Vegas tunnel delayed

Tunnelling for the third water intake at the Lake Mead reservoir in Las Vegas has been delayed after workers hit a pocket of water under the lake in early July.

Over a period of four days inflow from a pocket of loose material behind the face of the starter tunnel entered the area and the assembly chamber. Since then the inflow has been mucked out and the project is working to re-establish the face of the starter tunnel.

Following the May delivery of a 6.36km diameter Herrenknecht TBM to bore the 4.83km tunnel, the project had anticipated starting tunnelling in July.

Robin Rockey of the Southern Nevada Water Authority (SNWA) said this is an on-going issue because work is being done 600ft (183m) below surface, and there is a lot of thermal activity.

“Water comes in from thermal pockets at 90 degrees Fahrenheit,” she said. “There are a lot of fissures and cracks in the rock. Water comes in sometimes at 400 gallons per minute and sometimes up to 700 gallons a minute. It’s been constant.”

The USD447M design/build contract for the project was awarded to Vegas Tunnel Constructors, a joint venture consisting of Lombard, S. A Healy and Impreglio.

SNWA is uncertain when tunnelling will start and how much time the inflow has cost the project.

“We’re really optimistic that it won’t change the completion date of 2013,” Rockey said.