Structure I00015251+06841 · Cascade County, MT

I 15 over Sep Old US 91

Carries I 15 over Sep Old US 91, 3m S Cascade.

Overall conditionFair

Set by its lowest-rated component: Substructure at 6 of 9.

How ratings work
Deck7/9 · Good
Superstructure7/9 · Good
Substructuresets the rating6/9 · Satisfactory
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
CAR · 15 FT84 FT OVERALL25 FT0ELEVATION · LENGTHS TO SCALE
Deck 7/9Superstructure 7/9Substructure 6/9 · sets the rating

84 ft end to end, longest span 30 ft. Lengths and the car on the deck are drawn to the same scale. Each part is colored by its latest inspection rating. The inventory records lengths but not heights or the layout of the shorter spans, so those are drawn as typical for a tee-beam bridge.

Built196165 years old
Length84.0 ft25.6 m
Daily traffic2,218counted 2023
Last inspectedJune 2024every 24 months

Location

StateMontana
CountyCascade
Location3m S Cascade
CarriesI 15
CrossesSep Old US 91
Coordinates47.23064, -111.75634

Physical Characteristics

MaterialConcrete
DesignTee Beam
Total Length84.0 ft (25.6 m)
Max Span29.9 ft (9.1 m)
Deck Width47.6 ft (14.5 m)
Deck Area371.2 sq m
Main Spans3
Year Built1961

Traffic

Avg Daily Traffic2,218 (2023)
Truck Traffic16%
Lanes On Bridge2
Lanes Under Bridge2

Inspection & Ownership

Last InspectionJune 2024
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is not eligible for the National Register
Scour CriticalNot applicable
Structure NumberI00015251+06841

How Bridge Ratings Work

Inspectors rate each major part of a bridge (the deck you drive on, the superstructure of beams that holds it up, and the substructure of piers and abutments beneath) on a 0–9 scale. A bridge's overall condition is its lowest of those ratings, so one deteriorated component makes the whole bridge "poor."

0Failed
1Imminent failure
2Critical
3Serious
4Poor
5Fair
6Satisfactory
7Good
8Very good
9Excellent
Good · lowest component 7–9
Fair · lowest component 5–6
Poor · lowest component 0–4

A poor rating is not a closure. It means the bridge is flagged for priority repair or replacement; bridges judged unsafe are closed or posted with weight limits. The waterway (channel) rating is reported, but it does not count toward the overall classification.

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