Nearly 200 environmental groups in the US demanded that the government abandon plans to bury nuclear waste in the Nevada desert, arguing that the area’s geology might cause radioactivity to leak into the groundwater.

Environmentalists claim the discovery two years ago that rainwater had penetrated from the surface to the underground disposal vault raises questions about radioactive waste seeping into groundwater. They said that the discovery in 1997 that water had moved unexpectedly quickly through the rock formations requires the Energy Department, under its own guidelines, give up on the project.

The Energy Department stated that it would continue evaluating the movement of water through rock formations at Yucca Mountain as part of its site assessment. It said that the water moved at 15 mm per year, 15 times faster than had been expected. A final decision is expected in 2001.