloride 3308 samples
Sulfate 2425 samples
Manganese 376 samples
Arsenic 369 samples
Fluoride 2177 samples
Radon 37 samples
Uranium 26 samples
Lead 368 samples
Nitrate 388 samples
Nitrite 179 samples
pH 2423 samples
Sodium 2423 samples
Hardness 2163 samples
Total Coliform 26 samples

Limited data (<15 samples) — interpret with caution

E. coli 14 samples
Fecal Coliform 12 samples

No private-well PFAS data for Orange County

We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Orange 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 Orange County

114 Active public water systems

1,628,779 Residents on public water

Public water systems in Orange 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 Orange 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	Orange County Prevalence	FL Average	Source Year
Arsenic	Cancer prevalence	5.3%	6.8%	2020
Arsenic	Kidney disease rate	2.9%	3.4%	2020

Data Sources

This report aggregates data from the following public databases:

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