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NB I-29 over Drainage Ditch

Harrison County, Iowa · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

NB I-29 over Drainage Ditch in Harrison County, Iowa, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the superstructure, rated 5 (fair condition) on the 0-9 scale.
It was built in 1966, making it 59 years old at the 2025 inventory.
It carries about 7,250 vehicles a day (traffic count year 2022).
Its listed owner is the state highway agency.
It is one of 120 of the 222 inventoried bridges in Harrison County rated fair (54.1%); 41 (18.5%) are rated poor.
A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.

Component ratings


Structure	Continuous steel girder and floorbeam
Length	about 315 ft
Location	1.6 MI. N OF Jct. SR F-20
NBI structure number	000000000028380
Condition class	Fair

Source: FHWA National Bridge Inventory, 2025 data as reported by the Iowa department of transportation.

Bridge	Built	Vehicles/day	Condition
US 30 over Willow Creek	1972	10,300	Fair
US 30 over UPRR	1998	10,300	Good
NB I-29 over Boyer River	1958	10,050	Fair
SB I-29 over Boyer River	1958	10,050	Fair
SB I-29 over over UP RR	1967	7,750	Fair
NB I-29 over Allen Creek	1967	7,750	Fair