US Bridges

SE Mt. Si RD over Mf Snoqualmie R

Good

King County, Washington · 0.9 MI N of I-90 · Structure no. 087792000000000

Built
2008
17 years old
Condition
Good
inspected September 2024
Type
Truss - Thru
Steel
Length
366 ft
1 main span
Daily traffic
3,500
2020 count
Owner
County
County Highway Agency

About this bridge

SE Mt. Si RD over Mf Snoqualmie R is a steel truss - thru carrying SE Mt. Si RD over Mf Snoqualmie R in King County, Washington. It was built in 2008, so it is 17 years old, younger than the Washington average of 49.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 3,500 vehicles a day, roughly 5% of them trucks, projected to reach 7,500 by 2040. The structure is 366 ft (111.6 m) long and 45 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesSE Mt. Si RD
CrossesMf Snoqualmie R
Location0.9 MI N of I-90
RouteCounty Highway 86650
CountyKing County
StateWashington
Coordinates47.487, -121.75944
Functional classRural Minor Collector

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionSeptember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating42.5 US tons
Inventory rating31.4 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+2 approach)
Design loadHL 93
Structure length366 ft (111.6 m)
Longest span240 ft (73.2 m)
Deck width45 ft (13.6 m)
Roadway width34 ft (10.4 m)
Vertical clearance over deck17 ft (5.2 m)

Traffic and service

Average daily traffic3,500 (2020)
Projected traffic7,500 by 2040
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed98.8 mi (159 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedDeck replacement with only incidental widening
Estimated improvement cost$7.3 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SE Mt. Si RD over Mf Snoqualmie R built?

It was built in 2008, making it 17 years old in 2025.

What condition is SE Mt. Si RD over Mf Snoqualmie R in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in September 2024.

How much traffic does SE Mt. Si RD over Mf Snoqualmie R carry?

About 3,500 vehicles per day (2020 count), of which roughly 5% are trucks.

How long is SE Mt. Si RD over Mf Snoqualmie R?

The structure is 366 ft (111.6 m) long with a longest span of 240 ft (73.2 m) and a deck 45 ft wide.

Who owns SE Mt. Si RD over Mf Snoqualmie R?

It is owned by the County Highway Agency.