|Research showing what a sizable earthquake could do to Oregon’s bridges is included for the first time in the latest bridge condition report from the Oregon Department of Transportation – and it points the way to improving bridges statewide. The 2016 Bridge Condition Report (PDF), using research findings reported annually to the Federal Highway Administration, shows that almost three-quarters of the state’s bridges were built before modern seismic design specifications. Though investments in the past decade have shored up more than 270 bridges across the state, hundreds more remain vulnerable.
The 2016 report estimates that addressing anticipated preservation and backlog of replacement projects for the next 20 years would cost $435 million per year. Simply to maintain Oregon’s aging bridges in their current condition, ODOT would need to spend an estimated $240 million annually – approximately $155 million in additional funding for state highway bridges.
More than half of the bridges in the state’s inventory were built prior to 1970, and 57 percent will reach the end of their design lives by 2020. (See Figure 2, from the report’s executive summary.) With increased maintenance and repair, most of ODOT’s bridges can have a longer service life – but this does not hold true for a large number of bridges built during the Interstate-era of the 1950s and 1960s that are still in use today. Many of those bridges were designed for loads smaller than allowed by state law since the mid-1980s, and preserving them is not cost-effective.
Over the next two decades, ODOT expects approximately 900 state highway bridges to require repair or replacement, but limited funding will allow us to address only about 300 of those. Deferred maintenance will eventually require the bridges ODOT can’t repair to be weight restricted, meaning certain trucks have to take longer routes or break up heavy loads onto multiple trucks, increasing time and costs. These impacts are extremely harmful to Oregon as a heavily trade-dependent state.
The 2016 Bridge Condition Report is available online. In addition to seismic data, it includes tunnel evaluations, steel bridge paint conditions and case studies for the first time.