US Bridges

County Road 51B over N Fork Big Thompson Riv.

Fair

Larimer County, Colorado · 50 Ft N of CO RD 43 · Structure no. LR51B-0.0-43

Built
1977
48 years old
Condition
Fair
inspected May 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
36 ft
1 main span
Daily traffic
293
2023 count
Owner
County
County Highway Agency

About this bridge

County Road 51B over N Fork Big Thompson Riv. is a steel stringer/multi-beam or girder carrying County Road 51B over N Fork Big Thompson Riv. in Larimer County, Colorado. It was built in 1977, so it is 48 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 6 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 293 vehicles a day, roughly 20% of them trucks, projected to reach 366 by 2042. The structure is 36 ft (11.1 m) long and 26 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesCounty Road 51B
CrossesN Fork Big Thompson Riv.
Location50 Ft N of CO RD 43
RouteCounty Highway 0
CountyLarimer County
StateColorado
Coordinates40.45775, -105.42936
Functional classRural Major 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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMay 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation7: Better than present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating40 US tons
Inventory rating31.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length36 ft (11.1 m)
Longest span34 ft (10.3 m)
Deck width26 ft (8 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic293 (2023)
Projected traffic366 by 2042
Trucks20%
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 51B over N Fork Big Thompson Riv. built?

It was built in 1977, making it 48 years old in 2025.

What condition is County Road 51B over N Fork Big Thompson Riv. 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 May 2023.

How much traffic does County Road 51B over N Fork Big Thompson Riv. carry?

About 293 vehicles per day (2023 count), of which roughly 20% are trucks.

How long is County Road 51B over N Fork Big Thompson Riv.?

The structure is 36 ft (11.1 m) long with a longest span of 34 ft (10.3 m) and a deck 26 ft wide.

Who owns County Road 51B over N Fork Big Thompson Riv.?

It is owned by the County Highway Agency.