MADISON, Wis. -

A potentially dangerous chemical has shut down a city-run oil recycling facility.

Used oil dumped into a designated tank on the west side of Madison tested positive for polychlorinated biphenyls, more commonly referred to as PCBs.

“We're evaluating the program as a whole. We want to figure ways to prevent this from happening in the future, because it's good that it was contained within a tank like this rather than be in a stream, but it is costly,” Madison Landfill Supervisor Andrew Solberg said.

Solberg said the contractor assigned to monitoring and recycling the oil at each of the four city drop-off sites notified him of the contamination earlier this month. The city ran an additional set of tests and found the tank on Speedway Road did have a form of PCBs common in electrical transformers.

Solberg said he is aware that PCBs can inhibit neurological development in children and disrupt the endocrine system. He added that PCBs are a probable human carcinogen and have been thought to lead to cancer.

The collection point is also right next to the Glenway Golf Course, and some neighbors expressed concerns about the environmental impact.

Solberg said the chemicals in this oil tank are contained, and everyone is safe. The site has been shut down indefinitely, at least until the facility is cleaned and cleared of PCBs.

“Those are issues with PCB, but at the present, there's no risk to the public,” Solberg said.

Cleanups like the one that will be required on the west side site cost thousands of dollars that Solberg said are typically not budgeted for. On top of that, the contractor can no longer recycle the oil, and the city no longer collects money on that supply.

“It's just an additional expense that hopefully we can avoid,” Solberg said.

Solberg said the contamination is likely a result of someone dumping the wrong materials into the 500-gallon tank. The collection point is only supposed to store used motor oil.

"It could have been done knowingly, unknowingly. We don't know,” Solberg said. “So it's something we're going to try to put measures in place that would prevent that in the future.”

Solberg said a similar issue occurred in October at the site on Monona Drive. He wants to do more to prevent contamination from happening, mentioning more signage, surveillance at sites and supervised locations as options for the city.

For those unsure what is and is not allowed at city disposal sites, Solberg encouraged citizens to call the office or check out http://www.danecountycleansweep.com/ for detailed information on throwing out hazardous materials.