Digging for Gold
McDonald says that due to the customized nature of the TBM, “we keep several hundred thousand dollars worth of parts on hand in case of a breakdown. It would be too time intensive to wait for parts to arrive from Germany. Upon completion, we plan to sell the machine and parts back to Herrenknecht, who can recycle components.”
The machine will remove 260,000 cu yds of material, most of which will be recycled and used as a rip-rap screen to shield the construction area from public view. Remaining material will be used to build pads.
It marks the third tunneling boring machine used in Nevada; the other was used for a tunnel at Yucca Mountain, the site of defunct plans for a nuclear waste repository, and a pair of water delivery tunnels through the River Mountains.
The project, which had a 1,571-day schedule, was expected to finish July 2012. It’s now expected to conclude sometime in 2013. It’s too early yet to determine repair cost. SNWA has yet to rule the accident a force majeure or levy liquidated damages, says an agency spokesperson, although the project has a contingency fund.
“We always know in underground construction there are some unexpected risks and certain conditions,” Jensen says. “We are working together to remedy the situation. We have no expectation that this is devastating to the project. This is just a minor setback.”
Work still remains on track for separate, associated projects, including a $42-million, 14-ft-wide by 16-ft-tall connector tunnel between the third and second intake. Renda Pacific Contracting Inc., Roanoke, Texas, is the general contractor.
Barnard Construction Co. Inc., Bozeman, Mont., completed $32 million in connection modifications to the second intake in June.
Owner: Southern Nevada Water Authority
Design-Build Contractor: Vegas Tunnel Constructors LLC
Engineers: Arup; Brierley Associates; MWH; CH2M HILL
Owner’s Rep./CM: Parsons
Tunnel Boring Machine: Herrenknecht AG
Subcontractors: Crux Subsurface Inc.; Precast Management Corp.