US Bridges

Mosquito Lk RD over Middle Fork

Fair

Whatcom County, Washington · 05.2 SE Mt. Baker HWY · Structure no. 081574000000000

Built
1915
110 years old, rebuilt 2010
Condition
Fair
inspected August 2024
Type
Truss - Thru
Steel
Length
431 ft
1 main span
Daily traffic
117
2024 count
Owner
County
County Highway Agency

About this bridge

Mosquito Lk RD over Middle Fork is a steel truss - thru carrying Mosquito Lk RD over Middle Fork in Whatcom County, Washington. It was built in 1915 and reconstructed in 2010, so it is 110 years old, older 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 6 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 117 vehicles a day, roughly 4% of them trucks, projected to reach 250 by 2044. The structure is 431 ft (131.4 m) long and 16 ft wide. If it were closed, the detour would be 21.1 mi (34 km).

Location

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CarriesMosquito Lk RD
CrossesMiddle Fork
Location05.2 SE Mt. Baker HWY
RouteCounty Highway 84190
CountyWhatcom County
StateWashington
Coordinates48.78462, -122.11314
Functional classRural Minor 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
Deck8 Very GoodNo problems noted.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourCountermeasures installed to correct a previously existing problem
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment3: Basically intolerable, requiring high priority of corrective action
Operating rating26.5 US tons
Inventory rating20.4 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckClosed grating
Main spans1 (+2 approach)
Design loadH 20
Structure length431 ft (131.4 m)
Longest span338 ft (103 m)
Deck width16 ft (4.9 m)
Roadway width13 ft (4.1 m)
Vertical clearance over deck18 ft (5.5 m)

Traffic and service

Average daily traffic117 (2024)
Projected traffic250 by 2044
Trucks4%
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed21.1 mi (34 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusListed on the National Register of Historic Places
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$4.5 million (2030 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Mosquito Lk RD over Middle Fork built?

It was built in 1915, making it 110 years old in 2025. It was reconstructed in 2010.

What condition is Mosquito Lk RD over Middle Fork 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 August 2024.

How much traffic does Mosquito Lk RD over Middle Fork carry?

About 117 vehicles per day (2024 count), of which roughly 4% are trucks.

How long is Mosquito Lk RD over Middle Fork?

The structure is 431 ft (131.4 m) long with a longest span of 338 ft (103 m) and a deck 16 ft wide.

Who owns Mosquito Lk RD over Middle Fork?

It is owned by the County Highway Agency.