State officials closed indefinitely one of the Longfellow Bridge's sidewalks yesterday and announced they would block spectators from the entire span on the Fourth of July, eliminating a fireworks viewing spot for thousands of pedestrians and raising already steep concerns about the bridge's integrity.
The Department of Conservation and Recreation, which manages the bridge, announced the closure yesterday after an inspection late Thursday night showed a support beam below one sidewalk needs immediate repair. Pedestrians will be detoured to the opposite sidewalk, which will remain open to normal foot traffic but closed to large crowds, such as the Fourth of July audience.
"At the end of the day, DCR certainly recognizes this is a huge event for the City of Boston, but it's also a national event," Commissioner Richard K. Sullivan Jr. said in an interview. "First and foremost we are concerned with public safety and making that a safe event."
An estimated 400,000 spectators flock to the area of the Charles River Esplanade to watch the Fourth of July fireworks and the Boston Pops concert. Roughly 10,000 to 30,000 watch from the Longfellow Bridge's sidewalks and roadway, which is closed to traffic for the event, DCR officials said. An estimated 8 million more watch from home as the Pops concert and fireworks provide a televised backdrop for the nation's July Fourth celebrations.
"It's an inconvenience, but like everything with this event, public safety really comes first and will dictate what we can do and can't do," said Rich MacDonald, producer and managing director for Boston 4 Productions, which coordinates the event. "We anticipate a greater crowd along Storrow Drive and Memorial Drive. They'll find somewhere else to go and still be able to see it."
The agency has been conducting inspections and repairs on the bridge nearly every night since August, when the collapse of a bridge in Minneapolis heightened concerns about bridge safety nationwide. A Longfellow restoration has long been advised but postponed because of budget constraints. The most recent inspection, by an independent engineering firm, found the bridge to be in serious condition. Engineers hasten to note that the bridge's many redundant beams help reinforce it and diminish the chance of a catastrophic failure.
This week, DCR received a report from an independent engineering firm, Simpson Gumpertz & Heger, which began conducting load testing on sections of the sidewalks on April 30. That inspection found the bridge is capable of supporting normal loads, but the engineers advised against allowing large crowds on the sidewalks. The segment with the deteriorating beam discovered Thursday night was not tested by the engineers.
"The fact that the state is so closely monitoring the condition of the bridge and replacing the deteriorated beams as quickly as possible is very good news and demonstrates how seriously they are taking this," said Representative Martha M. Walz, a Back Bay Democrat who also represents Cambridge. "They are not taking any chances. And that is very comforting to me as a frequent pedestrian on that bridge."
The sidewalks drew particular concern because of their deterioration and their design: They are cantilevered off the sides of the bridge. The sidewalk on the side of the bridge that carries traffic from Boston to Cambridge was reinforced in the late 1950s. The sidewalk on the opposite side, where the deteriorating beam was found, has not been reinforced.
In a draft letter provided by DCR, the engineers stated that the load tests demonstrated that the sidewalks could handle about half the weight recommended under standards issued by the American Association of State Highway and Transportation Officials. Though the capacity could be higher, the engineers said they did not currently have the data to justify a higher rating.
DCR has spent more than $1 million on inspections and $4.5 million on repairs to the bridge since August. Crews have replaced more than 200 beams and repaired more than 180 railing brackets. The agency has also restricted heavy truck traffic in the lanes closest to the MBTA line that runs down its center.
Repairs are expected to be completed in the fall, and the bridge will be examined again for its load rating - to determine whether traffic needs to be further limited or the existing lane restriction can be lifted.
A more intensive reconstruction of the bridge is planned to begin in 2010 or 2011.
Besides pedestrians and bicyclists, roughly 135,000 commuters use the Longfellow Bridge each day in cars or on the trains that cross it. The Red Line will run during the Fourth of July celebrations, said T spokesman Joe Pesaturo.
Stephanie Ebbert can be reached at email@example.com.