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Bridge Inspection

Lewis and Clark bridge inspection
Inspecting the superstructure of the Lewis
and Clark Bridge, 340 feet above the
Columbia River.

The safety of bridge structures in Washington State is ensured through a meticulous inspection system, incorporating state and local agency inspection contributions. The condition of all bridge decks, superstructures and substructures are rated based on these inspections. There are roughly 7,000 bridges on the state, city and county road systems and most are inspected every two years.


  • In Fiscal Year 2015, WSDOT performed 2,106 bridge inspections, including 238 inspections that used an under-bridge-inspection-truck (UBIT) to allow inspectors to access every part of the bridge.
  • WSDOT’s Bridge office has 44 trained engineers and technicians to perform bridge inspections. These include specialized teams like the dive team that performs work under water and the mechanical and electrical inspectors that inspect moveable parts of a bridge.
  • WSDOT is nationally known for its high level of structural technical expertise.
  • The number of Bridge Inspectors has grown since 1998 to match the increasing inventory of state owned bridges.
  • Local agencies, which follow the same federal guidance for inspections, performed 2,412 bridge inspections in Fiscal Year 2015. Even though most local governments inspect their own bridges, WSDOT conducts field reviews and provides training and technical assistance to Washington cities and counties for inspecting bridges on local roads.

Inspection Schedules

Inspecting the Alaskan Way Viaduct
WSDOT’s Bridge Preservation office is responsible for keeping bridge inspections on schedule; however logistical challenges can make it difficult. Challenges include:

  • Reduced work windows because of high traffic demands thus limiting inspectors’ access to key sections of bridges.
  • More stringent regulatory obligations also require adjustments to inspection schedules to accommodate nesting periods of protected migratory bird species.
  • Inspection schedules have flexibility built to accommodate unplanned inspections in the case of a bridge suffering unexpected damage.
  • New FHWA inspection performance measures require a bridge to be inspected as close as possible to the date plus the inspection cycle (typically 2 years).