US Bridges

Mountain Loop HWY over Backman Creek

Fair

Snohomish County, Washington · 2.9 SE JCT SR 530 · Structure no. 084928000000000

Built
1979
46 years old
Condition
Fair
inspected April 2024
Type
Slab
Prestressed Concrete
Length
44 ft
1 main span
Daily traffic
812
2021 count
Owner
County
County Highway Agency

About this bridge

Mountain Loop HWY over Backman Creek is a prestressed concrete slab carrying Mountain Loop HWY over Backman Creek in Snohomish County, Washington. It was built in 1979, so it is 46 years old, younger than the Washington average of 49.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 812 vehicles a day, roughly 8% of them trucks, projected to reach 1,000 by 2044. The structure is 44 ft (13.4 m) long and 36 ft wide. If it were closed, the detour would be 93.8 mi (151 km).

Location

Open in Google Maps
CarriesMountain Loop HWY
CrossesBackman Creek
Location2.9 SE JCT SR 530
RouteCounty Highway 98960
CountySnohomish County
StateWashington
Coordinates48.22167, -121.57917
Functional classRural Major Collector

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating46 US tons
Inventory rating28 US tons

Structure

Structure typeSlab
MaterialPrestressed Concrete
DeckConcrete, precast panels
Main spans1
Design loadHS 20
Structure length44 ft (13.4 m)
Longest span41 ft (12.4 m)
Deck width36 ft (11.1 m)
Roadway width33 ft (10.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic812 (2021)
Projected traffic1,000 by 2044
Trucks8%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed93.8 mi (151 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 proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$1.9 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Mountain Loop HWY over Backman Creek built?

It was built in 1979, making it 46 years old in 2025.

What condition is Mountain Loop HWY over Backman Creek in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in April 2024.

How much traffic does Mountain Loop HWY over Backman Creek carry?

About 812 vehicles per day (2021 count), of which roughly 8% are trucks.

How long is Mountain Loop HWY over Backman Creek?

The structure is 44 ft (13.4 m) long with a longest span of 41 ft (12.4 m) and a deck 36 ft wide.

Who owns Mountain Loop HWY over Backman Creek?

It is owned by the County Highway Agency.