Thursday, December 2, 2010

Drilling Begins at the Vargas Shaft

The SFPUC took an important step forward towards the construction of the New Irvington Tunnel. The Southland/Tutor Perini Joint Venture and their subcontractor Malcolm Drilling drilled the first of 76 secant piles for the 120-ft deep Vargas Shaft. Secant piles are 39-inch concrete filled piles that provide support for the excavation of the shaft. When complete, the 41-ft diameter Vargas Shaft will be a starting point for tunneling activities.

The New Irvington Tunnel will run 3.5 miles and have an internal diameter of approximately 8.5 to 10.5 feet. The new tunnel will provide a seismically-designed connection between water supplies from the Sierra Nevada Mountains and the Alameda Watershed to Bay Area water distribution systems.

Wednesday, December 1, 2010

Tunneling Machine Has Finished Its Job!

A significant milestone has been achieved for the Alameda Siphon No. 4 project. In November, a 96-inch (eight-foot) diameter micro-tunneling machine completed its work to construct a 554-foot-long tunnel underneath Alameda Creek.

As work progressed to construct the tunnel, the team encountered some technical challenges with the micro-tunneling machine. However, the resourceful team and contractor came together and successfully overcame the obstacles to finish the work on a tight schedule.

Crews posed in front of the tunneling machine after it completed its work.

Crews removed the cutterhead portion of the machine from the retrieving pit.

“This tunneling accomplishment marks a significant milestone for the project. It required a great deal of hard work and coordination to work through some major challenges, and I want to commend the entire project team for their efforts,” explained Sunol Regional Project Manager Dan Wade.

This newly constructed tunnel is a significant component of the new Siphon No. 4 that will stretch across the Sunol Valley, connecting the existing Coast Range Tunnel at Alameda East Portal to the existing Irvington Tunnel and the New Irvington Tunnel (currently under construction) at Alameda West Portal. It will help ensure the SFPUC can deliver water to its customers after a major earthquake. This is necessary since the three existing siphons cross the Calaveras Fault and are vulnerable to earthquake damage.

Project Construction Manager Eric Gee explained that since the tunneling work is complete, the contractor efforts are now focused on the rest of the work inside the tunnel. This includes installing one 66-inch (5.5-foot) diameter and two 12-inch diameter pipes and securing it within the tunnel. This work will continue through the end of this year.

Project Manager David Tsztoo explained that the Alameda Siphon No. 4 project, which is more than 50% complete, also includes construction of a new pipe manifold and upgrades to the existing valves control facilities and the Town of Sunol pipeline near the three existing siphons. All work for the project is expected to be complete by December 2011.