Structure 36810 · Monona County, IA

Ia 175 over Missouri River

Carries Ia 175 over Missouri River, E.of Decatur NE.

Overall conditionFair

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

How ratings work
Deck7/9 · Good
Superstructuresets the rating6/9 · Satisfactory
Substructure7/9 · Good
Channelnot part of overall8/9 · Very Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT1,956 FT OVERALL250 FT0ELEVATION · LENGTHS TO SCALE
Deck 7/9Superstructure 6/9 · sets the ratingSubstructure 7/9

1,956 ft end to end, longest span 421 ft: about 5.4 football fields. 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 through truss.

Built195076 years old
Length1956.0 ft596.2 m
Daily traffic1,790counted 2022
Last inspectedSeptember 2022every 24 months

Location

StateIowa
CountyMonona
LocationE.of Decatur NE
CarriesIa 175
CrossesMissouri River
Coordinates42.00662, -96.24137

Physical Characteristics

MaterialSteel Continuous
DesignTruss - Thru
Total Length1956.0 ft (596.2 m)
Max Span420.9 ft (128.3 m)
Deck Width24.0 ft (7.3 m)
Deck Area4352.3 sq m
Main Spans2
Year Built1950

Traffic

Avg Daily Traffic1,790 (2022)
Truck Traffic27%
Lanes On Bridge2
Lanes Under Bridge2

Inspection & Ownership

Last InspectionSeptember 2022
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is eligible for the National Register
Scour Critical4 — Foundations need monitoring
Structure Number000000000036810

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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