US Bridges

Mooney Flat Road over Slacks Ravine

Fair

Nevada County, California · 0.7 MI North of Route 20 · Structure no. 17C0063

Built
1959
66 years old
Condition
Fair
inspected March 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
40 ft
2 main spans
Daily traffic
606
2014 count
Owner
County
County Highway Agency

About this bridge

Mooney Flat Road over Slacks Ravine is a steel stringer/multi-beam or girder carrying Mooney Flat Road over Slacks Ravine in Nevada County, California. It was built in 1959, so it is 66 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 606 vehicles a day, roughly 2% of them trucks, projected to reach 1,073 by 2041. The structure is 40 ft (12.2 m) long and 28 ft wide. If it were closed, the detour would be 9.9 mi (16 km).

Location

Open in Google Maps
CarriesMooney Flat Road
CrossesSlacks Ravine
Location0.7 MI North of Route 20
RouteCounty Highway 0
CountyNevada County
StateCalifornia
Coordinates39.21451, -121.27428
Functional classRural Minor 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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection9 ExcellentNo problems noted.
Last inspectionMarch 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourUnknown foundation; not evaluated for scour
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 adequacy5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating36.4 US tons
Inventory rating21.8 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans2
Design loadH 15
Structure length40 ft (12.2 m)
Longest span18 ft (5.5 m)
Deck width28 ft (8.6 m)
Roadway width26 ft (7.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic606 (2014)
Projected traffic1,073 by 2041
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed9.9 mi (16 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 Mooney Flat Road over Slacks Ravine built?

It was built in 1959, making it 66 years old in 2025.

What condition is Mooney Flat Road over Slacks Ravine 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 March 2023.

How much traffic does Mooney Flat Road over Slacks Ravine carry?

About 606 vehicles per day (2014 count), of which roughly 2% are trucks.

How long is Mooney Flat Road over Slacks Ravine?

The structure is 40 ft (12.2 m) long with a longest span of 18 ft (5.5 m) and a deck 28 ft wide.

Who owns Mooney Flat Road over Slacks Ravine?

It is owned by the County Highway Agency.