Greenway pedestrian bridge proposed

Boston Museum says walkway would span highway ramps

Executives of the Boston Museum, one of the visitor facilities planned for the Rose Fitzgerald Kennedy Greenway, are proposing to build a curvilinear, cable-stayed pedestrian bridge that would span one of the most forbidding of the Big Dig blocks.

The Boston Museum was originally supposed to build on a block built over the underground highway just north of Faneuil Hall Marketplace. But that block is disfigured by two traffic ramps, and museum executives said they determined it would cost $50 million more to build over ramps than on a vacant piece of land.

"It was so expensive that we couldn't do it," said Frank Keefe, the president of the group planning the facility.

So the Museum Project - intended to educate residents and visitors about history in Greater Boston, particularly the relatively neglected last 200 years - hopes to build instead on a nearby block of land, between Hanover and North streets, just off the main strip of new downtown parks.

Fund-raising, design, engineering, and construction of the five-story, 100,000-square-foot museum, which has been scaled back in size by about one-third, will take at least five years, Keefe acknowledged.

But the project is still obligated to solve the pedestrian access problem on the ramps parcel where the museum was initially planned, and Keefe said he hopes to win city approval for a steel span, which would link other blocks of the Greenway, as early as this year.

"It's a suspension bridge" over the ramps, he said. "A simple, elegant solution."

Keefe said Massachusetts Turnpike and city officials have reacted favorably so far, and the bridge could be completed well before the museum is done.

Mayor Thomas M. Menino said he'd seen the plan but still has questions. "Do they have the money to build it and maintain it?" he asked.

Thomas C. Palmer Jr. can be reached at tpalmer@globe.com.