Arapahoe County, Colorado: drinking water report. Arapahoe County stretches from Denver's southern suburbs to the eastern plains, home to about 660,000…
Arapahoe County stretches from Denver's southern suburbs to the eastern plains, home to about 660,000 residents. Water providers include Aurora Water, Centennial Water and Sanitation District, and numerous smaller metro districts. Aurora draws from the South Platte River and transmountain diversions from the Colorado River basin, while suburban districts use a mix of Denver Water purchases and Denver Basin aquifer groundwater.
Arapahoe County's water quality depends heavily on your provider. Aurora Water's surface supply is well-treated but travels long distances and is blended from multiple sources. Groundwater from the Denver Basin aquifers is generally clean but non-renewable, and some wells have shown naturally occurring uranium at levels requiring monitoring.
UCMR5 data shows low-level PFAS detections in some county systems. Buckley Space Force Base in Aurora is a potential PFAS source. According to the Colorado Department of Public Health and Environment's 2024 monitoring data, PFAS concentrations in county systems were below proposed federal MCLs.
Identify your specific water provider – the variation across Arapahoe County's many districts means neighboring homes may receive different water.
Check your water for data specific to your provider and ZIP code. For naturally occurring uranium in groundwater, reverse osmosis is the most effective treatment. Our water filter guide covers options. Pull your detailed report, and visit our Colorado page for statewide data.
Drinking water is one exposure route. These federal datasets also cover Arapahoe County, CO.
The EPA places Arapahoe County, CO in Zone 1 - the EPA's highest-risk category, where the predicted average indoor radon level is above 4 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
39% of homes in Arapahoe County, CO were built before 1980, and 3% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Arapahoe County, CO averages 6.4 µg/m³, within the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide