|SR20 Deception Pass Bridge |
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.
USDOT’s Federal Highway Administration (FHWA) requires all public bridge owners (state, city, and county ) to inspect and their bridges and report information including bridge condition ratings as part of their requirements in the National Bridge Inventory Standards (NBIS).
Important aspects of the NBIS were:
SR6 Wiliapa River bridge
All states must perform periodic inspections of bridges greater than 20 feet in span on at least a biennial basis.
Data collection was standardized and must be reported to FHWA.
Qualifications for inspection personnel were defined.
Training programs were developed and implemented.
The Bridge Replacement Program (BRP) was established to provide funding for bridge replacement on the system.
Structurally deficient means that a bridge requires repair or replacement of a certain component. This may include cracked or spalled concrete, the bridge deck, the support structure, or the entire bridge itself. If the condition is such that it no longer is able to carry its intended traffic loads it may be weight restricted. Being structurally deficient does not imply that the bridge is in danger of collapse or unsafe to the traveling public. If a bridge is open then it is considered safe.
Interstate 82 Columbia River bridge near Umatilla
A bridge is classified as “Structurally Deficient” when bridge inspectors give either the superstructure, deck, and/or substructure a rating of four or less on a scale of zero to nine. WSDOT’s poor condition category uses the same data, criteria, and rating scale.
WSDOT has 137 state owned bridges that are classified as structurally deficient as of Jan. 2015. A list of these bridges is available in pdf and web page and map format.
Functional obsolescence is assessed by comparing the existing design of each bridge to current standards.
SR6 bridge over an abandoned railroad near Raymond
A bridge can be categorized functionally obsolete a number of ways including: substandard bridge widths, low vertical clearance that can lead to repeated damage from over height trucks, load-carrying capacity, or flood potential.
There are 866 WSDOT bridges that are rated “Functionally Obsolete”
Good, Fair, Poor Condition Rating
Good: A range from no problems to some minor deterioration of structural elements.
Fair: All primary structural elements are sound but may have deficiencies such as minor section loss, deterioration, cracking, spalling, or scour.
Poor: Advanced deficiencies such as section loss, deterioration, cracking, spalling, scour, or seriously affected primary structural components. Bridges rated in poor condition may be posted with truck weight restrictions.
A summary of the WSDOT bridge network conditions is available in the 2014 Bridge Annual Report in the Gray notebook.