"The upwelling is a danger if people eat the tar," says Colleen Brown, project manager for the Seattle Parks and Recreation Dept. "It's not a danger to walk by it."

Browne says her agency keeps people safe from toxic substances by monitoring the air, ground water, and lake water nearby on a monthly basis. The report is sent to the Dept. of Ecology. In addition, someone from her department walks through the park weekly, looking for upwellings of tar. "So far, everything is OK," she says.

For now, that is.

Gas Works Park has closed several times over the years because of numerous tar eruptions. And the biggest concern of the past, Browne says, was children eating dirt. Presumably, there were more health risks to park visitors in the 1970s, before more sophisticated monitoring of toxic substances was in use.

"We discovered our study's original plan was not going to work," she says of the idea to cover the site and let outgassing occur naturally. That's where the 24 inches of topsoil is supposed to work its magic. "We feel it's under control," she says. "The park doesn't pose a health risk to people."

There are signs warning people to not swim or play in the water at Gas Works Park, but nothing to tell them about coal tar below the grass. The agencies in charge say signs aren't necessary because of the measures in place to protect the public.

Some people know about the coal tar under them, and others don't seem to care. ( Click here to listen to what park visitors have to say.) However, park visitors should have access to information on park grounds explaining the situation and allowing them the opportunity to decide for themselves just how close they want to be to toxic chemicals when they have a picnic.