US Bridges

US 17 Alt over Calfpen Swamp

Fair

Colleton County, South Carolina · Hendersonville · Structure no. 000000000000175

Built
1925
100 years old
Condition
Fair
inspected March 2024
Type
Culvert
Concrete
Length
23 ft
2 main spans
Daily traffic
1,350
2023 count
Owner
State
State Highway Agency

About this bridge

US 17 Alt over Calfpen Swamp is a concrete culvert carrying US 17 Alt over Calfpen Swamp in Colleton County, South Carolina. It was built in 1925, so it is 100 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 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 1,350 vehicles a day, roughly 16% of them trucks, projected to reach 1,971 by 2043. The structure is 23 ft (7 m) long and 49 ft wide. If it were closed, the detour would be 23 mi (37 km).

Location

Open in Google Maps
CarriesUS 17 Alt
CrossesCalfpen Swamp
LocationHendersonville
RouteU.S. Route 17
CountyColleton County
StateSouth Carolina
Coordinates32.75515, -80.74125
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
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Culvert5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionMarch 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 geometry9: Superior to present desirable criteria
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating47.2 US tons
Inventory rating28.2 US tons

Structure

Structure typeCulvert
MaterialConcrete
DeckNot applicable
Main spans2
Design loadUnknown
Structure length23 ft (7 m)
Longest span10 ft (3 m)
Deck width49 ft (14.8 m)
Roadway width47 ft (14.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,350 (2023)
Projected traffic1,971 by 2043
Trucks16%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed23 mi (37 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedWidening with deck rehabilitation or replacement
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was US 17 Alt over Calfpen Swamp built?

It was built in 1925, making it 100 years old in 2025.

What condition is US 17 Alt over Calfpen 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 2024.

How much traffic does US 17 Alt over Calfpen Swamp carry?

About 1,350 vehicles per day (2023 count), of which roughly 16% are trucks.

How long is US 17 Alt over Calfpen Swamp?

The structure is 23 ft (7 m) long with a longest span of 10 ft (3 m) and a deck 49 ft wide.

Who owns US 17 Alt over Calfpen Swamp?

It is owned by the State Highway Agency.