US Bridges

SH 21 over Mores Cr.;grimes Cr.Road

Fair

Boise County, Idaho · 9.5 S. Idaho City · Structure no. 000000000012835

Built
1958
67 years old
Condition
Fair
inspected October 2023
Type
Stringer/Multi-beam or Girder
Concrete
Length
40 ft
1 main span
Daily traffic
2,900
2023 count
Owner
State
State Highway Agency

About this bridge

SH 21 over Mores Cr.;grimes Cr.Road is a concrete stringer/multi-beam or girder carrying SH 21 over Mores Cr.;grimes Cr.Road in Boise County, Idaho. It was built in 1958, so it is 67 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 2,900 vehicles a day, roughly 5% of them trucks, projected to reach 4,350 by 2042. The structure is 40 ft (12.2 m) long and 36 ft wide.

Location

Open in Google Maps
CarriesSH 21
CrossesMores Cr.;grimes Cr.Road
Location9.5 S. Idaho City
RouteState Highway 21
CountyBoise County
StateIdaho
Coordinates43.72567, -115.95147
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionOctober 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating70 US tons
Inventory rating41 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length40 ft (12.2 m)
Longest span39 ft (11.8 m)
Deck width36 ft (11 m)
Roadway width34 ft (10.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,900 (2023)
Projected traffic4,350 by 2042
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed—
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.;grimes Cr.Road built?

It was built in 1958, making it 67 years old in 2025.

What condition is SH 21 over Mores Cr.;grimes Cr.Road 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 2023.

How much traffic does SH 21 over Mores Cr.;grimes Cr.Road carry?

About 2,900 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is SH 21 over Mores Cr.;grimes Cr.Road?

The structure is 40 ft (12.2 m) long with a longest span of 39 ft (11.8 m) and a deck 36 ft wide.

Who owns SH 21 over Mores Cr.;grimes Cr.Road?

It is owned by the State Highway Agency.