CHAMPAIGN — Health advocates say the test results from a sample taken from a pipe near the Boneyard Creek is "the smoking gun" they were looking for to prove that a former manufactured gas plant site continues to contaminate the neighborhood.

But an environmental engineer from the city, which tested the sample under the terms of a settlement agreement with the health group, maintained on Tuesday that there is no cause for concern — the pipe is plugged and the contamination is contained, she said.

Champaign County Health Care Consumers, an advocacy group that has been the leading drive toward plugging the pipe which they say used to drain into the Boneyard Creek, held a press conference on Tuesday to highlight the results of the most recent testing. Earlier this year, the group sued the city under the Clean Water Act and claimed it was responsible for eliminating the toxic drainage into the waterway from its property.

City officials still maintain that there was never any spilloff from the pipe into the creek — "the pipe outlet was dry every time" it was sampled, said Assistant City Engineer Eleanor Blackmon — but agreed to settle with the health care group. That agreement required the city to cap the pipe in two places and test its contents.

The results came back this month, and health advocates say the "semi-volatile organic compounds" that were detected are likely to have come from the manufactured gas plant that used to stand at the intersection of Fifth and Hill streets.

"The type and concentrations of the chemicals are of the same type that are identified with manufactured gas plant waste," said Grant Antoline, a community organizer with the group.

Blackmon said the test results do not point in any particular direction.

"They could be indicative of any one of a number of (former) uses east of the Boneyard there," said Assistant City Engineer Eleanor Blackmon. That could include other former businesses, like the site of a bulk oil facility or several gas stations. But there should be no alarm, she added, because the city has capped the pipe.

"I kind of think it's immaterial right now since the pipe has been plugged and it's eight feet underground," she said.

Blackmon is also skeptical of whether the pipe, which terminated at the creek north of Washington Street before it was dug back by city workers, originates at the Fifth and Hill site. Health advocates say it travels from the creek, along the railroad tracks and underneath the site that Ameren Illinois has been cleaning for years.

The contamination travels, they claim, when storm water infiltrates the pipes through cracks that have developed during the century the pipe has been underground. The toxic chemicals can wash out of the pipe with the water, contaminating adjacent soil or waterways, the group has said.

The distinction — which the health group has never been able to agree upon with the city, the Illinois Environmental Protection Agency and Ameren Illinois — is important because it would determine whether the full length of the pipe needs to be extracted and adjacent areas cleared of toxicity.

The city has completed its obligation under the Clean Water Act, said CCHCC executive director Claudia Lennhoff, but the group and some residents are now calling on the IEPA to initiate a full investigation of whether the rest of the area has been contaminated.

"We now know that a four-block-long pipe that is full of toxic contamination is sitting in our neighborhood and nobody is doing nothing about it," said resident Ebbie Cook.