US 395 over Farwell Rd in Spokane County
Washington bridges are critical transportation links whether you travel on a two-lane overpass or a unique floating bridge that carries thousands of vehicles each day. There are roughly 7,300 bridges (61.8M SF) on the state, City and county road systems that are over 20 feet in length and carry vehicular traffic. WSDOT is responsible for managing an inventory
of nearly 3,500 of these critical transportation links.
The safety of bridge structures in Washington State is ensured through a meticulous inspection system. All public bridge owners, such as WSDOT, Counties and Cities, follow the same bridge inspection procedures. The condition rating of all bridge decks, superstructures and substructures and other elements based on these inspections.
SR16 Tacoma Narrows bridge in between Tacoma and Gig Harbor
There has been significant national discussion on bridge safety and structural classification ratings following the span collapse on the I-5 Skagit River bridge in 2013 and the I-35W bridge in Minnesota in 2007.
Nationally, most bridges are inspected every two years. Some bridges with structural issues are inspected more frequently. The Alaskan Way Viaduct in Seattle, for example, is inspected thoroughly every six months. A select group of WSDOT owned concrete bridges in good condition are allowed to be inspected on a 4 year cycle.
The Federal Highway Administration (FHWA) requires all state transportation agencies to report state, city, and county Structurally Deficient
and Functionally Obsolete bridge ratings
each year. These ratings are used to help determine federal bridge replacement and rehabilitation funding levels to the states.
Bridge Asset Management
Interstate 5 Nisqually River bridges near Olympia
WSDOT’s Bridge Preservation Program includes a combination of cost effective actions, such as bridge repairs and rehabilitation, steel bridge painting, concrete deck rehabilitation, and bridge replacement. The objective of Bridge Asset Management is to use cost effective strategies and actions to maximize the useful life of bridges.
Each biennium, WSDOT Staff review the condition of bridges and develop a list of needs for a 10 year period. The needs are prioritized in order to select the best projects with the available funding. More information is available in the Bridge Annual Report in the Gray notebook.
Interstate 5 Beacon-Holgate UC in Seattle (Nisqually EQ)
There are a variety of risks related to bridges in Washington that have the potential to cause catastrophic results.
The two primary natural risks are Earthquakes and Scour of bridge foundations from flooding. Bridge s are also at risk of damaged from over height truck or marine vessel impact s and from fires.
A study performed by the Federal Emergency Management Agency in 2001 found that Washington has the second highest risk for economic loss in the nation due to earthquakes. California has the highest risk. The largest earthquakes in recent history in Washington occurred in 1949, 1965 and 2001 and killed 15 people. The most recent Nisqually earthquake killed one, injured 320 and caused over $2 billion dollars worth of damage.
WSDOT has addressed a number of bridges in its seismic retrofit program
and scour program with clear goals of minimizing loss of life and disruption of commerce, as well as reducing the risks of complete bridge collapse.
In July 2012, the Moving Ahead for Progress in the 21st Century Act (MAP-21) became federal law, which is specific to transportation. The cornerstone of this law is the transition to a performance and outcome-based federal aid program.
The primary objectives of MAP-21 are to increase the transparency and accountability of states for their investment of taxpayer dollars into transportation infrastructure and services nationwide, and to ensure that states invest money in transportation projects that collectively make progress toward the achievement of national goals. The new rules will require reporting on the condition of the bridge network over time.