Full contaminant data, sample history, and sourcing for Nobles County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
146 well testing events on record, covering
18 analytes.
Data spans 1955 to 2023.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. MN Avg
Manganese
125
1955–2022
95%
1062% of limit
↑ 116% above
Sulfate
139
1955–2022
100%
398% of limit
↑ 2005% above
Iron
140
1955–2022
86%
900% of limit
↑ 26% above
Arsenic
79
1993–2022
89%
12% of limit
↓ 87% below
Nitrate
63
1955–2007
100%
2% of limit
↓ 91% below
Lead
79
1993–2022
18%
1% of limit
↓ 97% below
Fluoride
120
1955–2022
92%
7% of limit
~ typical
Chloride
141
1955–2022
98%
2% of limit
↓ 76% below
HFPO-DA (GenX)
municipal
5
2025
0%
—
—
Nitrite
18
1994–1996
94%
0% of limit
↓ 75% below
PFHxS
municipal
5
2025
0%
—
—
PFNA
municipal
5
2025
0%
—
—
PFOA
municipal
5
2025
0%
—
—
PFOS
municipal
5
2025
0%
—
—
Sodium
132
1955–2022
100%
—
↑ 199% above
pH
35
1955–1997
100%
—
~ typical
PFBS
municipal
5
2025
0%
—
—
Hardness
35
1955–1976
100%
—
↑ 183% above
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 MN.
Compare your result with Nobles County
Of the 79 arsenic tests on record for Nobles County (1993–2022),
11% found none, and half were below 0.893 µg/L.
Of the 141 chloride tests on record for Nobles County (1955–2022),
2% found none, and half were below 4.29 mg/L.
Of the 120 fluoride tests on record for Nobles County (1955–2022),
8% found none, and half were below 290 µg/L.
Of the 140 iron tests on record for Nobles County (1955–2022),
14% found none, and half were below 1.94 mg/L.
Of the 79 lead tests on record for Nobles County (1993–2022),
82% found none.
Of the 125 manganese tests on record for Nobles County (1955–2022),
5% found none, and half were below 500 µg/L.
Of the 63 nitrate tests on record for Nobles County (1955–2007),
0% found none, and half were below 230 µg/L.
Of the 139 sulfate tests on record for Nobles County (1955–2022),
0% found none, and half were below 995 mg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Manganese 125 samples
Sulfate 139 samples
Iron 140 samples
Arsenic 79 samples
Nitrate 63 samples
Lead 79 samples
Fluoride 120 samples
Chloride 141 samples
Nitrite 18 samples
Sodium 132 samples
pH 35 samples
Hardness 35 samples
No private-well PFAS data for Nobles County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Nobles 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 Nobles County
15Active public water systems
18,302Residents on public water
15%Households on private wells
Public water systems in Nobles 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 Nobles 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 Nobles 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 Nobles County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Nobles 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 Nobles County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Nobles 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 MN with at least one sample for that analyte.