So how does a person remove tons of benzene gas and sticky coal tar that had collected for half a century? Not easily.

John Keeling, site manager for the Gas Works Park cleanup project under the direction of the Washington State Dept. of Ecology, says the coal tar is buried under the soil.

"If you're not in contact with the tar, then it's safe for people to be in." The benzene is different, he adds, because it enters the air and water freely. However, it is extracted from the ground through an air-sparging system and vacuum extraction. Equipment inside a fenced area, made to look like the rest of the machinery, houses a catalytic combustion converter. It extracts benzene from the ground and burns it.

Is that harmful to park goers?

"No," Keeling says. "It converts benzene to carbon and water. It prevents benzene vapors from coming up and coming into contact with people." The process has been in place for three years. Keeling hopes the benzene will be dissipated in two more years, but says the air sparging could take longer. "It will run until it's done," he says, noting that tests show less and less benzene vapors are taken out each year.

One of the attractions at Gas Works Park is its 20 acres of lush green lawn --perfect for playing Frisbee or getting a suntan while reading a good book. Children love to roll down Kite Hill. Dogs love to romp. People have picnics.

What about that coal tar buried under the grass?

"There is two feet of soil over it everywhere-people have no contact with it," Keely says. "Unfortunately, there is some movement (underground) that leads to upwelling of coal tar, but we put a fence around it and the city removes it."

The thick, black, sticky tar gets dug up and hauled away.

Next: But more comes up another day