US Bridges

SH 3 over ST Maries River

Poor

Shoshone County, Idaho · 3.3 N. Clarkia · Structure no. 000000000010090

Built
1955
70 years old
Condition
Poor
inspected October 2024
Type
Tee Beam
Concrete
Length
105 ft
3 main spans
Daily traffic
460
2023 count
Owner
State
State Highway Agency

About this bridge

SH 3 over ST Maries River is a concrete tee beam carrying SH 3 over ST Maries River in Shoshone County, Idaho. It was built in 1955, so it is 70 years old, older than the Idaho average of 45.3 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 460 vehicles a day, roughly 44% of them trucks, projected to reach 690 by 2042. The structure is 105 ft (32 m) long and 29 ft wide. If it were closed, the detour would be 18 mi (29 km).

Location

Open in Google Maps
CarriesSH 3
CrossesST Maries River
Location3.3 N. Clarkia
RouteState Highway 3
CountyShoshone County
StateIdaho
Coordinates47.05103, -116.28772
Functional classRural Minor Arterial

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionOctober 2024
Inspection intervalevery 12 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating55 US tons
Inventory rating33 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 15
Structure length105 ft (32 m)
Longest span34 ft (10.4 m)
Deck width29 ft (8.7 m)
Roadway width26 ft (7.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic460 (2023)
Projected traffic690 by 2042
Trucks44%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed18 mi (29 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$1.4 million (2020 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 3 over ST Maries River built?

It was built in 1955, making it 70 years old in 2025.

What condition is SH 3 over ST Maries River in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in October 2024.

How much traffic does SH 3 over ST Maries River carry?

About 460 vehicles per day (2023 count), of which roughly 44% are trucks.

How long is SH 3 over ST Maries River?

The structure is 105 ft (32 m) long with a longest span of 34 ft (10.4 m) and a deck 29 ft wide.

Who owns SH 3 over ST Maries River?

It is owned by the State Highway Agency.