US Bridges

S-21-721 over Grey Swamp #2

Good

Florence County, South Carolina · 3 MI N Coward · Structure no. 000000000009008

Built
1996
29 years old
Condition
Good
inspected March 2024
Type
Slab
Concrete
Length
33 ft
1 main span
Daily traffic
125
2023 count
Owner
State
State Highway Agency

About this bridge

S-21-721 over Grey Swamp #2 is a concrete slab carrying S-21-721 over Grey Swamp #2 in Florence County, South Carolina. It was built in 1996, so it is 29 years old, younger than the South Carolina average of 48 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 8 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 125 vehicles a day, roughly 5% of them trucks, projected to reach 160 by 2043. The structure is 33 ft (10.1 m) long and 36 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

CarriesS-21-721
CrossesGrey Swamp #2
Location3 MI N Coward
RouteState Highway 721
Coordinates34.00778, -79.7325
Functional classRural Local

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck8 Very GoodNo problems noted.
Superstructure8 Very GoodNo problems noted.
Substructure8 Very GoodNo problems noted.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation8: Equal to present desirable criteria
Deck geometry7: Better than present minimum criteria
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating54.2 US tons
Inventory rating41.8 US tons

Structure

Structure typeSlab
MaterialConcrete
DeckConcrete, precast panels
Main spans1
Design loadHS 25 or greater
Structure length33 ft (10.1 m)
Longest span33 ft (10.1 m)
Deck width36 ft (11.1 m)
Roadway width33 ft (10.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic125 (2023)
Projected traffic160 by 2043
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 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-21-721 over Grey Swamp #2 built?

It was built in 1996, making it 29 years old in 2025.

What condition is S-21-721 over Grey Swamp #2 in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in March 2024.

How much traffic does S-21-721 over Grey Swamp #2 carry?

About 125 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is S-21-721 over Grey Swamp #2?

The structure is 33 ft (10.1 m) long with a longest span of 33 ft (10.1 m) and a deck 36 ft wide.

Who owns S-21-721 over Grey Swamp #2?

It is owned by the State Highway Agency.