By Brandon Hansen / For The Chronicle
As the Washington State Department of Transportation (WSDOT) recently announced, approximately 7,500 bridges in Washington are currently open to traffic.
Although bridges open to traffic are safe to use, WSDOT has received less funding than needed to maintain and preserve these structures for several years, the department said in a news release last week.
There are 420 bridges in Lewis County, of which 49 require repair or corrective action, two are closed, 16 have received poor ratings from the U.S. Department of Transportation, and 20 have structural deficiencies.
WSDOT staff regularly inspect bridges and classify them as being in good, fair, or poor condition. Poor condition does not mean the bridge is failing, but rather that it needs more protection from WSDOT.
A good rating means there are no or only minor problems with structural elements. A fair rating means all primary structural elements are intact but may have some defects such as minor section loss, wear, cracking, spalling or scouring. A poor rating means these defects are advanced and affecting the primary structural components. Bridges with poor ratings may have weight restrictions for trucks but are not unsafe for travelers.
Bridges are inspected every two years. Bridges with concerns are inspected more frequently. Inspections may include dive teams for underwater work, aerial inspections, under-bridge inspections, and mechanical and electrical inspections for movable bridges.
Although King County has a much higher population and more bridges, it has fewer bridges with poor ratings compared to Lewis County – 22. WSDOT emphasizes that people should still feel safe crossing any open bridge and that the ratings are more reflective of the bridge’s long-term prospects.
WSDOT engineers say it’s more cost-effective to spend money on bridges earlier in their lifespan than to wait until their condition deteriorates. Bridges typically have a life expectancy of 75 years, but there are over 300 bridges in Washington that are 80 years old or older. But age is only one indicator of lifespan; the overall condition of the bridge is more important.
Preventative maintenance, such as painting steel bridges, protects them from corrosion. However, if the means to paint bridges are lacking, rust and weakening of the structure can occur, although the bridge would otherwise have survived.
WSDOT engineers say federal funding is helpful, but there is a significant backlog of work on the state’s bridges.
Bridge collapses have made national headlines as America’s infrastructure ages, including the 2013 bridge collapse over the Skagit River on Interstate 5 in northwest Washington. In Washington, there is another factor that affects the stability of bridges due to seismic activity. WSDOT has a seismic retrofit program aimed at minimizing or preventing collapses during an earthquake. More than 900 bridges in the state have gone through the program.
The state will also work to minimize scouring (the removal of soil by flowing water) around bridge piers and abutments. Streams and rivers can wash away soil, exposing and undermining a bridge foundation. In fact, scouring is the leading cause of bridge collapses across the country.
According to WSDOT, there are more than 600,000 bridges in the United States, and Washington is not the only state struggling with bridge condition problems.
