US Bridges

Rocky River Road over Big Thompson River

Fair

Larimer County, Colorado · 40 Ft S of US HWY 34 · Structure no. LRB20-2382BTC

Built
1977
48 years old
Condition
Fair
inspected June 2023
Type
Tee Beam
Prestressed Concrete
Length
50 ft
1 main span
Daily traffic
1
2023 count
Owner
County
County Highway Agency

About this bridge

Rocky River Road over Big Thompson River is a prestressed concrete tee beam carrying Rocky River Road over Big Thompson River 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 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 1 vehicles a day, roughly 4% of them trucks, projected to reach 1 by 2042. The structure is 50 ft (15.2 m) long and 12 ft wide. If it were closed, the detour would be 98.8 mi (159 km).

Location

Open in Google Maps
CarriesRocky River Road
CrossesBig Thompson River
Location40 Ft S of US HWY 34
RouteCounty Highway 0
CountyLarimer County
StateColorado
Coordinates40.39344, -105.44017
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJune 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating36 US tons
Inventory rating19.3 US tons

Structure

Structure typeTee Beam
MaterialPrestressed Concrete
DeckOther
Main spans1
Design loadH 15
Structure length50 ft (15.2 m)
Longest span48 ft (14.5 m)
Deck width12 ft (3.7 m)
Roadway width11 ft (3.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1 (2023)
Projected traffic1 by 2042
Trucks4%
Lanes on structure1
Traffic directionOne-lane bridge for two-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 byOther Local Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedWidening of existing bridge without deck rehabilitation
Estimated improvement cost$84,000 (2019 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Rocky River Road over Big Thompson River built?

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

What condition is Rocky River Road 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 Rocky River Road over Big Thompson River carry?

About 1 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is Rocky River Road over Big Thompson River?

The structure is 50 ft (15.2 m) long with a longest span of 48 ft (14.5 m) and a deck 12 ft wide.

Who owns Rocky River Road over Big Thompson River?

It is owned by the County Highway Agency and maintained by the Other Local Agency.