For 30 minutes Wednesday morning, Craig wastewater- treatment plant's 3,600-cubic foot grid chamber ran black.
Mike Frazier, wastewater plant manager, recognized the black water as petroleum product contamination.
There's no way to treat wastewater for petroleum contamination, Frazier said.
By this evening, 36 hours after the contamination occurred, the contaminated water will be discharged into the Yampa River.
"Today, somebody either made a mistake or was ignorant of the possible effects," Frazier said.
It's possible a 55-gallon drum of oil dumped into the sewer contained enough oil to turn the chamber grid black, he said.
When in the river, the oil will be so diluted with water its effect will be insignificant, Frazier said.
But if the dumping continues, it could pose a serious environmental risk to fish and wildlife that depend on the river for food and habitat, as well as water users downstream from the treatment plants.
It's a water-treatment manager's job to watch out for river users downstream from the plant, Frazier said.
Gilbert Anderson, superintendent of the Steamboat Springs Wastewater Plant, said he's never seen petroleum product contamination upriver from Craig.
That's good news for Moffat County residents.
Anderson's staff monitors wastewater for oil sheens. If a slick is spotted in the water, the crew has to test for petroleum, Anderson said.
Before Wednesday, Frazier hadn't spotted any petroleum products in the wastewater since last winter.
When he detects petroleum contamination in the wastewater, he tries to track the source of the contamination by following the petroleum's odor through the sewer lines.
But wastewater plant staff failed to track last winter's contamination. Nor did they know where Wednesday's petroleum came from.
The wastewater plant has had better luck other times, though. During one instance, staff tracked the odor and narrowed the source to several possible businesses. When notified a problem existed, one business admitted it had accidentally dumped the petroleum in the sewer system and promised to correct the problem.
"It's a public awareness issue," Anderson said. "Wastewater plants aren't an outlet for petroleum products."
Only water and human waste should be disposed of in the sewer system, Frazier said.
Penalties for intentionally dumping petroleum products into the sewer system are severe, Frazier said, and they can make a business unprofitable to run.
Although the problem is uncommon, when it happens, usually occurrences happen twice a week for as long as a month. That's when Frazier tries hard to trace the source. Other contaminations have proved to be isolated instances.
For residents looking for a place to dispose oil, City Market has a waste petroleum container in front of the store.
Rob Gebhart can be reached at 824-7031 or firstname.lastname@example.org.