US Bridges

SWANNACK/4060 over Unnamed Drainage

Good

Whitman County, Washington · 2.30 MI SE Potts · Structure no. 085819000000000

Built
1991
34 years old
Condition
Good
inspected November 2023
Type
Slab
Prestressed Concrete
Length
25 ft
1 main span
Daily traffic
20
2021 count
Owner
County
County Highway Agency

About this bridge

SWANNACK/4060 over Unnamed Drainage is a prestressed concrete slab carrying SWANNACK/4060 over Unnamed Drainage in Whitman County, Washington. It was built in 1991, so it is 34 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 20 vehicles a day, roughly 25% of them trucks, projected to reach 21 by 2044. The structure is 25 ft (7.6 m) long and 24 ft wide. If it were closed, the detour would be 8.7 mi (14 km).

Location

Open in Google Maps
CarriesSWANNACK/4060
CrossesUnnamed Drainage
Location2.30 MI SE Potts
RouteCounty Highway 40600
CountyWhitman County
StateWashington
Coordinates47.16317, -117.87125
Functional classRural Local

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 inspectionNovember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourUnknown foundation; not evaluated for scour
Structural evaluation7: Better than present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment3: Basically intolerable, requiring high priority of corrective action
Operating rating53.9 US tons
Inventory rating41.8 US tons

Structure

Structure typeSlab
MaterialPrestressed Concrete
DeckOther
Main spans1
Design loadHS 20
Structure length25 ft (7.6 m)
Longest span24 ft (7.3 m)
Deck width24 ft (7.3 m)
Roadway width24 ft (7.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic20 (2021)
Projected traffic21 by 2044
Trucks25%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.7 mi (14 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$1.3 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SWANNACK/4060 over Unnamed Drainage built?

It was built in 1991, making it 34 years old in 2025.

What condition is SWANNACK/4060 over Unnamed Drainage 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 November 2023.

How much traffic does SWANNACK/4060 over Unnamed Drainage carry?

About 20 vehicles per day (2021 count), of which roughly 25% are trucks.

How long is SWANNACK/4060 over Unnamed Drainage?

The structure is 25 ft (7.6 m) long with a longest span of 24 ft (7.3 m) and a deck 24 ft wide.

Who owns SWANNACK/4060 over Unnamed Drainage?

It is owned by the County Highway Agency.