Something is killing hundreds of ducks in a 2.2 million gallon treatment pond at a wastewater plant in north Denver.
The ducks – mostly northern shovelers – frequent the treatment plant by the thousands in the winter, drawn by warm water and plentiful food – tiny aquatic animals called zooplankton.
Since Jan. 2, at least 200 ducks have died in a chlorine treatment pool, and dozens of sick ducks have been sent to local wildlife rehabilitation experts, said Steve Frank, spokesman for the Metro Wastewater Reclamation District.
The state Division of Wildlife is investigating the deaths.
The problem does not appear to be bird flu or another avian disease, said officials who are baffled by the deaths.
“Something is impacting their waterproofing,” said Melanie Kaknes, the state DOW district wildlife manager.
Oily feathers normally help waterfowl repel water, but the dead and dying ducks “are getting soaked down real good” said Will Williams, a facilities maintenance worker at Metro Wastewater.
Williams helped chase down eight sick birds Saturday morning, spending more than 20 minutes to net a scared bird that kept diving toward the bottom of the 14-foot deep basin.
“We’re trying to help them, but they don’t know that,” Williams said.
In a small heated building on-site, two sick ducks cowered in a corner, five huddled quietly in a cage, and one sat nearly motionless in a pile of rags, drying off.
The bodies of scores of other ducks were sent to the Division of Wildlife’s Fort Collins research center for testing, Kaknes said.
Birds are dying only in the site’s chlorine contact pond, one of the last stages before treated water flows into the nearby South Platte River.
For the last few days, workers have been setting off a noisy propane cannon every 30 minutes, to startle birds from the surface of the chlorine pond, Frank said.
Five minutes after one burst scared six birds away, two flew back to settle on the steaming, warm water.
“It’s marginally effective,” Frank said.
Wastewater officials increased the concentration of chlorine in the tanks in mid-December in a routine procedure change, he said. Birds didn’t start dying for a week or so after that, Frank said, and since the original chemistry was restored Wednesday, they’re still dying.
Wastewater and wildlife officials said they didn’t know when tests results would be available.
Kaknes said whatever is killing the birds in the wastewater treatment tanks isn’t affecting those just downstream.
A few hundred feet away from the deadly pool, hundreds of waterfowl floated in the South Platte, in warm water released by the treatment plant.
Staff writer Katy Human can be reached at 303-954-1910 or khuman@denverpost.com.
