Contaminant Data — All Analytes
130 well testing events on record, covering
23 analytes.
Data spans 1953 to 2021.
| Contaminant |
Samples |
Years |
Detection Rate |
Distribution LowModHigh |
vs. Limit |
vs. NY Avg |
|
Radon
|
36 |
1996–2021
|
100% |
|
138% of limit
|
↑ 25% above
|
|
Manganese
|
69 |
1965–2021
|
88% |
|
134% of limit
|
↓ 57% below
|
|
Iron
|
83 |
1965–2021
|
99% |
|
53% of limit
|
↓ 72% below
|
|
Arsenic
|
48 |
1971–2021
|
96% |
|
10% of limit
|
↓ 46% below
|
|
Sulfate
|
87 |
1965–2021
|
95% |
|
5% of limit
|
↓ 65% below
|
|
Chloride
|
122 |
1965–2021
|
100% |
|
10% of limit
|
↓ 67% below
|
|
Fluoride
|
67 |
1965–2021
|
100% |
|
5% of limit
|
~ typical
|
|
HFPO-DA (GenX)
municipal
|
10 |
2023
|
0% |
|
— |
— |
|
Lead
|
48 |
1971–2021
|
54% |
|
1% of limit
|
↓ 71% below
|
|
Nitrate
|
82 |
1965–2021
|
74% |
|
1% of limit
|
↓ 93% below
|
|
Nitrite
|
39 |
1973–2021
|
18% |
|
0% of limit
|
↓ 63% below
|
|
PFHxS
municipal
|
10 |
2023
|
0% |
|
— |
— |
|
PFNA
municipal
|
10 |
2023
|
0% |
|
— |
— |
|
PFOA
municipal
|
10 |
2023
|
0% |
|
— |
— |
|
PFOS
municipal
|
10 |
2023
|
0% |
|
— |
— |
|
Uranium
|
35 |
2005–2021
|
49% |
|
0% of limit
|
↓ 89% below
|
|
Total Coliform
|
13 |
2005–2021
|
14% |
|
— |
~ typical
|
|
Sodium
|
78 |
1965–2021
|
100% |
|
— |
↓ 24% below
|
|
pH
|
86 |
1965–2021
|
100% |
|
— |
~ typical
|
|
PFBS
municipal
|
10 |
2023
|
0% |
|
— |
— |
|
Hardness
|
87 |
1965–2021
|
100% |
|
— |
↓ 30% below
|
|
Fecal Coliform
|
13 |
2005–2021
|
0% |
|
— |
— |
|
E. coli
|
13 |
2005–2021
|
0% |
|
— |
— |
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 NY.
Compare your result with Allegany County
Of the 48 arsenic tests on record for Allegany County (1971–2021),
4% found none, and half were below 0.945 µg/L.
Of the 122 chloride tests on record for Allegany County (1965–2021),
0% found none, and half were below 24.2 mg/L.
Of the 67 fluoride tests on record for Allegany County (1965–2021),
0% found none, and half were below 200 µg/L.
Of the 83 iron tests on record for Allegany County (1965–2021),
1% found none, and half were below 156 µg/L.
Of the 48 lead tests on record for Allegany County (1971–2021),
46% found none, and half were below 45 ng/L.
Of the 69 manganese tests on record for Allegany County (1965–2021),
12% found none, and half were below 50.3 µg/L.
Of the 82 nitrate tests on record for Allegany County (1965–2021),
26% found none, and half were below 20 µg/L.
Of the 87 sulfate tests on record for Allegany County (1965–2021),
5% found none, and half were below 11.7 mg/L.
Of the 35 uranium tests on record for Allegany County (2005–2021),
51% found none.
Data Sources
This report aggregates data from the following public databases:
- Water Quality Portal (WQP) — groundwater sample results for Allegany 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 Allegany County. Census data explorer →
- USGS Aquifer Atlas — principal aquifer type underlying Allegany 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 Allegany County, used in contamination risk scoring. TRI Explorer →
- EPA Superfund NPL — National Priorities List sites in or near Allegany 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 NY with at least one sample for that analyte.
Last updated: 2026-08-04
Full methodology →