The site posed some challenges: one side drops to the road below at a 30-degree angle.

Two 2007 interviews reflect differing opinions on the risks the unfilled site may pose.

EPA determines that the site poses a significant threat to public health.

Also, independent studies conclude that suitable alternative sites for the observatory pose no threat to endangered species.

The agency has said that while the site poses no immediate health threat, there are concerns over further pollution through leaching of the toxic waste.

Mr. Hritcko said the proposed site would pose no problems for shipping and should not be changed.

Rather than limiting the concentration of plutonium itself, the criteria limit the cancer risk the sites pose.

But, he said, many sites that have come in the wake of Napster pose a threat because they are populated by pirates.

The site posed several technical challenges; half a millennium of debris was at hand.

But even a vacant industrial site, which sits only a few feet above sea level, will pose challenges for Nascar.