US Bridges

Nfa 978 (sa 9406) over Flat Creek

Fair

Williamson County, Tennessee · 2.1 MI NW JCT SR11&MARSHA · Structure no. 94F00340001

Built
1941
84 years old
Condition
Fair
inspected May 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
37 ft
2 main spans
Daily traffic
821
2021 count
Owner
County
County Highway Agency

About this bridge

Nfa 978 (sa 9406) over Flat Creek is a steel stringer/multi-beam or girder carrying Nfa 978 (sa 9406) over Flat Creek in Williamson County, Tennessee. It was built in 1941, so it is 84 years old, older than the Tennessee average of 47.4 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 821 vehicles a day, roughly 3% of them trucks, projected to reach 752 by 2041. The structure is 37 ft (11.3 m) long and 24 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

Open in Google Maps
CarriesNfa 978 (sa 9406)
CrossesFlat Creek
Location2.1 MI NW JCT SR11&MARSHA
RouteCounty Highway 978
CountyWilliamson County
StateTennessee
Coordinates35.7206, -86.72778
Functional classRural Minor Collector

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 inspectionMay 2023
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 geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating46.6 US tons
Inventory rating29.8 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20
Structure length37 ft (11.3 m)
Longest span15 ft (4.6 m)
Deck width24 ft (7.2 m)
Roadway width18 ft (5.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic821 (2021)
Projected traffic752 by 2041
Trucks3%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed5 mi (8 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$560,000 (2021 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Nfa 978 (sa 9406) over Flat Creek built?

It was built in 1941, making it 84 years old in 2025.

What condition is Nfa 978 (sa 9406) over Flat 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 May 2023.

How much traffic does Nfa 978 (sa 9406) over Flat Creek carry?

About 821 vehicles per day (2021 count), of which roughly 3% are trucks.

How long is Nfa 978 (sa 9406) over Flat Creek?

The structure is 37 ft (11.3 m) long with a longest span of 15 ft (4.6 m) and a deck 24 ft wide.

Who owns Nfa 978 (sa 9406) over Flat Creek?

It is owned by the County Highway Agency.