Sunlight working to kill E.coli contamination in southern Colorado, other pathogens in Arkansas River after wastewater dump

More than 4.2 million gallons of untreated sewage containing harmful bacteria, including E.coli, was dumped into the Arkansas River near Pueblo last week. This was downstream of where the Fountain Creek and Arkansas River meet, down to at least the John Martin Reservoir.  

Fortunately, it's a sunny time of year, and a public health expert says the sunshine is helping clear the sewage contamination in the Arkansas River. 

"Wastewater plants use aeration and ultraviolet radiation to kill pathogens, and that's the exact same processes that are happening in the river now," explained Nicole Rowan, who serves as the division director for the Colorado Department of Public Health and Environment's Water Quality Control Division. "There's aeration, and with exposure to sunlight, that kills the bacteria. So through time, the bacteria will die off just because of exposure to sunlight. Additional dilution from rainfall could also help."

The hazardous spill was caused by a compromised wastewater pipe from the Pueblo wastewater treatment plant.

"It was a pipe that's a ways away from the facility that carried water from where the pipe broke to around the wastewater facility, and then that pipe came together with the wastewater effluent flow, and then discharged to the river," Rowan said. 

CDPHE is still warning people not to enter the river in areas near Blende down to La Junta and Las Animas, since there are still high levels of pathogens in the water. 

"We are sampling about every day this week to continue to monitor the situation," Rowan said.

The contamination reached the John Martin Reservoir, about 2 hours from Pueblo, on Monday. But officials have been working to find out whether it ends there.

"There are also some canals that divert the river around the reservoir ... so we're currently examining where those canals could release water back downstream of John Martin," Rowan said.