Crews will begin installing the huge steel cable that will hold up the new eastern span of the Bay Bridge this week. Currently, temporary steel structures support the bridge.

At a media briefing Monday morning, Malcolm Dougherty, the acting director of the California Department of Transportation, called the cable installation "the most significant and challenging" part of constructing the span.

The cable is 2.6 feet in diameter and nearly a mile long. It weighs 5,291 tons, or nearly 10.6 million pounds, and is made up of 137 steel strands, each one composed of 127 steel wires. Each wire is strong enough to hold up a Hummer, Caltrans spokesman Bart Ney said Monday.

The cable will travel from the Oakland side of the span to the San Francisco side and back again. The 2,047-foot self-anchored suspension span will be the longest of its kind in the world.

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On Monday, crews lifted a giant spool of steel strands from a barge onto the deck of the new span. Crews will anchor one end of each strand on the Oakland side of the span, underneath the deck.

Using machinery that looks like a ski lift, they will then thread the strands along the path of bright orange catwalks that have been attached to the new tower for several months. The strands will go up to the top of the center tower and down to the San Francisco side of the span, where they will be looped underneath the deck of the bridge, then threaded back up to the tower and back down to the Oakland side of the bridge. There, crews will anchor the other end of the strands.

Ney said it will take a few months to complete the installation. Once all the strands are installed, crews will bind them together and coat them with zinc paste.

The installation of the cable will mark a major milestone for Caltrans, which plans to open the new, seismically safer span in the fall of 2013, 24 years after the 1989 Loma Prieta earthquake damaged the existing bridge.

Like most of the steel on the bridge, the cable was made in China. It was manufactured by Shanghai Pujiang Cable Co. at a cost of $28 million, Ney said. 

Caltrans had proposed building a cheaper bridge without a suspension cable, but Bay Area lawmakers insisted on a "signature span." The new span will cost $6.3 billion, according to Ney.

The Golden Gate Bridge is also a suspension bridge, but it has two cables — one on the bay side and one on the ocean side of the span. Ney said Caltrans chose to use just one cable for the sake of efficiency and aesthetics.