Structure P00008047+09781 · Lewis and Clark County, MT

US 12 over Rr

Carries US 12 over Rr, 3m E Helena.

Overall conditionGood

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

How ratings work
Deck8/9 · Very Good
Superstructure8/9 · Very Good
Substructuresets the rating7/9 · Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT276 FT OVERALL50 FT0ELEVATION · LENGTHS TO SCALE
Deck 8/9Superstructure 8/9Substructure 7/9 · sets the rating

276 ft end to end, longest span 108 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.

Built197848 years old
Length275.9 ft84.1 m
Daily traffic19,327counted 2023
Last inspectedMay 2023every 24 months

Location

StateMontana
CountyLewis and Clark
Location3m E Helena
CarriesUS 12
CrossesRr
Coordinates46.59121, -111.94707

Physical Characteristics

MaterialPrestressed Concrete
DesignStringer/Multi-beam
Total Length275.9 ft (84.1 m)
Max Span107.9 ft (32.9 m)
Deck Width98.8 ft (30.1 m)
Deck Area2531.4 sq m
Main Spans3
Year Built1978

Traffic

Avg Daily Traffic19,327 (2023)
Truck Traffic1%
Lanes On Bridge4

Inspection & Ownership

Last InspectionMay 2023
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is not eligible for the National Register
Scour CriticalNot applicable
Structure NumberP00008047+09781

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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