US Bridges

S-21-106 over Lake Swamp

Fair

Florence County, South Carolina · 4MI SE Timmonsville · Structure no. 000000000002950

Built
1959
66 years old, rebuilt 1989
Condition
Fair
inspected April 2023
Type
Slab
Concrete
Length
60 ft
4 main spans
Daily traffic
250
2023 count
Owner
State
State Highway Agency

About this bridge

S-21-106 over Lake Swamp is a concrete slab carrying S-21-106 over Lake Swamp in Florence County, South Carolina. It was built in 1959 and reconstructed in 1989, so it is 66 years old, older 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 6 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 250 vehicles a day, roughly 5% of them trucks, projected to reach 320 by 2043. The structure is 60 ft (18.3 m) long and 28 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

Open in Google Maps
CarriesS-21-106
CrossesLake Swamp
Location4MI SE Timmonsville
RouteState Highway 106
CountyFlorence County
StateSouth Carolina
Coordinates34.09868, -79.88537
Functional classRural Local

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionApril 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourUnknown foundation; not evaluated for scour
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating28.5 US tons
Inventory rating17.2 US tons

Structure

Structure typeSlab
MaterialConcrete
DeckConcrete, precast panels
Main spans4
Design loadH 10
Structure length60 ft (18.3 m)
Longest span15 ft (4.6 m)
Deck width28 ft (8.4 m)
Roadway width26 ft (7.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic250 (2023)
Projected traffic320 by 2043
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed5 mi (8 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 S-21-106 over Lake Swamp built?

It was built in 1959, making it 66 years old in 2025. It was reconstructed in 1989.

What condition is S-21-106 over Lake 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 April 2023.

How much traffic does S-21-106 over Lake Swamp carry?

About 250 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is S-21-106 over Lake Swamp?

The structure is 60 ft (18.3 m) long with a longest span of 15 ft (4.6 m) and a deck 28 ft wide.

Who owns S-21-106 over Lake Swamp?

It is owned by the State Highway Agency.