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The 2013 National Bridge Inventory listed 34,498 county- owned bridges as structurally deficient, 15 percent of the nation’s 230,690 complement of county-owned bridges.
Bridges compare favorably to all other modes of transportation on the 2013 American Society of Civil Engineers (ASCE) Report Card for America’s Infrastructure. The association’s grade for bridges has risen steadily since they were first evalu- ated in 1998 (C-), to C in 2001, 2005 and 2009 and C+ in 2013.
ASCE found, from 2004 to 2009, the number of structur- ally deficient bridges increased in urban areas by more than 650, while those in rural areas decreased by more than 7,000.
A University of Kansas study found that the number of structurally deficient bridges was much higher for steel bridges than any other material, largely due to water infiltration. All materials — steel, cement, wood — are vulnerable to the ele- ments 24 hours a day, and in regions that see a lot of snowfall, the mass amounts of salt that goes onto the bridge decks bridges accelerates their deterioration.
“Structurally deficient” means one component of a bridge — the deck, superstructure, substructure, or culvert — is rated in “poor” condition by the Department of Transportation’s (DOT) National Bridge Index rating scale. A bridge can also be classified as structurally deficient if its load carrying capacity is significantly below current design standards or if a waterway frequently floods over.
Having Closure
When the loads get heavy enough that they exceed a bridge’s posted weight limit, or bridges deterneer. “Environmental requirements add time and cost to a project.”
Contra Costa County, Calif. Engineer Julie Bueren said the construction windows for many projects are constrained because of environmental concerns. Despite a mild, dry climate, construction season for bridges over water is limited to between May and September to avoid disrupting fish migrations.
“Not that it’s a bad thing, it’s all for a positive outcome; it’s just another factor in getting things done,” she said. “We seem to have a lot of endangered species habitats in our county.”
The Contra Costa County public works department has trained maintenance personnel to recognize those habitats and do assessments.
“They know to call the fish and wildlife department and bring them in when they suspect they’ll be working in an endangered habitat,” Buren said.¢orate to the point where few vehicles can cross them, the detours can get costly.
“That’s an extra five, 10 miles out of the way, each direction,” Keierleber said. “You start adding up the fuel and time lost because of a detour and you start to see things add up, especially if someone routinely makes several trips a day.”
With a large number of the structurally deficient bridges being found in rural areas with low average daily traffic, counties face a decision whether to repair or replace a bridge or close it permanently.
REPEAT: With a large number of the structurally deficient bridges being found in rural areas with low average daily traffic, counties face a decision whether to repair or replace a bridge or close it permanently.
Curveballs
Many public works departments replacing or rehabilitat- ing bridges encounter issues that were not prioritized when the original structures went up. Environmental protection regulations have added a layer of complexity to construction projects, especially if the bridges cross waterways.
“You can’t just replace a bridge with a similar bridge,” said Roman Gavarrete, the Highland County, Fla. engineer.
The Addis Ababa Action Agenda emphasizes the importance of infrastructure investment for achieving the SDGs. It notes that both public and private investment have key roles to play in infrastructure financing, including mechanisms such as blended finance and public-private partnerships (PPPs). Nonetheless, these have become fairly controversial in debates on implementation of the SDGs, with views ranging from the essential need for them to achieve the agenda to concerns that they will be used to privatize public services and subsidize the private sector. The Addis Agenda recognizes both the potential and challenges associated with these structures. It notes that “careful consideration should be given to the appropriate structure and use of … blended finance, including PPPs, [and that projects] should share risks and reward fairly, include clear accountability mechanisms and meet social and environmental standards.” To facilitate effective use of PPPs, the Addis Agenda identifies a number of principles, which should guide PPP activity.
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