On Aug. 1, 2007, during evening rush hour in Minneapolis, an eight-lane bridge collapsed, plunging 111 vehicles into the Mississippi River. The bridge fell 108 feet into the 15-foot-deep water, killing 13 people and injuring 145.
An investigation by the National Transportation Safety Board determined that 24 gusset plates—sheets of steel used to connect bridge beams to columns—were about half the thickness they should have been. Deficiencies were not detected in the initial review process and the plates were incorporated into the bridge’s construction, which contributed to the collapse.
While bridges are just one aspect of America’s aging infrastructure, it has been well publicized that they are a top priority and in need of a major fix nationwide. In fact, bridges received only a C+ rating in the American Society of Civil Engineers’ “2013 Report Card for America’s Infrastructure.” The ASCE report noted that the average age of the country’s 607,380 bridges is now 42 years.
“Right now, 11% of our bridges across the country are rated structurally deficient and another 13% are considered functionally obsolete,” said Andrew W. Herrmann, 2012 president of ASCE and principal with Hardesty & Hanover LLP, an infrastructure engineering firm. “This means they were designed to an older standard, so they may not have the same lane widths or turning radius or may have been designed to carry lesser loads.”
Deterioration of the nation’s infrastructure jeopardizes public safety, threatens quality of life, and drains the U.S. economy. “If they have to start closing down, restricting or putting mileage postings on bridges, the economy will be affected,” said Herrmann, who served on the advisory council for the 2003, 2005 and 2013 report cards and chaired the council for the 2009 edition. “Bridges are the most pressing need in the infrastructure overall. You can have all the roads and highways you want, but if you don’t have the bridges to cross the rivers and intersections, it slows everything down.”
He observed that, from a bridge engineer’s perspective, investments need to be made to keep bridges in good repair. The Federal Highway Administration (FHWA) estimates that it needs $20.5 billion annually to eliminate the nation’s backlog of bridge repairs by 2028, but only $12.8 billion has been budgeted. The challenge, then, for federal, state and local governments is to increase investments in bridges by $8 billion annually.
Because of the federal government’s involvement, bridge collapses are kept to a minimum. Federal law requires that every bridge in the country be inspected at least every two years. Engineers who inspect and find something wrong have a few options: they can do an emergency repair, reduce loads or reduce the speed of vehicles traveling over it. A bridge that needs to be watched may warrant more frequent inspections, even every few months, to assure public safety. A serious issue could be grounds for closure.
In the case of the Minneapolis bridge collapse, several factors may have caused the failure. “It had to do with the fact that the bridge was under construction, there was deterioration in the gusset plates and the construction loading on the bridge wasn’t symmetrical. All these things led to the unfortunate failure of the bridge,” Herrmann said.
High Cost of Ignoring the Problem
Deteriorating bridges can cost businesses and individuals more in the long run because of added inefficiencies. “It comes down to funding and the will to do something for our bridges. There is also an understanding that is needed by the public and our legislators that improving the infrastructure actually pays back,” Herrmann said.
Another report by ASCE, “Failure to Act: The Impact of Current Infrastructure Investment on American’s Economic Future,” found that the cascading impact of putting off repairs affects the entire economy. “The Failure to Act report on transportation shows that it will actually cost us more if we do nothing. It truly is an investment. You can get two to four times payback on that, because costs will go up for families and businesses, and jobs will be lost,” Herrmann said.
The report concluded that, between 2013 and 2020, there will be an investment gap of about $846 billion in surface transportation.
Al Gorski, chief risk officer for the Orange County, Calif. Transportation Authority (OCTA) noted that Orange County has a number of bridges that span freeways, waterways and railways. “Bridges are just one element of the infrastructure, so one story can’t be told without the other,” he said. “We’re already $300 billion in arrears just maintaining what we have.” Gorski explained that much of the money is spent staying even with the increasing numbers of drivers on the road. “The issue is, how long can you tread water? Getting ahead of this would take more money than anyone could raise.”
In California, 58% of roadways—which include bridges—require rehabilitation or pavement maintenance, 20% need major maintenance or preventative work and 6% need to be replaced. Traffic volume is also growing 10 times faster than lane miles, according to the California Transportation Commission.
Effect of Decreasing Fuel Revenue
Historically, gas taxes have funded a large portion of the country’s transportation infrastructure, but this revenue has declined. “The fact that we’re much more fuel efficient with our cars means people are buying less gas overall, causing a decrease in tax revenues,” Gorski said. According to OCTA, the average vehicle gets 25 miles per gallon of gas and the average gas tax for one gallon is 37 cents, meaning that drivers pay 37 cents for every 25 miles travelled. The problem is that the actual cost of building and maintaining 25 miles of road is $1.19.
Herrmann pointed out that the gas tax hasn’t been increased since about 1993. “We’re still living on 1993 dollars in 2013. Could you live on your 1993 salary in 2013?” he asked.
One solution Orange County has been considering is adding lanes to the I-405 Freeway and charging a toll on express lanes. The OCTA board voted on Dec. 9 to construct a general purpose lane in each direction at a cost of $1.3 billion, but it decided against charging the controversial toll.
