Engineers hired to examine problems with concrete work on the Bay Bridge have discovered apparently unrelated cracking on the underside that could add millions to the cost of repairs and extend the time it takes to restore the westbound span.
Maryland Transportation Secretary Robert L. Flanagan disclosed the problem at a news conference yesterday at the department's headquarters near Baltimore-Washington International Airport. He said the newly found cracks do not pose a threat to those who use the bridge.
Flanagan also emphasized that even if the damage is extensive, the newly discovered problem is unlikely to result in a repeat of the nightmarish traffic tie-ups that bedeviled motorists this fall when the westbound bridge was reduced to one lane for most of the day.
That is because the solution for the new problem -- if it turns out to be serious -- would likely involve replacing parts of the bridge deck with prefabricated sections rather than pouring new concrete on site, engineers said.
Engineers said the work with factory-made sections could be done almost entirely at night and outside peak travel seasons.
"Every effort will be made to minimize the impact on motorists," the secretary said. He added, however, that the May 2006 completion date might have to be extended.
Such work could add to the expense of a project that is expected to exceed its $60 million budget because of the earlier problem of surface cracking.
Flanagan said the discovery was made by members of an overview team led by Thomas Deen, a civil engineer with extensive experience in bridge projects. The secretary said that while it is not standard practice to do test borings from the underside of a bridge, the team took the unusual step out of caution.
Deen said the problem involves about 6,000 feet of the 21,000-foot westbound bridge that are covered by a relatively thin 6 1/2 -inch concrete overlay. Some other parts of the bridge still need repairs because of the surface cracks first reported in September but don't have damage to the undersurface.
Deen said that in the worst case, the entire 6,000-foot stretch of deck near the middle of the bridge would have to be replaced -- not just resurfaced. He added, however, that the samples they took from the underside might not have been representative. In that case, he said, the sites with deteriorated concrete could possibly be patched.
If a full deck replacement is necessary in the 6,000-foot stretch, it could mean that sections of the left lane where newly laid concrete was replaced this fall will have to be scraped up a second time, Deen said. Though the new concrete surface appears to have bonded better than the first, it would have to be removed to replace the undersurface.
Flanagan and his engineers said they hope to know by March how extensive a repair will be necessary.
Inspectors discovered the undersurface problem this weekend and reported it to the engineering panel Monday, Flanagan said. He said some loose debris fell from the area of the test borings, and that the Maryland Transportation Authority police sent a patrol boat to warn boaters to stay out of the area.
The prompt announcement of the new problem -- even before its full extent is known -- was in stark contrast to the Maryland Transportation Authority's handling in September of the earlier discovery of cracking in newly poured surface concrete. Then, after knowing about the cracks for months, the agency failed to disclose the problems to the public even as it was announcing stepped-up lane closings.
Flanagan would later tell lawmakers that he didn't know the extent of the problem until he was asked about it by a reporter. Within weeks, Thomas L. Osborne Sr. was pushed out as the authority's chief executive and later replaced by Trent M. Kittleman, a close Flanagan ally.
The secretary declined to give any estimates of the cost of repairing the problems on the bridge's undersurface. At the time the first round of cracking problems was disclosed, officials estimated the cost of repairs at $7 million but later conceded it would probably be more.
The surface cracking problems led Flanagan to adopt a drastic schedule of lane closings in October and November to finish the left lane resurfacing by September. The closings led to huge backups and waits of more than an hour to get onto the bridge.
Motorists have enjoyed the use of all of the Bay Bridge's lanes since the week before Thanksgiving, but the respite will end Jan. 3 when the center lane of the westbound span closes for work on the stretches not affected by the recently discovered damage.
The undersurface problem could go back to the original design of the bridge, which opened in 1973. It also could raise questions about the decision of the authority's engineers to rely solely on test borings from the surface to assess the state of the deck before the specifications were drawn for the rehabilitation project, which began in January 2001.
Flanagan and the engineers declined to second-guess the decisions of the past.
Mary Lou Ralls, an engineer on the overview team, said that if a bay crossing were being built today, it probably would be designed with about an 8-inch overlay. But the engineers said the bridge's design wasn't unusual for its era.
Flanagan said experts told him that engineers would not normally bore into the undersurface of the bridge unless there was a compelling reason to suspect there was a problem.
"What changed is, because we brought this task force of experts in and they were so diligent, they discovered something that hadn't been discovered before," he said.