U.S. aging bridges in critical condition
$17 billion, both in 2006 dollars.
State and local governments pay the costs themselves, then apply for reimbursement from the federal Highway Trust Fund. The fund, according to the Congressional Budget office (CBO), is anticipated to run dry in October. Revenues for the trust fund are derived from gasoline taxes, and have been declining over the past three years as drivers buy more fuel efficient cars and drive less because of higher gas prices.
Congress is at a standstill with regard to replenishing the funds. The Senate passed a 2-year $109 billion highway package which would raise the funds by recalculating how pension fund liabilities and contributions are assessed.
House speaker John Boehner has introduced a 5-year plan which would use royalties from oil and gas drilling, but has met with resistance from his own party members.
A third funding possibility is the creation of an Infrastructure Bank. First proposed in 2007 by Senators Chris Dodd (D-Connecticut) and Chuck Hagel (R-Nebraska).
President Obama has raised the idea as well, calling for the bank to be funded by $60 billion in borrowed federal funds, while leveraging up to $500 billion in private investment.
These funds, however, would be available for other transportation projects such as high-speed rail, energy efficiency, and clean energy, and would not be limited to bridge, tunnel, and road projects.
The bank would supplement other federal funding sources, such as the Highway Trust Fund, and State Revolving Funds.
Whatever legislation finally emerges for infrastructure support will likely look much different from what has been discussed so far.
There is also the problem of traffic handling during bridge closures during repairs. There is, however, a solution to this difficulty, that of the instant bridge.
The New York Times reports that Massachusetts has been leading the way in bridge replacement by using what are termed “accelerated bridge construction” techniques, a collection of different techniques that cut replacement time by months, if not years.
Boston officials realized that the River Bridge required replacement, and understood that the job would take up to two years, all that time causing traffic rerouting and delays.
Using the accelerated construction technique, the bridge was replaced in a weekend.
The technique involves pre-constructing the bridge nearby, then placing it on a set of trailers with high supports that adjust to keep the bridge level. The 400-ton bridge was then moved carefully into position and lowered onto its abutments.
Massachusetts has enthusiastically embraced the new techniques, replacing fourteen bridges on Interstate 93 in only ten weekends.
Similar techniques are being used around the United States, with the most dramatic example being San Francisco’s Golden Gate Bridge, a huge span that cannot be closed.
The bridge is getting 300 feet of new prefabricated roadway, one 25-foot section at a time. By using the prefabricated techniques, only one lane of the roadway needs to be closed, while workers tear out and replace a section of decking. At this point, the task is already one-third complete, without having to close the bridge.
The concepts employed in the various accelerated techniques allow for necessary alterations to be made concurrently, such as raising the clearance height of the bridge to accommodate double-decker trains.
