US Bridges

Interstate 15 NB over Flat Ditch

Fair

San Bernardino County, California · 08-SBD-015-R101.48 · Structure no. 54 0639R

Built
1963
62 years old
Condition
Fair
inspected September 2023
Type
Slab
Concrete Continuous
Length
98 ft
4 main spans
Daily traffic
28,000
2021 count
Owner
State
State Highway Agency

About this bridge

Interstate 15 NB over Flat Ditch is a concrete continuous slab carrying Interstate 15 NB over Flat Ditch in San Bernardino 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 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 28,000 vehicles a day, roughly 20% of them trucks, projected to reach 36,400 by 2043. The structure is 98 ft (30 m) long and 42 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesInterstate 15 NB
CrossesFlat Ditch
Location08-SBD-015-R101.48
RouteInterstate 15
CountySan Bernardino County
StateCalifornia
Coordinates34.99788, -116.56578
Functional classRural Principal Arterial - Interstate

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 protection8 Very GoodNo problems noted.
Last inspectionSeptember 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 geometry6: Equal to present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating72.5 US tons
Inventory rating43.5 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length98 ft (30 m)
Longest span25 ft (7.7 m)
Deck width42 ft (12.7 m)
Roadway width39 ft (11.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic28,000 (2021)
Projected traffic36,400 by 2043
Trucks20%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

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 Interstate 15 NB over Flat Ditch built?

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

What condition is Interstate 15 NB over Flat Ditch 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 2023.

How much traffic does Interstate 15 NB over Flat Ditch carry?

About 28,000 vehicles per day (2021 count), of which roughly 20% are trucks.

How long is Interstate 15 NB over Flat Ditch?

The structure is 98 ft (30 m) long with a longest span of 25 ft (7.7 m) and a deck 42 ft wide.

Who owns Interstate 15 NB over Flat Ditch?

It is owned by the State Highway Agency.