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Intake issues

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Intake issues

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    Because shaft and tunnel work is taking place in a constricted space between two existing intake pumping stations, special precautions and close coordination associated with explosive quantities and blasting schedules were required to avoid disruption to existing pumping operations. Photos: Southern Nevada Water Authority

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    The tunnel-boring machine will operate in open mode during low water and stable conditions with the ability to switch to closed mode in high water and unstable areas.

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    A central auger will remove muck from the face and convey it along 600 feet of trailing equipment. Probes will drill ahead of the cutterhead to assess the rock and place grout to reduce water inflows

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    When completed, Lake Mead's new intake will be more than 140 feet deeper than the lake's other two intakes, ensuring a consistent water supply to the Las Vegas Valley. Image: Southern Nevada Water Authority

PROJECT NUTS AND BOLTS

Three intake-related contracts to be completed by 2013.

Contract 070F 01 C1: Shafts and Tunnel

Contractor: Vegas Tunnel Constructors LLC

Contract Overview: This contract includes a 16-foot-diameter intake riser and structure, 15,000 feet of 20-foot-diameter tunnel by tunnel-boring machine, 30-foot-diameter tunnel access shaft, stub tunnel to interface with connection to Intake 2, and a future pumping station.

Current Status: The 600-foot tunnel access shaft is complete, and the tunnel-boring machine (TBM) erection chamber is in progress by drill-blast method. The TBM has been fabricated in Germany by Herrenknecht AG, and is shipped and staged onsite with assembly and testing down shaft scheduled to begin late 2009/early 2010. Crews are preparing the staging area for all marine operations, including underwater work on the intake inlet and intake riser fabrication. Offsite fabricating of precast, gasketed tunnel segments (2,500 rings and six segments, each weighing about 6 tons) is complete, and stockpiling completed segments is happening onsite.

Contract 070F 02 C2: Connector Tunnel

Contractor: Renda Pacific

Contract Overview: It includes a 20x20-foot modified horseshoe tunnel approximately 300 feet long and a 14x16-foot modified horseshoe tunnel approximately 2,100 feet long. It also includes a 26-foot-diameter access/surge shaft approximately 450 feet deep.

Current Status: The surface bench and rock wall are complete via ripping and bulk excavation equipment. Crews are beginning to construct the access shaft by drill-blast method.

Contract 070F 05 C1: Intake No. 2 Connection and Modifications

Contractor: Barnard of Nevada Inc.

Contract Overview: It includes a 22-foot-diameter isolation gate shaft, 12x14-foot isolation gate, 14x16-foot modified horseshoe interconnecting tunnel to Intake 2, and Intake 2 inlet modifications. It is a critical milestone to complete key work during the extended outage of Intake 2.

Current Status: The isolation gate shaft and tunnels are complete. The isolation gate and transition structure construction are in progress for a December gate placement and shutdown. Crews are mobilizing marine operations for intake work.

Web Extra

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