Full contaminant data, sample history, and sourcing for Plumas County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
31 well testing events on record, covering
20 analytes.
Data spans 1960 to 2023.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. CA Avg
Radon
7
2008–2010
100%
173% of limit
↑ 90% above
Fluoride
22
2008–2020
50%
1% of limit
↓ 82% below
HFPO-DA (GenX)
municipal
31
2024
0%
—
—
Nitrite
22
2008–2020
5%
0% of limit
↓ 92% below
Chloride
22
2008–2020
100%
0% of limit
↓ 99% below
PFNA
municipal
31
2024
0%
—
—
PFHxS
municipal
31
2024
0%
—
—
Nitrate
22
2008–2020
82%
3% of limit
↓ 86% below
Manganese
21
2008–2020
57%
2% of limit
↓ 99% below
Lead
12
2008–2020
50%
7% of limit
↓ 24% below
PFOS
municipal
31
2024
0%
—
—
Sulfate
22
2008–2020
95%
1% of limit
↓ 96% below
Uranium
22
2008–2020
100%
1% of limit
↓ 82% below
Arsenic
22
2008–2020
95%
5% of limit
↓ 87% below
Iron
22
2008–2020
27%
8% of limit
↓ 94% below
PFOA
municipal
31
2024
0%
—
—
PFBS
municipal
31
2024
0%
—
—
pH
22
2008–2020
100%
—
~ typical
Hardness
22
2008–2020
100%
—
↓ 69% below
Sodium
22
2008–2020
100%
—
↓ 92% 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 CA.
Compare your result with Plumas County
Of the 22 arsenic tests on record for Plumas County (2008–2020),
5% found none, and half were below 0.475 µg/L.
Of the 22 chloride tests on record for Plumas County (2008–2020),
0% found none, and half were below 1.11 mg/L.
Of the 22 fluoride tests on record for Plumas County (2008–2020),
50% found none, and half were below 5 µg/L.
Of the 22 iron tests on record for Plumas County (2008–2020),
73% found none.
Of the 21 manganese tests on record for Plumas County (2008–2020),
43% found none, and half were below 0.24 µg/L.
Of the 22 nitrate tests on record for Plumas County (2008–2020),
18% found none, and half were below 179 µg/L.
Of the 22 sulfate tests on record for Plumas County (2008–2020),
5% found none, and half were below 1.73 mg/L.
Of the 22 uranium tests on record for Plumas County (2008–2020),
0% found none, and half were below 0.295 µg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Fluoride 22 samples
Nitrite 22 samples
Chloride 22 samples
Nitrate 22 samples
Manganese 21 samples
Sulfate 22 samples
Uranium 22 samples
Arsenic 22 samples
Iron 22 samples
pH 22 samples
Hardness 22 samples
Sodium 22 samples
Limited data (<15 samples) — interpret with caution
Radon 7 samples
Lead 12 samples
No private-well PFAS data for Plumas County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Plumas 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 Plumas County
111Active public water systems
32,834Residents on public water
14%Households on private wells
Public water systems in Plumas 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 Plumas 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 Plumas 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 Plumas County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Plumas 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 Plumas County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Plumas 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 CA with at least one sample for that analyte.