US Bridges

SH 3 over Thorn Creek

Fair

Benewah County, Idaho · 4.5 S. ST Maries · Structure no. 000000000018875

Built
1939
86 years old
Condition
Fair
inspected October 2024
Type
Culvert
Concrete
Length
23 ft
1 main span
Daily traffic
2,300
2023 count
Owner
State
State Highway Agency

About this bridge

SH 3 over Thorn Creek is a concrete culvert carrying SH 3 over Thorn Creek in Benewah County, Idaho. It was built in 1939, so it is 86 years old, older than the Idaho average of 45.3 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 2,300 vehicles a day, roughly 20% of them trucks, projected to reach 3,450 by 2042. The structure is 23 ft (7 m) long and 56 ft wide. If it were closed, the detour would be 87 mi (140 km).

Location

Open in Google Maps
CarriesSH 3
CrossesThorn Creek
Location4.5 S. ST Maries
RouteState Highway 3
CountyBenewah County
StateIdaho
Coordinates47.26856, -116.50139
Functional classRural Minor Arterial

Condition and inspection

Fair

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

ComponentRatingMeaning
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Culvert5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionOctober 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating110.1 US tons
Inventory rating101 US tons

Structure

Structure typeCulvert
MaterialConcrete
DeckNot applicable
Main spans1
Design loadH 15
Structure length23 ft (7 m)
Longest span23 ft (7 m)
Deck width56 ft (17.2 m)
Roadway width0 ft (0 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,300 (2023)
Projected traffic3,450 by 2042
Trucks20%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed87 mi (140 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$535,000 (2020 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 3 over Thorn Creek built?

It was built in 1939, making it 86 years old in 2025.

What condition is SH 3 over Thorn 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 October 2024.

How much traffic does SH 3 over Thorn Creek carry?

About 2,300 vehicles per day (2023 count), of which roughly 20% are trucks.

How long is SH 3 over Thorn Creek?

The structure is 23 ft (7 m) long with a longest span of 23 ft (7 m) and a deck 56 ft wide.

Who owns SH 3 over Thorn Creek?

It is owned by the State Highway Agency.