Structure 11607000000069 · Mineral County, MT

RD 352 over Twelvemile Creek

Carries RD 352 over Twelvemile Creek, Henderson-thompson.

Overall conditionPoor

Set by its lowest-rated component: Substructure at 4 of 9.

How ratings work
Deck6/9 · Satisfactory
Superstructure7/9 · Good
Substructuresets the rating4/9 · Poor
Channelnot part of overall6/9 · Satisfactory
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
25 FT OVERALL25 FT0ELEVATION · LENGTHS TO SCALE
Deck 6/9Superstructure 7/9Substructure 4/9 · sets the rating

25 ft end to end. Lengths are drawn to scale; at this length a semi-truck would be a speck. 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.

Built195571 years old
Length24.6 ft7.5 m
Daily traffic501 lanes
Last inspectedJuly 2023every 24 months

Location

StateMontana
CountyMineral
LocationHenderson-thompson
CarriesRD 352
CrossesTwelvemile Creek
Coordinates47.43363, -115.24240

Physical Characteristics

MaterialWood or Timber
DesignStringer/Multi-beam
Total Length24.6 ft (7.5 m)
Max Span23.0 ft (7 m)
Deck Width15.4 ft (4.7 m)
Deck Area35.2 sq m
Main Spans1
Year Built1955

Traffic

Avg Daily Traffic50
Lanes On Bridge1

Inspection & Ownership

Last InspectionJuly 2023
Inspection FrequencyEvery 24 months
OwnerU.S. Forest Service
Historical SignificanceHistorical significance is not determined
Scour Critical4 — Foundations need monitoring
Structure Number011607000000069

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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