US Bridges

S-18-56 over Four Hole Swamp

Fair

Dorchester County, South Carolina · 4.1 MI SW Ridgeville · Structure no. 000000000005035

Built
1967
58 years old
Condition
Fair
inspected April 2023
Type
Slab
Concrete
Length
75 ft
5 main spans
Daily traffic
375
2023 count
Owner
State
State Highway Agency

About this bridge

S-18-56 over Four Hole Swamp is a concrete slab carrying S-18-56 over Four Hole Swamp in Dorchester County, South Carolina. It was built in 1967, so it is 58 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 375 vehicles a day, roughly 9% of them trucks, projected to reach 548 by 2043. The structure is 75 ft (22.9 m) long and 28 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

Location

Open in Google Maps
CarriesS-18-56
CrossesFour Hole Swamp
Location4.1 MI SW Ridgeville
RouteState Highway 56
CountyDorchester County
StateSouth Carolina
Coordinates33.08782, -80.38568
Functional classRural Major 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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
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 evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating30.8 US tons
Inventory rating18.2 US tons

Structure

Structure typeSlab
MaterialConcrete
DeckConcrete, precast panels
Main spans5
Design loadH 10
Structure length75 ft (22.9 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 traffic375 (2023)
Projected traffic548 by 2043
Trucks9%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.1 mi (13 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 proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$125,000 (2024 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was S-18-56 over Four Hole Swamp built?

It was built in 1967, making it 58 years old in 2025.

What condition is S-18-56 over Four Hole 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-18-56 over Four Hole Swamp carry?

About 375 vehicles per day (2023 count), of which roughly 9% are trucks.

How long is S-18-56 over Four Hole Swamp?

The structure is 75 ft (22.9 m) long with a longest span of 15 ft (4.6 m) and a deck 28 ft wide.

Who owns S-18-56 over Four Hole Swamp?

It is owned by the State Highway Agency.