Data & Methodology — Collier County Well Water

Contaminant Data — All Analytes

6659 well testing events on record, covering 23 analytes. Data spans 1901 to 2022.

Contaminant	Samples	Years	Detection Rate	vs. Limit	vs. FL Avg
Radon	5	2015–2019	100%	170% of limit	↑ 480% above
Iron	1002	1923–2024	99%	64% of limit	↓ 68% below
PFOS municipal	22	2023–2025	41%	195% of limit	~ typical
Chloride	6470	1901–2025	100%	20% of limit	↓ 59% below
PFOA municipal	22	2023–2025	14%	105% of limit	↓ 26% below
Sulfate	1289	1901–2025	99%	9% of limit	↓ 67% below
Manganese	849	1955–2024	98%	18% of limit	↓ 30% below
Arsenic	843	1970–2024	96%	6% of limit	↓ 58% below
Uranium	79	1965–2022	85%	2% of limit	↑ 69% above
Nitrate	671	1901–2020	95%	0% of limit	↓ 99% below
Lead	1026	1970–2024	79%	0% of limit	↓ 89% below
Fluoride	1237	1901–2025	99%	5% of limit	↓ 32% below
PFNA municipal	22	2023–2025	0%	—	—
PFHxS municipal	22	2023–2025	18%	33% of limit	↓ 36% below
HFPO-DA (GenX) municipal	22	2023–2025	0%	—	—
Nitrite	984	1970–2023	90%	0% of limit	↓ 95% below
E. coli	148	2015–2025	97%	—	~ typical
Fecal Coliform	89	1976–2021	57%	—	~ typical
PFBS municipal	22	2023–2025	9%	—	~ typical
Hardness	466	1901–2019	100%	—	↑ 42% above
Total Coliform	157	1976–2025	66%	—	~ typical
pH	1470	1901–2025	100%	—	~ typical
Sodium	1351	1901–2025	100%	—	↓ 47% 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 FL.

Data Coverage & Gaps

Well-sampled analytes (15+ samples)

Iron 1002 samples
Chloride 6470 samples
Sulfate 1289 samples
Manganese 849 samples
Arsenic 843 samples
Uranium 79 samples
Nitrate 671 samples
Lead 1026 samples
Fluoride 1237 samples
Nitrite 984 samples
E. coli 148 samples
Fecal Coliform 89 samples
Hardness 466 samples
Total Coliform 157 samples
pH 1470 samples
Sodium 1351 samples

Limited data (<15 samples) — interpret with caution

Radon 5 samples

No private-well PFAS data for Collier County

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

45 Active public water systems

385,870 Residents on public water

Public water systems in Collier 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 Collier 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	Collier County Prevalence	FL Average	Source Year
Arsenic	Cancer prevalence	5.8%	6.8%	2020
Arsenic	Kidney disease rate	2.7%	3.4%	2020
Lead	Heart disease rate	9.9%	7.7%	2020

Data Sources

This report aggregates data from the following public databases:

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