Structure P00007037+05961 · Ravalli County, MT

US 93 over Lost Horse Creek

Carries US 93 over Lost Horse Creek, 7m N Darby.

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
Channelnot part of overall8/9 · Very Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT163 FT OVERALL25 FT0ELEVATION · LENGTHS TO SCALE
Deck 7/9Superstructure 7/9Substructure 7/9

163 ft end to end, longest span 81 ft: about 2 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.

Built199036 years old
Length163.1 ft49.7 m
Daily traffic4,628counted 2023
Last inspectedJanuary 2025every 24 months

Location

StateMontana
CountyRavalli
Location7m N Darby
CarriesUS 93
CrossesLost Horse Creek
Coordinates46.11333, -114.18017

Physical Characteristics

MaterialPrestressed Concrete
DesignStringer/Multi-beam
Total Length163.1 ft (49.7 m)
Max Span80.7 ft (24.6 m)
Deck Width42.3 ft (12.9 m)
Deck Area641.1 sq m
Main Spans2
Year Built1990

Traffic

Avg Daily Traffic4,628 (2023)
Truck Traffic1%
Lanes On Bridge2

Inspection & Ownership

Last InspectionJanuary 2025
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is not eligible for the National Register
Scour Critical8 — Stable, low risk
Structure NumberP00007037+05961

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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