US Bridges

IRR CO RD 87 over Roberts Slough

Good

Modoc County, California · 0.9 MI NE Lkot Hkamore RD · Structure no. 03C0004

Built
1955
70 years old
Condition
Good
inspected April 2023
Type
Slab
Concrete
Length
23 ft
1 main span
Daily traffic
255
2012 count
Owner
County
County Highway Agency

About this bridge

IRR CO RD 87 over Roberts Slough is a concrete slab carrying IRR CO RD 87 over Roberts Slough in Modoc County, California. It was built in 1955, so it is 70 years old, older than the California average of 54.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 255 vehicles a day, roughly 10% of them trucks, projected to reach 561 by 2045. The structure is 23 ft (7 m) long and 29 ft wide. If it were closed, the detour would be 16.2 mi (26 km).

CarriesIRR CO RD 87
CrossesRoberts Slough
Location0.9 MI NE Lkot Hkamore RD
RouteCounty Highway 0
Coordinates41.21535, -121.12863
Functional classRural Major Collector

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionApril 2023
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating65 US tons
Inventory rating38.9 US tons

Structure

Structure typeSlab
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length23 ft (7 m)
Longest span20 ft (6.1 m)
Deck width29 ft (8.8 m)
Roadway width28 ft (8.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic255 (2012)
Projected traffic561 by 2045
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed16.2 mi (26 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 IRR CO RD 87 over Roberts Slough built?

It was built in 1955, making it 70 years old in 2025.

What condition is IRR CO RD 87 over Roberts Slough in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in April 2023.

How much traffic does IRR CO RD 87 over Roberts Slough carry?

About 255 vehicles per day (2012 count), of which roughly 10% are trucks.

How long is IRR CO RD 87 over Roberts Slough?

The structure is 23 ft (7 m) long with a longest span of 20 ft (6.1 m) and a deck 29 ft wide.

Who owns IRR CO RD 87 over Roberts Slough?

It is owned by the County Highway Agency.