US Bridges

Big Oak Flat Road over Cascade Creek

Fair

Mariposa County, California · 7.0 Miles East from El Po · Structure no. 8800018P0000000

Built
1939
86 years old
Condition
Fair
inspected September 2024
Type
Arch - Deck
Concrete
Length
229 ft
1 main span
Daily traffic
2,530
2022 count
Owner
Federal
National Park Service

About this bridge

Big Oak Flat Road over Cascade Creek is a concrete arch - deck carrying Big Oak Flat Road over Cascade Creek in Mariposa County, California. It was built in 1939, so it is 86 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 2,530 vehicles a day, roughly 1% of them trucks, projected to reach 3,036 by 2042. The structure is 229 ft (69.8 m) long and 35 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

Open in Google Maps
CarriesBig Oak Flat Road
CrossesCascade Creek
Location7.0 Miles East from El Po
RouteFederal Lands Road 13
CountyMariposa County
StateCalifornia
Coordinates37.72766, -119.71314
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionSeptember 2024
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 geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating40 US tons
Inventory rating24 US tons

Structure

Structure typeArch - Deck
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1 (+6 approach)
Design loadH 15
Structure length229 ft (69.8 m)
Longest span111 ft (33.8 m)
Deck width35 ft (10.7 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,530 (2022)
Projected traffic3,036 by 2042
Trucks1%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed123.7 mi (199 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerNational Park Service
Maintained byNational Park Service
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost$126,000 (2024 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Big Oak Flat Road over Cascade Creek built?

It was built in 1939, making it 86 years old in 2025.

What condition is Big Oak Flat Road over Cascade 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 September 2024.

How much traffic does Big Oak Flat Road over Cascade Creek carry?

About 2,530 vehicles per day (2022 count), of which roughly 1% are trucks.

How long is Big Oak Flat Road over Cascade Creek?

The structure is 229 ft (69.8 m) long with a longest span of 111 ft (33.8 m) and a deck 35 ft wide.

Who owns Big Oak Flat Road over Cascade Creek?

It is owned by the National Park Service.