SH 31
Carrying SH 31 over PINE CREEK
5 N. SWAN VALLEY, Bonneville, Idaho
Inventory: FHWA NBI 2024 · last ETL August 2026
FHWA NBI record, refreshed with each annual release.
SH 31 in Bonneville, Idaho sits above 62% of rated Idaho bridges on inventory load rating (35 t), while its 1938 build year is earlier than 96% of Bonneville's recorded-year cohort (213 bridges).
SH 31 in Bonneville, Idaho is rated Fair in the FHWA's 2024 National Bridge Inventory. Built in 1938, it carries 3 rated components on the inspecting agency's 0-9 scale, and its weakest reported component scores 6. The lowest applicable rating sets the federal condition category, so this Fair result describes the weakest reported component rather than the structure as a whole. No NBI category is a closure decision or a live crossing-safety verdict.
NBI record plate
Structure ID:000000000013835
PRE-1950 · STEEL · SINGLE-SPAN · TIED-CTRL · ARTERIAL-ADT · STANDARD-LOAD · CAT-FAIR
- PRE-1950 Pre-1950
- STEEL Steel
- SINGLE-SPAN Single span
- TIED-CTRL Tied control
- ARTERIAL-ADT Arterial ADT
- STANDARD-LOAD Standard load
- CAT-FAIR Fair
Inspection-sheet codes from this record’s year, material family, spans, controlling component, ADT, inventory load, and NBI category, not a live closure verdict.
Bridge Snapshot: SH 31
The SH 31 bridge in Bonneville, Idaho carries SH 31 over PINE CREEK. It was built in 1938, making it 88 years old today. It was last reconstructed in 2020, extending its service life. The structure is built primarily of steel and spans 1 section, stretching 162.2 meters (532 feet) end to end. Daily traffic averages 2,600 vehicles, placing it in the moderately-trafficked tier of Idaho bridges. It is owned and maintained by State Highway Agency.
The latest FHWA inspection records show a deck rating of 7/9, superstructure at 6/9, substructure at 6/9. The weakest component sits in fair condition. All reported major components score above the Poor range.
How SH 31 compares
Age against the county: built in 1938, earlier than 205 of Bonneville's 213 bridges with a recorded construction year (96%), against a county median build year of 1971. Age is not a defect on its own, but it is the population from which future Poor ratings are drawn.
Live comparison across Idaho bridges with a recorded inventory load rating (4,574 of 4,616 rated).
SH 31 vs every rated Idaho bridge
Inventory load rating (metric tons), FHWA NBI, this state
35 Top 38% higher than 62% of 4,574 bridges
rated Idaho bridges, bucketed by value
Each bar is a band; taller bars hold more bridges. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source FHWA National Bridge Inventory · August 2026
Condition Ratings
Full 0–9 scale + sufficiency-rating breakdown: how condition ratings work.
Reported 0–9 component ratings from the FHWA NBI. The highlighted component is the lowest reported input to this record’s current condition category; it is not a closure or live crossing-safety decision.
Bonneville inventory by recorded NBI category
Exclusive Good/Fair/Poor bands across all 213 bridges in this county. Orthogonal to this structure's component profile above: a county catalog share, not a live crossing-safety verdict.
Structural Details
- Year Built
- 1938
- Last Reconstructed
- 2020
- Material
- Steel
- Number of Spans
- 1
- Structure Length
- 162.2 m (532 ft)
- Deck Width
- 9.3 m (31 ft)
- Owner
- State Highway Agency
- Avg Daily Traffic
- 2,600 vehicles/day
- Structure Number
- 000000000013835
Condition Analysis
- • The deck (driving surface) rates good at 7/9, with no significant deterioration on file.
- • The superstructure (beams and supports above the deck) rates fair at 6/9, minor deterioration that routine maintenance should address.
- • The substructure (piers and abutments) is in fair condition (6/9), with minor deterioration that may require routine maintenance.
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗How to read this record
This page shows what the last federal inspection recorded, not whether SH 31 is safe to cross today. Here is how to use it.
- NBI condition ratings reflect the latest record in this annual dataset, not a live status. Current routine inspection intervals are risk-based.
- Learn how the 0–9 condition scale and Good/Fair/Poor categories are defined. How condition ratings work
- Compare SH 31 against other structures in Bonneville and across Idaho. Idaho bridges
- Noticed visible damage or a safety concern? Report it to the agency that owns the bridge, or call 911 in an emergency. How to report a bridge
Condition codes come straight from the FHWA National Bridge Inventory and are not a real-time safety judgment. Only the owning agency, a state DOT, county, or other owner, can post, restrict, or close a bridge.
Frequently Asked Questions
What do the condition ratings mean for SH 31?
SH 31 in Bonneville, Idaho has a deck rating of 7/9, superstructure rating of 6/9, and substructure rating of 6/9 on the FHWA's 0–9 scale.
How often is SH 31 inspected?
SH 31's responsible agency sets its routine interval under FHWA's risk-based inspection rules; this page does not expose the scheduled interval. It carries about 2,600 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. SH 31 is currently shown as Fair condition from its component ratings; that category is not a live closure or safety decision.
What is the inventory load rating for SH 31?
SH 31 has an NBI inventory load rating of 35.4 metric tons.
Who is responsible for maintaining SH 31?
SH 31 is owned and maintained by State Highway Agency.
How old is SH 31 and does age affect safety?
SH 31 was built in 1938, making it 88 years old and last reconstructed in 2020.
Disclaimer: Bridge condition data is from the FHWA NBI and reflects the last reported inspection. A Poor condition rating is not a live declaration that a bridge is closed or unsafe for travel. For current closure, posting, or safety information, contact the responsible transportation agency.
Share this inspection record
Send this source-bounded record or download its data card. An NBI condition category is not a closure or live crossing-safety verdict.
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. Component ratings, ADT, and condition category on this page are copied from the NBI record for this structure; no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2024 NBI release. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.