Compare your result with San Bernardino County
Of the 4294 arsenic tests on record for San Bernardino County (1951–2023),
10% found none, and half were below 2.6 µg/L.
Of the 9241 chloride tests on record for San Bernardino County (1908–2023),
0% found none, and half were below 44.9 mg/L.
Of the 61 chromium (total) tests on record for San Bernardino County (2006–2023),
23% found none, and half were below 1.7 µg/L.
Of the 8263 fluoride tests on record for San Bernardino County (1932–2023),
1% found none, and half were below 600 µg/L.
Of the 6746 iron tests on record for San Bernardino County (1916–2023),
45% found none, and half were below 4 µg/L.
Of the 1390 lead tests on record for San Bernardino County (1959–2023),
77% found none.
Of the 5307 manganese tests on record for San Bernardino County (1932–2023),
44% found none, and half were below 0.34 µg/L.
Of the 59 nitrate tests on record for San Bernardino County (2006–2023),
8% found none, and half were below 616 µg/L.
Of the 25 pfoa tests on record for San Bernardino County (2021–2025),
72% found none.
Of the 25 pfos tests on record for San Bernardino County (2021–2025),
76% found none.
Of the 8687 sulfate tests on record for San Bernardino County (1908–2023),
0% found none, and half were below 80.2 mg/L.
Of the 60 tds tests on record for San Bernardino County (2006–2023),
0% found none, and half were below 339 mg/L.
Of the 1129 uranium tests on record for San Bernardino County (1993–2023),
1% found none, and half were below 4.78 µg/L.
Public vs. Private Water in San Bernardino County
321
Active public water systems
2,828,393
Residents on public water
0%
Households on private wells
Public water systems in San Bernardino 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.
Data Sources
This report aggregates data from the following public databases:
- Water Quality Portal (WQP) — groundwater sample results for San Bernardino 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 San Bernardino County. Census data explorer →
- USGS Aquifer Atlas — principal aquifer type underlying San Bernardino 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 San Bernardino County, used in contamination risk scoring. TRI Explorer →
- EPA Superfund NPL — National Priorities List sites in or near San Bernardino 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.
Last updated: 2026-09-10
Full methodology →