In California and across the country, experts are studying new sources of funding and alternative transportation modes for people and goods. The current model, however, is based on continuous building of roads for a growing number of cars, “and at some point we will run out of space,” Gorski said.
To help, the city of Los Angeles—notorious for traffic tie-ups—added a significant number of light rails. More people using alternative transportation such as ride share decrease stress on the infrastructure, he said.
States Step up Creative Funding
States are increasingly going to have to search for new funding methods, Gorski said. One alternative is something like Measure M, a local provision for Orange County that increases the sales tax a half-cent, with proceeds going to transportation. Another option could be a tax on miles driven instead of a gas tax.
“All cars that were manufactured after a certain date have a black box that records the vehicle miles on every car,” he said, adding that insurers are already considering getting an annual readout of miles from the black box to help set individualized auto rates.
Oregon did a test on usage with a black box or transponder measuring and charging per miles driven rather than paying at the pump. “This is much fairer because, if you look across the board, everybody is using the roads and bridges, so why shouldn’t they share by how many miles they drive?” Herrmann asked. “It’s not in play right now, but it’s one of the options for raising funds for transportation. This would also help to regulate traffic.”
A number of other states, including Maryland, Wyoming and Vermont, are financing improvement of their bridges with added gasoline tax, and other creative measures. For example, Virginia passed a bill in May 2013 that changes the tax structure by raising the sales tax and wholesale fuel tax and lowering the retail price of gas taxed at the pump. They have a six-year plan based on that increase.
Maintaining the Bridges We Have
States and municipalities are also increasing efforts to protect their bridges. “We are absolutely seeing more and more municipalities engage in proactive measures,” said Richard Grant, principal at Russell Corrosion Consultants in Columbia, Md. “We’ve assessed infrastructures built in the early 1900s and sometimes the late 1800s. The design life for these structures was not 150 years—and some have already exceeded that. We’re in catch-up mode now.”
Areas of the country that are most proactive about protecting their bridges from corrosion are older cities and those located on coastlines. “New York, Boston, Washington, D.C., Philadelphia and San Francisco—the larger cities with aging infrastructure —are paying attention to corrosion,” he said. These cities’ corrosion rates are accelerated due to high chloride concentrations in soils because as coastline cities, they have higher exposure to salt. Bridge corrosion is even more prevalent in the Northeast and the Mid-Atlantic, where roads are also salted for ice and snow.
Corrosion of metals is a major issue with aging bridges, Grant said. “Corrosion is a natural process that can’t be stopped and anything that is metal will eventually corrode. We try to assess how quickly and to what effect, and what designs we can come up with to help mitigate it.”
Many of the materials on structures, such as steel, ductile iron and cast iron, have been around for a long time. To help preserve those structures, determinations are made about protective coatings that can be applied, including paint. “There are different coatings for different environments, whether marine or desert,” Grant explained.
A technology used to protect a bridge’s metal structure from corrosion is called cathodic protection. In this process, a more corrosive material, such as magnesium, is connected to the iron or steel on a bridge. In essence, he explained, “We’re connecting materials to a pipe or a bridge structure that will corrode instead of the actual structure corroding. We’re using the natural state of corrosion. We know it’s going to occur, so we’re making something else corrode besides the structure itself.”
Because those metals corrode faster than iron or steel, they will corrode faster than the structure being protected, Grant said, “so we can design something to be put in place for a set period of time, whether the design life is 20, 50 or 100 years.”
Infrastructure Risk Management
When working with municipalities, power utilities and publicly-traded utilities, the federal government and private industries, Grant said, “we go with the risk managers, look at their infrastructures and help them prioritize, because they have to have a plan in place.” Risk managers know the age of their infrastructure, the issues they are having and their budget constraints and are looking for help.
Grant noted that organizations dealing with aging infrastructures fall into three categories of awareness. In the first are owners who don’t know the condition of their assets. “They are just trying to deal within their budget constraints as they have always done,” he said.
The second level consists of those taking a reactive approach because something has failed. “There could be loss of life or just a water leak and they want to deal with it on a project-by-project reactive basis,” he explained.
Those at the third level want to know how to implement solutions across their municipality or utility so they can address issues on a program level. In the case of an aging bridge, for example, they would look at reviews of materials, corrosion surveys and operations and maintenance issues.
But while there are more risk managers interested in taking an overall, program approach to managing aging infrastructure, they are in the minority, Grant said.
Prioritizing Repairs
Regardless of funding issues, bridge maintenance needs to be done annually with regular, systematic programs, so ongoing risk management is especially important, Grant said. When funds are tight, the reality is that departments of transportation have to make hard choices between whether to repair bridges or defer maintenance. Unfortunately, by necessity, the work often gets put off. This only exacerbates the problem.
“The longer you defer it, the more costly it is to repair,” Grant explained. “Think about your roof. If you lose a few shingles and you repair them right away that’s a small charge. But if you don’t, those couple of shingles will turn into a lot of shingles and soon you have to repair your whole roof—and that’s a lot of dollars. This is a huge risk management issue. It’s a disaster in the making if they don’t get on top of it.”