S-21-1491 over Middle Swamp
FairFlorence County, South Carolina · Forest Lake-W Florence · Structure no. 000000000008158
- Built
- 1988
- 37 years old
- Condition
- Fair
- inspected March 2023
- Type
- Slab
- Prestressed Concrete
- Length
- 120 ft
- 4 main spans
- Daily traffic
- 9,300
- 2023 count
- Owner
- State
- State Highway Agency
About this bridge
S-21-1491 over Middle Swamp is a prestressed concrete slab carrying S-21-1491 over Middle Swamp in Florence County, South Carolina. It was built in 1988, so it is 37 years old, younger than the South Carolina average of 48 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 9,300 vehicles a day, roughly 7% of them trucks, projected to reach 5,580 by 2043. The structure is 120 ft (36.6 m) long and 38 ft wide. If it were closed, the detour would be 3.7 mi (6 km).
Location
Open in Google MapsCondition and inspection
The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 7 Good | Some minor problems. |
| Superstructure | 7 Good | Some minor problems. |
| Substructure | 5 Fair | All primary structural elements are sound but may have minor section loss, cracking, spalling or scour. |
| Channel and channel protection | 7 Good | Some minor problems. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was S-21-1491 over Middle Swamp built?
It was built in 1988, making it 37 years old in 2025.
What condition is S-21-1491 over Middle Swamp 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 S-21-1491 over Middle Swamp carry?
About 9,300 vehicles per day (2023 count), of which roughly 7% are trucks.
How long is S-21-1491 over Middle Swamp?
The structure is 120 ft (36.6 m) long with a longest span of 30 ft (9.1 m) and a deck 38 ft wide.
Who owns S-21-1491 over Middle Swamp?
It is owned by the State Highway Agency.