The Bridges of King County

Saturday, May 25, 2013

The Alvord T Bridge will close June 5, 2013
(date moved up because of safety concerns)
Photo courtesy King County


King County Bridges — Information provided by the King County Road Services Division

  • Total number of steel trusses - 11
  • Number of steel through trusses (same type of bridge as Skagit/I-5 bridge) - 8
  • Average Sufficiency Rating of all King County steel trusses – 63.0
  • 4 of the 11 trusses have a Sufficiency Rating less than 50, meaning they are eligible for Federal Bridge Replacement funds
  • Total number of wholly or half-owned King County bridges - 180
  • Average Sufficiency Rating of all county bridges (2012) – 71.1
  • Average age of entire King County bridge inventory = 46 years
  • In the past 10 years, 32 King County bridges have been replaced.
  • All bridges have been inspected within the past two years, except for Alvord T which is on a 12 month cycle
  • For entire King County bridge inventory, 19 bridges are Structurally Deficient1
  • For entire King County bridge inventory, 35 bridges are Functionally Obsolete2
  • Of the 11 steel trusses, 3 are Structurally Deficient - Foss River, Alvord T (closing June 28, 2013), and Miller River (closed).
  • Of the 11 steel trusses, 2 are Functionally Obsolete - Green River Gorge and Stossel.

1 – Bridges are considered structurally deficient if they have been restricted to light vehicles, closed to traffic or require rehabilitation. Structurally deficient means there are elements of the bridge that need to be monitored and/or repaired. The fact that a bridge is "structurally deficient" does not imply that it is likely to collapse or that it is unsafe. It means the bridge must be monitored, inspected and maintained.

2 – A functionally obsolete bridge is one that was built to standards that are not used today. These bridges are not automatically rated as structurally deficient, nor are they inherently unsafe. Functionally obsolete bridges are those that do not have adequate lane widths, shoulder widths, or vertical clearances to serve current traffic demand, or those that may be occasionally flooded.

Updated 06-05-2013 8:16pm

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