10 Years After the I-35 Bridge Collapse: What’s Changed With the Nation’s Bridges?


It’s been 10 years since a bridge carrying Interstate 35 West over the Mississippi River in downtown Minneapolis collapsed, killing 13 people and injuring 145 more. The eight-lane bridge was Minnesota’s third busiest, carrying 140,000 people a day.  Its failure opened many people’s eyes to the danger of taking our infrastructure for granted and led to leaders at all levels of government to take a closer look at how the country was maintaining its aging infrastructure. The I-35 bridge was structurally deficient, meaning that it required significant maintenance, rehabilitation, or replacement. It was one of over 74,000 bridges that were rated structurally deficient in 2007 or 12.3% of total bridges in the U.S. However, the National Transportation Safety Board later concluded that is was a design flaw that caused the bridge to fail. The bridge’s gusset plates, which connect the steel beams, were too thin and had been further stressed by the presence of nearly 300 tons of construction equipment and materials that had been stored on the bridge deck for ongoing repair work.

The past 10 years have garnered some positive changes in our nation’s bridges. Despite the fact it was a design flaw and not deferred maintenance that led to the failure of I-35, the collapse led to a concerted effort at all levels of government to improve bridge conditions in the U.S. On September 20, 2007, not two months after the collapse and before the causes of the failure were clear, the Senate Environment and Public Works Committee held a hearing on “Structurally Deficient Bridges in the United States,” which included testimony from Andy Herrmann on behalf of ASCE. ASCE’s testimony pointed out that increased federal funding was needed for bridge rehabilitation. In recent years more money has been spent on bridges. The federal government estimates that $17.5 billion was spent on bridge capital projects in 2012, with $6 billion from the federal government and $11.5 billion from state and local sources. This is a substantial increase from the $11.5 billion that was spent on bridges in 2006. However, investment in our nation’s bridges remains insufficient. The most recent federal estimate puts the backlog of rehabilitation projects for the nation’s bridges at $123 billion. In 2016, 9.1% or approximately 56,000 of the country’s bridges were structurally deficient. This is a strong decrease from the 74,000 or 12.3% in 2007, but still far too many. The nation’s bridges are also getting older, with the average bridge now 43 years old and 39% over 50 years old. Most of the nation’s bridges were designed for a lifespan of 50 years, so an increasing number of bridges will soon need major rehabilitation or retirement.

While there have been some positives over the past decade, the need for investment remains. One of the major challenges facing the nation’s bridges is uncertainty regarding its primary federal funding source, the Highway Trust Fund (HTF). The HTF is primarily funded through the federal motor fuels tax (aka the ‘gas tax’) of 18.4 cents per gallon on gasoline and 24.4 cents per gallon on diesel. At the federal level, the gas tax has not been raised since 1993 and inflation has reduced its purchasing power by 40%. To make up for the dwindling value of the gas tax, Congress has transferred $140 billion from the General Fund to the HTF since 2008, including $70 billion in 2015’s FAST Act. Unless Congress takes action to fix the HTF and provide it with a sustainable and adequate funding source, they will again have to look elsewhere to find billions to fully fund the next surface transportation bill when the FAST Act expires in December 2020. With Congress talking about doing a broad tax reform package, many see an opportunity to fix the HTF. In June, 253 House members (including a majority of both Republicans and Democrats) sent a letter to the leadership of the Ways & Means Committee asking that a long-term fix for the HTF be included in their tax reform efforts. ASCE’s 2017 Infrastructure Report Card graded our nation’s bridges a ‘C+.’ Policymakers need to take several steps raise the grade and improve our nation’s bridges, starting with fixing the trust fund.

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