Monday, February 27, 2012

Lasers: Inline and On-Target

“Record Day of Tunneling: DS- Laser Road Header Blasts through Miles of Rock!”

This is what a headline could say in the year 2082 during the construction of the New New Irvington Tunnel. Today, lasers serve a much different but very important purpose of keeping tunnel excavation inline and on-target.

The alignment of the New Irvington Tunnel stretches 3.5 miles from the Sunol Valley to Fremont. At depths of up to 700 feet below ground surface, crews are working in four headings to excavate the new tunnel. With miners deep underground tunneling in four different directions, how do they make sure the tunnels line up? How do they keep from tunneling into Livermore or Union City? The answer: Lasers.

Inside of each tunnel heading laser beams cut through low light conditions and provide alignment control. The lasers are mounted on the left and right side of the tunnel near the tunnel entry and project their beams on the rock face that is being excavated. Crews operating the road headers keep the machine between these beams to stay on target. Surveyors are brought in between each tunnel set (typically four feet of tunneling) to verify that the alignment of the tunnel is accurate.

Laser Road Headers and Lightsabres may never become more than the wishful thinking of science fiction enthusiasts. But for miners and the 2.5 million people that depend on a safe and secure Hetchy Hetchy Water System lasers keep the New Irvington Tunnel on-target!

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