US Bridges

SR-121 over S.Prong St.Marys R. O/F

Fair

Baker County, Florida · 1.2 Mi. N. of CR-23C · Structure no. 270008

Built
1962
63 years old
Condition
Fair
inspected February 2024
Type
Slab
Prestressed Concrete
Length
150 ft
5 main spans
Daily traffic
2,967
2022 count
Owner
State
State Highway Agency

About this bridge

SR-121 over S.Prong St.Marys R. O/F is a prestressed concrete slab carrying SR-121 over S.Prong St.Marys R. O/F in Baker County, Florida. It was built in 1962, so it is 63 years old, older than the Florida average of 41.3 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 2,967 vehicles a day, roughly 11% of them trucks, projected to reach 5,148 by 2044. The structure is 150 ft (45.7 m) long and 34 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesSR-121
CrossesS.Prong St.Marys R. O/F
Location1.2 Mi. N. of CR-23C
RouteState Highway 121
CountyBaker County
StateFlorida
Coordinates30.35047, -82.12847
Functional classRural Minor Arterial

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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionFebruary 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating55.4 US tons
Inventory rating42.8 US tons

Structure

Structure typeSlab
MaterialPrestressed Concrete
DeckConcrete, precast panels
Main spans5
Design loadHS 20
Structure length150 ft (45.7 m)
Longest span30 ft (9.1 m)
Deck width34 ft (10.4 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,967 (2022)
Projected traffic5,148 by 2044
Trucks11%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesRelief for waterway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemNo

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 SR-121 over S.Prong St.Marys R. O/F built?

It was built in 1962, making it 63 years old in 2025.

What condition is SR-121 over S.Prong St.Marys R. O/F 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 February 2024.

How much traffic does SR-121 over S.Prong St.Marys R. O/F carry?

About 2,967 vehicles per day (2022 count), of which roughly 11% are trucks.

How long is SR-121 over S.Prong St.Marys R. O/F?

The structure is 150 ft (45.7 m) long with a longest span of 30 ft (9.1 m) and a deck 34 ft wide.

Who owns SR-121 over S.Prong St.Marys R. O/F?

It is owned by the State Highway Agency.