SH 21 over Chapman Creek
GoodBoise County, Idaho · 18.7 Ne. Lowman · Structure no. 000000000012915
- Built
- 1988
- 37 years old
- Condition
- Good
- inspected October 2024
- Type
- Stringer/Multi-beam or Girder
- Prestressed Concrete
- Length
- 170 ft
- 3 main spans
- Daily traffic
- 1,200
- 2023 count
- Owner
- State
- State Highway Agency
About this bridge
SH 21 over Chapman Creek is a prestressed concrete stringer/multi-beam or girder carrying SH 21 over Chapman Creek in Boise County, Idaho. It was built in 1988, so it is 37 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 1,200 vehicles a day, roughly 9% of them trucks, projected to reach 1,800 by 2042. The structure is 170 ft (51.8 m) long and 34 ft wide. If it were closed, the detour would be 98.8 mi (159 km).
Location
Open in Google MapsCondition and inspection
All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 7 Good | Some minor problems. |
| Superstructure | 8 Very Good | No problems noted. |
| Substructure | 8 Very Good | No problems noted. |
| Channel and channel protection | 8 Very Good | No problems noted. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was SH 21 over Chapman Creek built?
It was built in 1988, making it 37 years old in 2025.
What condition is SH 21 over Chapman Creek 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 2024.
How much traffic does SH 21 over Chapman Creek carry?
About 1,200 vehicles per day (2023 count), of which roughly 9% are trucks.
How long is SH 21 over Chapman Creek?
The structure is 170 ft (51.8 m) long with a longest span of 55 ft (16.8 m) and a deck 34 ft wide.
Who owns SH 21 over Chapman Creek?
It is owned by the State Highway Agency.