CHAMPAIGN — The health care advocacy group that has made itself a watchdog of the cleanup of the site of a former manufactured gas plant again found fault with the operation on Thursday.

Advocates said open-air excavation was leaving nearby residents at risk to harmful dust and vapors escaping from the ground, while a site supervisor and an Ameren Illinois spokesman said there was no issue and that workers had not detected any chemicals.

Most of the cleanup at the Ameren Illinois-owned site at Fifth and Hill streets, which workers have been excavating for about two years, has occurred underneath a large tent meant to control any dust or vapors escaping while crews dig up contaminated soil. The contaminants were byproducts of a process that turned coal into gas at a plant which was razed decades ago.

Thursday's work at a small area on the south end of the lot, just north of the Center for Women in Transition at 508 E. Church St., was not under the tent.

"Ameren is gambling with the health of the people who live in this neighborhood," said Grant Antoline, an organizer with Champaign County Health Care Consumers.

But Ameren Illinois spokesman Leigh Morris said there was no issue — Thursday's work was approved and supervised by the Illinois Environmental Protection Agency, and workers carried special detectors to monitor the levels of chemicals in the air.

"The monitors detected nothing that would have been of health and safety concerns," Morris said.

Morris said the open-air work began mid-Thursday morning and was completed by mid-afternoon.

Morris said Ameren Illinois received one complaint when dust started traveling on to a neighbor's property. He said workers watered down the area to eliminate dust, but the dust was not harmful to begin with.

"This is the same dust that could be found in any gravel," Morris said.

The excavation on Thursday was up against a fence at the south end of the property. Site supervisor Jacob Blanton said the fence would have been in the way of the large white tent, which is why workers could not move the tent to shroud the excavation.

Antoline said that is no excuse. The workers were "cutting corners," he said, and Health Care Consumers Director Claudia Lennhoff said there is no reason to believe the soil workers dug up Thursday is any less harmful than what they have been insulating for two years.

"What they're digging up there is the same as what's underneath the tent," she said.