US Bridges

Forest Road 640 over North Fork Caspar Creek

Fair

Mendocino County, California · East of JCT RD 600 · Structure no. 10F0059

Built
1994
31 years old
Condition
Fair
inspected May 2023
Type
Arch - Deck
Steel
Length
22 ft
1 main span
Daily traffic
50
2009 count
Owner
State
State Park, Forest, or Reservation Agency

About this bridge

Forest Road 640 over North Fork Caspar Creek is a steel arch - deck carrying Forest Road 640 over North Fork Caspar Creek in Mendocino County, California. It was built in 1994, so it is 31 years old, younger 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 50 vehicles a day, roughly 2% of them trucks, projected to reach 65 by 2043. The structure is 22 ft (6.7 m) long. If it were closed, the detour would be 123.7 mi (199 km).

Location

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CarriesForest Road 640
CrossesNorth Fork Caspar Creek
LocationEast of JCT RD 600
RouteState Lands Road 0
CountyMendocino County
StateCalifornia
Coordinates39.34641, -123.75506
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
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 inspectionMay 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
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating59.6 US tons
Inventory rating35.7 US tons

Structure

Structure typeArch - Deck
MaterialSteel
DeckNot applicable
Main spans1
Design loadUnknown
Structure length22 ft (6.7 m)
Longest span22 ft (6.7 m)
Deck width0 ft (0 m)
Roadway width0 ft (0 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic50 (2009)
Projected traffic65 by 2043
Trucks2%
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed123.7 mi (199 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Park, Forest, or Reservation Agency
Maintained byState Park, Forest, or Reservation Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was Forest Road 640 over North Fork Caspar Creek built?

It was built in 1994, making it 31 years old in 2025.

What condition is Forest Road 640 over North Fork Caspar 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 May 2023.

How much traffic does Forest Road 640 over North Fork Caspar Creek carry?

About 50 vehicles per day (2009 count), of which roughly 2% are trucks.

How long is Forest Road 640 over North Fork Caspar Creek?

The structure is 22 ft (6.7 m) long with a longest span of 22 ft (6.7 m).

Who owns Forest Road 640 over North Fork Caspar Creek?

It is owned by the State Park, Forest, or Reservation Agency.