El Dorado County, California: drinking water report. El Dorado County stretches from the Sacramento Valley foothills to the Sierra Nevada crest, with about…
El Dorado County stretches from the Sacramento Valley foothills to the Sierra Nevada crest, with about 193,000 residents. Placerville is the county seat. Water sources include the American River and its tributaries, treated by the El Dorado Irrigation District, and private wells in the more rural areas. The county's Gold Rush history means the landscape is riddled with abandoned mines and mercury-laden tailings from 19th-century hydraulic mining.
Mercury contamination from historic gold mining is embedded in El Dorado County's waterways. According to the Central Valley Regional Water Quality Control Board's 2024 assessment, mercury concentrations in sediment along the South Fork American River remain elevated, with fish tissue mercury levels triggering consumption advisories. While municipal water treatment removes mercury from drinking water, private surface water diversions and wells near historic mining areas may be affected.
The El Dorado Irrigation District's treated water meets all federal standards, but naturally occurring manganese and iron in the granitic groundwater cause aesthetic issues for well users. A 2024 State Water Board PFAS survey detected low-level PFAS in one EID monitoring point, likely from diffuse urban sources rather than military activity.
El Dorado County well owners in areas with historic mining activity should test for mercury and arsenic – both are associated with Gold Rush-era operations. If you see orange or black staining from your well water, iron and manganese are the likely culprits and warrant treatment.
Check your water for available data. For mining-legacy metals, specific media filters and reverse osmosis are the effective options. Our water filter guide covers systems suited to Sierra foothill well water. Pull your detailed report for local data, and visit our California page for statewide context.