It may not be considered the most iconic or the most elegant bridge in the Bay, but one could make the case that it’s the most important.

After a five-day closure to complete construction, the Bay Bridge is reopening with a new and reportedly safer eastern span that has been in the works for about 15 years. The $6.4 billion project began in 1997 after part of the eastern span collapsed in the 1989 Loma Prieta earthquake.

Since 1936, the Bay Bridge has served as one of the main links between the East Bay and San Francisco. About 280,000 vehicles cross the Bay Bridge each day, compared with the 100,000 vehicles that traverse the Golden Gate Bridge. The bridge is also a key means of transportation for about 100 UC Berkeley students who use it to commute on a typical school day, said Beth Piatnitza, associate director of the Physical and Environmental Planning unit of UC Berkeley Capital Projects.

“The Bay Bridge (passage) is critically important to the region,” said Karen Frick, assistant director of the University of California Transportation Center. “When I think about the Bay Bridge, I think about the corridor instead of the structure itself that is served by the bridge. (Especially) for those in Berkeley, there needs to be a means to get across the bay.”

Originally estimated to cost about $1.5 billion, the new bridge ultimately came with a $6.4 billion price tag due to rising steel and construction costs, greater staffing needs than predicted and a longer construction schedule than expected, Frick said.

According to Rafael Manzanarez, who worked as a design manager for the new bridge, the new eastern span was built to last at least 150 years and be able to withstand a large-scale earthquake.

“We designed the bridge using up-to-date standards for seismic design,” Manzanarez said. “The designs have been tested in labs at UC Berkeley and UC San Diego, so we have proof that these designs do work during an earthquake.”

The foundations of the new bridge go down 350 feet and are made of steel, as opposed to the wood foundations that were beneath the old Bay Bridge, making the bridge “safer than most facilities in the Bay Area,” Manzanarez said.

However, one UC Berkeley professor is claiming that the new bridge is less stable than the the old bridge.

Professor Abolhassan Astaneh-Asl from the campus Department of Civil and Environmental Engineering told California Magazine that self-supported suspension bridges such as the new Bay Bridge are not secure, because they are not anchored to the ground as conventional suspension bridges are.

“If a single component fails, the whole thing comes down,” Astaneh-Asl told California Magazine. “When you look at this new span, there are many things that can go wrong.”

UC Berkeley professor Thomas Devine, a metallurgist from the department of materials science and engineering, similarly has doubts regarding the bridge’s components, specifically about 32 fractured bolts that were discovered in March.

According to Devine, fundamental engineering practice requires a comprehensive examination of all the factors that may have contributed to the failure of each of the bolts. Devine’s concern is that the process for identifying the cause and contributing factors was incomplete.

Devine also noted that the high-strength steel wires that connect Oakland to the suspension bridge were left ungrouted for up to 15 months, even though they generally are grouted within seven days.

“In my opinion, the procedure that was used to assess potential corrosion-related damage of the high-strength steel tendons was highly inadequate,” Devine said. “As a result, it simply is not known if the tendons were severely damaged or not.”

Even with these concerns, the new Bay Bridge opened ahead of schedule Monday night, although with significantly less fanfare than the original bridge’s opening nearly 80 years ago.

At the weeklong opening ceremonies in 1936, no one could have predicted the monumental effects the bridge would have on the Bay Area, said Martin Meeker, acting associate director of the Bancroft Library’s Regional Oral History Office.

Cities along the side of the East Bay, such as Hayward, Fremont and Walnut Creek, became viable suburbs. Downtown Oakland, once bustling with people, found itself losing business as people chose to cross the bay for shopping.

“Populations move when transit changes,” said Samuel Redman, formerly a historian from the Regional Oral History Office who worked with Meeker on the Bancroft Library’s Bay Bridge Oral History Project. “There was much worry that a lot of people would leave San Francisco after the bridge was built, but that didn’t happen.”

In the early 1930s, President Herbert Hoover approved funding for a bridge to connect the east and west sides of the San Francisco Bay. After three and a half years of construction and $77 million, the Bay Bridge was opened to the public in 1936.

“The bridge, at the time it was built, was an amazing engineering feat,” Meeker said. “On the western side, the two bridges essentially suspend each other, which had never been done before. The tunnel through Yerba Buena Island was the biggest of its type.”

On Oct. 17, 1989, the Bay Bridge experienced perhaps the most memorable moment in its history — the Loma Prieta earthquake. The 6.9-magnitude earthquake struck the Bay Area just before the start of an Oakland versus San Francisco World Series game, causing a chunk of the bridge’s eastern span to collapse and killing one person.

The collapse of the bridge prompted a retrofitting of the western span and the decision to replace the eastern span with an entirely new bridge.

Discussion about the new bridge’s design began in 1997, when officials decided they wanted a bridge that was not only seismically safe but was also aesthetically appealing, said Frick, the assistant director of the University of California Transportation Center. A single-tower suspension-bridge design was eventually chosen, despite criticism from local elected officials about its aesthetics.

The Bay Bridge is “key to the aesthetic flavor and culture of the Bay Area,” said recent UC Berkeley alumnus Jim Tang, who uses the bridge to commute to work in San Francisco from his home in Emeryville every day, in an email. “(The old bridge) blended into its surroundings and was surprisingly well juxtaposed with its western counterpart. This new bridge, in contrast, is very bright, shiny and sticks out.”

Despite these reservations, Tang believes a new Bay Bridge is long overdue.

“The Bay Area deserves an upgrade,” Tang said. “I’m looking forward to riding on it on Tuesday.”