Structure L50069002+07001 · Teton County, MT

20th RD NE over Sep I 15 001

Carries 20th RD NE over Sep I 15 001, 4m N Dutton.

Overall conditionGood

Set by its lowest-rated component: Deck and Superstructure and Substructure at 7 of 9.

How ratings work
Decksets the rating7/9 · Good
Superstructuresets the rating7/9 · Good
Substructuresets the rating7/9 · Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT298 FT OVERALL50 FT0ELEVATION · LENGTHS TO SCALE
Deck 7/9Superstructure 7/9Substructure 7/9

298 ft end to end, longest span 107 ft: about 4 semi-trucks nose to tail. Lengths and the semi-truck 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 multi-beam bridge.

Built197749 years old
Length297.9 ft90.8 m
Daily traffic100counted 2025
Last inspectedAugust 2023every 24 months

Location

StateMontana
CountyTeton
Location4m N Dutton
Carries20th RD NE
CrossesSep I 15 001
Coordinates47.89936, -111.71853

Physical Characteristics

MaterialPrestressed Concrete
DesignStringer/Multi-beam
Total Length297.9 ft (90.8 m)
Max Span107.0 ft (32.6 m)
Deck Width30.2 ft (9.2 m)
Deck Area835.4 sq m
Main Spans4
Year Built1977

Traffic

Avg Daily Traffic100 (2025)
Truck Traffic3%
Lanes On Bridge2
Lanes Under Bridge2

Inspection & Ownership

Last InspectionAugust 2023
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is not eligible for the National Register
Scour CriticalNot applicable
Structure NumberL50069002+07001

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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