US Bridges

IRR County RD 306 over Grindstone Creek

Fair

Glenn County, California · 23 MI N Colusa CO Line · Structure no. 11C0035

Built
1950
75 years old
Condition
Fair
inspected August 2023
Type
Tee Beam
Concrete Continuous
Length
155 ft
3 main spans
Daily traffic
396
2004 count
Owner
County
County Highway Agency

About this bridge

IRR County RD 306 over Grindstone Creek is a concrete continuous tee beam carrying IRR County RD 306 over Grindstone Creek in Glenn County, California. It was built in 1950, so it is 75 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 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 396 vehicles a day, roughly 15% of them trucks, projected to reach 429 by 2043. The structure is 155 ft (47.2 m) long and 27 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

Open in Google Maps
CarriesIRR County RD 306
CrossesGrindstone Creek
Location23 MI N Colusa CO Line
RouteCounty Highway 0
CountyGlenn County
StateCalifornia
Coordinates39.67894, -122.53027
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 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 geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating36.8 US tons
Inventory rating28.2 US tons

Structure

Structure typeTee Beam
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length155 ft (47.2 m)
Longest span50 ft (15.2 m)
Deck width27 ft (8.3 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic396 (2004)
Projected traffic429 by 2043
Trucks15%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed123.7 mi (199 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 County RD 306 over Grindstone Creek built?

It was built in 1950, making it 75 years old in 2025.

What condition is IRR County RD 306 over Grindstone Creek 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 August 2023.

How much traffic does IRR County RD 306 over Grindstone Creek carry?

About 396 vehicles per day (2004 count), of which roughly 15% are trucks.

How long is IRR County RD 306 over Grindstone Creek?

The structure is 155 ft (47.2 m) long with a longest span of 50 ft (15.2 m) and a deck 27 ft wide.

Who owns IRR County RD 306 over Grindstone Creek?

It is owned by the County Highway Agency.