"It's something that we're taking seriously but we're aggressively investigating it and we're confident that we'll solve it," Caltrans spokesman Andrew Gordon said while taking reporters on a tour of the span.
A recent routine maintenance inspection revealed that rainwater is dripping into the steel structure beneath the road deck on the 0.3-mile self-anchored suspension portion of the bridge, Gordon said.
The concern is that the leaks could cause corrosion at some point in the future, he said.
"We don't want this to continue for the life of the bridge," Gordon said, noting that the $6.4 billion new eastern span, which just opened on Labor Day, is expected to last at least 100 years.
Caltrans officials haven't yet determined how the rainwater is getting in or the exact location where the water is leaking.
"We're exploring all possibilities of how it got in and all possible locations for where it has gotten in," Gordon said.
Caltrans Chief Deputy Director Richard Land took reporters to one area where a small amount of water is dripping, which is underneath westbound road deck a short distance east of Yerba Buena Island.
Pointing to bolts inside the bridge deck, Land said, "There's a drip here every once in a while but there are no locations where there is running water and some bolts aren't leaking at all."
Land said, "We hope to figure out a solution in the next several weeks."
Gordon said the bridge is safe and said Caltrans officials aren't surprised that water is going beneath the road deck, saying, "We expected water to get in somewhere."
Gordon said there are three levels of protection for the steel structure underneath the road deck: caulking, epoxy coating and the roadbed itself.
"You protect the bridge as best as you can," he said.
Gordon said Caltrans should have a better idea of where and how the water is getting in now that it's finally begun to rain heavily.
"During the rainy period we hope to get a sense of how it's getting in," he said.
Engineers "scoured" the bridge over the weekend to see what they could discover," Gordon added.
The leaks are only one of several problems that have plagued the new eastern span.
Last March, about one third of the 96 bolts that secure earthquake shock absorbers known as shear keys to the deck of the eastern span failed when they were tightened. The shear keys are designed to prevent swaying during an earthquake.
The problem threatened to delay plans to open the new eastern span over Labor Day weekend last year but transportation officials figured out a short-term fix that enabled the span to open on time after all and a permanent fix for the problem was completed in December.
The cost of fixing the bolt problems was about $25 million.
Gordon said today that although the leaking problem is "a complex issue to solve" he doesn't think it's as serious as the bolt issue.