US Bridges

I-77 SB over US 21

Poor

Richland County, South Carolina · 10 MI N. Columbia · Structure no. 000000000006918

Built
1976
49 years old
Condition
Poor
inspected January 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
270 ft
4 main spans
Daily traffic
36,350
2023 count
Owner
State
State Highway Agency

About this bridge

I-77 SB over US 21 is a steel stringer/multi-beam or girder carrying I-77 SB over US 21 in Richland County, South Carolina. It was built in 1976, so it is 49 years old, older than the South Carolina average of 48 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 36,350 vehicles a day, roughly 14% of them trucks, projected to reach 45,074 by 2043. The structure is 270 ft (82.3 m) long and 49 ft wide.

Location

Open in Google Maps
CarriesI-77 SB
CrossesUS 21
Location10 MI N. Columbia
RouteInterstate 77
CountyRichland County
StateSouth Carolina
Coordinates34.17115, -80.97161
Functional classUrban Principal Arterial - Interstate

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJanuary 2024
Inspection intervalevery 12 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating41.4 US tons
Inventory rating31.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length270 ft (82.3 m)
Longest span93 ft (28.3 m)
Deck width49 ft (15 m)
Roadway width46 ft (14 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic36,350 (2023)
Projected traffic45,074 by 2043
Trucks14%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed—
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

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$564,000 (2024 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-77 SB over US 21 built?

It was built in 1976, making it 49 years old in 2025.

What condition is I-77 SB over US 21 in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in January 2024.

How much traffic does I-77 SB over US 21 carry?

About 36,350 vehicles per day (2023 count), of which roughly 14% are trucks.

How long is I-77 SB over US 21?

The structure is 270 ft (82.3 m) long with a longest span of 93 ft (28.3 m) and a deck 49 ft wide.

Who owns I-77 SB over US 21?

It is owned by the State Highway Agency.