In the wake of a disconcerting engineering analysis that blames Caltrans for the Bay Bridge rod failures, three transportation agencies overseeing construction must commission an independent outside investigation before the new span opens.

With so much at stake, the current probe lacks essential neutrality. The three engineers assigned to determine the cause of the failures are a consultant for the bridge contractor, a Caltrans engineer and a Caltrans consultant. While they might be smart, they are too closely tied to parties with vested interests.

The search for the cause must ensure the public's safety, not protection of an insular state agency. The 32 rods that snapped were part of a system designed to provide stability when an earthquake strikes.

Caltrans, the California Transportation Commission and the Metropolitan Transportation Commission jointly oversee the bridge construction. But it's Caltrans that handles the day-to-day operations and, according to metallurgist Yun Chung, dropped the ball.


As a result, they were too hard and susceptible to a common form of corrosion known as hydrogen embrittlement. Chung warns that other rods could fail too.


Experts agree that embrittlement caused the failure. However, the cause of that embrittlement remains officially undetermined. It makes a big difference not only for assessing blame but, more importantly, for determining which rods must be replaced.

At issue are two sets of rods. The first 96 were manufactured in 2008 and embedded in concrete so that water around them could not drain. The 32 failures came from that batch. All 96 are now covered by the roadway and inaccessible for replacement. So the three agencies are devising a workaround that doesn't rely on the rods for stability.

The second set, 192 rods manufactured in 2010, were not left sitting in water, and are accessible for replacement. Thus far, none have failed. But the looming questions are whether they might in the future as Chung warns, and whether they need to be replaced before the bridge opens.

Chung concludes the corrosion was not due to hydrogen present in the rods before they were installed. Rather, it was due to hydrogen from the environment that penetrated the steel. For that, Chung blames Caltrans specifications that allowed production of susceptible rods.

For the three agencies to determine whether to replace the 2010 rods before opening the bridge, they must figure out what caused the embrittlement in the 32 that failed. That will inherently require determining blame. Chung says Caltrans is the culprit.

We wish we had more trust in the transportation department to objectively analyze the problem. But, given its contribution to the problem and its continuing record of obfuscation, we don't.

Outside experts must lead this critical investigation.