US Bridges

STC6702;SMELTER RD over Big Lost River

Fair

Custer County, Idaho · 0.2 S. Mackay · Structure no. 000000000031715

Built
1974
51 years old
Condition
Fair
inspected July 2023
Type
Tee Beam
Prestressed Concrete
Length
77 ft
1 main span
Daily traffic
260
2023 count
Owner
Local
Other Local Agency

About this bridge

STC6702;SMELTER RD over Big Lost River is a prestressed concrete tee beam carrying STC6702;SMELTER RD over Big Lost River in Custer County, Idaho. It was built in 1974, so it is 51 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 260 vehicles a day, projected to reach 390 by 2042. The structure is 77 ft (23.5 m) long and 26 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesSTC6702;SMELTER RD
CrossesBig Lost River
Location0.2 S. Mackay
RouteCounty Highway 6702
CountyCuster County
StateIdaho
Coordinates43.90272, -113.61703
Functional classRural Major 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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection4 PoorAdvanced section loss, deterioration, spalling or scour.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; action required to protect exposed foundations
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating30 US tons
Inventory rating18 US tons

Structure

Structure typeTee Beam
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length77 ft (23.5 m)
Longest span73 ft (22.3 m)
Deck width26 ft (8 m)
Roadway width24 ft (7.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic260 (2023)
Projected traffic390 by 2042
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.8 mi (159 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerOther Local Agency
Maintained byOther Local Agency
Historic statusHistorical significance not determinable at this time
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$665,000 (2019 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was STC6702;SMELTER RD over Big Lost River built?

It was built in 1974, making it 51 years old in 2025.

What condition is STC6702;SMELTER RD over Big Lost River 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 July 2023.

How much traffic does STC6702;SMELTER RD over Big Lost River carry?

About 260 vehicles per day (2023 count).

How long is STC6702;SMELTER RD over Big Lost River?

The structure is 77 ft (23.5 m) long with a longest span of 73 ft (22.3 m) and a deck 26 ft wide.

Who owns STC6702;SMELTER RD over Big Lost River?

It is owned by the Other Local Agency.