Adams County, Colorado: drinking water report. Adams County north of Denver has about 519,000 residents in communities including Thornton, Westminster, and…
Adams County north of Denver has about 519,000 residents in communities including Thornton, Westminster, and Brighton. Water comes from multiple sources – the Northern Colorado Water Conservancy District, the South Platte River, and Denver Water wholesaling. The county's transformation from agricultural to suburban has been dramatic, and the South Platte River corridor carries the accumulated inputs of the Denver metro area.
The South Platte River at Adams County carries treated wastewater effluent from upstream metro Denver communities. According to Colorado DPHE's 2024 river monitoring, the South Platte downstream of Denver shows elevated pharmaceuticals and PFAS at concentrations above background but below health advisory levels. The river is not a direct drinking water source for most Adams County residents, but it recharges the alluvial aquifer that some systems tap.
The former Rocky Mountain Arsenal – a 27-square-mile chemical weapons and pesticide manufacturing facility – occupies the county's southeastern corner. Now a National Wildlife Refuge, the site has documented contamination including organophosphate pesticides, sarin precursors, and heavy metals. According to the Army's 2024 monitoring report, groundwater contamination remains under active containment.
Adams County's water quality depends on which utility serves your area. Most residents receive treated water from well-managed systems that meet all standards. The Rocky Mountain Arsenal's contamination is contained, but if you are on a private well east of Commerce City, testing provides peace of mind.
Check your water for current data at your address. For the range of metro-area contaminants, a quality carbon filter handles most concerns. For comprehensive protection, reverse osmosis adds PFAS and broader contaminant removal. Our water filter guide covers systems for Front Range water. Pull your detailed report for local data, and visit our Colorado page for statewide patterns.