A pipe failure near Pueblo released millions of gallons of untreated wastewater into a drought-stricken stretch of one of Colorado’s most popular rivers, triggering high E. coli warnings.
People raft down the Arkansas River in Buena Vista, Colorado, on May 17, 2023. A healthy Rocky Mountain snowpack looks set to offer a bumper season for thrill-seeking white water rafters on Colorado’s rivers. Operators plying waterways fed by the US mountain range say a decent winter and a slow snowmelt should offer months of fun for those intent on hurtling over bubbling rapids. (Photo by CHANDAN KHANNA / AFP) (Photo by CHANDAN KHANNA/AFP via Getty Images) (Photo: Chandan Khanna/Getty Images)
Published September 2, 2026 05:39PM
Health officials in Colorado are warning people to stay out of a more than 100-mile stretch of the Arkansas River, one of America’s most popular river recreation destinations, after over 4 million gallons of untreated sewage spilled into the waterway.
Authorities with the City of Pueblo say a pipeline failure caused the untreated waste to flow into the river. Health officials then detected extremely high levels of E. coli and other dangerous bacteria, as well as viruses and parasites, as the sewage has made its way down the waterway. It’s unknown when the stretch of the Arkansas River below the spill site will be safe for the public.
“This is a disastrously large sewage spill for a river of this size, already under pressure from low flows and serious drought,” Gary Belan, senior director of the clean water program at American Rivers, told Outside. “Because of this, the E. coli threat is likely very high and the potential for health impacts is significant if someone swims in it or swallows it.”
No Word On When the River Will Be Safe
The spill happened near the City of Pueblo, and the advisory extends from Fountain Creek 105 miles downstream to John Martin Reservoir, near the Colorado-Kansas state line. The Colorado Department of Public Health says that workers stopped the leak]on August 27, but that sections of the river still contain dangerously high levels of contaminant as the most recent testing from August 31.
Untreated sewage includes anything flushed down a toilet, run through a shower, or drained in a sink. The failure involved a wastewater pipe located inside a stormwater pipe, according to the City of Pueblo.
Arkansas River At the Heart of Colorado Outdoor Summer Rec
The spill comes on the heels of an ongoing drought that has left the Arkansas River Basin at unusually low flow levels. A historically low snowpack has already stunted Colorado’s angling, whitewater and recreation industries this summer, and such low river flows means the effects of the spill could be intensified, water officials told the Colorado Sun.
Pueblo, a city of about 112,000, is one of Colorado’s busiest summer cities for river recreation and has 11 designated public access points along the Arkansas River. The river is known for its whitewater and features several iconic sections managed across the Arkansas Headwaters Recreation Area. About 250,000 commercial rafting visitors explore the Arkansas River in Colorado every summer, according to the Colorado Sun.
However, the busiest whitewater parts of the river—Royal Gorge, Browns Canyon, and Salida—are well upstream from the spill site and likely won’t be impacted.
Haley Sue Robinson, City of Pueblo director of public affairs, told Outside. The spill contained “water that has not been treated by the water reclamation facility to remove debris, human waste, harmful germs, viruses, parasites, metals, and grease.”
Belan adds that the sewage may also contaminate the wider ecosystem.
“Such a large amount of sewage in such a small amount of water also risks making wildlife and livestock sick, could contaminate crops that are watered with it, and has the potential to lead to significant harmful toxic algae blooms,” Belan said.
Sewage Leaks on Public Waterways
In January, a similar sewage spill released an estimated 5.5 million gallons of untreated water into California’s Russian River, and affected nearby popular beaches like those at Campbell Cove and Salmon Creek.
Also in January, a sewer line in Maryland failed, releasing roughly 240 million gallons of raw sewage into the Potomac River. Officials closed areas near the leak along the Chesapeake and Ohio (C&O) National Historic Park, one of the 75 historic sites managed by the National Park Service (NPS).
