US Bridges

Nelson RD over Black Slough

FairPosted for load

Whatcom County, Washington · 00.5 E Valley HWY · Structure no. 082644000000000

Built
1934
91 years old, rebuilt 1958
Condition
Fair
inspected September 2023
Type
Channel Beam
Concrete
Length
31 ft
1 main span
Daily traffic
80
2019 count
Owner
County
County Highway Agency

About this bridge

Nelson RD over Black Slough is a concrete channel beam carrying Nelson RD over Black Slough in Whatcom County, Washington. It was built in 1934 and reconstructed in 1958, so it is 91 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 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. Its operating status is: posted for load restriction.

It carries about 80 vehicles a day, roughly 10% of them trucks, projected to reach 185 by 2041. The structure is 31 ft (9.4 m) long and 21 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

Open in Google Maps
CarriesNelson RD
CrossesBlack Slough
Location00.5 E Valley HWY
RouteCounty Highway 89570
CountyWhatcom County
StateWashington
Coordinates48.77091, -122.19485
Functional classRural Local

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusPosted for load restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating25 US tons
Inventory rating17 US tons

Structure

Structure typeChannel Beam
MaterialConcrete
DeckOther
Main spans1
Design loadH 20
Structure length31 ft (9.4 m)
Longest span30 ft (9.1 m)
Deck width21 ft (6.5 m)
Roadway width20 ft (6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic80 (2019)
Projected traffic185 by 2041
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.7 mi (6 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$1.5 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Nelson RD over Black Slough built?

It was built in 1934, making it 91 years old in 2025. It was reconstructed in 1958.

What condition is Nelson RD over Black Slough 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 September 2023.

How much traffic does Nelson RD over Black Slough carry?

About 80 vehicles per day (2019 count), of which roughly 10% are trucks.

How long is Nelson RD over Black Slough?

The structure is 31 ft (9.4 m) long with a longest span of 30 ft (9.1 m) and a deck 21 ft wide.

Who owns Nelson RD over Black Slough?

It is owned by the County Highway Agency.