US Bridges

State Route 255 over Mcdaniel Slough

Fair

Humboldt County, California · 01-HUM-255-7.77 · Structure no. 04 0222

Built
1963
62 years old
Condition
Fair
inspected November 2023
Type
Culvert
Concrete Continuous
Length
22 ft
2 main spans
Daily traffic
4,160
2010 count
Owner
State
State Highway Agency

About this bridge

State Route 255 over Mcdaniel Slough is a concrete continuous culvert carrying State Route 255 over Mcdaniel Slough in Humboldt County, California. It was built in 1963, so it is 62 years old, older than the California average of 54.8 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 4,160 vehicles a day, roughly 8% of them trucks, projected to reach 8,259 by 2045. The structure is 22 ft (6.7 m) long and 86 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesState Route 255
CrossesMcdaniel Slough
Location01-HUM-255-7.77
RouteState Highway 255
CountyHumboldt County
StateCalifornia
Coordinates40.86786, -124.10212
Functional classUrban Minor Arterial

Condition and inspection

Fair

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

ComponentRatingMeaning
Channel and channel protection8 Very GoodNo problems noted.
Culvert6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionNovember 2023
Inspection intervalevery 48 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry9: Superior to present desirable criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating59.6 US tons
Inventory rating35.7 US tons

Structure

Structure typeCulvert
MaterialConcrete Continuous
DeckNot applicable
Main spans2
Design loadHS 20
Structure length22 ft (6.7 m)
Longest span10 ft (3 m)
Deck width86 ft (26.2 m)
Roadway width86 ft (26.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,160 (2010)
Projected traffic8,259 by 2045
Trucks8%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState 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 State Route 255 over Mcdaniel Slough built?

It was built in 1963, making it 62 years old in 2025.

What condition is State Route 255 over Mcdaniel Slough 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 November 2023.

How much traffic does State Route 255 over Mcdaniel Slough carry?

About 4,160 vehicles per day (2010 count), of which roughly 8% are trucks.

How long is State Route 255 over Mcdaniel Slough?

The structure is 22 ft (6.7 m) long with a longest span of 10 ft (3 m) and a deck 86 ft wide.

Who owns State Route 255 over Mcdaniel Slough?

It is owned by the State Highway Agency.