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S-21-66 over Big Swamp

Florence County, South Carolina · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

S-21-66 over Big Swamp in Florence County, South Carolina, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the substructure, rated 6 (satisfactory condition) on the 0-9 scale.
It was built in 1981, making it 44 years old at the 2025 inventory.
It carries about 200 vehicles a day (traffic count year 2023).
Its listed owner is the state highway agency.
It is one of 173 of the 275 inventoried bridges in Florence County rated fair (62.9%); 10 (3.6%) are rated poor.
A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.

Component ratings


Structure	Prestressed concrete channel beam
Length	about 120 ft
Location	3.0 Mi NW Salem
NBI structure number	000000000007454
Condition class	Fair

Source: FHWA National Bridge Inventory, 2025 data as reported by the South Carolina department of transportation.

Bridge	Built	Vehicles/day	Condition
I-95 over US 52&s-21-498&rr Csxt	1966	57,700	Fair
I-95 SB over I-20 EB	1967	57,700	Fair
I-95 over S-21-26	1966	54,300	Fair
US 52 over Middle Swamp	1927	35,600	Fair
US 52 over Middle Swamp	1927	35,600	Fair
I-95 SB over S-21-13	1966	28,850	Fair