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Trosper Rd over I-5

Thurston County, Washington · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

Trosper Rd over I-5 in Thurston County, Washington, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the superstructure, rated 6 (satisfactory condition) on the 0-9 scale.
It was built in 1991 and reconstructed in 2003, making it 34 years old at the 2025 inventory.
It carries about 21,420 vehicles a day (traffic count year 2012).
Its listed owner is the state highway agency.
It is one of 79 of the 199 inventoried bridges in Thurston County rated fair (39.7%); 2 (1.0%) are rated poor.
A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.

Component ratings


Structure	Continuous prestressed concrete single box beam
Length	about 242 ft
Location	3.5 N Jct SR 121
NBI structure number	0013692A0000000
Condition class	Fair

Source: FHWA National Bridge Inventory, 2025 data as reported by the Washington department of transportation.

Bridge	Built	Vehicles/day	Condition
I-5 over Owr N RR	1957	69,477	Fair
I-5 over Henderson Blvd	1957	69,477	Good
I-5 over Nisqually River	1937	62,815	Fair
I-5 over Nisqually River	1967	62,815	Fair
US 101 NB over I-5 Ramps Street	1990	62,306	Good
I-5 over Pacific Ave	1957	59,814	Fair