US Bridges

County Road 69B over Big Thompson River

Fair

Larimer County, Colorado · 0.1 MI S of End of SH S66 · Structure no. LR69B-S0.1-S66A

Built
1940
85 years old, rebuilt 2009
Condition
Fair
inspected June 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
58 ft
1 main span
Daily traffic
3,417
2023 count
Owner
County
County Highway Agency

About this bridge

County Road 69B over Big Thompson River is a steel stringer/multi-beam or girder carrying County Road 69B over Big Thompson River in Larimer County, Colorado. It was built in 1940 and reconstructed in 2009, so it is 85 years old, older than the Colorado average of 42.2 years.

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

It carries about 3,417 vehicles a day, roughly 14% of them trucks, projected to reach 4,272 by 2042. The structure is 58 ft (17.7 m) long and 38 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

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CarriesCounty Road 69B
CrossesBig Thompson River
Location0.1 MI S of End of SH S66
RouteCounty Highway 0
CountyLarimer County
StateColorado
Coordinates40.34869, -105.56856
Functional classUrban Collector

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck8 Very GoodNo problems noted.
Superstructure7 GoodSome minor problems.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJune 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; action required to protect exposed foundations
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 adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating61.9 US tons
Inventory rating37.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length58 ft (17.7 m)
Longest span51 ft (15.6 m)
Deck width38 ft (11.6 m)
Roadway width35 ft (10.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,417 (2023)
Projected traffic4,272 by 2042
Trucks14%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed98.8 mi (159 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway 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 County Road 69B over Big Thompson River built?

It was built in 1940, making it 85 years old in 2025. It was reconstructed in 2009.

What condition is County Road 69B over Big Thompson River 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 June 2023.

How much traffic does County Road 69B over Big Thompson River carry?

About 3,417 vehicles per day (2023 count), of which roughly 14% are trucks.

How long is County Road 69B over Big Thompson River?

The structure is 58 ft (17.7 m) long with a longest span of 51 ft (15.6 m) and a deck 38 ft wide.

Who owns County Road 69B over Big Thompson River?

It is owned by the County Highway Agency.