Yucca tunnel to test earthquake fault features

Monday, Dec. 22, 1997 | 10:44 a.m.

U.S. Department of Energy workers have begun drilling additional tunnels inside Yucca Mountain, 90 miles northwest of Las Vegas, to test the block of rock proposed as a high-level nuclear waste dump.

The new excavation, called a cross-drift, was recommended to the DOE by the Nuclear Waste Technical Review Board to further examine possible earthquake faults and other features in the complex volcanic tuff.

The new tunnel extends the exploratory studies facility, a five-mile long tunnel completed by the DOE in April.

The cross-drift begins inside the facility about 6,000 feet from the northern entrance. It will cross proposed burial rock and go through the Solitario Canyon fault, which borders Yucca Mountain on its western edge.

Along the way, scientists and engineers will examine and test the rocks.

The cross-drift will offer scientists a more three-dimensional picture of Yucca Mountain, the rocks in contact with each other and their structure, including fractures and faults, said Russ Dyer, acting Yucca Mountain Project manager.

"Before we begin crossing the mountain, scientists will predict the conditions we expect to see," Dyer said. "During construction (of the drift) we will compare the predictions to the conditions actually encountered."

This will confirm predictions, or reveal surprises that scientists could not have anticipated.

The roughly 8,400-foot-long cross-drift will be excavated with a tunnel boring machine 16.5 feet wide, 9 feet smaller than the one used to dig the original facility.

The cross-drift should be completed by September.

The testing inside will continue for several years after excavation.