US Bridges

SH 21 over Mores Cr.;stierman Gulch

Good

Boise County, Idaho · 8.3 S. Idaho City · Structure no. 000000000012850

Built
1990
35 years old
Condition
Good
inspected October 2023
Type
Box Beam or Girders - Multiple
Prestressed Concrete
Length
70 ft
1 main span
Daily traffic
2,000
2023 count
Owner
State
State Highway Agency

About this bridge

SH 21 over Mores Cr.;stierman Gulch is a prestressed concrete box beam or girders - multiple carrying SH 21 over Mores Cr.;stierman Gulch in Boise County, Idaho. It was built in 1990, so it is 35 years old, younger than the Idaho average of 45.3 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 2,000 vehicles a day, roughly 18% of them trucks, projected to reach 3,000 by 2042. The structure is 70 ft (21.3 m) long and 40 ft wide. If it were closed, the detour would be 29.8 mi (48 km).

Location

Open in Google Maps
CarriesSH 21
CrossesMores Cr.;stierman Gulch
Location8.3 S. Idaho City
RouteState Highway 21
CountyBoise County
StateIdaho
Coordinates43.73747, -115.93208
Functional classRural Minor Arterial

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 inspectionOctober 2023
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating94 US tons
Inventory rating49.1 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialPrestressed Concrete
DeckConcrete, precast panels
Main spans1
Design loadHS 25 or greater
Structure length70 ft (21.3 m)
Longest span67 ft (20.4 m)
Deck width40 ft (12.2 m)
Roadway width37 ft (11.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,000 (2023)
Projected traffic3,000 by 2042
Trucks18%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed29.8 mi (48 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 proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 21 over Mores Cr.;stierman Gulch built?

It was built in 1990, making it 35 years old in 2025.

What condition is SH 21 over Mores Cr.;stierman Gulch 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 October 2023.

How much traffic does SH 21 over Mores Cr.;stierman Gulch carry?

About 2,000 vehicles per day (2023 count), of which roughly 18% are trucks.

How long is SH 21 over Mores Cr.;stierman Gulch?

The structure is 70 ft (21.3 m) long with a longest span of 67 ft (20.4 m) and a deck 40 ft wide.

Who owns SH 21 over Mores Cr.;stierman Gulch?

It is owned by the State Highway Agency.