US Bridges

Backbone ST Pk over Stream

Fair

Delaware County, Iowa · In Backbone State Park · Structure no. 000000000699010

Built
1934
91 years old
Condition
Fair
inspected March 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
42 ft
1 main span
Daily traffic
—
2022 count
Owner
State
State Park, Forest, or Reservation Agency

About this bridge

Backbone ST Pk over Stream is a steel stringer/multi-beam or girder carrying Backbone ST Pk over Stream in Delaware County, Iowa. It was built in 1934, so it is 91 years old, older than the Iowa average of 45.5 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 6 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

No traffic count is recorded. The structure is 42 ft (12.8 m) long and 21 ft wide. If it were closed, the detour would be 6.8 mi (11 km).

Location

Open in Google Maps
CarriesBackbone ST Pk
CrossesStream
LocationIn Backbone State Park
RouteState Lands Road 0
CountyDelaware County
StateIowa
Coordinates42.63741, -91.55672
Functional classRural Local

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourCountermeasures installed to correct a previously existing problem
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment5: Somewhat better than minimum adequacy to tolerate being left in place as is
Operating rating36 US tons
Inventory rating21.6 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadUnknown
Structure length42 ft (12.8 m)
Longest span42 ft (12.8 m)
Deck width21 ft (6.5 m)
Roadway width20 ft (6.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic—
Projected traffic—
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.8 mi (11 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Park, Forest, or Reservation Agency
Maintained byState Park, Forest, or Reservation Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Backbone ST Pk over Stream built?

It was built in 1934, making it 91 years old in 2025.

What condition is Backbone ST Pk over Stream in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in March 2024.

How much traffic does Backbone ST Pk over Stream carry?

No traffic count is recorded for this structure.

How long is Backbone ST Pk over Stream?

The structure is 42 ft (12.8 m) long with a longest span of 42 ft (12.8 m) and a deck 21 ft wide.

Who owns Backbone ST Pk over Stream?

It is owned by the State Park, Forest, or Reservation Agency.