Anchor rod on Bay Bridge may have snapped

Caltrans engineer Brian Maroney holds a section of a three-inch rod while providing an update on the tower anchor rod testing on the new eastern span of the Bay Bridge in Oakland, Calif. on Saturday, Feb. 21, 2015. less Caltrans engineer Brian Maroney holds a section of a three-inch rod while providing an update on the tower anchor rod testing on the new eastern span of the Bay Bridge in Oakland, Calif. on Saturday, Feb. 21, ... more Photo: Paul Chinn, The Chronicle Buy photo Photo: Paul Chinn, The Chronicle Image 1 of / 32 Caption Close Anchor rod on Bay Bridge may have snapped 1 / 32 Back to Gallery

Caltrans has uncovered evidence that one of the 25-foot-long rods that anchor the new Bay Bridge eastern span’s tower may have snapped after being installed, a finding that could cast doubt on hundreds of other rods exposed to corrosion-causing water for two years before a construction defect was discovered.

Agency officials cautioned that tests are needed to determine whether the rod, which is encased in a grout-filled sleeve at the base of the tower, is indeed broken.

An ultrasonic test performed late last month indicates that the steel fastener may be as much as 6 inches shorter than the other rods, Caltrans officials say. It could have snapped at the bottom because of corrosion, or it could simply have been cut or made shorter than the other 400-plus rods at the tower’s base, they say.

The answer could determine whether Caltrans must bolster the tower’s anchoring system.

All 422 rods in the tower underwent an ultrasonic test to determine their viability after Caltrans discovered that many of them had sat in water because of a contractor’s failure to seal and grout their sleeves properly.

One of an additional two rods that were removed earlier showed microscopic cracking, and Caltrans is conducting more tests on that fastener to determine the cause.

The rod that showed signs of being short was the only fastener that appeared to have any problems based on the ultrasonic tests, Caltrans officials said.

“The good news is that 421 passed the test,” said Dan McElhinney, a Caltrans district manager. “One was short, and there was not a clear understanding of why.”

To determine whether the rod is broken or was simply shorter for some other reason, Caltrans officials plan to pull up on the fastener in what is called a load test. If the rod gives way, that will show it was broken.

If the rod holds fast, engineers will be satisfied that it was cut either before or during installation. However, they have yet to find evidence to support that theory.

If the rod failed, it could be because it corroded after it was installed. That would mean that even the 421 rods that passed the ultrasonic test could eventually fail from corrosion.

If it turns out that the rod passes the load test, however, it does not mean that Caltrans can eliminate the potential that corrosion caused the tiny cracks found in the steel fastener that was earlier removed from the tower base.

Caltrans officials have long maintained that the water that poured into the rod sleeves after the fasteners were installed poses little threat. Unlike rods that snapped on bridge seismic stabilizers in 2013, they said, the tower rods were not highly tensioned.

However, the tower rods were put under unusual stress in 2011 and 2012 to ensure that the 525-foot tower stood straight.

Caltrans is optimistic that the latest scare will turn out to be nothing more than a scare.

“We need to figure out if something did get dinged up — maybe they ended up cutting the rod,” said Brian Maroney, chief engineer on the project. “Sometimes there is a judgment made in the field.”

McElhinney said, “We are really confident that 421 out of 422 did not fail and are in good shape.”

Yun Chung, a retired Bechtel engineer and fastener specialist, is less optimistic. The rod could be 6 inches shorter, but 6 inches from the bottom of the fastener is also where it would be most likely to fail, he said.

“The only conclusion you could have is that something happened at the bottom end — there is no other explanation,” Chung said. “I can’t think of one.”

Jaxon Van Derbeken is a San Francisco Chronicle staff writer. E-mail: jvanderbeken@sfchronicle.com