Larimer County, Colorado: drinking water report. Larimer County stretches from the Front Range suburbs of Fort Collins and Loveland into Rocky Mountain…
Larimer County stretches from the Front Range suburbs of Fort Collins and Loveland into Rocky Mountain National Park, with a population of about 360,000. Fort Collins Utilities and the City of Loveland each operate their own water systems, drawing from the Cache la Poudre River, Horsetooth Reservoir (Colorado-Big Thompson Project), and local treatment plants. The 2012 High Park Fire and 2020 Cameron Peak Fire both burned significant portions of the county's water supply watersheds, creating lasting impacts on source water quality.
Post-fire watershed degradation is the dominant water quality story in Larimer County. When forest burns, it strips the ground of vegetation that holds soil in place and absorbs rainfall. For years afterward, storms wash ash, sediment, and dissolved organic matter into reservoirs at rates far above pre-fire levels. According to Fort Collins Utilities' 2024 water quality report, turbidity spikes in the Poudre River following summer storms have been three to five times higher than pre-fire baselines, forcing the treatment plant to use more chemicals – which produces more disinfection byproducts.
The EPA's UCMR5 data shows PFAS detections at low levels in Fort Collins' system. A 2024 CDPHE assessment documented one public water system in the county with PFAS above detection limits. The Northern Colorado Regional Airport in Loveland has used AFFF foam, creating a localized contamination concern.
Fire-impacted watersheds take a decade or more to stabilize, and Larimer County is still in that recovery window. Heavy summer storms can temporarily degrade source water quality in ways that ripple through the treatment process.
Check your water for the latest monitoring data. A carbon block filter reduces disinfection byproducts and taste/odor compounds. For PFAS, reverse osmosis is more thorough. Our water filter guide covers both scenarios. Get your detailed report for trend data, and visit our Colorado page for statewide context.
Drinking water is one exposure route. These federal datasets also cover Larimer County, CO.
The EPA places Larimer 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.
33% of homes in Larimer County, CO were built before 1980, and 7% 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 Larimer County, CO averages 6 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
35 public water systems serving Larimer County, CO have EPA lead testing on record. The reported lead sample skews toward systems that already flagged a problem, so its exceedance rate is not directly comparable with other areas. 17 water systems serving Larimer County, CO carry a health-based EPA Safe Drinking Water Act violation.
| Most-cited violation type | Systems affected |
|---|---|
| Surface Water Treatment Rule | 7 |
| Interim Enhanced Surface Water Treatment Rule | 7 |
| Lead and Copper Rule Revisions | 4 |
| Stage 1 Disinfectants and Disinfection Byproducts Rule | 3 |
| Lead and Copper Rule | 3 |
Source: EPA Lead and Copper Rule 90th-percentile tap sampling and EPA SDWIS Safe Drinking Water Act enforcement records, aggregated from the public water systems serving this county. Figures are counts of water systems, not a test of any individual home or tap.