US Bridges

US 278 WB over Mackay Creek

Fair

Beaufort County, South Carolina · Hilton Head Island · Structure no. 000000000007650

Built
1983
42 years old
Condition
Fair
inspected September 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
2,231 ft
1 main span
Daily traffic
28,950
2023 count
Owner
State
State Highway Agency

About this bridge

US 278 WB over Mackay Creek is a steel stringer/multi-beam or girder carrying US 278 WB over Mackay Creek in Beaufort County, South Carolina. It was built in 1983, so it is 42 years old, younger 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 28,950 vehicles a day, roughly 4% of them trucks, projected to reach 45,162 by 2043. The structure is 2,231 ft (679.9 m) long and 39 ft wide.

CarriesUS 278 WB
CrossesMackay Creek
LocationHilton Head Island
RouteU.S. Route 278
Coordinates32.23068, -80.79177
Functional classUrban Other Principal 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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionSeptember 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 geometry6: Equal to present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating63.6 US tons
Inventory rating32.2 US tons

Structure

MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+54 approach)
Design loadHS 20
Structure length2,231 ft (679.9 m)
Longest span71 ft (21.6 m)
Deck width39 ft (12 m)
Roadway width36 ft (11 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic28,950 (2023)
Projected traffic45,162 by 2043
Trucks4%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed—
TollOn a free road
National Highway SystemYes

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—
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was US 278 WB over Mackay Creek built?

It was built in 1983, making it 42 years old in 2025.

What condition is US 278 WB over Mackay Creek 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 September 2024.

How much traffic does US 278 WB over Mackay Creek carry?

About 28,950 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is US 278 WB over Mackay Creek?

The structure is 2,231 ft (679.9 m) long with a longest span of 71 ft (21.6 m) and a deck 39 ft wide.

Who owns US 278 WB over Mackay Creek?

It is owned by the State Highway Agency.