Over the last two weekends of October, highway crews will replace two bridges over the Baltimore-Washington Parkway that serve the airport and hotel district by rolling the old ones out and rolling the new ones in.
The "bridge on wheels" swap, used in other states but making its debut in Maryland, saves time and money, reduces traffic disruptions and cuts the potential for work-zone accidents, State Highway Administration officials said.
"We looked at traditional methods and with the traffic level there, closing the bridges wasn't an option for an extended period," said Jeff Robert, a state project engineer. "If ever there was a bridge to try this with, this is it."
Replacing the aging West Nursery Road spans, built in 1948, has been on the SHA books for about six years. As the $6 million project moved up in priority, state engineers began looking for ways to expedite what was expected to be a two-year project.
Parkway traffic in that area is about 121,000 vehicles a day; West Nursery Road handles about 22,000 vehicles a day. The roads are critical for the two dozen hotels that serve Baltimore-Washington International Thurgood Marshall Airport and major employers such as Northrop Grumman, which has 8,000 workers.
"You're talking about a major artery for businesses and visitors. It is a gateway to BWI," said Linda Greene, executive director of the 200-member BWI Business Partnership. "It's a great relief that they can do it that quickly and give people that much less to worry about."
SHA staff have met several times with hotel managers, community associations, airport officials and business leaders to walk through the logistics and devise a campaign to warn motorists and tourists to use other routes those weekends.
Hotels will be handing out directions and signs will alert motorists to alternate routes, such as Interstate 95, I-97 and Route 29.
"We're trying to blitz everybody," said James Folden, SHA District 5 assistant engineer for construction. "We have plenty of north-south routes and that's a plus."
Since May, crews have been cultivating a bridge farm in the parkway median. Steel girders and concrete slabs have grown into two, 70-foot-long spans weighing 500 tons each. They perch on a latticework of support beams about 19 feet in the air — the same height as the West Nursery crossing.
Other crews have been stripping away all but the essentials from the old bridges and conducting stress tests to ensure they can withstand the move intact.
This week, a team of expert heavy lifters from Pearland, Texas-based Fagioli Inc. are assembling the centipede-like mechanical behemoth that makes the entire move possible: a 36-axle flatbed with wheels that operate independently.
"Each wheel can turn 90 degrees so we could spin the bridge around," Robert said.
On the evening of Friday, Oct. 19, West Nursery Road will close for the duration of the project and the parkway will close overnight. The Self-Propelled Modular Transport will maneuver under the old bridge on the parkway's northbound side, the foot-long bolts anchoring the bridge will be released and the transport will piggyback the 300-ton span up the road at a 4 mile-per-hour crawl and place it on a cradle in the median.
The parkway will reopen Saturday morning, then close again that night, so the transport can haul the new bridge into place.
On the weekend of Oct. 26, the crews will repeat the process on the parkway's southbound side.
The hold-your-breath moments for engineers will come as the transport slides the old bridge out and when it slides in the new span. There's little room for error and no give in the steel.
"We'll have extra men and equipment in the event of a breakdown. We'll have mechanics on site. We've done extra planning and we have experienced movers," Robert said. "But there is a learning curve. What we learn the first night we'll apply to the next three."
Robert said state engineers compute "road user cost" to determine the impact of delays and detours on motorists during a project. For this project the cost was $2,000 a day.
"So if you can do the project in nine months versus two years, that's really a savings," he said. "And the shorter construction period means more safety and fewer accidents in the construction zone."
SHA scheduled the work for the only two weekends between late September and early November without a Ravens home game. Yet even with that potential traffic jam averted, engineers hope drivers will avoid the area so that people who need access have it.
But for the sidewalk superintendents or the merely curious who can't stand the thought of a bridge swap happening without an audience, fear not. The SHA website will stream real-time video of the event.
West Nursery Road: Closing the evening of Friday, Oct. 19, reopening when project is complete.
Baltimore-Washington Parkway: Closing the evening of Friday, Oct. 19, reopening the next morning, then closing again Saturday evening. The next weekend, the same schedule will be repeated, beginning the evening of Friday, Oct. 26.Copyright © 2015, The Baltimore Sun