US Bridges

US 17 Alt over Great Swamp

Fair

Colleton County, South Carolina · In Walterboro · Structure no. 000000000000855

Built
1938
87 years old, rebuilt 1970
Condition
Fair
inspected January 2024
Type
Tee Beam
Concrete
Length
90 ft
3 main spans
Daily traffic
11,500
2023 count
Owner
State
State Highway Agency

About this bridge

US 17 Alt over Great Swamp is a concrete tee beam carrying US 17 Alt over Great Swamp in Colleton County, South Carolina. It was built in 1938 and reconstructed in 1970, so it is 87 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 11,500 vehicles a day, roughly 7% of them trucks, projected to reach 16,215 by 2043. The structure is 90 ft (27.4 m) long and 55 ft wide. If it were closed, the detour would be 6.2 mi (10 km).

Location

Open in Google Maps
CarriesUS 17 Alt
CrossesGreat Swamp
LocationIn Walterboro
RouteU.S. Route 17
CountyColleton County
StateSouth Carolina
Coordinates32.89111, -80.68361
Functional classUrban 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
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJanuary 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating39.7 US tons
Inventory rating30.3 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans3
Design loadH 15
Structure length90 ft (27.4 m)
Longest span30 ft (9.1 m)
Deck width55 ft (16.8 m)
Roadway width50 ft (15.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic11,500 (2023)
Projected traffic16,215 by 2043
Trucks7%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.2 mi (10 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$107,000 (2024 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was US 17 Alt over Great Swamp built?

It was built in 1938, making it 87 years old in 2025. It was reconstructed in 1970.

What condition is US 17 Alt over Great 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 January 2024.

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

About 11,500 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is US 17 Alt over Great Swamp?

The structure is 90 ft (27.4 m) long with a longest span of 30 ft (9.1 m) and a deck 55 ft wide.

Who owns US 17 Alt over Great Swamp?

It is owned by the State Highway Agency.