US Bridges

Nfa 978 (sa 9406) over Flat Creek

Fair

Williamson County, Tennessee · 2.8 MI NW JCT SR11&MARSHA · Structure no. 94F00340003

Built
1971
54 years old
Condition
Fair
inspected May 2023
Type
Culvert
Concrete Continuous
Length
26 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 concrete continuous culvert carrying Nfa 978 (sa 9406) over Flat Creek in Williamson County, Tennessee. It was built in 1971, so it is 54 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 26 ft (7.9 m) long. If it were closed, the detour would be 5 mi (8 km).

Location

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CarriesNfa 978 (sa 9406)
CrossesFlat Creek
Location2.8 MI NW JCT SR11&MARSHA
RouteCounty Highway 978
CountyWilliamson County
StateTennessee
Coordinates35.71665, -86.73953
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
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Culvert5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
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
Waterway adequacy5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating71.4 US tons
Inventory rating35.7 US tons

Structure

Structure typeCulvert
MaterialConcrete Continuous
DeckNot applicable
Main spans2
Design loadH 20
Structure length26 ft (7.9 m)
Longest span10 ft (3 m)
Deck width0 ft (0 m)
Roadway width0 ft (0 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 proposedWidening of existing bridge without deck rehabilitation
Estimated improvement cost$274,000 (2021 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

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

It was built in 1971, making it 54 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 26 ft (7.9 m) long with a longest span of 10 ft (3 m).

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

It is owned by the County Highway Agency.